Substorm growth and expansion onset as observed with ideal ground‐spacecraft THEMIS coverage

We present a fortuitous case of an isolated substorm on 29 March 2009, observed by the Time History of Events and Macroscale Interaction during Substorms (THEMIS) probes clustered at ∼11–14 RE with simultaneous coverage by the THEMIS ground network. The four probes are at roughly the same radial and azimuthal location, with one probe staying near the neutral sheet during entire growth phase and during the ensuing transition to the substorm …