Transcript Savin

|B| on MHD model MP
Bin
Bout
|B|
small
large
MP from [Maynard, 2003] -last closed field lines for the northern axis of dipole,
deflected by 23 degrees anti-sunward (colored by - |B|)
Energy transformation in MSH
Magnetosheath (MSH)
niTi + niMi/2(<Vi>2+(<dVi2>) + |B|2/8p
{1} >
{2}
{3}
Low latitude boundary layer (LLBL)
niTi + niMi/2(<Vi>2+(<dVi2>) + |B|2/8p
{1} >
{2}
<< {3}
macro
RECONNECTION
niMiVA2/2
micro
RECONNECTION
Turbulent Boundary Layer (TBL) and outer cusp
niTi + niMi/2(<Vi>2+(<dVi2>)+|B|2/8p +|dB|2/8p
{1} ~
{2}
>>
{3} <
{4}
MSH
MP
BIMF
Bin
Fx ,
u
magnetosphere
Fz
Relation of viscous gyro-stress to that of Maxwell:
~ const
u/B 3
0
where ru- directed ion gyroradius, and L – the MP width. For b ~ 1-10
near MP the viscous gyro-stress is of the order of that of Maxwell. Velocity
u,
rises downstream of the subsolar point, magnetic field B0 - has the
minimun over cusp, i.e. the gyroviscous interaction is most significant at the outer
border of the cusp, that results in the magnetic flux diffusion
(being equivalent to the microreconnection)
Cluster OT crossing on 2002.02.13
theta
L ~ RE
En
magnetosphere
OT
MSH
dipole tilt~14 d
phi
energetic ions
|B|
ions
energetic electrons
Surface charge decelerates plasma flow along normal
electrons
and accelerates
it along magnetopause tailward
• Quicklook for OT
encounterMSH
(09:00-09:30
MP
cusp
Plasma jet interaction with MP
niMiVi2/2 < k (Bmax)2 /m0
[k ~ (0.5-1) – geometric factor]
niMiVi2/2 > k (Bmax)2 /m0
The plasma jets, accelerated sunward, often are regarded as proof for a
macroreconnection; while every jet, accelerated in MSH should be reflected by a
magnetic barrier for
niMiVi2 < (Bmax)2/m0 in the absence of effective
dissipation (that is well known in laboratory plasma physics)
Resonance interaction of ions with
electrostatic cyclotron waves
Diffusion across the magnetic field can
be due to resonance interaction of ions
with electrostatic cyclotron waves
et al.,
Part of the time, when ions are in resonance with the wave
- perpendicular ion energy
s that can provide the particle flow
across the southern and northern TBL, which is large
enough i.e. for populating of the dayside magnetosphere
Measurements of ioncyclotron waves on Prognoz-8,
10, Interball-1 in the turbulent
boundary layer (TBL) over
polar cusps. Maximums are at
the proton-cyclotron
frequency.
Shown also are the data from
HEOS-2 (E=1/c[VxB]),
and from the low-latitude MP
AMPTE/IRM and ISEE-1.
Estimation of the diffusion
coefficient due to electrostatic
ion-cyclotron waves
demonstrates that the dayside
magnetosphere can be
populated by the solar plasma
through the turbulent
boundary layer
Plasma percolation via the
structured magnetospheric
boundary
Percolation is able to provide the plasma inflow comparable with
that due to electrostatic ion cyclotron waves [Galeev et al.,
1985, Kuznetsova & Zelenyi, 1990] :
Dp~0.66(dB/B0)ri2 Wi ~const/B02 ~(5-10)109 m2/s
-----------------------------------------------------------------------------------------------------------------
One can get a similar estimate for the kinetic Alfven
waves (KAW in [Hultquist et al., ISSI, 1999, p. 399]):
DKAW~k^2ri2Te/Ti VA/k||(dB/B0)2~
~ const/B03 ~ 1010 m2/s
Interpretation of
the early data
from Prognoz-8
in terms of the
surface charge at
MP
Ion flux
magnetosphere
re ~
MSH
[Vaisberg, Galeev, Zelenyi, Zastenker, Omel’chenko, Klimov И.,
Savin et al., Cosmic Researches, 21, p. 57-63, (1983)]
Mass and momentum
transfer across MP of
finite-gyroradius ion
scale
~90 km  ri at 800 eV
Cluster 1, February 13,
2001.
