research

Overview

Space weather refers to the dynamic conditions and processes in the near-Earth space (geospace), particularly those influenced by the Sun. These conditions can have significant impacts on technological systems and human activities in space, on the ground, and underwater. There are various space weather phenomena such as solar flares, Coronal Mass Ejection (CME)-driven Geomagnetic Disturbances (GMDs), solar eclipses, and Travel Ionospheric Disturbances (TIDs), etc. Broadly, my research interest belongs to the area of impulsive space weather and its impacts on ionospheric-thermospheric (IT) systems and man-made technological systems, which are still in their infancy.

Prior Research Experience

My research interests primarily focused on solar flare impact on the High Frequency (HF:3-30 MHz) radio wave propagation. Solar flares can severely disrupt the trans-ionospheric signals by increasing the HF absorption at the D-region heights and introducing signal phase/frequency shifts. During my PhD in the SuperDARN research group at Virginia Tech, I characterized¹ and modeled² the flare-driven HF absorption, commonly referred to as shortwave fadeout (SWF), using the SuperDARN HF radar observation and first-principle-based modeling. I found flare-driven disruption affects the HF signal frequency, which produces a sudden rise in Doppler velocity observation, referred to as the ‘Doppler flash’, which occurs before the HF absorption effect. I used NCAR/WACCM-X physical model and HF raytracing techniques to understand the sources of flare-driven sudden phase/frequency shifts recorded by the SuperDARN observations³. Additionally, I revisited one of the less discussed ionospheric properties, namely sluggishness⁴, which is an inertial property of the ionosphere. I also studied its variations with solar flare intensity and made some inferences about D-region ion chemistry using a simulation study.

Machine Learning on Space Weather

I hold a strong conviction regarding the utility of deep learning models in advancing space weather research. My belief in this approach was reinforced during my doctoral studies when I was honored with the prestigious ‘Vella Fellowship’ from Los Alamos National Laboratory (LANL), specifically from the ISR-1 division. I had the opportunity to collaborate closely with Dr. Steven K. Morley on a study in the field of space weather, leveraging machine learning (neural network with Gaussian Processes Regression) techniques⁵. Our work centered on the development of a neural network-based model, employing a two-layer framework. This model was meticulously designed to deliver probabilistic forecasts for the geomagnetic storm and index Kp. To enhance the accuracy of our predictions, I incorporated critical data sources, including solar wind and X-ray flux observations. This achievement was notable not only for its precision but also for its capacity to generate probabilistic forecasts, an asset in space weather prediction. Since that enlightening experience, I have continued to employ both numerical models and data-driven approaches (particularly neural networks and deep learning models) as per the requirements of my research endeavors. This holistic approach ensures that I am well-equipped to tackle the multifaceted challenges within the field of space weather.

Current Research

Currently, I am working on the following projects: (1) solar flare impact on high latitude ionospheric electrodynamics, (2) impact of geomagnetic disturbance (GMD) on submarine cables, and (3) characterization of acoustic gravity wave (AGW) driven MSTID using multipoint dataset.

1. Ground-based HF radar observations show the sudden appearance of ionospheric backscatters, that represent decameter scale field-aligned ionospheric irregularities, near the dawn terminator followed by a massive X9.3 solar flare. These irregularities, reaching radar line-of-sight Doppler velocity of nearly 300 m/s, aligned with equatorward reverse convection flow. I have recently been awarded the prestigious ‘Japan Society for the Promotion of Science (JSPS) Postdoctoral Fellowship (Short-term)’ and ‘ISEE international joint research fellowship from Nagoya University’ to conduct this research international collaborative research in Japan.
2. Geomagnetic disturbances (GMDs) stemming from various space weather phenomena that induce geoelectric fields (GEFs) at different spatiotemporal scales within the Earth and water bodies. These GEFs generate currents, referred to as geomagnetically induced currents (GICs), that can flow through electrical infrastructure. GICs are a major concern for critical infrastructure including submarine cables, especially during intense space weather phenomena. The overarching goal of my research is to ‘Characterize the induced underwater GEFs and potential along the submarine cables during various geomagnetic disturbances’. We (me and others in the SCUBAS team^{6 7}) have developed an open-source computational model developed using the Python programming language, named SCUBAS⁶ that stands for Submarine Cable Upset By Auroral Streams. The SCUBAS provides estimates of the induced underwater GEFs, and voltage experienced by submarine cables in the presence of any geomagnetic perturbations recorded by ground-based magnetometers. By harnessing the latest advancements in magnetotelluric (MT) studies and the understanding of GICs, SCUBAS represents a significant leap forward in our ability to analyze and predict the impact of space weather on submarine cable systems⁷.
3. Gravity Waves (GWs) generated from terrestrial sources, such as winter and thunderstorms, are one of the primary drivers of the atmospheric circulation and may create medium-scale TID (MSTIDs) and large-scale TIDs (LSTIDs). Recently I, as a Co-I (institutional PI), have received a grant from the NASA LWS program to characterize the GWs generated TIDs using multipoint measurements. I am specifically interested in studying the impact of thunderstorm/snowstorm-generated TIDs on HF communication systems using SuperDARN radars. My recent study uses a 3D raytracing tool, named Provision of High-Frequency Raytracing Laboratory for Propagation Studies (PHaRLAP), to quantify the change in Maximum Usable Frequency (MUF).

Future Research Plan

I plan to continue my research along with my current research focus. Specifically, I plan to investigate: (1) How does solar flare create the impulse in the ionospheric electrodynamics (Sq, Equatorial, and Auroral Electrojets)? (2) How do various types of GMDs with varying spatiotemporal scales impact the underwater induction process and modulate the strength of the induced GEFs? My research will quantify the impact of the geophysical parameters, such as ocean depth, Earth conductivity below the ocean, morphology of the current source, etc., on the intensity of the induced underwater GEFs and voltages on the submarine cables. (3) I plan to continue my current funded project on the characterization of GWs-generated MS/LSTIDs and their impact on HF propagation. I have recently submitted a few proposals to NASA/NSF solicitations to research the above topics and hopefully, they will get funded soon.