Abstract Details


Name: Keshav Aggarwal
Affiliation: Indian Institute of Technology Indore
Conference ID: TVS202510205
Title: Estimating Solar Wind Speeds Using Doppler Broadening: Results from MOM and Akatsuki
Authors and Co-Authors: R. K. Choudhary, Abhirup Datta
Abstract Type: Contributory Presentation
Abstract: We present a method to estimate solar wind velocities in the near-Sun corona using Doppler spectral broadening of spacecraft radio signals, developed and validated using radio occultation data from India’s Mars Orbiter Mission (MOM) and Japan’s Akatsuki. The technique was first formulated using S-band data from MOM during its superior conjunction in October 2021, when the radio signal passed through the inner corona at heliocentric distances of 5-8 Rsun. By establishing an empirical relation between the observed Doppler spectral width and solar wind velocity, we derived wind speeds of 100-150 km s-1 and estimated corresponding electron densities on the order of 10'10 m-3. These results showed good agreement in radial trends with established empirical models, while indicating slightly lower absolute densities, likely due to the low coronal activity during the observation window. To test the adaptability of this method, we modified it for use with X-band data from Akatsuki, collected during solar conjunctions in June 2016 and October 2022. These occultation geometries extended our observational reach from 1.4 to 10 Rsun and included varying latitudes in 2022, where fast solar wind outflows were expected. The modified X-band approach captured a wider range of wind speeds, from 150 km s-1 near the equator to 400 km s-1 near coronal holes, highlighting latitudinal and temporal variations across solar cycle phases. This work establishes Doppler spectral broadening as a viable tool for remotely sensing solar wind properties and emphasizes the critical role of accurate coronal electron density models. The technique offers a valuable complement to in-situ measurements and can support future coronal diagnostics from spacecraft radio links.