(a) ion flux ‘nVix’, blue
lines – full CIS energy
range), black – partial ion
flux for > 300 eV, red – for
> 1keV ions;
(b)
the same for ‘nViy’; (c) the
same for ‘nViz’; (d): ion
density ni (blue), partial
ion density for energies >
300 eV (black) and that of
> 1 keV (red).
~ along MP
normal
dominant flow
along MP
Cluster 1, February 13, 2001
Thin current (TCS) sheet at MP
(~ 90 km) is transparent for ions
with larger gyroradius, which
transfer both parallel and
perpendicular momentum and
acquire the cross-current potential.
The TCS is driven by the Hall
current, generated by a part of the
surface charge current at the TCS
dF ~300 V
1
Mechanisms for acceleration of
plasma jets
Besides macroreconnection of anti-parallel magnetic
fields (where the magnetic stress can accelerate the
plasma till niMiViA2 ~ B2/8p), there are experimental
evidences for:
-Fermi-type acceleration by moving (relative the
incident flow) boundary of outer boundary layer;
- acceleration at similar boundaries by inertial
(polarization) drift
.
Magneto
sonic jet
-Acceleration in the
perpendicular nonuniform electric field
by the inertial drift
-Fermi-type
acceleration by a
moving boundary;
Bi-coherence & the
energy source for
the magnetosonic
jet
Fl + Fk = F
mHz
Inertial drift
Vd(1) = 1/(M wH2) dF/dt = Ze/(M wH2) dE/dt
d Wkin ~ d(nM(Vd(0))2/2) ~ 30 keV/сm3 (28 measured)
Vd(0) = с[ExB] ; J ~ e2/(MpwHp2)dE/dt
Electric field
in the MSH
flow frame
Cherenkov nonlinear resonance
1.4 +3 mHz = fl + f k = (kV)/2p ~ 4.4 mHz
L = |V| /( fl + fk ) ~ 5 RE
Maser-like ?
Comparison of the TBL dynamics and
model Lorentz system in the state of intermitten
chaos
In the jets kinetic energy Wkin rises from ~ 5.5 to 16.5 keV/cm3
For a reconnection acceleration till Alfvenic speed VA it is foreseen
WkA ~ ni VA2 /2 ~ const |B|2
that requires magnetic field of 66 nT
(120 nT inside MP if averaged with MSH)
[Merka,
Safrankova,
Nemecek,
Fedorov,
Borodkova,
Savin,
Adv. Space
Res., 25,
No. 7/8,
pp. 14251434,
(2000)]
Ms~2
magnetosphere
Ms~1.2
MSH
[ Shevyrev and
Zastenker, 2002 ]
23/04-1998,
MHD model,
magnetic field
at 22:30 UT;
blue – Earth
field; red SW; yellow reconnected;
right bottom
slide – plasma
density;
I- Interball-1,
G- Geotail;
P- Polar
Reconnection
X
Reconnection
X
Reconnection
X
The jet is also
seen by
POLAR
(~ 4 Re apart
in TBL closer
to MP)
BS
MP
Conclusions
- Penetration of
solar plasma into magnetosphere correlate with the low magnitude of
magnetic field (|B|) (e.g. with outer cusp and antiparallel magnetic fields at MP).
-A mechanism for the transport in this situation is the ‘primary’ reconnection, which
releases the energy stored in the magnetic field, but it depends on the IMF and can
hardly account for the permanent presence of cusp and low latitude boundary layer.
Instead, we outline the ‘secondary’ small-scale time-dependent reconnection.
Other mechanisms, which maximize the transport with falling |B|:
- finite-gyroradius effects (including gyro-viscosity and charged current sheets of finitegyroradius scale,
-filamentary penetrated plasma (including jets, accelerated by inertial drift in nonuniform electric fields),
-diffusion and percolation,
In minimum |B| over cusps and ‘sash’ both percolation and diffusion due to kinetic Alfven waves
provide diffusion coefficients ~ (5-10) 109 m2/s, that is enough for populating of dayside
boundary layers. Another mechanism with comparable effectiveness is electrostatic ion-cyclotron
resonance. While the cyclotron waves measured in the minimum |B| over cusps on Prognoz-8, 10
and Interball-1 have characteristic amplitude of several mV/m, the sharp dependence of the
diffusion on |B| provides the diffusion ~ that of the percolation.