publications | Shibaji Chakraborty

2025

GRL
Evidence of Unusually Strong Equatorial Ionization Anomaly at Three Local Time Sectors During the Mother’s Day Geomagnetic Storm On 10–11 May 2024

Diptiranjan Rout, A. Kumar, R. Singh, and 6 more authors

Geophysical Research Letters, 2025

e2024GL111269 2024GL111269

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Abstract This study uses multiple ground and satellite-based measurements to investigate the extreme ionospheric response to the Mother’s Day storm on May 10–11, 2024. Prompt penetration electric field caused a significant enhancement in the ionospheric vertical drift (∼ {∼ 95 m/s) and the equatorial electrojet strength (∼ {∼ 275 nT) over Jicamarca. These extreme eastward electric field perturbations, along with the large meridional wind, significantly altered the F-region plasma fountain at different local times. The afternoon equatorial ionization anomaly (EIA) not only sustained for an exceptionally long duration (∼ {∼ 12 hr) but also expanded spatially over time. The separation between the two peaks of EIA crests exceeded ∼48° {∼ 48^∘ and ∼70° {∼ 70^∘ in the morning and evening sectors, respectively. This study shows, for the first time, that unusually strong EIA can not only develop at different local times but can also sustain for long duration under favorable conditions, which has implications for space weather applications.
@article{https://doi.org/10.1029/2024GL111269, author = {Rout, Diptiranjan and Kumar, A. and Singh, R. and Patra, S. and Karan, D. K. and Chakraborty, S. and Scipion, D. and Chakrabarty, D. and Riccobono, Juanita}, title = {Evidence of Unusually Strong Equatorial Ionization Anomaly at Three Local Time Sectors During the Mother's Day Geomagnetic Storm On 10–11 May 2024}, journal = {Geophysical Research Letters}, volume = {52}, number = {2}, pages = {e2024GL111269}, keywords = {space weather, mother's day storm, plasma fountain, penetration electric field, overshielding electric field, disturbance dynamo electric field}, doi = {https://doi.org/10.1029/2024GL111269}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2024GL111269}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2024GL111269}, note = {e2024GL111269 2024GL111269}, year = {2025}, dimensions = {true}, }
JGR
Statistical Characterization of Joule Heating Associated With Ionospheric ULF Perturbations Using SuperDARN Data

Xueling Shi, Shibaji Chakraborty, Joseph B. H. Baker, and 7 more authors

Journal of Geophysical Research: Space Physics, 2025

e2024JA033452 2024JA033452

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Abstract Ultra low frequency (ULF; 1 mHz - several Hz) waves are key to energy transport within the geospace system, yet their contribution to Joule heating in the upper atmosphere remains poorly quantified. This study statistically examines Joule heating associated with ionospheric ULF perturbations using Super Dual Auroral Radar Network (SuperDARN) data spanning middle to polar latitudes. Our analysis utilizes high-time-resolution measurements from SuperDARN high-frequency coherent scatter radars operating in a special mode, sampling three “camping beams” approximately every 18 s. We focus on ULF perturbations within the Pc5 frequency range (1.6–6.7 mHz), estimating Joule heating rates from ionospheric electric fields derived from SuperDARN data and height-integrated Pedersen conductance from empirical models. The analysis includes statistical characterization of Pc5 wave occurrence, electric fields, Joule heating rates, and azimuthal wave numbers. Our results reveal enhanced electric fields and Joule heating rates in the morning and pre-midnight sectors, even though Pc5 wave occurrences peak in the afternoon. Joule heating is more pronounced in the high-latitude morning sector during northward interplanetary magnetic field conditions, attributed to local time asymmetry in Pedersen conductance and Pc5 waves driven by Kelvin-Helmholtz instability. Pc5 waves observed by multiple camping beams predominantly propagate westward at low azimuthal wave numbers (|m|<50) \(\vert m\vert < 50) while high-m waves propagate mainly eastward. Although Joule heating estimates may be underestimated due to assumptions about empirical conductance models and the underestimation of electric fields resulting from SuperDARN line-of-sight velocity measurements, these findings offer valuable insights into ULF wave-related energy dissipation in the geospace system.
@article{https://doi.org/10.1029/2024JA033452, author = {Shi, Xueling and Chakraborty, Shibaji and Baker, Joseph B. H. and Hartinger, Michael D. and Wang, Wenbin and Ruohoniemi, J. Michael and Lin, Dong and Lotko, William and Sterne, Kevin and McWilliams, Kathryn A.}, title = {Statistical Characterization of Joule Heating Associated With Ionospheric ULF Perturbations Using SuperDARN Data}, journal = {Journal of Geophysical Research: Space Physics}, volume = {130}, number = {3}, pages = {e2024JA033452}, keywords = {ULF wave, joule heating, superdarn}, doi = {https://doi.org/10.1029/2024JA033452}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2024JA033452}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2024JA033452}, note = {e2024JA033452 2024JA033452}, year = {2025}, dimensions = {true}, }
SGeo
Impact of Terrestrial Weather on the Space Weather of the Ionosphere-Thermosphere: Initial Results from a NASA Living with a Star Focused Science Topic

J. Oberheide, D. Aggarwal, B. Bergsson, and 21 more authors

Surveys in Geophysics, Jul 2025

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The ionosphere-thermosphere (IT) is a convergence point of energy and processes that interconnect Earth’s atmosphere with space. Processes generated by terrestrial weather in the lower atmosphere (i.e., troposphere and stratosphere, altitudes less than\thinspace~\thinspace50 km) are recognized by the scientific community as sources of variability in both the structure and composition of the IT. Exposed to persistent wave forcing from terrestrial weather sources and solar and magnetic forcing, the IT is a domain of compelling scientific inquiry that connects thermodynamics, fluid dynamics, electrodynamics and plasma physics. Predicting its space weather is of significant national interest for space situation awareness including the very low earth orbit as the new frontier of space operations. Advancing the understanding of whole atmosphere interconnections between terrestrial and space weather requires coordinated modeling and observational efforts across different spatial and temporal scales. Toward this goal, the National Aeronautics and Space Administration (NASA), through the living with a star (LWS) program, established in 2022 a focused science topic (FST) to study the problem from various angles. In this manuscript we report on the vision, goals and status of the ongoing FST “Impact of Terrestrial Weather on the Ionosphere—Thermosphere”. Initial results show bigger impacts on the IT than hitherto thought and help to more clearly define the state-of-the-art in the context of future NASA missions such as EZIE, DYNAMIC and GDC.
@article{Oberheide2025, author = {Oberheide, J. and Aggarwal, D. and Bergsson, B. and Chakraborty, S. and Debchoudhury, S. and Dhadly, M. and Gasperini, F. and Goncharenko, L. and Harvey, V. L. and Heale, C. and Inchin, P. and Li, J. and Liu, G. and Liu, H.-L. and Lu, X. and McDonald, S. and Neogi, M. and Pedatella, N. and Sassi, F. and Singh, D. and Volz, R. and Yudin, V. A. and Zettergren, M. and Zhang, S.-R.}, title = {Impact of Terrestrial Weather on the Space Weather of the Ionosphere-Thermosphere: Initial Results from a NASA Living with a Star Focused Science Topic}, journal = {Surveys in Geophysics}, year = {2025}, month = jul, day = {09}, issn = {1573-0956}, doi = {10.1007/s10712-025-09895-7}, url = {https://doi.org/10.1007/s10712-025-09895-7}, dimensions = {true}, }
ESS
Formation of the Ionospheric G-Condition Following the 2017 Great American Eclipse

