Mechanisms and Evolution of Geoeffective Large-Scale Plasma Jets in the Magnetosheath

Geoeffective magnetosheath plasma jets (those that interact with the magnetopause) are an important area of research and technology, since they affect the “space-weather” around the Earth. We identified such large-scale magnetosheath plasma jets with a duration of >30 s using plasma and magnetic data acquired from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) multi-spacecraft experiment during the years 2007 to 2009. We present a statistical survey of 554 of such geoeffective jets and elaborate on four mechanisms for the generation of these jets as the upstream solar wind structures of tangential discontinuities (TDs), rotational discontinuities (RDs), the quasi-radial interplanetary magnetic field (rIMF) and the collapsing foreshock (CFS) interrupting the rIMF intervals. We found that 69% of the jets are generated due to the interaction between interplanetary discontinuities (TD: 24%, RD: 25%, CFS: 20%) with the bow shock. Slow and weak jets due to the rIMF contributed to 31% of these jets. The CFS and rIMF were found to be similar in their characteristics. TDs and RDs contributed to most of the fast and powerful jets, with large spatial scales, which might be attributed to transient effects in the travelling foreshock.