Particle Acceleration in Collapsing Magnetic Traps with a Braking Plasma Jet

TL;DR

This paper introduces a novel analytical model of collapsing magnetic traps incorporating a braking plasma jet, revealing new particle acceleration behaviors relevant to solar flares and Earth's magnetotail.

Contribution

It is the first to include a braking plasma jet in a CMT model, demonstrating its impact on particle trapping and acceleration in solar and space plasma environments.

Findings

Electrons can be trapped in the braking jet region and loop legs.

Particle trajectories and energy gains vary with model parameters.

New particle behaviors emerge due to the magnetic structure of the jet region.

Abstract

Collapsing magnetic traps (CMTs) are one proposed mechanism for generating non-thermal particle populations in solar flares. CMTs occur if an initially stretched magnetic field structure relaxes rapidly into a lower-energy configuration, which is believed to happen as a by-product of magnetic reconnection. A similar mechanism for energising particles has also been found to operate in the Earth's magnetotail. One particular feature proposed to be of importance for particle acceleration in the magnetotail is that of a braking plasma jet, i.e. a localised region of strong flow encountering stronger magnetic field which causes the jet to slow down and stop. Such a feature has not been included in previously proposed analytical models of CMTs for solar flares. In this work we incorporate a braking plasma jet into a well studied CMT model for the first time. We present results of test particle calculations in this new CMT model. We observe and characterise new types of particle behaviour caused by the magnetic structure of the jet braking region, which allows electrons to be trapped both in the braking jet region and the loop legs. We compare and contrast the behaviour of particle orbits for various parameter regimes of the underlying trap by examining particle trajectories, energy gains and the frequency with which different types of particle orbit are found for each parameter regime.