S. Chakraborty, L. Qian, S. Mrak, and 4 more authors

Earth and Space Science, Jul 2025

e2024EA004007 2024EA004007

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Abstract A total solar eclipse (TSE) traversed the continental US (CONUS) from west to east on 21 August 2017. Ionosondes located under the eclipse totality at Lusk (Wyoming) and Boulder (Colorado) observed the ionospheric G-condition 20 min after totality. The Millstone Hill mid-latitude incoherent scatter radar recorded an anomalous low altitude F2 peak during the recovery phase of the eclipse, which can be attributed to an ionospheric G-condition. We perform WACCM-X simulations to investigate the physical processes that drive the ionospheric G-condition. Specifically, we conducted a diagnostic analysis of the simulated atomic oxygen ion continuity equation to examine the source of the G-condition. We defined two metrics describing the G-condition: (a) the duration and (b) the maximum difference between {\mathrmN_\mathrmm\mathrmF_1 and {\mathrmN_\mathrmm\mathrmF_2\. Results indicate that E- and F1 plasma density reduction closely follow the eclipse obscuration, whereas the F2-layer density depletion lags the obscuration by {∼ \20 min. This delay increases with altitude and is caused by slower radiative recombination and transport processes in the diffusion-dominated F2-region. The delay creates a period during the eclipse recovery when the F1-plasma density exceeds that of the F2-peak, which manifests as the ionospheric G-condition. The simulation study illuminates the space-time behavior of the G-condition indicating that this state can last for more than 50 min during the recovery phase of the eclipse.
@article{https://doi.org/10.1029/2024EA004007, author = {Chakraborty, S. and Qian, L. and Mrak, S. and Mabie, J. and Goncharenko, L. and Mclnerney, J. M. and Bullett, T.}, title = {Formation of the Ionospheric G-Condition Following the 2017 Great American Eclipse}, journal = {Earth and Space Science}, volume = {12}, number = {8}, pages = {e2024EA004007}, keywords = {great American eclipse, solar eclipse, G-condition, transport, ionosonde}, doi = {https://doi.org/10.1029/2024EA004007}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2024EA004007}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2024EA004007}, note = {e2024EA004007 2024EA004007}, year = {2025}, dimensions = {true}, }
The Impact of Receiver-Satellite Line-of-Sight Orientation on GNSS TEC Observations of TIDs Induced by GWs From Convective Sources

Björn Bergsson, Shantanab Debchoudhury, Pavel Inchin, and 3 more authors

Journal of Geophysical Research: Space Physics, Jul 2025

e2025JA033938 2025JA033938

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Abstract Total electron content (TEC) measurements recorded by a dense network of ground receivers tracking signals from Global Navigation Satellite System satellites provide a large number of data points and are one of the most effective methods for observing the horizontal characteristics of traveling ionospheric disturbances (TIDs). Conventionally, the receiver-satellite line-of-sight (LOS) geometry of TEC measurements is not considered except for applying an elevation cut-off angle to exclude measurements of high signal noise. However, as TEC is the total number of electrons spatially integrated along its LOS, its effectiveness in observing TIDs is heavily influenced by the LOS alignment with respect to the electron density perturbations. LOSs that pass through regions of both increased and decreased electron densities are ineffective at detecting the perturbations from ambient waves. This is because the opposite phases are canceled, yielding a TEC measurement that is not sensitive to the wave characteristic. In this paper, we investigate the effectiveness of different LOS azimuth orientations for TEC observations of concentric TIDs induced by gravity waves (GWs) generated by a tropospheric convective source over the Continental United States (CONUS). Results indicate that the observation and characterization of TIDs from GWs can be significantly improved by using only LOSs with certain azimuth angles.
@article{https://doi.org/10.1029/2025JA033938, author = {Bergsson, Björn and Debchoudhury, Shantanab and Inchin, Pavel and Heale, Christopher and Chakraborty, Shibaji and Zettergren, Matthew}, title = {The Impact of Receiver-Satellite Line-of-Sight Orientation on GNSS TEC Observations of TIDs Induced by GWs From Convective Sources}, journal = {Journal of Geophysical Research: Space Physics}, volume = {130}, number = {9}, pages = {e2025JA033938}, doi = {https://doi.org/10.1029/2025JA033938}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2025JA033938}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2025JA033938}, note = {e2025JA033938 2025JA033938}, year = {2025}, dimensions = {true}, }

2024

SW
An Examination of Geomagnetic Induction in Submarine Cables

David H. Boteler, Shibaji Chakraborty, Xueling Shi, and 2 more authors

Space Weather, Jul 2024

e2023SW003687 2023SW003687

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Abstract Submarine cables have experienced problems during extreme geomagnetic disturbances because of geomagnetically induced voltages adding or subtracting from the power feed to the repeaters. This is still a concern for modern fiber-optic cables because they contain a copper conductor to carry power to the repeaters. This paper provides a new examination of geomagnetic induction in submarine cables and makes calculations of the voltages experienced by the TAT-8 trans-Atlantic submarine cable during the March 1989 magnetic storm. It is shown that the cable itself experiences an induced electromotive force (emf) and that induction in the ocean also leads to changes of potential of the land at each end of the cable. The process for calculating the electric fields induced in the sea and in the cable from knowledge of the seawater depth and conductivity and subsea conductivity is explained. The cable route is divided into 9 sections and the seafloor electric field is calculated for each section. These are combined to give the total induced emf in the cable. In addition, induction in the seawater and leakage of induced currents through the underlying resistive layers are modeled using a transmission line model of the ocean and underlying layers to determine the change in Earth potentials at the cable ends. The induced emf in the cable and the end potentials are then combined to give the total voltage change experienced by the cable power feed equipment. This gives results very close to those recorded on the TAT-8 cable in March 1989.
@article{Boteler2023SW003687, author = {Boteler, David H. and Chakraborty, Shibaji and Shi, Xueling and Hartinger, Michael D. and Wang, Xuan}, title = {An Examination of Geomagnetic Induction in Submarine Cables}, journal = {Space Weather}, volume = {22}, number = {2}, pages = {e2023SW003687}, keywords = {submarine cables, geomagnetic storm, geomagnetically induced currents}, doi = {https://doi.org/10.1029/2023SW003687}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2023SW003687}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2023SW003687}, note = {e2023SW003687 2023SW003687}, year = {2024}, dimensions = {true}, }

Calculating the High-Latitude Ionospheric Electrodynamics Using a Machine Learning-Based Field-Aligned Current Model

