Propagation of transient shocks from 1 AU to the Voyagers during 2012-2015

Abstract:

The heliopause is a rich, dynamic surface affected by the time-dependent solar wind. Stream interactions due to coronal mass ejections (CMEs), corotating interaction regions (CIRs), and other transient phenomena are known to merge producing global merged interaction regions (GMIRs). Numerical simulations of the solar wind interaction with the local interstellar medium (LISM) show that GMIRs, as well other time-dependent structures in the solar wind, may produce compression and rarefaction waves and shocks in the LISM behind the heliopause. These shocks may initiate wave activity observed by the Voyager spacecraft. The magnetometer onboard Voyager 1 indeed observed a few structures that may be interpreted as shocks. Starting from OMNI data at 1 AU, we present numerical simulations of such shocks in 2012, when Voyager 1 observed traveling shocks. We analyze the shock properties such as strength, propagation speed, and inter-shock separation by enhancing the resolution locally with adaptive mesh refinement. We compare these results with the plasma and magnetic field behavior after Voyager 1 crossed the heliospheric boundary. Lastly, we perform timing tests on the fully 3-D propagation of solar transients through the termination shock and heliopause, and determine if the transient features observed by Voyagers 1 and 2 beyond the heliopause might correspond to particular solar transients observed at 1 AU.