Effects of Coulomb collisions on cyclotron maser and plasma wave growth in magnetic loops

Russell J Hamilton, Vahé Petrosian

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The evolution of nonthermal electrons accelerated in magnetic loops is determined by solving the kinetic equation, including magnetic field convergence and Coulomb collisions in order to determine the effects of these interactions on the induced cyclotron maser and plasma wave growth. We find that the growth rates are larger and the possibility of cyclotron maser action is stronger for smaller loop column density, for larger magnetic field convergence, for a more isotropic injected electron pitch angle distribution, and for more impulsive acceleration. For modest values of the column density in the coronal portion of a flaring loop, the growth rates of instabilities are significantly reduced, and the reduction is much larger for the cyclotron modes than for the plasma wave modes. The rapid decrease in the growth rates with increasing loop column density suggests that, in flare loops when such phenomena occur, the densities are lower than commonly accepted. This may be related to the fact that the spike bursts are usually observed during the rise of the impulsive phase of flares before evaporation increases the loop density. We also find that the resulting distributions are much more complicated than the idealized distributions used in many theoretical studies, that the dominant modes can be different than for the idealized situations, and that more than one mode can be simultaneously amplified.

Original languageEnglish (US)
Pages (from-to)778-788
Number of pages11
JournalAstrophysical Journal
Volume365
Issue number2
StatePublished - Dec 20 1990
Externally publishedYes

Fingerprint

Coulomb collisions
plasma waves
masers
cyclotrons
collision
plasma
flares
magnetic field
electron
theoretical study
pitch (inclination)
magnetic fields
spikes
kinetic equations
evaporation
effect
bursts
electrons
kinetics
collisions

Keywords

  • Earth: aurorae
  • Hydromagnetics
  • Particle acceleration
  • Radiation mechanisms
  • Sun: corona
  • Sun: radio radiation
  • Wave motions

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Effects of Coulomb collisions on cyclotron maser and plasma wave growth in magnetic loops. / Hamilton, Russell J; Petrosian, Vahé.

In: Astrophysical Journal, Vol. 365, No. 2, 20.12.1990, p. 778-788.

Research output: Contribution to journalArticle

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