Issue A&A Volume 421, Number 1, July I 2004 Page(s) L9 - L12 Section Letters DOI http://dx.doi.org/10.1051/0004-6361:20040169

A&A 421, L9-L12 (2004)
DOI: 10.1051/0004-6361:20040169

Letter

Diamagnetic effects of heliospheric Pick-up ions and magnetic fluxes in the outer heliosphere

H. J. Fahr and K. Scherer

Institut für Astrophysik und Extraterrestrische Forschung der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

(Received 29 March 2004 / Accepted 12 May 2004)

Abstract
For a long time it has been suggested that at larger solar distances the interplanetary magnetic field may not be behaving as predicted by Parker`s Archimedian spiral field model. This phenomenon, partly identified as the "magnetic flux deficit" paradox, appears as deficits in the azimuthal magnetic field components connected with "underwound" magnetic fields, though the pick-up ion decelerated solar wind should rather lead to excesses. Up to now no satisfactory explanation for this phenomenon has been presented. In this paper we study for the first time the diamagnetic effect of pick-up ions which systematically load the solar wind with suprathermal ions at its expansion to larger distances and diamagnetize the plasma. We shall demonstrate that such ions mainly reduce the azimuthal magnetic field component by their diamagnetic action. As we can show the field deficits can easily theoretically be explained by this effect. Also some new light is now shed on the problem of the magnetic field jump to be expected at the termination shock.

Key words: magnetic fields -- plasma

Offprint request: H. J. Fahr, hfahr@astro.uni-bonn.de

© ESO 2004

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