Where and when

speaker: Paolo Massa
affiliation: Department of Physics & Astronomy, Western Kentucky University, USA
date: July 4^th, 2022
venue: on-line seminar (Google Meet) organized by "Gruppo outreach and media public relations" of SWICo

Hard X-ray imaging of solar flares by Solar Orbiter STIX

abstract: The Spectrometer/Telescope for Imaging X-rays (STIX) is the instrument on board Solar Orbiter dedicated to the observation of solar flares. The telescope relies on an indirect Fourier imaging technique realized by means of thirty sub-collimators, i.e., pairs of grids mounted in front of detectors. The X-ray photon flux that is modulated by the grids of a sub-collimator produces a Moiré pattern on the detector surface, whose amplitude and phase are related to amplitude and phase of a Fourier component (or visibility) of the flaring X-ray source. Hence, STIX measurements can be interpreted as a set of as many visibilities as the subcollimators, and the image reconstruction problem is a Fourier inversion from limited data. In this talk, we describe the STIX imaging concept and the algorithms implemented for solving the image reconstruction problem. We show STIX reconstructions of several flaring events and we compare the results with observations provided by other instruments such as the Extreme Ultraviolet Imager (EUI) and Metis on board Solar Orbiter, and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory.