Properties of a Supercritical Quasi-perpendicular Interplanetary Shock Propagating in the Terrestrial Foreshock Region

We investigate the properties of an interplanetary (IP) shock (M ( f ) = 2.1, theta = 80 degrees) that was detected by Wind on 1999 September 12 and was magnetically connected to the terrestrial bow shock. Key results are obtained concerning how the IP shock modifies the terrestrial foreshock electron and ion dynamics: (1) Intensive Langmuir waves were detected downstream of the IP shock due to the enhanced penetrating terrestrial foreshock electron beams. (2) Whistler heat flux instabilities associated with the oblique precursor whistler pitch-angle scatter the suprathermal electrons, together with the normal betatron acceleration that occurs across the IP shock. (3) The IP shock interacts with the antisunward propagating Alfven waves/fluctuations, and the shocked plasma shows both Alfvenic and mirror-mode features where Alfven waves were separated into two parts propagating in opposite directions. (4) Intense specularly reflected gyrating ions were detected around the IP shock, which indicates that the energy dissipation effects at the IP shock depend on both reflected ions and the waves intrinsic to the shock. These results provide new insights into the interaction between an IP shock and the terrestrial foreshock.