André Balogh's Web Pages
The Heliospheric Magnetic Field
The heliospheric magnetic field (HMF) is an important component of the
heliospheric medium. It has been the subject of extensive studies for the
past thirty five years. There is a very large observational data base,
mostly from the vantage point of the ecliptic plane, but now also from
the solar polar regions, from the Ulysses mission. This review aims to
present its most important large scale characteristics. A key to understand
the HMF is to understand the source functions of the solar wind and magnetic
fields close to the sun. The development of new modelling techniques for
determining the extent and geometry of the open magnetic field regions
in the corona, the sources of the solar wind and the HMF has provided a
new insight into the variability of the source functions. These are now
reasonably well understood for the state of the corona near solar minimum.
The HMF at low-to-medium heliolatitudes is dominated, near solar minimum,
by the Corotating Interaction Regions (CIRs) which arise from the interaction
of alternating slow and fast solar wind streams, and which, in turn, interact
in the outer heliosphere to form the large scale Merged Interaction Regions.
The radial component of the HMF is independent of heliolatitude; the average
direction is well organised by the Parker geometry, but with wide distributions
around the mean, due, at high latitudes, to the presence of large amplitude,
Alfvénic fluctuations. The HMF at solar maximum is less well understood,
due in part to the complexity of the solar source functions, and partly
to the lack of three dimensional observations which Ulysses is planned
to remedy at the next solar maximum. It is suggested that the in-ecliptic
conditions in the HMF, largely determined by the dynamics of transients
(Coronal Mass Ejections) may also be found at high latitudes, due to the
wide latitude distribution of the CMEs.
Balogh, A., The heliospheric magnetic field, Space Sci. Rev., 78, 15-28,
Balogh, A., Magnetic fields in the inner heliosphere, Space Sci. Rev.,
83, 93-104, 1998
Balogh, A., and Forsyth, R.J., The results of the Ulysses mission: A
survey of the heliosphere in three dimensions, in Proc. "A Crossroads for
European Solar and Heliospheric Physics", ESA SP-417, p.45-54, 1998.
Balogh, A. and Riley, P., Overview of heliospheric shocks, in Cosmic
Winds and the Heliosphere, edited by J.R. Jokipii and C.P. Sonett, University
of Arizona Press, Tucson, 359-387, 1997.
For further information, go to Ulysses
André Balogh 18 December