V. Sai Gowtam, Hyunju Connor, Bharat S. R. Kunduri, and 8 more authors

Space Weather, Apr 2024

Bib

@article{2024SpWea2203683G,
  author = {{Gowtam}, V. Sai and {Connor}, Hyunju and {Kunduri}, Bharat S.~R. and {Raeder}, Joachim and {Laundal}, Karl M. and {Tulasi Ram}, S. and {Ozturk}, Dogacan S. and {Hampton}, Donald and {Chakraborty}, Shibaji and {Owolabi}, Charles and {Keesee}, Amy},
  title = {{Calculating the High-Latitude Ionospheric Electrodynamics Using a Machine Learning-Based Field-Aligned Current Model}},
  journal = {Space Weather},
  keywords = {auroral electrodynamics, magnetosphere-ionosphere coupling, cross polar cap potential, field aligned currents, auroral conductance, machine learning},
  year = {2024},
  month = apr,
  volume = {22},
  number = {4},
  eid = {e2023SW003683},
  pages = {e2023SW003683},
  doi = {10.1029/2023SW003683},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2024SpWea..2203683G},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  dimensions = {true},
}

JGR

Atmospheric and Ionospheric Responses to Orographic Gravity Waves Prior to the December 2022 Cold Air Outbreak

P. A. Inchin, A. Bhatt, M. Bramberger, and 3 more authors

Journal of Geophysical Research (Space Physics), Jun 2024

Bib

@article{2024JGRA12932485I,
  author = {{Inchin}, P.~A. and {Bhatt}, A. and {Bramberger}, M. and {Chakraborty}, S. and {Debchoudhury}, S. and {Heale}, C.},
  title = {{Atmospheric and Ionospheric Responses to Orographic Gravity Waves Prior to the December 2022 Cold Air Outbreak}},
  journal = {Journal of Geophysical Research (Space Physics)},
  keywords = {mountain waves, traveling ionospheric disturbances, cold air outbreak, gravity waves, ionosphere, thermosphere},
  year = {2024},
  month = jun,
  volume = {129},
  number = {6},
  eid = {e2024JA032485},
  pages = {e2024JA032485},
  doi = {10.1029/2024JA032485},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2024JGRA..12932485I},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  dimensions = {true},
}

JGR
The Morphology and Oscillations of Nightside Mid-Latitude Ionospheric Trough at Designated Longitudes in the Northern Hemisphere

Xinlong Liu, Donghe Zhang, Anthea J. Coster, and 3 more authors

Journal of Geophysical Research: Space Physics, Jun 2024

e2024JA032864 2024JA032864

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Abstract The mid-latitude ionospheric trough (MLIT), an anomaly in the ionosphere’s F layer caused by various mechanisms, affects radio wave propagation. In this study, we investigated the morphology and oscillations of the MLIT using global Global Positioning System total electron content map data between 1 January 2018, and 31 December 2020. The MLIT position varies longitudinally, reaching its farthest equatorward at 60° {^∘\W and its farthest poleward at 30° {^∘\E. The MLIT occurrence rates peak during the winter and equinoxes and dip in summer, while seasonal variations in MLIT position vary across longitude bands. Heightened geomagnetic activities, quantified by the SME6 index, promote MLIT occurrence, especially during pre-midnight hours in summer and equinoxes, and shift the MLIT equatorward, particularly during midnight and post-midnight hours. The MLIT position shows clear local time variation, with a gradual decrease before midnight, stabilization afterward, and a minor resurgence around dawn. Wavelet analysis reveals three distinct periodic components in the MLIT position: 27, 13.5, and 9, with the 27-day period being the most persistent. Cross-wavelet and wavelet coherence analyses suggest that solar wind (SW) velocity variations precede changes in the MLIT position. The main factors responsible for the equatorward movement of MLIT are the electric fields in high-speed SW that enhance the ionospheric convection pattern, and the intensified geomagnetic activities induced by interplanetary shocks.
@article{2024JA032864, author = {Liu, Xinlong and Zhang, Donghe and Coster, Anthea J. and Xu, Zhonghua and Shi, Xueling and Chakraborty, Shibaji}, title = {The Morphology and Oscillations of Nightside Mid-Latitude Ionospheric Trough at Designated Longitudes in the Northern Hemisphere}, journal = {Journal of Geophysical Research: Space Physics}, volume = {129}, number = {9}, pages = {e2024JA032864}, keywords = {ionospheric trough, TEC, SME6 index, solar wind, high latitude plasma convection}, doi = {https://doi.org/10.1029/2024JA032864}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2024JA032864}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2024JA032864}, note = {e2024JA032864 2024JA032864}, year = {2024}, dimensions = {true}, }

2023

GRL
Substorms and Solar Eclipses: A Mutual Information Based Study

S. E. Coyle, J. B. H. Baker, S. Chakraborty, and 5 more authors

Geophysical Research Letters, Jun 2023

e2023GL106432 2023GL106432

Abs Bib HTML PDF

Abstract Solar eclipses present a rare glimpse into the impact of ionospheric electrodynamics on the magnetosphere independent of other well studied seasonal influences. Despite decades of study, we still do not have a complete description of the conditions for geomagnetic substorm onset. We present herein a mutual information based study of previously published substorm onsets and the past two decades of eclipses which indicates the likelihood of co-occurrence is greater than random chance. A plausible interpretation for this relation suggests that the abrupt fluctuations in ionospheric conductivity during an eclipse may influence the magnetospheric preconditions of substorm initiation. While the mechanism remains unclear, this study presents strong evidence of a link between substorm onset and solar eclipses.
@article{Coyle2023GL106432, author = {Coyle, S. E. and Baker, J. B. H. and Chakraborty, S. and Hartinger, M. D. and Freeman, M. P. and Clauer, C. R. and Xu, Z. and Weimer, D. R.}, title = {Substorms and Solar Eclipses: A Mutual Information Based Study}, journal = {Geophysical Research Letters}, volume = {50}, number = {24}, pages = {e2023GL106432}, keywords = {solar eclipse, substorm, mutual information, conductivity}, doi = {https://doi.org/10.1029/2023GL106432}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2023GL106432}, note = {e2023GL106432 2023GL106432}, year = {2023}, dimensions = {true}, }

ApJS

A Community Dataset for Comparing Automated Coronal Hole Detection Schemes

Martin A Reiss, Karin Muglach, Emily Mason, and 8 more authors

Astrophysical Journal Supplement, Jun 2023

Bib HTML PDF

@article{reiss2023community,
  title = {A Community Dataset for Comparing Automated Coronal Hole Detection Schemes},
  author = {Reiss, Martin A and Muglach, Karin and Mason, Emily and Davies, Emma E and Chakraborty, Shibaji and Delouille, Veronique and Downs, Cooper and Garton, Tadhg M and Grajeda, Jeremy A and Hamada, Amr and others},
  journal = {Astrophysical Journal Supplement},
  year = {2023},
  publisher = {American Astronomical Society/IOP Publishing},
  dimensions = {true},
}

Transmission Line Modelling of Geomagnetic Induction in the Ocean/Earth Conductivity Structure

