An Investigation of the Role of Propagation Effects in the Formation of Drifting Narrowband Type II Fiber Bursts on the Dynamic Spectrum

Abstract

This paper investigates one of the kinds of fine structure of solar decametric type II radio bursts in the form of drifting narrowband fibers. The appearance of such a structure is customarily explained by the features of the radio emission mechanism in the source, which is formed when the shock wave catches up the previously-generated coronal mass ejection. On the other hand, the characteristics of radio emission in the process of its propagation from the source to the observation point are affected by inhomogeneities in the corona. Hence it is of considerable interest to estimate the role of the propagation effects on the formation of fiber structures in radio bursts. Our calculations show that strong refraction effects (caustics) can give rise to narrowband structures in the dynamic spectrum, resembling in their characteristics the fibers observed.

Phase fluctuations of radio waves experiencing total reflection from a randomly inhomogeneous plasma layer

“…However, the problem of small-angle scattering of radio waves experiencing reflection from some regions of plasma has been studied to a lesser extent (Denisov and Erukhimov, 1966;Fuks, 1974;Gusev and Radzhabov, 1983;Gershman et al, 1984;Alimov et al, 1997;Yakovlev et al, 2009), although there are a number of cases where the reflection of waves is fundamentally important. One example is scattering of radio waves in the solar coronal plasma with large inhomogeneities of dielectric permittivity, being capable of reflecting radio waves (Kucheryavenkov et al, 1985;Efimov and Rudash, 2002;Afanasiev, 2009Afanasiev, , 2010. Under such circumstances the characteristics of the scattered radio waves can be affected by regular refraction effects.…”