Paper: astro-ph/0507065
Date: Mon, 4 Jul 2005 12:38:58 GMT (309kb)

Title: Sungrazing comets as source of pickup ions at Earth orbit and Ulysses

Authors: M. Bzowski, M. Krolikowska (Space Research Centre PAS, Warsaw)
Comments: 4 pages, 3 figures. Submitted to the Proceedings of Solar Wind
11/SOHO 16 Conference, Whistler BC, Canada, June 2005
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Most of the sungrazing comets observed by LASCO at SOHO belong to the Kreutz
group of comets and follow trajectories that are tightly clumped in space.
Statistical analysis of 9 years of SOHO observations suggests that the true
apparition rate of these comets is as high as one every other day. Practically
all these comets break up before perihelion passage. Their material is
dissociated and ionized, and subsequently transported away from the Sun as
pickup ions in the solar wind. Their mean mass flux is about $3.1 10^4 g/s.
Since the breakup occurs between 40 and 4 solar radii and the ionization is
almost immediate, the expected location of these ions in the phase space is
close to the location of the inner source of pickup ions. Assuming radial
propagation, the cometary pickups should be observable at Earth between August
and January, with peak probability at the end of September. At Ulysses, they
should be observable approximately between -25 and 40 degrees ecliptic latitude
during the fast latitude scans, the first of which occurred in 1995 and the
second in 2001. The population of cometary pickup ions should be augmented by
about 40% by solar wind protons as a result of charge exchange with the
cometary neutral hydrogen and oxygen atoms and subsequent reionization of the
newly-created Energetic Neutral Atoms, streaming with respect to the solar
wind. In total, the average flux of the pickup ions related to the sungrazing
comets at 1 AU should be about 1.6 10^5 g/s/sr within the detection area (and
null outside it). This value is comparable to the flux of the inner
source-pickup ions.

\\ ( http://arXiv.org/abs/astro-ph/0507065 , 309kb)