D. Boteler, S. Chakraborty, X. Shi, and 2 more authors

International Journal of Geosciences, Jun 2023

Abs Bib HTML PDF

Abstract Solar eclipses present a rare glimpse into the impact of ionospheric electrodynamics on the magnetosphere independent of other well studied seasonal influences. Despite decades of study, we still do not have a complete description of the conditions for geomagnetic substorm onset. We present herein a mutual information based study of previously published substorm onsets and the past two decades of eclipses which indicates the likelihood of co-occurrence is greater than random chance. A plausible interpretation for this relation suggests that the abrupt fluctuations in ionospheric conductivity during an eclipse may influence the magnetospheric preconditions of substorm initiation. While the mechanism remains unclear, this study presents strong evidence of a link between substorm onset and solar eclipses.
@article{Botelerijg.2023.148041, author = {Boteler, D. and Chakraborty, S. and Shi, X. and Hartinger, M. and Wang, X.}, title = {Transmission Line Modelling of Geomagnetic Induction in the Ocean/Earth Conductivity Structure}, journal = {International Journal of Geosciences}, volume = {14}, pages = {767-791}, keywords = {Geomagnetic Induction, Generalised Thin Sheet, Transmission Line Modelling, Coast Potentials, Submarine Cables}, doi = {https://doi.org/10.4236/ijg.2023.148041}, year = {2023}, dimensions = {true}, }
The Growth of Ring Current/SYM-H Under Northward IMF Bz Conditions Present During the 21–22 January 2005 Geomagnetic Storm

Diptiranjan Rout, S. Patra, S. Kumar, and 6 more authors

Space Weather, Jun 2023

e2023SW003489 2023SW003489

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Abstract The total energy transfer from the solar wind to the magnetosphere is governed by the reconnection rate at the magnetosphere edges as the Z-component of interplanetary magnetic field (IMF Bz) turns southward. The geomagnetic storm on 21–22 January 2005 is considered to be anomalous as the SYM-H index that signifies the strength of ring current, decreases and had a sustained trough value of −101 nT lasting more than 6 hr under northward IMF Bz conditions. In this work, the standard WINDMI model is utilized to estimate the growth and decay of magnetospheric currents by using several solar wind-magnetosphere coupling functions. However, it is found that the WINDMI model driven by any of these coupling functions is not fully able to explain the decrease of SYM-H under northward IMF Bz. A dense plasma sheet along with signatures of a highly stretched magnetosphere was observed during this storm. The SYM-H variations during the entire duration of the storm were only reproduced after modifying the WINDMI model to account for the effects of the dense plasma sheet. The limitations of directly driven models relying purely on the solar wind parameters and not accounting for the state of the magnetosphere are highlighted by this work.
@article{Rout2023SW003489, author = {Rout, Diptiranjan and Patra, S. and Kumar, S. and Chakrabarty, D. and Reeves, G. D. and Stolle, C. and Pandey, K. and Chakraborty, S. and Spencer, E. A.}, title = {The Growth of Ring Current/SYM-H Under Northward IMF Bz Conditions Present During the 21–22 January 2005 Geomagnetic Storm}, journal = {Space Weather}, volume = {21}, number = {10}, pages = {e2023SW003489}, keywords = {ring current, space weather, northward IMF Bz, WINDMI model, solar wind-magnetosphere-ionosphere coupling}, doi = {https://doi.org/10.1029/2023SW003489}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2023SW003489}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2023SW003489}, note = {e2023SW003489 2023SW003489}, year = {2023}, dimensions = {true}, }
Transient Response of Polar-Cusp Ionosphere to an Interplanetary Shock

Jianjun Liu, Shibaji Chakraborty, Xiangcai Chen, and 11 more authors

Journal of Geophysical Research: Space Physics, Jun 2023

e2022JA030565 2022JA030565

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Abstract Interplanetary (IP) shock-driven sudden compression of the Earth’s magnetosphere produces electromagnetic disturbances in the polar ionosphere. Several studies have examined the effects of IP shock on magnetosphere-ionosphere coupling systems using all-sky cameras and radars. In this study, we examine responses and drivers of the polar ionosphere following an IP shock compression on 16 June 2012. We observe the vertical drift and concurrent horizontal motion of the plasma. Observations from digisonde located at Antarctic Zhongshan station (ZHO) showed an ionospheric thick E region ionization and associated vertical downward plasma motion at F region. In addition, horizontal ionospheric convection reversals were observed on the Super Dual Auroral Radar Network ZHO and McMurdo radar observations. Findings suggest that the transient convective reversal breaks the original shear equilibrium, it is expected that the IP shock-induced electric field triggers an enhanced velocity shear mapping to the E region. The horizontal motion of the plasma was attributed to only the dusk-to-dawn electric field that existed during the preliminary phase of sudden impulse. We also found that ionospheric convection reversals were driven by a downward field-aligned current. The results of these observations reveal, for the first time, the immediate and direct cusp ionosphere response to the IP shock, which is critical for understanding the global response of the magnetosphere following an abrupt change in Interplanetory Magnetic Field (IMF) and solar wind conditions.
@article{Liu2022JA030565, author = {Liu, Jianjun and Chakraborty, Shibaji and Chen, Xiangcai and Wang, Zhiwei and He, Fang and Hu, Zejun and Liu, Erxiao and Bat-Erdene, Amarjargal and Han, Desheng and Ruohoniemi, J. Michael and Baker, Joseph B. H. and Yang, Huigen and Zong, Qiugang and Hu, Hongqiao}, title = {Transient Response of Polar-Cusp Ionosphere to an Interplanetary Shock}, journal = {Journal of Geophysical Research: Space Physics}, volume = {128}, number = {3}, pages = {e2022JA030565}, keywords = {space weather, IP shock, SSC, SuperDARN, reverse convection, vertical drift}, doi = {https://doi.org/10.1029/2022JA030565}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022JA030565}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2022JA030565}, note = {e2022JA030565 2022JA030565}, year = {2023}, dimensions = {true}, }
Crowdsourced Doppler measurements of time standard stations demonstrating ionospheric variability

