Searcharxiv⌕ Search

arXiv subjects

Sylwester Kołomański

Publications and source records attributed to Sylwester Kołomański.

2 recordsLinked to original sources

Triple coronal hard X-ray source observed by STIX during a failed filament eruption

{Observations reveal hard X-ray sources in the solar corona with morphologies and locations distinct from typical solar flares. One expected mechanisms for hard X-ray (HXR) production in the solar corona is eruptions of various types. Failed eruptions are promising targets for detecting non-flare-related HXR sources because most of their energy is expected to be dissipated in the corona. } {We investigated the SOL2022-0 to determine the nature of coronal HXR sources associated with the event.} {We used Solar Orbiter's STIX, EUI, and SDO AIA observations. We reconstructed STIX images using the MARLIN algorithm. We used EUI data to cross-check the view of the event from two vantage points. The AIA images enabled kinematic analysis and reconstruction of differential emission measure (DEM) maps. We then used the AIA DEM to predict X-ray emission maps and compared them with STIX images. } {We find temporal and spatial correlations between the failed eruption and HXR sources. During the braking of the filament eruption, we observed non-thermal HXR emission from coronal sources along the path of the eruption. Thermal HXR emission was concentrated in three coronal sources formed with two separate mechanisms: chromospheric evaporation and direct heating. Directly heated sources are the result of the interaction of the eruption with the overlying magnetic field, and were observed to cool for an extremely long time.} {The HXR emission sources related to the interaction between the eruption and the overlying magnetic field might be typical structures in all flares. However, they appear to be weak, since their emission is only 5-20~\% of that from the flare coronal source. If footpoint sources were not occulted, then these weak coronal emission sources would not be visible due to the low dynamic range of HXR telescopes.}

astro-ph.SR↗

Relative yield of thermal and nonthermal emission during weak flares observed by STIX during September 20-25, 2021

The disparate nature of thermal-nonthermal energy partition during flares, particularly during weak flares, is still an open issue. Following the Neupert effect, quantifying the relative yield of X-ray emission in different energy bands can enable inferring the underlying energy release mechanism. During September 20-25, 2021, the Solar Orbiter mission - being closer to the Sun ($\sim$0.6 AU) and having a moderate separation angle (<40$^{\circ}$) from the Sun-Earth line provided a unique opportunity to analyze multi-wavelength emission from $\sim$200 (mostly weak) flares, commonly observed by the Spectrometer Telescope for Imaging X-rays (STIX), STEREO-A, GOES, and SDO observatories. Associating the quotient (q$_{f}$) of hard X-ray fluence (12-20 keV) and soft X-ray flux (4-10 keV) with the peak SXR flux enabled us to identify strongly non-thermal flares. Multi-wavelength investigation of spectral and imaging mode observations of the 20 strongly non-thermal weak flares reveals an inverse relationship of q$_{f}$ with the emission measure (EM) (and density), and a positive relationship with the flare plasma temperature. This indicates that plasma in tenuous loops attains higher temperatures compared to that in the denser loops, in response to nonthermal energy deposition. This is in agreement with the plasma parameters of the coronal loops, as derived by applying the one-dimensional Palermo Harvard (PH) hydrodynamical code to the coronal loop plasma having different initial coronal loop base pressures when subjected to similar heating input. Our investigation, therefore, indicates that the plasma parameters of the flaring loop in the initial phase have a decisive role in thermal-nonthermal energy partitioning.

astro-ph.SR↗