Reflection of fast magnetosonic waves near magnetic reconnection region

TL;DR

This study analytically investigates how fast magnetosonic waves reflect and refract near magnetic reconnection sites in the solar corona, revealing dependence on plasma parameters and wave frequency, with implications for particle acceleration and FIP fractionation.

Contribution

It provides an analytical solution for wave reflection near reconnection sites considering non-uniform plasma, highlighting the influence of plasma-$eta$ and wave frequency.

Findings

Waves reflect more efficiently in low-$eta$ plasma.

Lower frequency waves are reflected more; high frequency waves propagate outward.

Reflection depends strongly on plasma-$eta$ and wave frequency.

Abstract

Magnetic reconnection in the solar corona is thought to be unstable to the formation of multiple interacting plasmoids, and previous studies have shown that plasmoid dynamics can trigger MHD waves of different modes propagating outward from the reconnection site. However, variations in plasma parameters and magnetic field strength in the vicinity of a coronal reconnection site may lead to wave reflection and mode conversion. In this paper we investigate the reflection and refraction of fast magnetoacoustic waves near a reconnection site. Under a justified assumption of an analytically specified Alfv\'{e}n speed profile, we derive and solve analytically the full wave equation governing propagation of fast mode waves in a non-uniform background plasma without recourse to the small-wavelength approximation. We show that the waves undergo reflection near the reconnection current sheet due to the Alfv\'en speed gradient and that the reflection efficiently depends on the plasma-$\beta$ parameter as well as on the wave frequency. In particular, we find that waves are reflected more efficiently near reconnection sites in a low-$\beta$ plasma which is typical for the solar coronal conditions. Also, the reflection is larger for lower frequency waves while high frequency waves propagate outward from the reconnection region almost without the reflection. We discuss the implications of efficient wave reflection near magnetic reconnection sites in strongly magnetized coronal plasma for particle acceleration, and also the effect this might have on First Ionization Potential (FIP) fractionation by the ponderomotive force of these waves in the chromosphere.