K. Collins, J. Gibbons, N. Frissell, and 15 more authors

Earth System Science Data, Jun 2023

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Ionospheric variability produces measurable effects in Doppler shift of HF (high-frequency, 3–30 MHz) skywave signals. These effects are straightforward to measure with low-cost equipment and are conducive to citizen science campaigns. The low-cost Personal Space Weather Station (PSWS) network is a modular network of community-maintained, open-source receivers, which measure Doppler shift in the precise carrier signals of time standard stations. The primary goal of this paper is to explain the types of measurements this instrument can make and some of its use cases, demonstrating its role as the building block for a large-scale ionospheric and HF propagation measurement network which complements existing professional networks. Here, data from the PSWS network are presented for a period of time spanning late 2019 to early 2022. Software tools for the visualization and analysis of this living dataset are also discussed and provided. These tools are robust to data interruptions and to the addition, removal or modification of stations, allowing both short- and long-term visualization at higher density and faster cadence than other methods. These data may be used to supplement observations made with other geospace instruments in event-based analyses, e.g., traveling ionospheric disturbances and solar flares, and to assess the accuracy of the bottomside estimates of ionospheric models by comparing the oblique paths obtained by ionospheric ray tracers with those obtained by these receivers. The data are archived at https://doi.org/10.5281/zenodo.6622111 (Collins, 2022).
@article{essd-15-1403-2023, author = {Collins, K. and Gibbons, J. and Frissell, N. and Montare, A. and Kazdan, D. and Kalmbach, D. and Swartz, D. and Benedict, R. and Romanek, V. and Boedicker, R. and Liles, W. and Engelke, W. and McGaw, D. G. and Farmer, J. and Mikitin, G. and Hobart, J. and Kavanagh, G. and Chakraborty, S.}, title = {Crowdsourced Doppler measurements of time standard stations demonstrating ionospheric variability}, journal = {Earth System Science Data}, volume = {15}, year = {2023}, number = {3}, pages = {1403--1418}, url = {https://essd.copernicus.org/articles/15/1403/2023/}, doi = {10.5194/essd-15-1403-2023}, dimensions = {true}, }

2022

Modeling geomagnetic induction in submarine cables

Shibaji Chakraborty, David H. Boteler, Xueling Shi, and 5 more authors

Frontiers in Physics, Jun 2022

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Submarine cables have become a vital component of modern infrastructure, but past submarine cable natural hazard studies have mostly focused on potential cable damage from landslides and tsunamis. A handful of studies examine the possibility of space weather effects in submarine cables. The main purpose of this study is to develop a computational model, using Python, of geomagnetic induction on submarine cables. The model is used to estimate the induced voltage in the submarine cables in response to geomagnetic disturbances. It also utilizes newly acquired knowledge from magnetotelluric studies and associated investigations of geomagnetically induced currents in power systems. We describe the Python-based software, its working principle, inputs/outputs based on synthetic geomagnetic field data, and compare its operational capabilities against analytical solutions. We present the results for different model inputs, and find: 1) the seawater layer acts as a shield in the induction process: the greater the ocean depth, the smaller the seafloor geoelectric field; and 2) the model is sensitive to the Ocean-Earth layered conductivity structure.
@article{scubas2022, author = {Chakraborty, Shibaji and Boteler, David H. and Shi, Xueling and Murphy, Benjamin S. and Hartinger, Michael D. and Wang, Xuan and Lucas, Greg and Baker, Joseph B. H.}, title = {Modeling geomagnetic induction in submarine cables}, journal = {Frontiers in Physics}, volume = {10}, year = {2022}, url = {https://www.frontiersin.org/articles/10.3389/fphy.2022.1022475}, doi = {10.3389/fphy.2022.1022475}, issn = {2296-424X}, dimensions = {true}, }
Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares

S. Chakraborty, L. Qian, J. B. H. Baker, and 3 more authors

Journal of Geophysical Research: Space Physics, Jun 2022

e2022JA030342 2022JA030342

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Abstract Sudden enhancement in high-frequency absorption is a well-known impact of solar flare-driven Short-Wave Fadeout (SWF). Less understood, is a perturbation of the radio wave frequency as it traverses the ionosphere in the early stages of SWF, also known as the Doppler flash. Investigations have suggested two possible sources that might contribute to it’s manifestation: first, enhancements of plasma density in the D-and lower E-regions; second, the lowering of the F-region reflection point. Our recent work investigated a solar flare event using first principles modeling and Super Dual Auroral Radar Network (SuperDARN) HF radar observations and found that change in the F-region refractive index is the primary driver of the Doppler flash. This study analyzes multiple solar flare events observed across different SuperDARN HF radars to determine how flare characteristics, properties of the traveling radio wave, and geophysical conditions impact the Doppler flash. In addition, we use incoherent scatter radar data and first-principles modeling to investigate physical mechanisms that drive the lowering of the F-region reflection points. We found, (a) on average, the change in E- and F-region refractive index is the primary driver of the Doppler flash, (b) solar zenith angle, ray’s elevation angle, operating frequency, and location of the solar flare on the solar disk can alter the ionospheric regions of maximum contribution to the Doppler flash, (c) increased ionospheric Hall and Pedersen conductance causes a reduction of the daytime eastward electric field, and consequently reduces the vertical ion-drift in the lower and middle latitude ionosphere, which results in lowering of the F-region ray reflection point.
@article{Chakraborty2022JA030342, author = {Chakraborty, S. and Qian, L. and Baker, J. B. H. and Ruohoniemi, J. M. and Kuyeng, K. and Mclnerney, J. M.}, title = {Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares}, journal = {Journal of Geophysical Research: Space Physics}, volume = {127}, number = {6}, pages = {e2022JA030342}, keywords = {space weather, shortwave fadeout, Doppler flash, solar flare, magnetic crochet, SuperDARN}, doi = {https://doi.org/10.1029/2022JA030342}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2022JA030342}, note = {e2022JA030342 2022JA030342}, year = {2022}, dimensions = {true}, }
AnGeo
Multi-instrument observations of polar cap patches and traveling ionospheric disturbances generated by solar wind Alfvén waves coupling to the dayside magnetosphere

Paul Prikryl, Robert G. Gillies, David R. Themens, and 3 more authors

Annales Geophysicae, Nov 2022

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During minor to moderate geomagnetic storms, caused by corotating interaction regions (CIRs) at the leading edge of high-speed streams (HSSs), solar wind Alfvén waves modulated the magnetic reconnection at the dayside magnetopause. The Resolute Bay Incoherent Scatter Radars (RISR-C and RISR-N), measuring plasma parameters in the cusp and polar cap, observed ionospheric signatures of flux transfer events (FTEs) that resulted in the formation of polar cap patches. The patches were observed as they moved over the RISR, and the Canadian High-Arctic Ionospheric Network (CHAIN) ionosondes and GPS receivers. The coupling process modulated the ionospheric convection and the intensity of ionospheric currents, including the auroral electrojets. The horizontal equivalent ionospheric currents (EICs) are estimated from ground-based magnetometer data using an inversion technique. Pulses of ionospheric currents that are a source of Joule heating in the lower thermosphere launched atmospheric gravity waves, causing traveling ionospheric disturbances (TIDs) that propagated equatorward. The TIDs were observed in the SuperDual Auroral Radar Network (SuperDARN) high-frequency (HF) radar ground scatter and the detrended total electron content (TEC) measured by globally distributed Global Navigation Satellite System (GNSS) receivers.
@article{2022AnGeo.40.619P, author = {{Prikryl}, Paul and {Gillies}, Robert G. and {Themens}, David R. and {Weygand}, James M. and {Thomas}, Evan G. and {Chakraborty}, Shibaji}, title = {{Multi-instrument observations of polar cap patches and traveling ionospheric disturbances generated by solar wind Alfv{\'e}n waves coupling to the dayside magnetosphere}}, journal = {Annales Geophysicae}, year = {2022}, month = nov, volume = {40}, number = {6}, pages = {619-639}, doi = {10.5194/angeo-40-619-2022}, adsurl = {https://ui.adsabs.harvard.edu/abs/2022AnGeo..40..619P}, adsnote = {Provided by the SAO/NASA Astrophysics Data System}, dimensions = {true}, }
pyDARN: A Python software for visualizing SuperDARN radar data

