Electron-cyclotron maser emission by power-law electrons in coronal loops

被引：0
|
作者：
Tang, J.F. [1 ,2 ]
Wu, D.J. [1 ]
机构：
[1] Purple Mountain Observatory, 2 West Beijing Road, Nanjing 210008, China
[2] Graduate School of Chinese, Academy of Sciences, Beijing 100039, China
来源：
Astronomy and Astrophysics | 2009年 / 493卷 / 02期
关键词：
Context. The electron-cyclotron maser (ECM) instability is an important mechanism that amplifies electromagnetic radiation directly by nonthermal electrons trapped in magnetic fields. The nonthermal electrons frequently have a negative power-law distribution with a lower energy cutoff Ec); which will depress the instability. Aims. In this paper; it is shown that the lower energy cutoff behavior of power-law electrons trapped in coronal loops can drive the ECM instability efficiently. Methods. Based on the dispersive relation for high-frequency waves and distribution function for power-law electrons with a lower energy cutoff in a coronal loop; the growth rates of the O and X mode waves at fundamental and harmonic frequencies are calculated. Results. The results show that the instability is driven when δ > α because of a population inversion below the cutoff energy Ec; where δ is the steepness index describing the cutoff behavior and α the power-law spectrum index. The growth rates increase with δ and E c; but decrease with α; σ; and; Ω; where σ is the magnetic mirror ratio of the loop and Ω the ratio frequency in the loop. Conclusions. This novel driving mechanism for the ECM emission can be expected to have a potential importance for understanding the mierophysies of radio bursts from the Sun and others. © ESO 2009;
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页码：623 / 628
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