AGU: Geophysical Research Letters

 

Editors' Highlight

Cold plasma plumes help form aurora

The THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission is NASA's five-satellite mission whose prime science objective is to measure the trigger mechanism and dynamics of substorms, explosive energy releases in near-Earth space that create spectacular eruptions of the auroras. During a 9-month coast phase before the prime mission, dayside studies of the magnetosphere, magnetopause, and bow shock were performed. During this period, McFadden et al. (2008) uncovered dense plumes of cold plasma that extend from the inner magnetosphere out to the magnetopause, the boundary where the Earth's magnetic field deflects the solar wind. THEMIS's multisatellite measurements resolved the layered structure and evolution of these plumes, and its high time resolution experiments allowed definitive demonstrations that this dense, cold plasma participates in dayside magnetic reconnection. Such observations provide a much more extensive, high-resolution data set of in situ cold plasma observations than was previously available. These first results suggest that future missions that intend to study the magnetopause should include cold plasma sensors to better quantify the role cold plasma plays in magnetic reconnection.

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