Shi X, Schmidt M, Martin CJ, and 10 more authors

Front. Astron. Space Sci., Nov 2022

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The Super Dual Auroral Radar Network (SuperDARN) is an international network of high frequency coherent scatter radars that are used for monitoring the electrodynamics of the Earth’s upper atmosphere at middle, high, and polar latitudes in both hemispheres. pyDARN is an open-source Python-based library developed specifically for visualizing SuperDARN radar data products. It provides various plotting functions of different types of SuperDARN data, including time series plot, range-time parameter plot, fields of view, full scan, and global convection map plots. In this paper, we review the different types of SuperDARN data products, pyDARN’s development history and goals, the current implementation of pyDARN, and various plotting and analysis functionalities. We also discuss applications of pyDARN, how it can be combined with other existing Python software for scientific analysis, challenges for pyDARN development and future plans. Examples showing how to read, visualize, and interpret different SuperDARN data products using pyDARN are provided as a Jupyter notebook.
@article{pydarn, author = {X, Shi and M, Schmidt and CJ, Martin and DD, Billett and E, Bland and FH, Tholley and NA, Frissell and K, Khanal and S, Coyle and S, Chakraborty and M, Detwiller and B, Kunduri and K, McWilliams}, title = {pyDARN: A Python software for visualizing SuperDARN radar data}, journal = {Front. Astron. Space Sci.}, volume = {9}, year = {2022}, number = {1022690}, doi = {10.3389/fspas.2022.1022690}, dimensions = {true}, }
Data-based optimization of a simple shortwave fadeout absorption model

R.A.D. Fiori, S. Chakraborty, and L. Nikitina

Journal of Atmospheric and Solar-Terrestrial Physics, Nov 2022

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Electron density enhancement caused by electromagnetic radiation emitted during a solar X-ray flare has the potential to increase high frequency (HF; 3–30 MHz) absorption in the dayside D-region ionosphere, impacting shortwave radio signals by reducing the signal strength, a phenomenon commonly referred to as shortwave fadeout. Data-based optimization of a simple absorption model is performed incorporating solar X-ray flux data and 30 MHz riometer data from stations distributed across Canada. In a single event study the data-based optimization model is shown to overestimate absorption by 1% for the duration of an X2.1 solar X-ray flare. This corrects an underestimation by the NOAA D-region Absorption Prediction (D-RAP) model. In a statistical study, based on 87 events, data-based optimization performed on an event-by-event basis showed excellent overall agreement between measured and modelled data: the Pearson correlation coefficient was R = 0.88, and the slope of the best-fit line to the data was m = 0.91. A generalized model was developed using data from all 87 events collectively. Although good agreement was found between the measured and modelled data sets, correlation and slope were slightly reduced to R = 0.75 and m = 0.80. Model accuracy is characterized by prediction efficiency (PE) which peaked at PE = 0.78 for the event-by-event evaluation and PE = 0.48 for the collective data set. The results of this study highlight the advantages of data-based optimization in modelling absorption due to shortwave fadeout.
@article{FIORI2022105843, title = {Data-based optimization of a simple shortwave fadeout absorption model}, journal = {Journal of Atmospheric and Solar-Terrestrial Physics}, volume = {230}, pages = {105843}, year = {2022}, issn = {1364-6826}, doi = {https://doi.org/10.1016/j.jastp.2022.105843}, author = {Fiori, R.A.D. and Chakraborty, S. and Nikitina, L.}, keywords = {Shortwave fadeout, Ionospheric HF absorption, HF absorption Model, HF radiowave Propagation}, dimensions = {true}, }

2021

The Role of Flare-Driven Ionospheric Electron Density Changes on the Doppler Flash Observed by SuperDARN HF Radars

S. Chakraborty, L. Qian, J. M. Ruohoniemi, and 3 more authors

Journal of Geophysical Research: Space Physics, Nov 2021

e2021JA029300 2021JA029300

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Abstract Trans-ionospheric high frequency (HF: 3–30 MHz) signals experience strong attenuation following a solar flare-driven sudden ionospheric disturbance (SID). Solar flare-driven HF absorption, referred to as short-wave fadeout, is a well-known impact of SIDs, but the initial Doppler frequency shift phenomena, also known as “Doppler flash” in the traveling radio wave is not well understood. This study seeks to advance our understanding of the initial impacts of solar flare-driven SID using a physics-based whole atmosphere model for a specific solar flare event. First, we demonstrate that the Doppler flash phenomenon observed by Super Dual Auroral Radar Network (SuperDARN) radars can be successfully reproduced using first-principles based modeling. The output from the simulation is validated against SuperDARN line-of-sight Doppler velocity measurements. We then examine which region of the ionosphere, D, E, or F, makes the largest contribution to the Doppler flash. We also consider the relative contribution of change in refractive index through the ionospheric layers versus lowered reflection height. We find: (a) the model is able to reproduce radar observations with an root-median-squared-error and a mean percentage error (δ) of 3.72 m/s and 0.67%, respectively; (b) the F-region is the most significant contributor to the total Doppler flash (∼48%), 30% of which is contributed by the change in F-region’s refractive index, while the other ∼18% is due to change in ray reflection height. Our analysis shows lowering of the F-region’s ray reflection point is a secondary driver compared to the change in refractive index.
@article{Chakraborty2021JA029300, author = {Chakraborty, S. and Qian, L. and Ruohoniemi, J. M. and Baker, J. B. H. and Mclnerney, J. M. and Nishitani, N.}, title = {The Role of Flare-Driven Ionospheric Electron Density Changes on the Doppler Flash Observed by SuperDARN HF Radars}, journal = {Journal of Geophysical Research: Space Physics}, volume = {126}, number = {8}, pages = {e2021JA029300}, keywords = {solar flare effects, Doppler flash, sudden ionospheric disturbances, HF propagation}, doi = {https://doi.org/10.1029/2021JA029300}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021JA029300}, note = {e2021JA029300 2021JA029300}, year = {2021}, dimensions = {true}, }
A Modeling Framework for Estimating Ionospheric HF Absorption Produced by Solar Flares

