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Astron. Astrophys. 316, 304-312 (1996)

Latitudinal dependence of the radial IMF component- interplanetary imprint

S.T. Suess1, E.J. Smith2, J. Phillips3, B.E. Goldstein2, and S. Nerney4

1 NASA Marshall Space Flight Center, MS ES82, Huntsville, AL 35812, USA
2 MS 169-506, Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109-8099, USA
3 MS D438, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
4 1570 Granville Pike, Ohio University, Lancaster, OH 43130, USA

Received 15 February 1996 / Accepted 14 June 1996

Abstract. Ulysses measurements have confirmed that there is no significant gradient with respect to heliomagnetic latitude in the radial component, img1.gif , of the interplanetary magnetic field. There are two processes responsible for this observation. In the corona, the plasma img2.gif is img3.gif , except directly above streamers, so both longitudinal and latitudinal (meridional) gradients in field strength will relax, due to the transverse magnetic pressure gradient force, as the solar wind carries magnetic flux away from the Sun. This happens so quickly that the field is essentially uniform by img4.gif . Beyond img5.gif , img6.gif and it is possible for a meridional thermal pressure gradient to redistribute magnetic flux - an effect apparently absent in Ulysses and earlier ICE and IMP data. We discuss this second effect here, showing that its absence is mainly due to the perpendicular part of the anisotropic thermal pressure gradient in the interplanetary medium being too small to drive significant meridional transport between the Sun and img7.gif 4 AU. This is done using a linear analytic estimate of meridional transport. The first effect was discussed in an earlier paper.

Key words: Sun; corona; solar wind; magnetic field

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Last change: December 30, 1996
© European Southern Observatory (ESO) 1996