below: a thick plasma structure in motion (often the case) can look like a thinner structure at rest

below: By studying the data from two satellites you can figure out that the structure is moving, and hence its actual thickness. The speed of motion is reflected in the time difference between its detection on the two satellites.

below: The first two figures above refer to motion and distances in the up-down direction, and assume no variation in the transverse direction. This figure shows how the four satellites can be used to identify a thinner point on a structure. An example of where this might be useful is for identifying the region of plasma sheet thinning thought to precede a substorm.

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Images by Andrew Fazakerley - please do NOT reproduce without permission
Last updated on 08/08/00 by Sarah Szita