Low-frequency Alfven Waves Produced by Magnetic Reconnection in the Sun's Magnetic Carpet

TL;DR

This study explores how magnetic reconnection in the Sun's magnetic carpet generates low-frequency Alfven waves, which could significantly influence coronal heating and solar wind dynamics.

Contribution

It introduces a Monte Carlo simulation to predict reconnection-driven MHD waves and highlights their potential dominance at low frequencies in the solar corona.

Findings

Reconnection-driven waves have lower frequencies than photosphere-driven waves.

These waves dominate the power spectrum at periods longer than 30 minutes.

They carry more magnetic energy than kinetic energy, affecting observational signatures.

Abstract

The solar corona is a hot, dynamic, and highly magnetized plasma environment whose source of energy is not yet well understood. One leading contender for that energy source is the dissipation of magnetohydrodynamic (MHD) waves or turbulent fluctuations. Many wave-heating models for the corona and the solar wind presume that these fluctuations originate at or below the Sun's photosphere. However, this paper investigates the idea that magnetic reconnection may generate an additional source of MHD waves over a gradual range of heights in the low corona. A time-dependent Monte Carlo simulation of the mixed-polarity magnetic field is used to predict the properties of reconnection-driven coronal MHD waves. The total power in these waves is typically small in comparison to that of photosphere-driven waves, but their frequencies are much lower. Reconnection-driven waves begin to dominate the total power spectrum at periods longer than about 30 minutes. Thus, they may need to be taken into account in order to understand the low-frequency power-law spectra observed by both coronal spectropolarimetry and in-situ particle/field instruments. These low-frequency Alfven waves should carry more magnetic energy than kinetic energy, and thus they may produce less nonthermal Doppler broadening (in comparison to photosphere-driven high-frequency waves) in emission lines observed above the solar limb.