Propagation into the heliosheath of a large-scale solar wind disturbance bounded by a pair of shocks

TL;DR

This study uses a 3D MHD multi-fluid model to analyze how pairs of shocks originating from the Sun propagate through the heliosphere, interact with the termination shock, and influence the variability of plasma and cosmic rays in the heliosheath.

Contribution

It provides new insights into the effects of solar wind shocks on heliosheath dynamics and the resulting wave phenomena, which were not fully understood before.

Findings

Shocks weaken and decelerate as they travel in the solar wind.

Shock interactions with the termination shock generate new waves and discontinuities.

Forward shock collision with the heliopause reflects fast magnetosonic waves inside the heliosheath.

Abstract

After the termination shock (TS) crossing, the Voyager 2 spacecraft has been observing strong variations of the magnetic field and solar wind parameters in the heliosheath. Anomalous cosmic rays, electrons, and galactic cosmic rays present strong intensity fluctuations. Several works suggested that the fluctuations might be attributed to spatial variations within the heliosheath. Additionally, the variability of the solar wind in this region is caused by different temporal events that occur near the Sun and propagate to the outer heliosphere. To understand the spatial and temporal effects in the heliosheath, it is important to study these effects separately. In this work we explore the role of shocks as one type of temporal effects in the dynamics of the heliosheath. Although currently plasma in the heliosheath is dominated by solar minima conditions, with increasing solar cycle shocks associated with transients will play an important role. We used a 3D MHD multi-fluid model of the interaction between the solar wind and the local interstellar medium to study the propagation of a pair of forward-reverse shocks in the supersonic solar wind, interaction with the TS, and propagation to the heliosheath. We found that in the supersonic solar wind the interaction region between the shocks expands, the shocks weaken and decelerate. The fluctuation amplitudes of the plasma parameters vary with heliocentric distance. The interaction of the pair of shocks with the TS creates a variety of new waves and discontinuities in the heliosheath, which produce a highly variable solar wind flow. The collision of the forward shock with the heliopause causes a reflection of fast magnetosonic waves inside the heliosheath.