Role of alpha particles in penetration of solar wind diamagnetic structures into the magnetosphere

Abstract

We present the results of studies showing the presence of simultaneous jumps in the density of protons (N2/N1)p and alpha particles (N2/N1)α at the boundaries of diamagnetic structures (DS) of various types both in the quasi-stationary slow solar wind (SW) and in sporadic SW. For DS of quasi-stationary slow SW, associated with streamer belt or chains, in the statistics considered in the paper there is a single linear dependence of (N2/N1)α on (N2/N1)p. This means that these jumps have the same physical nature and are related to diamagnetism at the boundaries of DS of quasi-stationary SW streams of various types. At the front of interplanetary shock waves (ISW), the (N2/N1)α jump is approximately twice as large as the (N2/N1)p jump. This reflects the features of the collective collisionless plasma heating at ISW fronts and requires further studies. A maximum excess (almost 3 times) of the increase in the alpha-particle density (N2/N1)α over the increase in the proton density (N2/N1)p is observed in eruptive prominences. The magnetospheric response in such phenomena as auroras, proton and alpha particle fluxes, geomagnetic field, and geomagnetic pulsations is similar under the influence of DS of various types and ISW. The detected features of the magnetospheric response to the contact with DS of different types and ISW can be interpreted as impulsive passage of the DS matter (plasmoid) into the magnetosphere. The results of studies of the (N2/N1)α jumps can be used as an additional important argument in identifying cases of impulsive penetration of DS into the magnetosphere and in examining the physical nature of these penetrations.