Multi-instrument STIX microflare study

Abstract

During its commissioning phase in 2020, the Spectrometer/Telescope for Imaging X-rays (STIX) on board the Solar Orbiter spacecraft observed 69 microflares. The two most significant events from this set (of GOES class B2 and B6) were observed on-disk from the spacecraft as well as from Earth and analysed in terms of the spatial, temporal, and spectral characteristics. We complement the observations from the STIX instrument with EUV imagery from SDO/AIA and GOES soft X-ray data by adding imaging and plasma diagnostics over different temperature ranges for a detailed microflare case study that is focussed on energy release and transport. Spectral fitting of the STIX data shows clear nonthermal emission for both microflares studied here. The deduced plasma parameters from DEM reconstruction as well as spectral fitting roughly agree with the values in the literature for microflares as do the nonthermal fit parameters from STIX. The observed Neupert effects and impulsive and gradual phases indicate that both events covered in this study are consistent with the standard chromospheric evaporation flare scenario. For the B6 event on 7 June 2020, this interpretation is further supported by the temporal evolution seen in the DEM profiles of the flare ribbons and loops. For this event, we also find that accelerated electrons can roughly account for the required thermal energy. The 6 June 2020 event demonstrates that STIX can detect nonthermal emission for GOES class B2 events that is nonetheless smaller than the background rate level. We demonstrate for the first time how detailed multi-instrument studies of solar flares can be performed with STIX.

References in corpus (19)

• The Solar Orbiter mission -- Science overview
• An Observational Overview of Solar Flares
• Differential Emission Measures from the Regularized Inversion of Hinode and SDO data
• Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares
• Differential Emission Measure Analysis of Multiple Structural Components of Coronal Mass Ejections in the Inner Corona
• CHIANTI - an atomic database for emission lines - Paper XV: Version 9, improvements for the X-ray satellite lines
• RHESSI Microflare Statistics II. X-ray Imaging, Spectroscopy & Energy Distributions
• Microflares and the Statistics of X-ray Flares
• Investigation of the Neupert effect in solar flares. I. Statistical properties and the evaporation model
• Global Energetics of Solar Flares: II. Thermal Energies
• Microflare Heating of a Solar Active Region Observed with NuSTAR, Hinode/XRT, and SDO/AIA
• Accelerated electrons observed down to <7 keV in a NuSTAR solar microflare
• Thermal-nonthermal energy partition in solar flares derived from X-ray, EUV, and bolometric observations
• Coronal response to an EUV wave from DEM analysis
• Constraining Solar Flare Differential Emission Measures with EVE and RHESSI
• Investigating the differential emission measure and energetics of microflares with combined SDO/AIA and RHESSI observations
• Multi-thermal representation of the kappa-distribution of solar flare electrons and application to simultaneous X-ray and EUV observations
• Sunspot number second differences as a precursor of the following 11-year sunspot cycle
• The Multi-Instrument (EVE-RHESSI) DEM for Solar Flares, and Implications for Non-Thermal Emission

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