Electron and proton fluxes in the tail of the magnetosphere

Observation and energy spectra of electrons and protons in islands at the back of the magnetosphere are presented. It is shown that typically for electrons J(> 20 kev) 8 × 106/cm2-sec-ster and for protons J(> 125 kev) 104/cm2-sec-ster. The electron spectra for particles with 20 kev E 70 kev can be characterized by e-folding energies ranging from 15 to 5 kev or by γ from 2.6 to 4.3 for differential power law spectra. For protons with energies E > 125 kev, the spectra display e-folding energies in the range from 20 to 40 kev and γ between 7.8 and 4.9 for differential power law spectra. The electron spectrum in the islands shows a characteristic softening with time. A comparison is made with electron fluxes observed with the Alouette, IMP 1, and Vela satellites. The similarity between particles in the islands and those observed in the aurora is discussed.