Abstract
Charge-transfer collisions between solar-wind protons and neutral interstellar hydrogen in the vicinity of the sun have been considered. Due to the focusing effect of the sun's gravitational field interstellar particles entering the solar system in free flights produce a specific density distribution in the circumsolar space. On their way from the sun to the orbit of the earth solar protons will therefore generate fast neutrals by collisions with neutral hydrogen. Depending on the position at its orbit the earth will be hit by these fast neutrals which will come down directly into the thermosphere and will produce temperature and density increases. It is shown that the corpuscular energy flux connected with these fast neutrals will have a semi-annually varying profile along the earth's orbit. Interstellar particle densities of about 5 cm−3 at infinity would produce energy fluxes of the order of 0.1 erg/cm2 sec. Assuming a specific proper motion of interstellar matter surrounding the solar system we obtain a neutral corpuscular energy flux having nearly the same shape and phase as the wellknown semi-annual effect in atmospheric temperatures and densities. Collision-generated, fast neutrals reaching the earth could therefore possibly give an explanation of this effect.
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Mitteilungen der Astronomischen Institute Bonn, Nr. 102.
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Fahr, H.J. Neutral corpuscular energy flux by charge-transfer collisions in the vicinity of the sun. Astrophys Space Sci 2, 496–503 (1968). https://doi.org/10.1007/BF02175924
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DOI: https://doi.org/10.1007/BF02175924