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Solar Microflares Observed by SphinX and RHESSI  

Tomasz Mrozek   Submitted: 2018-07-12 02:19

In 2009 the Russian Complex Orbital Observations Near-Earth of Activity of the Sun (CORONAS-Photon) satellite was launched carrying the Polish Solar PHotometer In X-rays (SphinX). The SphinX was the most sensitive in the spectral range 1.2-15 keV thus an excellent opportunity appeared for comparison with low-energy end of Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spectra. Common spectral measurements with these instruments cover the range where most of the flare energy is accumulated. We have chosen four consecutive small solar events observed on 4 July 2009 at 13:43 UT, 13:48 UT, 13:52 UT, and 13:55 UT, ( RHESSI flare peak times) and used them for comparison of the data and results from both instruments. Moreover, we included Geostationary Operational Environmental Satellite (GOES) records in our analysis. In practice the range of comparison performed for SphinX and RHESSI is limited roughly to 3-6 keV. RHESSI's fluxes measured with a use of one, four, and nine detectors in the 3-4 keV energy band agree with SphinX measurements. However, we observed that SphinX spectral irradiances are three times higher than RHESSI in the 4-6 keV energy band. This effect contributes to the difference in obtained emission measures, but the derived temperatures of plasma components are similar. RHESSI spectra were fitted using a model with two thermal components. We have found that RHESSI hot component is in agreement with GOES and RHESSI hotter component fits well with the SphinX flaring component.Moreover, we calculated the so-called thermodynamic measure and the total thermal energy content in the four microflares studied. The results obtained show that SphinX is a very sensitive complementary observatory for RHESSI and GOES.

Authors: Tomasz Mrozek, Szymon Gburek, Marek Siarkowski, Barbara Sylwester, Janusz Sylwester, Anna Kepa, Magdalena Gryciuk

Publication Status: published
Last Modified: 2018-07-17 10:51
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Coronal Mass Ejections Associated with Slow Long Duration Flares  

Tomasz Mrozek   Submitted: 2013-02-28 02:11

It is well known that there is temporal relationship between coronal mass ejections (CMEs) and associated flares. The duration of the acceleration phase is related to the duration of the rise phase of a flare. We investigate CMEs associated with slow long duration events (LDEs), i.e. flares with the long rising phase. We determined the relationships between flares and CMEs and analyzed the CME kinematics in detail. The parameters of the flares (GOES flux, duration of the rising phase) show strong correlations with the CME parameters (velocity, acceleration during main acceleration phase and duration of the CME acceleration phase). These correlations confirm the strong relation between slow LDEs and CMEs. We also analyzed the relation between the parameters of the CMEs, i.e. a velocity, an acceleration during the main acceleration phase, a duration of the acceleration phase, and a height of a CME at the end of the acceleration phase. The CMEs associated with the slow LDEs are characterized by high velocity during the propagation phase, with the median equal 1423 km s-1. In half of the analyzed cases, the main acceleration was low (a<300 m s-2), which suggests that the high velocity is caused by the prolongated acceleration phase (the median for the duration of the acceleration phase is equal 90 minutes). The CMEs were accelerated up to several solar radii (with the median 7 Rsun), which is much higher than in typical impulsive CMEs. Therefore, slow LDEs may potentially precede extremely strong geomagnetic storms. The analysis of slow LDEs and associated CMEs may give important information for developing more accurate space weather forecasts, especially for extreme events.

Authors: U. Bak-Steslicka, S. Kolomanski, T. Mrozek
Projects: GOES X-rays ,Other,SoHO-EIT,SoHO-LASCO,Yohkoh-SXT

Publication Status: Solar Physics, accepted
Last Modified: 2013-02-28 12:33
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Extreme-ultraviolet and hard X-ray signatures of electron acceleration during the failed eruption of a filament  

Tomasz Mrozek   Submitted: 2012-11-28 06:47

Aims. We search for extreme-ultraviolet (EUV) brightenings in TRACE 171 Å images and hard X-ray (HXR) bursts observed during failed eruptions. We expect that if an eruption is confined by interaction with overlaying magnetic structures, we should observe effects caused by reconnection between magnetic structures and acceleration of particles. Methods. We used TRACE observations of three well-observed failed eruptions. A semi-automated method was used to search for abrupt brightness changes in the TRACE field of view. The EUV images were compared to the HXR spatial distribution reconstructed from YOHKOH/HXT and RHESSI data. The EUV light curves of a selected area were compared to height profiles of eruption, HXR emission, and the HXR photon spectral index of a power-law fit to the HXR data. Results. We have found that EUV brightenings are closely relatedto the eruption velocity decrease, to HXR bursts, and to episodes of hardening of the HXR spectra. The EUV-brightened areas are observed far from the flaring structure, in footpoints of large systems of loops observed 30?60 min after the maximum of a flare. These are not ?post-flare? loops, which are also observed, but at significantly lower heights. The high-lying systems of loops are observed at heights equal to the height at which the eruption was observed to stop. We observed only one HXR source that was spatially correlated with EUV brightening. For other EUV-brightened areas we estimated the expected brightness of HXR sources. Conclusions. We find that EUV brightenings are produced by interaction between the erupting structure with overlaying loops. The interaction is strong enough to heat the system of high loops. These loops cool and are visible in the EUV range about 30?60 min later. The estimated brightness of HXR sources associated with EUV brightenings shows that they are too weak to be detected with present instruments. However, next-generation instruments will have sufficient dynamic range and sensitivity to enable such observations.

Authors: A. Netzel, T. Mrozek, S. Kołomański, and S. Gburek
Projects: None

Publication Status: A&A 548, A89
Last Modified: 2012-11-28 09:41
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Failed Eruption of a Filament as a Driver for Vertical Oscillations of Coronal Loops  

Tomasz Mrozek   Submitted: 2011-05-12 08:28

This abstract was corrupted following database problems and is being recovered. It will be restored as quickly as possible. Any questions, please send them to Alisdair. Sorry for any incovenience.

Authors: T. Mrozek
Projects: TRACE

Publication Status: Solar Physics, accepted
Last Modified: 2011-05-12 15:06
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Abstracts by Author
Solar Microflares Observed by SphinX and RHESSI
Coronal Mass Ejections Associated with Slow Long Duration Flares
Extreme-ultraviolet and hard X-ray signatures of electron acceleration during the failed eruption of a filament
Failed Eruption of a Filament as a Driver for Vertical Oscillations of Coronal Loops

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