Gregory Fleishman, Valentin D. Pal'Shin, Natalia Meshalkina, Alexandra L. Lysenko, Larisa K. Kashapova, Alexander T. Altyntsev

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Recently, a number of peculiar flares have been reported that demonstrate significant nonthermal particle signatures with low, if any, thermal emission, which implies a close association of the observed emission with the primary energy release/electron acceleration region. This paper presents a flare that appears "cold" at the impulsive phase, while displaying delayed heating later on. Using hard X-ray data from Konus-Wind, microwave observations by SSRT, RSTN, NoRH, and NoRP, context observations, and three-dimensional modeling, we study the energy release, particle acceleration, and transport, and the relationships between the nonthermal and thermal signatures. The flaring process is found to involve the interaction between a small loop and a big loop with the accelerated particles divided roughly equally between them. Precipitation of the electrons from the small loop produced only a weak thermal response because the loop volume was small, while the electrons trapped in the big loop lost most of their energy in the coronal part of the loop, which resulted in coronal plasma heating but no or only weak chromospheric evaporation, and thus unusually weak soft X-ray emission. The energy losses of the fast electrons in the big tenuous loop were slow, which resulted in the observed delay of the plasma heating. We determined that the impulsively accelerated electron population had a beamed angular distribution in the direction of the electric force along the magnetic field of the small loop. The accelerated particle transport in the big loop was primarily mediated by turbulent waves, which is similar to other reported cold flares.

Original languageEnglish (US)
Article number71
JournalAstrophysical Journal
Issue number2
StatePublished - May 10 2016

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Sun: flares
  • Sun: radio radiation
  • acceleration of particles
  • diffusion
  • magnetic fields
  • turbulence


Dive into the research topics of 'A COLD FLARE with DELAYED HEATING'. Together they form a unique fingerprint.

Cite this