First observations of foreshock bubbles upstream of Earth's bow shock: Characteristics and comparisons to HFAs

摘要: [1] Using multipoint in situ observations upstream of Earth's bow shock from the THEMIS mission, we present first foreshock bubbles (FBs) and compare them to hot flow anomalies (HFAs). FBs are recently conceptualized kinetic phenomena that can form under commonplace condition a rotational discontinuity interplanetary magnetic field interacting with backstreaming energetic ions quasi-parallel foreshock. may have remained elusive until now due their many observational similarities HFAs lack coordinated measurements. Here introduce identification criteria for distinguishing between using observations, use analyze five example events occurred on Bastille Day (14 July) 11–12 August 2008. Three these satisfy inconsistent multiple HFAs. The remaining two consistent traditional picture Furthermore, involve converging shocks, events, demonstrate effectiveness at particle acceleration. Considering formation conditions not extraordinary, be ubiquitous collisionless, shocks variety astrophysical settings.