Energetic Particle Contamination in STIX During Solar Orbiter's Passage Through Earth's Radiation Belts and an Interplanetary Shock

• Published in: IEEE transactions on nuclear science Vol. 71; no. 8; pp. 1606 - 1613
• Main Authors: Collier, Hannah, Limousin, Olivier, Xiao, Hualin, Claret, Arnaud, Schuller, Frederic, Dresing, Nina, Valkila, Saku, Lara, Francisco Espinosa, Fedeli, Annamaria, Foucambert, Simon, Krucker, Sam
• Format: Journal Article
• Language: English
• Published: IEEE 01.08.2024
• Subjects: Contamination; Detectors; Electric shock; Instruments; Ions; Orbits (stellar); Radiation environments; solar energetic particles (SEPs); space instrumentation; Space vehicles; X-rays
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2024.3355473

The Spectrometer/Telescope for Imaging X-rays (STIX) is a hard X-ray imaging spectrometer on board the ESA and NASA heliospheric mission Solar Orbiter. STIX has been operational for three years and has observed X-ray emission from <inline-formula> <tex-math notation="LaTeX">{\sim }35\,000 </tex-math></inline-formula> solar flares. Throughout its lifetime, Solar Orbiter has been frequently struck by a high flux of energetic particles usually of flare origin, or from coronal mass ejection (CME) shocks. These solar energetic particles (SEPs) are detected on board by the purpose-built energetic particle detector (EPD) instrument suite. During SEP events, the X-ray signal is also contaminated in STIX. This work investigates the effect of these particles on the STIX instrument for two events. The first event occurred during an interplanetary shock crossing and the second event occurred when solar orbiter passed through Earth's radiation belts while performing a gravity assist maneuver. The induced spectra consist of tungsten fluorescence emission lines and secondary Bremsstrahlung emission produced by incident particles interacting with spacecraft components. For these two events, we identify >100 keV electrons as significant contributors to the contamination via Bremsstrahlung emission and tungsten fluorescence.