Magnetosheath Injections Deep Inside the Closed LLBL: A Review of Observations

Since the late 1970s, reports of temporal injections of sheath plasma deep inside the magnetosphere have recurred. Most reports favor northward (especially weakly so) IMF conditions, and there may be a preference for the dawn flank. Injections occur preferentially when solar wind pressure is high, and during intervals of incident pressure pulses. Many low-altitude observations lie in 0800-1000 MLT sector. High altitude observations of sheath injections into the closed magnetosphere extend downstream of dawn or dusk. Some cases initially assumed to be cusp injections are, based on the spectral properties, the local time, and other characteristics, actually in the closed LLBL. It is unclear whether these injection events are a relatively minor aspect of solar wind-magnetosphere coupling, or whether they play a significant role, say, in LLBL formation. Nonetheless, the evidence for sheath plasma entering onto closed field lines by processes other than merging is strong.