EXOS-D SMS によって測定された陽子の半分のジャイロ周波数を持つイオンについて

概要

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Radio waves with right-hand polarization of extremely low frequency (ELF), emitted by lightning strikes, can penetrate the ionosphere into the lower level of the magnetosphere. The right-hand polarized waves change to left-hand polarized waves (ioncyclotron waves) at the crossover frequency in the multicomponent and inhomogeneous plasma. Upward and transequatorial (downward) deuteron whistlers caused by the minor ionic component of the ionospheric and magnetos-pheric thermal plasma, principally deuteron (density ratio of deuteron to proton perhaps 10^<-3>) and a small amount of He^<++>, have been found [4,5] from ISIS VLF data. Usually we cannot observe the large flux of thermal M/Q=2ions, however, the large flux of descending M/Q=2ions, measured with the density ratio to H^+ of 10^<-1>, appeared in the geomagnetical calm period in the low altitude (1000km) cusp region. In the morning side of the auroral region, a large flux of M/Q=2ions was observed as principally omnidirectional thermal plasma during a geomagnetic storm at a relatively high altitude (10000km). These cases seem to be caused by He^<++> from the solar wind. In these case, then, the density of M/Q=2ions which make up the deuteron whistler may also depend on He^<++> from the solar wind.
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