Applications of Fast Magnetic Reconnection Models to the Atmospheres of the Sun and Protoplanetary Disks

TL;DR

This paper explores how partially-ionized plasmas in the Sun's atmosphere and protoplanetary disks undergo fast magnetic reconnection, leading to heating and particle acceleration, with implications for observed emissions.

Contribution

It analyzes the collisional regimes enabling fast magnetic reconnection in partially-ionized environments, highlighting the role of collisionally-decoupled regimes in energy release.

Findings

Resistive current sheets form in coupled plasmas but break down under ideal tearing instability.

Repeated collapse of current sheets leads to smaller-scale magnetic islands and rapid energy conversion.

Localized heating from reconnection explains observed infrared emissions in protoplanetary disks.

Abstract

Partially-ionized plasmas consist of charged and neutral particles whose mutual collisions modify magnetic reconnection compared with the fully-ionized case. The collisions alter the rate and locations of the magnetic dissipation heating and the distribution of energies among the particles accelerated into the non-thermal tail. We examine the collisional regimes for the onset of fast reconnection in two environments: the partially-ionized layers of the solar atmosphere and the protoplanetary disks that are the birthplaces for planets around young stars. In both these environments, magnetic nulls readily develop into resistive current sheets in the regime where the charged and neutral particles are fully coupled by collisions, but the current sheets quickly break down under the ideal tearing instability. The current sheets collapse repeatedly, forming magnetic islands at successively smaller scales, till they enter a collisionally-decoupled regime where the magnetic energy is rapidly turned into heat and charged-particle kinetic energy. Small-scale, decoupled fast reconnection in the solar atmosphere may lead to preferential heating and energization of ions and electrons that escape into the corona. In protoplanetary disks such reconnection causes localized heating in the atmospheric layers that produce much of the infrared atomic and molecular line emission observed with the Spitzer and James Webb Space Telescopes.