Solar Physics

, 293:50 | Cite as

Millimeter and X-Ray Emission from the 5 July 2012 Solar Flare

  • Y. T. Tsap
  • V. V. Smirnova
  • G. G. Motorina
  • A. S. Morgachev
  • S. A. Kuznetsov
  • V. G. Nagnibeda
  • V. S. Ryzhov


The 5 July 2012 solar flare SOL2012-07-05T11:44 (11:39 – 11:49 UT) with an increasing millimeter spectrum between 93 and 140 GHz is considered. We use space and ground-based observations in X-ray, extreme ultraviolet, microwave, and millimeter wave ranges obtained with the Reuven Ramaty High-Energy Solar Spectroscopic Imager, Solar Dynamics Observatory (SDO), Geostationary Operational Environmental Satellite, Radio Solar Telescope Network, and Bauman Moscow State Technical University millimeter radio telescope RT-7.5. The main parameters of thermal and accelerated electrons were determined through X-ray spectral fitting assuming the homogeneous thermal source and thick-target model. From the data of the Atmospheric Imaging Assembly/SDO and differential-emission-measure calculations it is shown that the thermal coronal plasma gives a negligible contribution to the millimeter flare emission. Model calculations suggest that the observed increase of millimeter spectral flux with frequency is determined by gyrosynchrotron emission of high-energy (\(\gtrsim 300\) keV) electrons in the chromosphere. The consequences of the results are discussed in the light of the flare-energy-release mechanisms.


Flares, energetic particles Radio bursts, association with flares X-ray bursts 



We would like to thank the anonymous referees for very useful comments, which we found to be very constructive and helpful to improve our manuscript. Yu.T. Tsap was supported by the Russian Science Foundation (project N 16-12-10448). G.G. Motorina and V.V. Smirnova acknowledge support by RFBR grants 16-32-00535-mol_a and 16-02-00749, respectively. The work of A.S. Morgachev was supported by the Program of the Presidium of RAS P-7 and scientific school SC-7241.2016.2. We would like to thank Gordon Holman and Natasha Jeffrey for discussions of the model and RHESSI data analysis, respectively. We are grateful to the teams of the RHESSI, SDO, RSTN, and RT-7.5, who have provided open access to their data. SDO data are courtesy of NASA/SDO and the AIA and HMI science teams.

Disclosure of Potential Conflicts of Interest

The authors declare that they have no conflicts of interest.


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Authors and Affiliations

  • Y. T. Tsap
    • 1
    • 2
  • V. V. Smirnova
    • 2
    • 3
    • 4
  • G. G. Motorina
    • 2
  • A. S. Morgachev
    • 2
    • 5
  • S. A. Kuznetsov
    • 2
    • 5
  • V. G. Nagnibeda
    • 3
  • V. S. Ryzhov
    • 6
  1. 1.Crimean Astrophysical ObservatoryNauchnyRussia
  2. 2.Pulkovo ObservatorySt. PetersburgRussia
  3. 3.Sobolev Astronomical InstituteSaint Petersburg State UniversitySt. PetersburgRussia
  4. 4.University of TurkuTurkuFinland
  5. 5.Radiophysical Research Institute of Lobachevsky UniversityNizhny NovgorodRussia
  6. 6.Bauman Moscow State Technical UniversityMoscowRussia

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