Friday, April 04, 2025 at 12:15 pm

JILA Foothills Room

Atul Mohan, NASA Goddard Space Flight Center

"Exploring the Activity across Cool Stars using Sub-Terahertz Imaging Tomography"

Abstract:

Stellar activity drives space weather, influencing planetary atmospheres and habitability. The Sun remains the only known host star of a long-sustained biosphere, despite that cool main-sequence stars (Spectral type: F - M) are prolific Earth-like exoplanet hosts. Owing to the wealth of spatially resolved observations the standard flare model is primarily based on solar observations, raising a question of how standard is the `standard flare model' across sun-like stars. To address the fundamental questions of whether our Sun is a unique host star, and if life can exist elsewhere given the host stellar activity, it is important to do a comparative study of the nature of activity across the cool main-sequence stars with the Sun as a template. Activity emerges due to various processes across the chromosphere to the corona. Millimeter-to-radio (Sub-terahetrz) frequencies probe varying heights across the chromosphere to the corona facilitating a tomographic exploration of the active atmospheric layers. Sensitive modern sub-terahertz interferometers let us perform <~ 1s scale imaging tomography in the Sun and cool stars. In this talk, I will present the discovery of solar-type radio bursts usually found during fast solar-CMEs in a non-solar type young M dwarf. I will present our results comparing the chromospheric activity of the sun and cool stars using mm imaging observations that provide insights into the rise of chromospheric activity in the cool main sequence. I will also discuss the upcoming cutting-edge future sub-terahertz facilities.

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