Temporal and Spatial Evolution of Energetic Ion Injections in the Inner Magnetosphere: Multi-Point Observations of a Substorm Event.
Monday, 15 December 2014: 2:49 PM
Plasma transport and energization of ions in the magnetotail has been shown to largely occur in the form of injections of hot plasma, localized in MLT, associated with bursty bulk flows and sharp dipolarizations of the magnetic field. However, the relationship of these transient tail phenomena to energetic particle injections into the inner magnetosphere is not well understood. Recent results by the RBSPICE instrument of the Van Allen Probes mission showed that the occurrence of energetic ion injections inside geosynchronous orbit can be very frequent throughout the main phase of a geomagnetic storm, and indicated that the contribution of such injections to the ring current buildup could be substantial. Understanding the formation and evolution of energetic ion injections in the inner magnetosphere and their relationship to transient phenomena in the tail is, therefore, of great importance. In order to differentiate between temporal and spatial variations, it is essential to investigate injections via multi-point observations. We study a substorm event that occurred during a small storm (Dst ~-40 nT), where two injections of energetic ions (50 – 300 keV), 10 minutes apart, were observed by RBSPICE instrument inside geosynchronous orbit, and six LANL and two GOES spacecraft at geosynchronous orbit. Geosynchronous spacecraft ETS-8, at a similar MLT with Van Allen Probe B, also observed the dipolarization signatures associated with these two injections. At the same time, two THEMIS spacecraft were monitoring the night-side magnetosphere at ~ 10 RE. Using ground-based magnetometer data, we are able to identify the eastward and westward edges of the current wedge associated with each one of these injections. The two injections, as observed in the inner magnetosphere, exhibit distinct differences in their dipolarization signatures as well as their duration. With all the above data at hand, we investigate the inward propagation of the injections into the inner magnetosphere, their MLT extent, their duration, as well as their relationship to activity farther down the magnetotail, in order to address the causes of the differences in the injection signatures.