Statistics of fine dispersion structures events in energetic particle spectra: their origin and role in the outer magnetosphere

Abstract. Fine Dispersion Structures (FDS) in energetic particle spectra in outer magnetosphere were discovered in DOK-2 experiments onboard of Interball-1 and -2 spacecrafts (1995–2000). First results of these studies were published in 2000–2005. It was shown that FDS can be a result of a gradient-curvature drift of ions and electrons around the Earth after their pulse injection from the geotail plasma sheet to some point in the night side of the outer magnetosphere. Since that time hundreds of such events have been examined additionally. They proved to be a rather common phenomenon in the outer Earth's magnetosphere. We present here statistics of FDS observations and properties which confirms our interpretation and clarifies the role of magnetotail plasma sheet and FDS particles in dynamics and replenishment of the outer radiation belt population.