Scaling of the growth rate of magnetic islands in the heliosheath

TL;DR

This study uses particle-in-cell simulations to analyze the growth rate of magnetic islands in the heliosheath, revealing that their growth is system-size independent and can continue until reaching sector width, with implications for magnetic reconnection.

Contribution

It demonstrates that magnetic island growth in the heliosheath is independent of system size and can persist until reaching sector width, using detailed particle-in-cell simulations.

Findings

Growth rate is independent of system size.

Magnetic islands grow until reaching sector width.

Growth occurs faster than heliosheath convection time.

Abstract

Current sheets thinner than the ion inertial length are unstable to the tearing instability and will develop magnetic islands that grow due to magnetic reconnection. We investigate whether the growth of magnetic islands in a current sheet can continue indefinitely, or in the case of the heliosheath until reaching a neighboring current sheet, and at what rate the islands grow. We investigate the development and growth of magnetic islands using a particle-in-cell code, starting from particle noise. Performing a scaling of the growth of magnetic islands versus the system size, we find that the growth rate is independent of the system size up to the largest simulation we were able to complete. The islands are able to continue growing as long as they merge with each other and maintain a high aspect ratio. Otherwise there is not enough magnetic tension to sustain reconnection. When applied to the sectored magnetic fields in the heliosheath, we show that the islands can continue growing until they reach the sector width and do so in much less time than it takes for the islands to convect through the heliosheath.