Geotail Observations of Solar Wind and Interplanetary Phenomena

Abstract

Abstract In this review, based on the recent GEOTAIL observation I will cover three broad topics, bow shock and foreshock phenomena, interplanetary phenomena, interstellar medium, and solar flare effects. (1) I will concentrate on the physics of energetic diffuse ions found in the bow shock and foreshock regions, and discuss three subtopics, namely, the origin of these ions, their nonlinear reaction to the shock structure, and their transport process from the region upstream of the nose bow shock to the predawn foreshock region. (2) I will discuss two subtopics about propagating interplanetary shocks ahead of coronal mass ejecta: It is shown that in addition to the well-known diffusive ionacceleration at these shocks there sometimes occurs diffusive electronacceleration. The nonlinear reaction of the accelerated particles, the same phenomenon as found in the bow shock case, is identified at least once in an moderately strong interplanetary shock. (3) In addition to the above 'normal' bow shock/interplanetary phenomena, CEOTAIL has provided unique 3D phase space information on a 'stranger', namely pickup He+ions of local interstellar medium origin. (4) I will then describe unexpected direct observations of solar flare signals on GEOTAIL: the spiky enhancements (duration ~ several minutes) of the sunward electric fields and background counts of plasma detectors, both of which occur concurrently with the peaks of large solar X-ray flares.