Hot flow anomaly formation and evolution: Cluster observations

摘要: [1] In this study, we have examined the formation and evolution of 513 hot flow anomalies (HFAs) from 2003 to 2009 observed by Cluster spacecraft. Our results show that an original upstream discontinuity in vicinity HFAs and/or at least one side HFA with convective electric field pointing toward may help growing, but it is not a necessary condition generate HFA. It shown significant part thermal energy inside converted kinetic solar wind, although additional heating process(es) required heat plasma In order learn HFA, electron spectrum ion velocity distribution function (VDF) young mature HFAs. found particle spectra are good indicators or Inside HFAs, can be fitted single drift-κ distribution, while combination drift-Maxwellian peak below ∼10 eV heated distribution. On other hand, VDF shows whereas two clear populations—one wind reflected population. population scattered more than 180° Vpara-Vperp1 plane, where Vperp1 V-B plane perpendicular B, which similar foreshock This indicates could diffusive all directions rather unidirectional beam when forming.