A Porous, Layered Heliopause

TL;DR

Recent Voyager 1 data and advanced simulations suggest the heliopause is a porous, layered boundary with magnetic reconnection, challenging previous notions of a pristine, sharply defined interface.

Contribution

The paper introduces a new model of the heliopause as a porous, multi-layered structure with magnetic islands, supported by both observations and simulations, revising prior simplified views.

Findings

Magnetic field rotation across the HP is small.

Magnetic islands form and reconnect in the heliosheath.

Voyager 1 has likely already crossed the HP.

Abstract

The picture of the heliopause (HP) -- the boundary between the domains of the sun and the local interstellar medium (LISM) -- as a pristine interface with a large rotation in the magnetic field fails to describe recent Voyager 1 (V1) spacecraft data. Magnetohydrodynamic (MHD) simulations of the global heliosphere reveal that the rotation angle of the magnetic field across the HP at V1 is small. Particle-in-cell simulations, based on cuts through the MHD model at the location of V1, suggest that the sectored region of the heliosheath (HS) produces large-scale magnetic islands that reconnect with the interstellar magnetic field and mix LISM and HS plasma. Cuts across the simulation data reveal multiple, anti-correlated jumps in the number densities of LISM and HS particles at the magnetic separatrices of the islands, similar to those observed by V1. A model is presented, based on both the observations and simulation data, of the HP as a porous, multi-layered structure threaded by magnetic fields. This model further suggests that, contrary to the conclusions of recent papers, V1 has already crossed the HP.