Effect of a sausage oscillation on radio zebra-pattern structures in a solar flare

TL;DR

This paper investigates how sausage oscillations in solar coronal loops influence radio zebra-pattern structures, demonstrating that ZP wiggles can serve as diagnostics for detecting and studying these oscillations.

Contribution

It introduces a numerical simulation approach to link sausage oscillations with observable ZP wiggles, revealing distinct signatures for standing and propagating modes.

Findings

ZP wiggles correlate with sausage oscillation periods

Standing and propagating modes produce different ZP signatures

ZP wiggles can be used for coronal seismology

Abstract

Sausage modes that are axisymmetric fast magnetoacoustic oscillations of solar coronal loops are characterized by variation of the plasma density and magnetic field, and hence cause time variations of the electron plasma frequency and cyclotron frequency. The latter parameters determine the condition for the double plasma resonance (DPR), which is responsible for the appearance of zebra-pattern (ZP) structures in time spectra of solar type IV radio bursts. We perform numerical simulations of standing and propagating sausage oscillations in a coronal loop modeled as a straight, field-aligned plasma slab, and determine the time variation of the DPR layer locations. Instant values of the plasma density and magnetic field at the DPR layers allowed us to construct skeletons of the time variation of ZP stripes in radio spectra. In the presence of a sausage oscillation, the ZP structures are shown to have characteristic wiggles with the time period prescribed by the sausage oscillation. Standing and propagating sausage oscillations are found to have different signatures in ZP patterns. We conclude that ZP wiggles can be used for the detection of short-period sausage oscillations and the exploitation of their seismological potential.