Proton precipitation to the equator of the isotropic boundary during the geomagnetic storm on November 20–29, 2003

Using NOAA satellite data, we consider the peculiarities of precipitation dynamics for energetic protons to the equator of the isotropy boundary during a geomagnetic storm. In addition to two well-known types of proton precipitation events, a new third type of precipitation is distinguished, which is observed on the dayside at relatively high latitudes. The assumption is made that the third-type precipitation in the dayside sector is associated with the development of ion-cyclotron instability. Apparently, the transverse anisotropy of energetic protons, which is necessary for the development of instability, is caused by splitting of drift shells. All three types of precipitation have different generation regions and different time dynamics during storms. The maximum precipitation intensity takes place in the evening sector during the main phase of a storm. At the storm’s recovery phase major losses of protons of the ring current are due to precipitation in the day and morning sectors.