SOLAR EXTREME EVENTS AND GRATE GEOMAGNETIC STORMS

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SOLAR EXTREME EVENTS AND GRATE GEOMAGNETIC
STORMS   E.E. Antonova, M.V. Stepanova   Skobelts
yn Institute of Nuclear Physics Moscow State
University, Moscow, 119992, Russia tel.
7-095-9392488 fax [phone], e-mail
antonova_at_orearm.msk.ru
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• Iyemori and Rao 1996 problem (decay of the Dst
  field of geomagnetic disturbance after substorm
  onset)
• The topology of high latitude magnetosphere
• Formation of plasma pressure profile during
  magnetic storm
• Upper limit of the increase of the inner
  magnetospheric plasma pressure
• Comparison of theory predictions with the results
  of experimental observations

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si12_2000_197_mapped.mpeg
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Difficulties of the concept of contribution of TC
in Dst 1. Problem of pressure balance on the
magnetopause
In the condition of magnetostatic equilibrium
plasma pressure is constant on the current line as
Plasma pressure on the tail current line can not
be larger then dynamic staticmagnetic
pressure in the magnetosheath.
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Limitation on the contribution of TC in Dst
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• CRC is concentrated in the region of
  quasitrapping.
• CRC is mapped on the most part of the auroral
  oval.
• Current lines in CRC are closed inside the
  magnetosphere.
• CRC is a high latitude continuation of ordinary
  ring current (RC).
• It is necessary to introduce energy content of
  CRC in DPC relation.

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Sketch illustrated the mechanisms of the
storm-time redistribution of plasma pressure
transport from the tail
avalanche-like behavior
transport from the ionosphere
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Plasma pressure inside the magnetosphere can be
increased infinitely or definite limitations
exist?
The upper limit of the inner magnetospheric
particle feeling is determined by the stability
of the distribution of the plasma pressure. This
limit exists in spite of the action of different
acceleration and transport mechanisms of plasma
particles.
Kadomtsevs 1963 criterion of the stability of
the azimuthally symmetric distribution of
isotropic plasma pressure in the magnetic trap in
the region of low ? has the form
pltpcrit, where
pp(W), W?dl/B is the flux tube volume,
pcritW?const, ?const equal to 7/4 for the case
of the dipole magnetic field. Plasma tongues
begin to form if pgtpcrit and the magnetic trap
loses part of plasma population.
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The existence of maximal possible plasma pressure
profile and sharp equatorial RC boundary give the
possibility to obtain the dependence of Dst on
the position of plasma pressure maximum
Dessler and Parker 1959 Sckopke 1966
relation has the form
p(L)pex(Lex/L)7
Lin is the position of the internal boundary of
the ring current.
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Tverskoy 1997 relation
Win and Wex are the values of flux tube volume at
the inward and outward boundaries of the ring
current
in the dipole magnetic field
In case of a quasidipole magnetic field accuracy
of the Tverskoy 1997 relation reaches 20 when
the equatorial magnetic field differs from the
dipole one in less than 100
If p(L)pex(Lex/L)7 and
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If Lex 10, Blobe21,4 nTl
Dependence
where Lmax determines also the position of the
peak intensity of fluxes of relativistic
electrons, which appear during storm recovery
phase, was obtained experimentally by Tverskaya
1986, Tverskaya et al. 2003.
L-position of auroral electrojet latitude
coincides with the L-position of the plasma
pressure maximum and L-position of the peak
intensity of fluxes of relativistic electrons
during grate magnetic storm.
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Tverskaya et al. 2003
Analysis of the maximal possible plasma pressure
profile inside the magnetosphere gives
possibility to obtain the natural explanation of
Dst dependence on L-position of the plasma
pressure maximum
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Geomagnetic storm March 1-8
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March 01, 1982 passage, the storm main phase

IGRF model is used. Fitting by the dependences
p?L-s s7.8?1.1. Theory prediction s7
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• CONCLUSIONS
• The contribution of tail current in Dst value is
  limited by the condition of the magnetopause
  pressure balance.
• It is possible to restore the traditional
  interpretation of Dst as the measure of particle
  energy inside the magnetosphere and the
  applicability of DPS relation taking into account
  the existence of CRC - the high latitude
  continuation of the ring current
• The analysis of the formation of the convectively
  equilibrated distribution of the radial plasma
  pressure gives the possibility to explain the
  dependence of maximum of Dst-variation on the
  position of plasma pressure maxima, which is near
  to the position of auroral electrojets.
• Plasma pressure radial profile obtained on the
  basis of low orbiting Aureol satellite confirm
  the theory prediction on the formation of plasma
  pressure distribution during storm time main
  phase corresponding to p?L-7.