Propagation of Interplanetary Shocks in the Inner Heliosphere

TL;DR

This paper analyzes two interplanetary shock events using spacecraft data to understand their properties, orientations, and drivers, revealing consistent shock parameters in one event and complex, twisted shock shapes in another.

Contribution

It provides a detailed comparison of shock parameters and geometries for two IP shocks, highlighting differences in their structure and drivers using multi-spacecraft measurements.

Findings

Shock parameters remained consistent across spacecraft in the May 7, 2007 event.

The shock surface was aligned with the Parker spiral in the May event.

The April 23, 2007 shock was twisted and rippled, indicating complex structure.

Abstract

Interplanetary shocks are one of the crucial dynamic phenomena in the Heliosphere. They can accelerate particles to high energies, generate plasma waves, and can trigger geomagnetic storms in Earth's magnetosphere, significantly impacting technological infrastructure. In this study, two IP shock events are selected to study the temporal variations of the shock parameters using magnetometer and ion plasma measurements of the STEREO$-$A and B, the Wind, Cluster fleet, and the ACE spacecraft. The shock normal vectors are determined using the minimum variance analysis (MVA) and the magnetic coplanarity methods. During the May 7, 2007, event, the shock parameters and the shock normal direction remain consistent across each spacecraft crossing of the shock. The shock surface appears to be tilted almost the same degree as the Parker spiral, and the driver could be a Co$-$rotating Interaction Region (CIR). During the April 23, 2007 event, the shock parameters do not change significantly except for the shock angle $\theta_{B_{n}}$, however, the shape of the IP shock appears to be twisted along the perpendicular direction to the Sun-Earth line as well. The driver of this rippled shock is Stream Interaction Region (SIR)/CIR as well.