Presentation #411.04 in the session High-energy Solar Investigations through Next-generation Remote Sensing: Spectroscopy, Imaging, and Beyond II.
The Spectrometer/Telescope for Imaging X-rays (STIX) is one of the remote sensing instruments on-board Solar Orbiter that provides hard X-ray imaging spectroscopy in the energy range of 4-150 keV. The trajectory of Solar Orbiter around the Sun provides a new opportunity to measure the X-ray emission from solar flares with different viewing angles to the Sun-Earth line. By combining STIX measurements with Earth-based X-ray observatories, systematic X-ray stereoscopic measurements of flares can be reliably made for the first time. By analyzing and comparing the X-ray fluxes from a single flare from different viewing angles, the hard X-ray directivity can be measured, providing a link to the underlying angular distribution of the accelerated electrons — a measurement that will help constrain the acceleration mechanism. In this talk, a presentation of the first results will be given comparing STIX X-ray spectral observations with Earth-based spectral measurements from FERMI/GBM. This will include both flares from similar viewing angles for calibration, and then those at significantly different angles to attempt to calculate the directivity. We will also discuss the modeling efforts that these observations build upon, and the new opportunities that the proposed PADRE cubesat mission brings that will fly cross-calibrated spare STIX detectors with an aim to also perform these measurements.