Solar Physics

, Volume 105, Issue 1, pp 73–85 | Cite as

Energy of microwave-emitting electrons and hard X-ray/microwave source model in solar flares

  • Nariaki Nitta
  • Takeo Kosugi
Article
Received:
Revised:

Abstract

We present a new method of estimating the energy of microwave-emitting electrons from the observed rate of increase of the microwave flux relative to the hard X-ray flux measured at various energies during the rising phase of solar flares. A total of 22 flares observed simultaneously in hard X-rays (20–400 keV) and in microwaves (17 GHz) were analyzed in this way and the results are as follows:
  1. (1)

    The observed energy of X-rays which vary in proportion to the 17 GHz emission concentrates mostly below 100 keV with a median energy of 70 keV. Since the mean energy of electrons emitting 70 keV X-rays is ≲130 keV or ≲180 keV, depending on the assumed hard X-ray emission model (thin-target and thick-target, respectively), this photon energy strongly suggests that the 17 GHz emission comes mostly from electrons with an energy of less than a few hundred keV.

     
  2. (2)

    Correspondingly, the magnetic field strength in the microwave source is calculated to be 500–1000 G for the thick-target case and 1000–2000 G for the thin-target case. Finally, judging from the values of the source parameters required for the observed microwave fluxes, we conclude that the thick-target model in which precipitating electrons give rise to both X-rays and microwaves is consistent with the observations for at least 16 out of 22 flares examined.

     

Keywords

Microwave Flare Field Strength Photon Energy Magnetic Field Strength 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© D. Reidel Publishing Company 1986

Authors and Affiliations

  • Nariaki Nitta
    • 1
  • Takeo Kosugi
    • 2
  1. 1.Tokyo Astronomical Observatory, University of TokyoTokyoJapan
  2. 2.Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight CenterGreenbeltU.S.A.

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