α-particle observations in the solar wind |
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| Authors: | V Formisano F Palmiotto G Moreno |
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| Institution: | (1) Laboratorio per lo Studio del Plasma nello Spazio, C.N.R., Roma;(2) Istituto di Fisica dell'Università, Roma;(3) Laboratorio per le Radiazioni Extra-terrestri, C.N.R., Bologna, Firenze;(4) Cattedra di Fisica dello Spazio, Università, Firenze |
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| Abstract: | The plasma experiment on board of the ESRO satellite HEOS-1 detects solar wind positive ions in the energy range from 200 eV/Z–16000 eV/Z.  -particles have been observed for 10% of the time, from December 1968 to March 1969, when in the interplanetary medium -particle and proton bulk velocities are on average equal. The average relative abundance of -particles is 5.5 %.Although in general the two species, hydrogen and helium, have a similar behaviour, very often -particles have an independent time history. Strong discontinuities may be observed in one species, without occurring in the other, or having different characteristics. At certain times, -particles seem to behave as an independent fluid.Well defined fluxes of -particles are observed within the magnetosheath: in several cases -particles, present in the unperturbed solar wind, are found with unchanged energy spectrum through a certain layer behind the proton shock front inside the magnetosheath. This suggests that thermalization of -particles does not occur at the same place as that of protons. |
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