PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
related to the formation of elongated electromagnetic magnetotail/streamer structures provided by the vector
potential A r field describing transversal inductive fields. The definition of Mach number based on dispersive
properties of the sonic waves in the flow, and these properties are not so sensitive to the choice between
MHD and kinetic approaches to the plasma modeling. It is weak dependence of the acoustic wave dispersion
properties ω = ( k)
k is chosen among ideal M HD, nonideal MHD and kinetics. On the basis of the
Mach
c s
2 1/
2
number we obtain the aerodynamic coefficient cx = δ /( M −1)
related with a form factor δ ( r0
) of the
magnetization (X )
r r
μ with a scale r 0 , which, along with dynamic pressure, determines the aerodynamic drag
force on the magnetosphere due to sonic wave radiation in the supersonic regime M > 1.
The electromagnetic part of the magnetosphere/streamer is determined by the dimensionless
parameter G V which is a new parameter for the incoming flow characteristic, considered further as a space
weather parameter and related to excitation by a flow of transversal e.m. vector potential A r fields. This
parameter characterizes the topological state of the magnetosphere with two basic elements:
magnetopause/mantle and magnetotail with neu sheet inside as well as the state of the solar
streamer with the ray structures. The parameter V ≈ j d / jr
which we call a “quality” characterize ratio of
densities of the large-scale dia gnetic current d j to the resistive current tral current
G
ma
j r components excited in plasma
r r
flow by the magnetization μ (X ) . We note that in a common case, electromagnetic properties of the flow are
characterized by the tensor of the dielectric permittivity ij ( , k )
r
ε ω . Parameter
G V describes the particular
rr
electromagnetic properties of the solar wind flow calculated for ω = kv'
as app lied to the stationary
solution
of the CFP. Thus, G V does
n metrical form factor
of the (X )
r
2 2 r
the geo ~ exp( X / 2r0
) μ
r
not depend o
−
defined by the scale r 0 .
We get the “resistive” state solar wind when G V > 1 where the
magnetotail/streamer is absent.
Parameter G V as a dissipative parameter is much more sensitive to the choice between the nonideal
MHD model, where dissipation is postulated, and the kinetic
plasma model where dissipation is self-
−1
consistent with VDF form. In the ideal MHD, G V = 0 and the magnetosphere/streamer
formed by
r
tangential discontinuities provided by diamagnetic current of density jd
. Inst ead of G V , we can operate
2 −1/
2
with the “loss” angle GV
= ctgγ
V or with “reactivity” angle ϕ V ensuring cosϕV
= ( 1+
GV
) for the
magnetosphere and streamer equivalent ele ctro-technical circuits (Fig.3).
On the other hand the parameter Rem = r 0 / rskin
. is the magnetic Reynolds number defined by the
r r
spatial scale r 0 of magnetization μ (X ) and a skin scale r skin which is defined by the resistive properties of
the plasma.
The parameter characterizes the role of the flow conductivity and defines the ideal conductor
Re m → ∞ and nonconductive
media Rem → 0 in the limiting cases. Another parameter is the magnetic
Debye number D M = r0
/ rDM
, which characterizes the role of diamagnetic currents around magnetization
r r
μ (X ) . The quantity r DM is the diamagnetic scale related to the plasma pressure anisotropy, and in
particular, to the dynamical pressure of the flow and defines diamagnetic currents thickness relative to r 0 in
2 2 2 2
the moving media. It can be shown that G V ≈ jd
/ jr
= Rem/
DM
= rskin
/ rDM
is independent of the r 0 value
and is characteristic of the incoming flow only. Determination
of the parameter G V from the CFP solution
strongly depends on the physical model of plasma flow.
87