Are the sungrazing comets the inner source of pickup ions and energetic neutral atoms?

Abstract

We present arguments that at least part of the inner source of pickup ions in the solar wind might be the material released by sungrazing comets. Based on a statistical analysis of sungrazing comets detected over almost eight years of LASCO operation (1996 -- September 09 2004) an overwhelming majority of the observed sungrazers belong to the Kreutz group of comets, follows tightly clumped orbits and break up at $\sim 40 - 4$ solar radii in a well defined region of space. The material released from these comets could be (after ionization) an important portion of the inner source of pickup ions (PUIs), as the local mass flux of the inner source and cometary PUIs seem comparable. We indicate time intervals during the year when the cometary PUIs could be observed from a spacecraft on the Earth's orbit (from the end of July until the end of the year) and show three time intervals when they should be observable by Ulysses (from its launch time until the end of 1990, from the end of November 1994 until mid-May 1995 and from February 2001 until the end of July, 2001). We argue that the PUIs from the inner source should include both singly and doubly charged ions and that this cometary hypothesis alleviates some difficulties (in particular, the issue of hydrogen deficit) in the interpretation of the inner source as solar wind neutralized on dust grains close to the Sun.