S. Chakraborty, J. B. H. Baker, R. A. D. Fiori, and 2 more authors

Radio Science, Nov 2021

e2021RS007285 2021RS007285

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Abstract Over-the-Horizon communication is strongly dependent on the state of the ionosphere, which is susceptible to solar flares. Trans-ionospheric high frequency (HF, 3–30 MHz) signals can experience strong attenuation following a solar flare that lasts typically for an hour, commonly referred to as shortwave fadeout (SWF). In this study, we examine the role of dispersion relation and collision frequency formulations on the estimation of SWF in riometer observations using a new physics-based model framework. The new framework first uses modified solar irradiance models incorporating high-resolution solar flux data from the GOES satellite X-ray sensors as input to compute the enhanced ionization produced during a flare event. The framework then uses different dispersion relation and collision frequency formulations to estimate the enhanced HF absorption. The modeled HF absorption is compared with riometer data to determine which formulation best reproduces the observations. We find the Appleton-Hartree dispersion relation in combination with the averaged collision frequency profile reproduces riometer observations with an average skill score of 0.4, representing 40% better forecast ability than the existing D-region Absorption Prediction model. Our modeling results also indicate that electron temperature plays an important role in controlling HF absorption. We suggest that adoption of the Appleton-Hartree dispersion relation in combination with the averaged collision frequency be considered for improved forecasting of ionospheric absorption following solar flares.
@article{Chakraborty2021RS007285, author = {Chakraborty, S. and Baker, J. B. H. and Fiori, R. A. D. and Ruohoniemi, J. M. and Zawdie, K. A.}, title = {A Modeling Framework for Estimating Ionospheric HF Absorption Produced by Solar Flares}, journal = {Radio Science}, volume = {56}, number = {10}, pages = {e2021RS007285}, keywords = {shortwave fadeout, HF absorption, modeling, collision frequency, dispersion relations, electron temperature}, doi = {https://doi.org/10.1029/2021RS007285}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021RS007285}, note = {e2021RS007285 2021RS007285}, year = {2021}, dimensions = {true}, }
Ionospheric Sluggishness: A Characteristic Time-Lag of the Ionospheric Response to Solar Flares

S. Chakraborty, J. M. Ruohoniemi, J. B. H. Baker, and 3 more authors

Journal of Geophysical Research: Space Physics, Nov 2021

e2020JA028813 2020JA028813

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Abstract The term “sluggishness” was coined by E. V. Appleton in the 1950s to describe the time delay between peak irradiance at solar noon and the resulting peak in ionospheric electron density. Sluggishness can be understood as an inertial property of the ionosphere that manifests as a lag of the ionospheric response to a solar driver. As shown by Appleton, estimates of sluggishness can be used to study the chemistry of the lower ionosphere, of the D-region in particular. In this study, for the first time, we have examined ionospheric sluggishness in terms of the time delay between the peak irradiance during a solar flare and the resulting peak in ionospheric electron density using HF instruments. Estimates of the delay are obtained using HF observations from riometers and SuperDARN radars that are primarily sensitive to absorption in the D-region. Two new methods for measuring delay are introduced. Sluggishness is shown to be anti-correlated with peak solar X-ray flux and positively correlated with zenith angle and latitude. The choices of instrument, method, and reference solar waveband affect the sluggishness estimation. A simulation study was performed to estimate the effective recombination coefficient in the D-region. The coefficient was found to vary by orders of magnitude with peak flare intensity. We argue that the variation in effective recombination coefficient with peak flare intensity is highly sensitive to changes in the negative and positive ion chemistry of the D-region, which is sensitive to the incoming solar X-ray and EUV radiation.
@article{Chakraborty2020JA028813, author = {Chakraborty, S. and Ruohoniemi, J. M. and Baker, J. B. H. and Fiori, R. A. D. and Bailey, S. M. and Zawdie, K. A.}, title = {Ionospheric Sluggishness: A Characteristic Time-Lag of the Ionospheric Response to Solar Flares}, journal = {Journal of Geophysical Research: Space Physics}, volume = {126}, number = {4}, pages = {e2020JA028813}, keywords = {ion chemistry, ionosphere, photo-ionization, recombination coefficient, sluggishness, solar flare}, doi = {https://doi.org/10.1029/2020JA028813}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JA028813}, note = {e2020JA028813 2020JA028813}, year = {2021}, dimensions = {true}, }
IEEE
Probabilistic Short-wave Fadeout Detection in SuperDARN Time Series Observations

Shibaji Chakraborty, Joseph B. H. Baker, and J. Michael Ruohoniemi

In 2021 IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE), Nov 2021

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Short-wave fadeout (SWF) is one of the first space weather effects to occur in the ionosphere following a solar flare and leads to severe disruption of ionospheric HF systems. The disruption is produced by flare-enhanced energetic radiations that penetrate to the D-layer where they enhance ionization that leads to heavy absorption of high-frequency (HF, 3–30 MHz) radio signal over much of the dayside for an hour or more. In this paper, we describe two probabilistic anomaly detection schemes that have been used to detect SWF events produced by M and X class flares in Super Dual Auroral Radar Network (SuperDARN) observations. The two schemes are based on statistical Z-score and nonlinear energy operators. Performance of the detection schemes varies with flare intensity and parameters of the detection schemes. We find a correlation coefficient 0.73 between flare counts per month and SWF counts per month detected using the Z-score scheme.
@inproceedings{9613835, author = {Chakraborty, Shibaji and Baker, Joseph B. H. and Ruohoniemi, J. Michael}, booktitle = {2021 IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE)}, title = {Probabilistic Short-wave Fadeout Detection in SuperDARN Time Series Observations}, year = {2021}, volume = {}, number = {}, pages = {43-48}, doi = {10.1109/WiSEE50203.2021.9613835}, dimensions = {true}, }

2020

Probabilistic prediction of geomagnetic storms and the Kp index

Chakraborty, Shibaji, and Morley, Steven Karl

J. Space Weather Space Clim., Nov 2020

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@article{refId0,
  author = {{Chakraborty, Shibaji} and {Morley, Steven Karl}},
  title = {Probabilistic prediction of geomagnetic storms and the Kp index},
  doi = {10.1051/swsc/2020037},
  journal = {J. Space Weather Space Clim.},
  year = {2020},
  volume = {10},
  pages = {36},
  dimensions = {true},
}

Conductance Model for Extreme Events: Impact of Auroral Conductance on Space Weather Forecasts

Agnit Mukhopadhyay, Daniel T. Welling, Michael W. Liemohn, and 3 more authors

Space Weather, Nov 2020

e2020SW002551 10.1029/2020SW002551

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Abstract Ionospheric conductance is a crucial factor in regulating the closure of magnetospheric field-aligned currents through the ionosphere as Hall and Pedersen currents. Despite its importance in predictive investigations of the magnetosphere-ionosphere coupling, the estimation of ionospheric conductance in the auroral region is precarious in most global first-principles-based models. This impreciseness in estimating the auroral conductance impedes both our understanding and predictive capabilities of the magnetosphere-ionosphere system during extreme space weather events. In this article, we address this concern, with the development of an advanced Conductance Model for Extreme Events (CMEE) that estimates the auroral conductance from field-aligned current values. CMEE has been developed using nonlinear regression over a year’s worth of 1-min resolution output from assimilative maps, specifically including times of extreme driving of the solar wind-magnetosphere-ionosphere system. The model also includes provisions to enhance the conductance in the aurora using additional adjustments to refine the auroral oval. CMEE has been incorporated within the Ridley Ionosphere Model (RIM) of the Space Weather Modeling Framework (SWMF) for usage in space weather simulations. This paper compares performance of CMEE against the existing conductance model in RIM, through a validation process for six space weather events. The performance analysis indicates overall improvement in the ionospheric feedback to ground-based space weather forecasts. Specifically, the model is able to improve the prediction of ionospheric currents, which impact the simulated dB/dt and ΔB, resulting in substantial improvements in dB/dt predictive skill.
@article{Mukhopadhyay2020SW002551, author = {Mukhopadhyay, Agnit and Welling, Daniel T. and Liemohn, Michael W. and Ridley, Aaron J. and Chakraborty, Shibaji and Anderson, Brian J.}, title = {Conductance Model for Extreme Events: Impact of Auroral Conductance on Space Weather Forecasts}, journal = {Space Weather}, volume = {18}, number = {11}, pages = {e2020SW002551}, keywords = {ionospheric conductance}, doi = {https://doi.org/10.1029/2020SW002551}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020SW002551}, note = {e2020SW002551 10.1029/2020SW002551}, year = {2020}, dimensions = {true}, }

