A Modeling Investigation for Solar Flare X-Ray Stereoscopy with Solar Orbiter/STIX and Earth-orbiting Missions

Natasha L. S. Jeffrey*, Säm Krucker, Morgan Stores, Eduard P. Kontar, Pascal Saint-Hilaire, Andrea F. Battaglia, Laura Hayes, Hannah Collier, Astrid Veronig, Yang Su, Srikar Paavan Tadepalli, Fanxiaoyu Xia

*Corresponding author for this work

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The Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter (SolO) provides a unique opportunity to systematically perform stereoscopic X-ray observations of solar flares with current and upcoming X-ray missions at Earth. These observations will produce the first reliable measurements of hard X-ray (HXR) directivity in decades, providing a new diagnostic of the flare-accelerated electron angular distribution and helping to constrain the processes that accelerate electrons in flares. However, such observations must be compared to modeling, taking into account electron and X-ray transport effects and realistic plasma conditions, all of which can change the properties of the measured HXR directivity. Here, we show how HXR directivity, defined as the ratio of X-ray spectra at different spacecraft viewing angles, varies with different electron and flare properties (e.g., electron angular distribution, highest-energy electrons, and magnetic configuration), and how modeling can be used to extract these typically unknown properties from the data. Finally, we present a preliminary HXR directivity analysis of two flares, observed by the Fermi Gamma-ray Burst Monitor and SolO/STIX, demonstrating the feasibility and challenges associated with such observations, and how HXR directivity can be extracted by comparison with the modeling presented here.
Original languageEnglish
Article number145
Pages (from-to)1-14
Number of pages14
JournalThe Astrophysical Journal
Issue number2
Early online date27 Mar 2024
Publication statusPublished - 1 Apr 2024

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