Observations from Magnetospheric MultiScale (~8 Re) and Van Allen Probes (~5 and 4 Re) show that the initial dayside response to a small interplanetary shock is a double-peaked dawnward electric field, which is distinctly different from the usual bipolar (dawnward and then duskward) signature reported for large shocks. The associated E × B flow is radially inward. The shock compressed the magnetopause to inside 8 Re, as observed by Magnetospheric MultiScale (MMS), with a speed that is comparable to the E × B flow. The magnetopause speed and the E × B speeds were significantly less than the propagation speed of the pulse from MMS to the Van Allen Probes and GOES-13, which is consistent with the MHD fast mode. There were increased fluxes of energetic electrons up to several MeV. Signatures of drift echoes and response to ULF waves also were seen. These observations demonstrate that even very weak shocks can have significant impact on the radiation belts.
Bibliographical noteFunding Information:
The authors thank J.H. King and N. Papatashvilli at AdnetSystems and NASA/GSFC for access to the OMNI data through CDAWeb and the World Data Center. We also thank the EFW instru ment teams at Space Sciences Lab of UCB and LASP of CU, the EMFISIS suite teams at University of Iowa and UNH, and the APL satellite team. The Van Allen Probes data sets are available from http://www.space.umn.edu/rbspefw-data/, http://emfisis.physics.uiowa.edu/ data/ and https://rbsp-ect.lanl.gov/ science/DataDirectories.php; GOES-13 data were obtained from from https:// satdat.ngdc.noaa.gov/sem/goes/, Wind and ACE data were obtained from http://cdaweb.gsfc.nasa.gov/, ARTEMIS data are available from http://themis.ssl. berkeley.edu/overview_data.shtml, and MMS data are available from https:// lasp.colorado.edu/mms/sdc/public/. Work at the University of Minnesota was supported contract from APL, under NASA prime contact NAS5-01072. The work at Aerospace was supported in part by contract 792084 N/E99017JD from Southwest Research Institute (MMS/FEEPS), and JHU/APL contract 967399 (RBSP/MagEIS and ECT). MMS work at SWRI was supported by NASA contract NNG04EB99C.
- electric field response
- interplanetary shock
- radiation belt