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

¹ Boston University, 725 Commonwealth Ave, Boston, MA 02215, USA
e-mail: eprovorn@bu.edu; mopher@bu.edu
² Space Research Institute (IKI), Russian Academy of Sciences, 84/32 Profsoyuznaya St, 117997 Moscow, Russia
³ Lomonosov Moscow State University, Faculty of Mechanics and Mathematics, 119991 Moscow, Russia
⁴ Institute for Problems in Mechanics, Russian Academy of Sciences, 101-1 Prospect Vernadskogo, 119526 Moscow, Russia
e-mail: izmod@ipmnet.ru
⁵ University of Michigan, 2455 Hayward, Ann Arbor MI 48109, USA
e-mail: gtoth@umich.edu

Received: 12 December 2012
Accepted: 22 February 2013

Abstract

Context. 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.

Aims. 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.

Methods. 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.

Results. 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.