2019

A Study of SuperDARN Response to Co-occurring Space Weather Phenomena

S. Chakraborty, J. B. H. Baker, J. M. Ruohoniemi, and 3 more authors

Space Weather, Nov 2019

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Abstract The Sun was remarkably active during the first week of September 2017 producing numerous solar flares, solar radiation storms, and coronal mass ejections. This activity caused disruption to terrestrial high-frequency (HF, 3–30 MHz) radio communication channels including observations with the Super Dual Auroral Radar Network (SuperDARN) HF radars. In this paper, we analyze the response of SuperDARN groundscatter observations and decreases in background sky noise level in response to multiple solar flares occurring in quick succession and co-occurring with solar energetic protons and auroral activity. We estimate the attenuation in HF signal strength using an approach similar to riometry and find that the radars exhibit a nonlinear response to compound solar flare events. Additionally, we find that the three different space weather drivers have varying degrees of influence on the HF signal properties at different latitudes. Our study demonstrates that in addition to monitoring high-latitude convection, SuperDARN observations can be used to study the spatiotemporal evolution of disruption to HF communication during extreme space weather conditions.
@article{Chakraborty2019SW002179, author = {Chakraborty, S. and Baker, J. B. H. and Ruohoniemi, J. M. and Kunduri, B. and Nishitani, N. and Shepherd, S. G.}, title = {A Study of SuperDARN Response to Co-occurring Space Weather Phenomena}, journal = {Space Weather}, volume = {17}, number = {9}, pages = {1351-1363}, keywords = {space weather, radio wave, absorption, shortwave fadeout, polar cap absorption, auroral absorption}, doi = {https://doi.org/10.1029/2019SW002179}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019SW002179}, year = {2019}, dimensions = {true}, }

2018

Characterization of Short-Wave Fadeout Seen in Daytime SuperDARN Ground Scatter Observations

S. Chakraborty, J. M. Ruohoniemi, J. B. H. Baker, and 1 more author

Radio Science, Nov 2018

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Abstract Short-wave fadeout (SWF) is a well-known radio wave anomaly which follows Earth-directed solar flares and leads to severe disruption of transionospheric high-frequency systems. The disruption is produced by flare-enhanced soft and hard X-rays that penetrate to the D layer where they dramatically enhance ionization leading to heavy high-frequency absorption over much of the dayside for an hour or more. In this paper, we describe how Super Dual Auroral Radar Network (SuperDARN) observations can be exploited to analyze SWF events. Superposed epoch analysis of multiple signatures reveals the typical characteristics of SWF. The number of SuperDARN ground scatter echoes drops suddenly (≈100 s) and sharply after a solar flare, reaching a maximum depth of suppression within a few tens of minutes, and then recovering to pre-SWF conditions over half an hour or so. The depth of echo suppression depends on the solar zenith angle, radio wave frequency, and intensity of the flare. Furthermore, ground scatter echoes typically exhibit a sudden phase change leading to a dramatic increase in apparent Doppler velocity (the so-called “Doppler flash”), which statistically precedes the dropout in ground scatter echoes. We report here on the characterization of SWF effects in SuperDARN ground scatter observations produced by several X class solar flares. We also describe the functional dependence of peak Doppler flash on solar zenith angle, frequency, and peak intensity of solar flux.
@article{Chakraborty2017RS006488, author = {Chakraborty, S. and Ruohoniemi, J. M. and Baker, J. B. H. and Nishitani, N.}, title = {Characterization of Short-Wave Fadeout Seen in Daytime SuperDARN Ground Scatter Observations}, journal = {Radio Science}, volume = {53}, number = {4}, pages = {472-484}, keywords = {short-wave fadeout, characterization, SuperDARN, SWF, ground scatter}, doi = {https://doi.org/10.1002/2017RS006488}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017RS006488}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017RS006488}, year = {2018}, dimensions = {true}, }
Examining the Potential of the Super Dual Auroral Radar Network for Monitoring the Space Weather Impact of Solar X-Ray Flares

R. A. D. Fiori, A. V. Koustov, S. Chakraborty, and 4 more authors

Space Weather, Nov 2018

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Abstract Increased electron density in the ionosphere due to photoionization by radiation emitted during a solar X-ray flare impacts high-frequency (HF) radio wave propagation. Shortwave fadeout (SWF) due to the enhanced D region absorption that results is characterized by the level of cosmic radio noise attenuation derived from riometer measurements. SWF impacts HF radio propagation and has been identified in the Super Dual Auroral Radar Network (SuperDARN) data. An X2.1 solar X-ray flare that erupted on 11 March 2015 is examined to determine its effects on HF radio propagation. Riometer data indicate a sharp enhancement in absorption, which falls off with increasing solar zenith angle. SuperDARN radars observed a suppression of both ground scatter and ionospheric echoes. Ground scatter data indicated a rapid weakening of signal from far to near ranges followed by a 20-min interval of complete signal loss. Recovery lasted 30 min and proceeded from near to far ranges. Prior to the complete signal loss, an apparent sharp velocity impulse (Doppler flash) lasting 1–2 min was observed in the ground scatter data. The peak of this flash preceded the onset of enhanced absorption. The onset of signal loss by SuperDARN preceded the onset of enhanced absorption observed by riometers. Both data sets observed a positive correlation between increasing delay in onset and increasing solar zenith angle with onset progressing at an average rate of 16.7°/min (0.060 min/°). Agreement between riometer and SuperDARN indicates the possibility of using a joint data set for improved monitoring of the space weather impact of solar X-ray flares.
@article{Fiori2018SW001905, author = {Fiori, R. A. D. and Koustov, A. V. and Chakraborty, S. and Ruohoniemi, J. M. and Danskin, D. W. and Boteler, D. H. and Shepherd, S. G.}, title = {Examining the Potential of the Super Dual Auroral Radar Network for Monitoring the Space Weather Impact of Solar X-Ray Flares}, journal = {Space Weather}, volume = {16}, number = {9}, pages = {1348-1362}, keywords = {D region absorption, riometer, SuperDARN, solar X-ray flare, space weather}, doi = {https://doi.org/10.1029/2018SW001905}, eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018SW001905}, year = {2018}, dimensions = {true}, }