### 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 language | English (US) |
---|---|

Pages (from-to) | 778-788 |

Number of pages | 11 |

Journal | Astrophysical Journal |

Volume | 365 |

Issue number | 2 |

State | Published - Dec 20 1990 |

Externally published | Yes |

### Fingerprint

### 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

*Astrophysical Journal*,

*365*(2), 778-788.

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

Research output: Contribution to journal › Article

*Astrophysical Journal*, vol. 365, no. 2, pp. 778-788.

}

TY - JOUR

T1 - Effects of Coulomb collisions on cyclotron maser and plasma wave growth in magnetic loops

AU - Hamilton, Russell J

AU - Petrosian, Vahé

PY - 1990/12/20

Y1 - 1990/12/20

N2 - 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.

AB - 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.

KW - Earth: aurorae

KW - Hydromagnetics

KW - Particle acceleration

KW - Radiation mechanisms

KW - Sun: corona

KW - Sun: radio radiation

KW - Wave motions

UR - http://www.scopus.com/inward/record.url?scp=0005343628&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0005343628&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0005343628

VL - 365

SP - 778

EP - 788

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

ER -