Solar Physics

, 293:101 | Cite as

Solar Microflares Observed by SphinX and RHESSI

  • Tomasz MrozekEmail author
  • Szymon Gburek
  • Marek Siarkowski
  • Barbara Sylwester
  • Janusz Sylwester
  • Anna Kepa
  • Magdalena Gryciuk


In 2009, the Russian Complex Orbital Observations Near-Earth of Activity of the Sun (CORONAS-Photon) spacecraft was launched, carrying the Polish Solar PHotometer In X-rays (SphinX). The SphinX was most sensitive in the spectral range 1.2 – 15 keV, thus an excellent opportunity appeared for comparison with the 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 to compare the data and results from the two 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 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 those of 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 the RHESSI hot component is in agreement with GOES, and the RHESSI hotter component fits the SphinX flaring component well. Moreover, we calculated the so-called thermodynamic measure and the total thermal energy content in the four microflares that we studied. The results obtained show that SphinX is a very sensitive complementary observatory for RHESSI and GOES.


Flares, microflares and nanoflares Spectrum, X-ray Instrumental effects 



First, we thank the anonymous reviewer for very helpful comments that significantly improved the article. We wish to thank the SphinX Team for the really hard work and dedication, which has made this research possible. The SphinX spectrophotometer is a Polish instrument onboard the Russian Coronas-Photon spacecraft. The RHESSI spacecraft is a NASA Small Explorer (SMEX) mission. This work was supported by the Polish National Science Centre grant number 2015/19/B/ST9/02826.

Disclosure of Potential Conflicts of Interest

The authors declare that they have no conflicts of interest.


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© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Solar Physics DivisionSpace Research Centre Polish Academy of SciencesWrocławPoland
  2. 2.Astronomical InstituteUniversity of WrocławWrocławPoland

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