# The formation of magnetic depletions and flux annihilation due to reconnection in the heliosheath

## TL;DR

This paper uses particle-in-cell simulations to study magnetic reconnection in the heliosheath, explaining observed magnetic field depressions, flux annihilation, and sector reduction seen by Voyager spacecraft.

## Contribution

It provides a detailed simulation-based explanation for magnetic reconnection effects and flux loss in the heliosheath, matching Voyager observations.

## Key findings

- Magnetic reconnection creates long-lived magnetic islands and depressions.
- Flux annihilation leads to a reduction in sector number and magnetic flux.
- Simulations match Voyager data on magnetic field and plasma fluctuations.

## Abstract

The misalignment of the solar rotation axis and the magnetic axis of the Sun produces a periodic reversal of the Parker spiral magnetic field and the sectored solar wind. The compression of the sectors is expected to lead to reconnection in the heliosheath (HS). We present particle-in-cell simulations of the sectored HS that reflect the plasma environment along the Voyager 1 and 2 trajectories, specifically including unequal positive and negative azimuthal magnetic flux as seen in the Voyager data \citep{Burlaga03}. Reconnection proceeds on individual current sheets until islands on adjacent current layers merge. At late time bands of the dominant flux survive, separated by bands of deep magnetic field depletion. The ambient plasma pressure supports the strong magnetic pressure variation so that pressure is anti-correlated with magnetic field strength. There is little variation in the magnetic field direction across the boundaries of the magnetic depressions. At irregular intervals within the magnetic depressions are long-lived pairs of magnetic islands where the magnetic field direction reverses so that spacecraft data would reveal sharp magnetic field depressions with only occasional crossings with jumps in magnetic field direction. This is typical of the magnetic field data from the Voyager spacecraft \citep{Burlaga11,Burlaga16}. Voyager 2 data reveals that fluctuations in the density and magnetic field strength are anti-correlated in the sector zone as expected from reconnection but not in unipolar regions. The consequence of the annihilation of subdominant flux is a sharp reduction in the "number of sectors" and a loss in magnetic flux as documented from the Voyager 1 magnetic field and flow data \citep{Richardson13}.