NASA Goddard Space Flight Center, Laboratory for Extraterrestrial Physics, Greenbelt, Maryland 20771

Traveling compression regions (TCRs) are short duration, ~1-3 min, small amplitude, D B/B ~ 10%, perturbations of the lobe magnetic field caused by the downstream passage of plasmoids. Their characteristic signature, a north-then-south tilting of the lobe field centered upon a smooth compression, was first noted in the Explorer 35 observations about a decade prior to the first definitive observations of plasmoids by ISEE 3. Since that time, TCRs have been studied extensively using observations from the ISEE 3, IMP 8, Galileo and GEOTAIL missions. In addition to providing a unique example of magnetic field draping in a low b plasma (i.e., tail lobes), TCRs have been used very successfully to determine the number and size of plasmoids being ejected down the tail during substorms and to infer the time of near-Earth neutral line formation relative to substorm onset. In this article we review the previous experimental and theoretical investigations of traveling compression regions and discuss new research directions and applications involving this space physics phenomenon.

in New Perspectives on the Earth's Magnetotail, Geophysical Monograph, pg. 225, 1998