Characteristics of stripes-pattern radio-emission sources

Abstract

ABSTRACT An investigation of the generation mechanism for stripes-pattern radio spectra is important for an understanding of the dynamics of non-thermal electrons in several astronomical objects, including the Sun, Jupiter, and the Crab Pulsar. A new analytical study is carried out to identify the plasma characteristics of fiber- and zebra-pattern emission sources without an underlying density or magnetic model. The analysis demonstrates that the source region of the stripes emission is located underneath the reconnection point, where the ratio s of the instability growth rate to the electron gyrofrequency ωc does not equal unity; that is, s = k⊥v⊥/ωc ≠ 1. When |s| < 1, the plasma condition of the source region becomes k⊥v⊥ < ωp < ωc, where ωp is the plasma frequency, and the emission source is likely to produce a fiber radio burst. For |s| > 1, the plasma condition of the source region is ωc < ωp < k⊥v⊥, and the emission source is likely to produce zebra-pattern emission. This indicates that the magnetic field in the source region of zebra-pattern radio emission is weak and it is relatively high in the source region of fiber-pattern emission. An approach is applied to estimate the plasma parameters of a zebra-pattern emission source observed on 2011 June 21. The behaviour of the blasted medium, which is produced by magnetic reconnection, is investigated. The results show that the blasted medium propagates isothermally as a sausage-like wave for a short time during the emission. The study discusses the conditions for producing different types of striped radio emission and provides a simple computational approach that could be useful in a number of astronomical contexts.