PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
ON A NEW PARAMETER OF SPACE WEATHER AND TOPOLOGY OF
THE EARTH’S MAGNETOSPHERE BASED ON THE FORM FACTOR OF
THE INCOMING SOLAR-WIND PARTICLE-VELOCITY DISTRIBUTION
FUNCTION
V.M. Gubchenko
Institute of Applied Physics, Russian Academy of Science, 603950 Nizhny Novgorod, Russia,
e-mail: ua3thw@appl.sci-nnov.ru
Abstract. We consider the result of theoretical analysis of the 3D global classical Chapman-
Ferraro problem (CFP) where unmagnetized plasma flow inductively interacts with the resting
magnetic dipole. As a result, we obtain the 3D magnetosphere topology with a tail, magnetopause
and the energy/pulse exchange with the SW flow. We take into account the VDF form factor to
describe the incoming hot collisionless plasma flow. The electromagnetic part of the
magnetosphere structures (magnetopause and magnetotail) with large spatial scales of non-MHD
nature are determined by the dimensionless parameter GV of the incoming SW flow. Parameter GV
is the ratio of the large-scale diamagnetic current to the resistive current in the magnetospheric
plasma. This parameter is determined by the kinetic effects of the moving plasma and depends on
the VDF form factor. Calculations of GV in the kinetic CFP are based on simplification of the
nonlinearity by division of plasma particles into a “flyby” group forming the moving medium and
a “trapped” group forming the resting magnetization. Parameter GV that we introduced here is a
new parameter of space weather, which is related to the properties of the kinetic inductive
electromagnetic mode of a hot collisionless moving plasma formed by the “flyby particles”. In
particular we find that the parameter GV governs the topology of the electromagnetic part of the
structure. We obtain the adiabatic/bifurcation transition with return from the resistive state GV 1. This can explain in a new way the effects of the magnetic substorm. Parameter GV is the
ratio of the “momentum anisotropy”, which is determined by a flow of resonant particles, to the
“energy anisotropy” determined by a flow of nonresonant particles. The dimensionless parameter
GV as a function of the form factor of the VDF of the incoming flow can be rewritten via the ratio
of the squared anomalous skin scale to the squared magnetic Debye scale. New dispersion scales
in a plasma induced by the SW flow are responsible for “thick” and “thin” structures.
1. Introduction. Inner and outer parts of the magnetosphere
Space weather is at the beginning of a chain of events connecting the state of space which is filled by
the solar wind plasma with the topological state of the 3d magnetosphere formed by the “outer” and the
“inner” parts. Finally, the chain is connected via polar Birkeland currents with the state of the global
electrojet formed in the Earth’s atmosphere/ionosphere. The electrojet heats the atmosphere, which
inductively interacts with large scale electrical power line systems generating hazardous geomagnetically
induced currents (GIC) (Fig. 1).
Space weather is characterized by a group of dimensionless parameters determined from plasma
theory or observations as functions of the incoming solar wind plasma parameters such as plasma
concentration nw , solar wind velocity v' , thermal velocity of the species α , and interplanetary magnetic field
v
Bw r . We include in the analysis of the space weather a form factor of the particle velocity distribution
function (VDF) f (v)
(Fig. 1, Fig. 2). All these physical parameters are measured by modern space probes.
r
85