firstname.lastname@example.org - last update: 27 November 1998, 1050 UT (RR)
As first proposed by Axford (1962) and Kellogg (1962),
all planetary bodies having either a
magnetosphere or a highly conducting
ionosphere have also a bow
with the deflection of the solar wind around them.
This shock wave develops because the information
needed to deflect the solar wind plasma around the obstacle travels at a velocity
that is less than that of the
solar wind flow. In general three waves are needed:
It is the last, fast magnetosonic wave that creates the bow shock also in front of the Earth 's magnetosphere. The other two waves are present in the
- slow magnetosonic wave
- intermediate wave
- fast magnetosonic wave
In the upstream region, i.e., in front of the bow shock, is the so-called foreshock region. This
region is important for the magnetospheric physics because of a wealth of
wave activity that can
be found inside of it, and because it creates, together with the most typical IMF direction close to the inner planets, a strong dusk-dawn asymmetry
around the magnetopause (upstream foreshock in the dawn side is much larger than the downstream
foreshock in the dusk side).
The waves in the foreshock region are coming from several sources:
For example, the compressional ULF waves observed in the foreshocks of
several planets are due to backstreaming ions. The frequency of these waves is controlled by the strength
of the IMF, and in Earth 's case they are labelled as Pc 3 pulsations with periods about 30-40 s.
- Some of the waves are generated in the bow shock and propagate upstream.
- Other waves are generated by electrons and ions accelerated at the bow shock and reflected
back into the solar wind or leaked from the magnetosheath back upstream. These backstreaming
particles generate waves through various instabilities and these waves are then convected with the
solar wind flow toward the shock.
- Still other waves originate as newly created ions scatter and thermalize both in the extended
coronas surrounding comets and in the exospheres of unmagnetized planets.
- Axford, W. I., The interaction between the solar wind and the earth's
magnetosphere, J. Geophys. Res., 67, 3791, 1962.
- Kellogg, P. J., Flow of plasma around the earth, J. Geophys. Res., 67,
- Cairns, I. H., and C. L. Grabbe, Towards an
MHD theory for the standoff distance of Earth's bow shock,
Geophys. Res. Lett., 21, 2781-2784, 1994.
- Farris, M. H., and C. T. Russell,
Determining the standoff distance of the bow shock: Mach
number dependence and use of models, J. Geophys. Res.,
99, 17,681-17,689, 1994.
- Farris, M. H., C. T. Russell, R. J.
Fitzenreiter, and K.W. Ogilvie, The subcritical, quasi-
parallel, switch-on shock, Geophys. Res. Lett., 21,
- Spreiter, J. R., A. L. Summers, and A. Y.
Alksne, Hydromagnetic flow around the magnetosphere,
Planet. Space Sci., 14, 223-253, 1966.
- Spreiter, J. R., and S. S. Stahara, The
location of planetary bow shocks: A critical overview of
- Zhuang, H. C., and C. T. Russell, An
analytic treatment of the structure of the bow shock and
magnetosheath, J. Geophys. Res., 86, 2191-2205,