Injection of solar wind particles into the magnetosphere in the neighbourhood of a neutral point

As a result of the interaction of the solar wind with the geomagnetic field, on the noon boundary of the Earth's magnetosphere, high-latitude neutral points are formed in whose neighbourhood the injection of charged particles into the magnetosphere is possible. The magnetic field near these points is similar to the cusped magnetic trap. The paper considers the motion of an individual charged particle in the field of such a configuration. Due to the great angular anisotropy of the flux of particles injected into the magnetosphere, centrifugal instability should arise. The study of the motion of individual particles makes it possible to construct a model suitable for investigations of collective effects. The development of centrifugal instability leads to a decrease of the magnetic field and the formation of the 'neutral region'. The size of this region in different models is evaluated. It is shown that within the instability region the decrease of the field strength is about 10 γ.