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Abstract:
Ballooning-interchange heads are fundamental dynamic objects in the nightside Earth's magnetosphere, which represent magnetic structures that are similar in shape to the atmospheric mushroom clouds resulting from a sudden formation of a volume of lower-density gases. The heads appear in series and drive geomagnetic east-west oriented aurora, which glows like a pearl necklace across the night sky. Identifying the ballooning-interchange heads from in situ data is a challenging task due to sparse spacecraft coverage. This task becomes particularly difficult during head’s non-linear development, in the need of discerning the head’s driven plasma flows from magnetotail reconnection outflows. In this talk we demonstrate THEMIS and MMS events with a number of ballooning-interchange signatures during non-linear development. Particularly, we demonstrate that the magnetospheric ions appear to sense the heads and modify their circular paths perpendicular to the magnetospheric magnetic field, because their gyration radius is on the order of the head's size. Such a modification of the ion motion appears to lead to ion redistribution on the two sides of the head according to the ion energy. Another signature appears as a finer ion structuring, which occurs along the magnetic field lines as a consequence of growing electromagnetic ion-cyclotron waves.
