Multipoint observations of substorm pre‐onset flows and time sequence in the ionosphere and magnetosphere

In this paper, we use a rare and close longitudinal conjunction of the THEMIS spacecraft with the Sondrestrom radar to present multipoint observations of important features of the time sequence of substorm pre‐onset plasma flows in the ionosphere and magnetotail on March 5, 2008. We found that the onset was preceded sequentially by enhanced polar cap flows heading equatorward near the polar cap boundary, and then by tail fast flows from the …