С.П. Савин, Л.М. Зеленый, Е.А. Кузнецов

(ИКИ РАН)

О взаимосвязи 2 фундаментальных явлений:

концентрированных плазменных струй и альвеновского коллапса

 

From: EGU06-A-00787

Kartalev, M.; Savin, S. ; Dobreva, P.; Amata, E.; Shevyrev, N.From: EGU06-A-00787

Kartalev, M.; Savin, S. ; Dobreva, P.; Amata, E.; Shevyrev, N.From: EGU06-A-00787

Kartalev, M.; Savin, S. ; Dobreva, P.; Amata, E.; Shevyrev, N.

February 13, 2001, CLUSTER

BS

MP

Jets in SW?

- (a) Cluster 3, Wk – ram

pressure, Wt –ion thermal

pressure, Wb– magnetic

pressure, lagged Wk in SW

(ACE);

- (b) Cluster 3, angles sin-1(Vz/|V|), sin-1(Vy/|V|),

GDCF – model prediction; Insert: jet directions in XZ plane; V=(-26;15;7) km/s – GSE velocity of the outermost jet as a whole; V=(-117;-37;31) km/s – velocity of the innermost jet. Dashed lines – the most deflected jets at 15.03 UT and at 14.97 UT.;

- (c) comparison of Wk ,

[keV/cm3], ion density N, [1/cm3], and ion velocity (|V|/20, [(km/s)/20]), Cluster 3;

- (d) the GSE electric component Ey from 4 Clusters

Jet going to SW?

Jet inside MP?

decay?

Deflected jets with compara-ble input from “Ni” and “V2” as a probable result of the MSH flow decay GDCF angle V_XY

From magnetic disturbance at

leading jet front

(-196;-230;90) km/s (-185;106;-219)km/s

Cluster 3, February 13, 2001

630

Jet width ~ 200 km ~ (2-3) i

A summary plot of the Cluster data during the cusp interval 05:00 - 10:00 UT on March 17, 2001. The panels show, from top to bottom, the HIA ion omni-directional energy fluxes, the HIA ion density, velocity and temperature, the FGM magnetic field, all from spacecraft 1, and the lagged IMF from the ACE spacecraft. (Figure provided by B. Lavraud)

[ISSI book: CLUSTER AT THE MAGNETOSPHERIC CUSPS]

GSE, 6-12 UT

IMFBz>0

 

(a) Comparison of |B| on 4 SC (colors for SC 1-4: black, blue, violet, red) on March 17, 2001 associated with the MP jets (see Fig. 1);

(b) Ram pressure Wk from

3 SC and that of SC1 at 11.995-12.075 UT (‘source jet’, dashed line, lagged);

(c) Cluster 1: Wk (black),

Wt – thermal ion

pressure (blue), Wb –

magnetic pressure (violet) and Wk in SW

from Wind (magenta);

(d) Ey from 4 Clusters.

niMiVi2/2 < k (Bmax)2 /0

[k ~ (0.5-1) – geometric factor]

niMiVi2/2 > k (Bmax)2 /0

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)2/0 in the absence of effective

dissipation (that is well known in laboratory plasma physics)

Plasma jet interaction with MP

MSH

magnetosphere

Ms~2

Ms~1.2Wk_SW

IMF Bz<0

While the low-latitude

reconnection for the IMF Bz<0 can

account for the jet ram pressure,

it can’t do so for the jet direction as all background energy densities on the jets’ paths are negligible versus the jet ram

pressure and magnetic field gradient force is opposite to that

required for the jet rotation

 

Interball-1, June 19, 1998. (a) Tailward ion flux nVx

from Interball-1, that of Geotail in SW and gasdynamic proxy (‘GDCF’); Insert: jet directions in XZ GSE plane relative to average MP and BS;

[ Shevyrev and Zastenker, 2002 ]

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. 1425-

1434, (2000)]

Cluster1, February 2, 2003Cluster3, February 2, 2003

WkWb

Wt

[eV/cc]

UTMP MP

Wb,t,k- cross-correlation < 0.35

Supersonic flow

Magnetic barrier with ~sonic flow

stagnant turbulent boundary layer

(closer to the Earth)

cusp

‘plasma ball’

• For collapse at ion gyroradius scale we estimate equilibrium from

We estimate DH from characteristic shift by squared ion gyroradius i

2 at ion gyroperiod for the gradient scale ~ ion gyroradius

The Alfvenic collapse would stop at the scales of ~ ion gyroradius (i.e. at the MHD validity breaking), when magnetic field diffusion due to the finite ion gyroradius effects can neutralize the field growth

TiVu

• Interball-1 MSH/stagnation region border encounter on April 21, 1996.

• Comparison with switch-off slow shock [Karimabadi et al., 1995] displays strong magnetic barrier with pressure of the order of the MSH ram pressure. Inside ‘diamagnetic bubble’ ion temperature balances the external pressure

Locations in Geocentric Solar Magnetospheric

(GSM) coordinates of 208 magnetic barriers detected in Interball-1

magnetic field data between 1995 and 2000.

Reflected sunward jets (IMF Bz<0) Spiraling down the cusp throat (370

to B)

(65;-215;-82)km/s GSE

(-263;-127;161)km/s

eV/cc eV/cc

reflected from MP jet, spiralling downcusp

reflected from cusp, spiralling upward

Alfven wave filamentation: Self-focusing instability

[T. Passot et P.L. Sulem, Landau fluids for space plasmas]

Time traces (in microseconds) in turbulent boundary layer in tokamak T-10, r=34 cm,

(a) electric field Ep, [Volts]

(a) (b) plasma density fluctuations n(t) [1/cm3]

(b) particle flux due to ExB drift across magnetic field [1/(cm2 sec)]

В ы в о д ы

«Плазменные струи», редко объясняемые пересоединением магнитных силовых линий, регулярно наблюдаются в магнитослое между ударной

волной и магнитопаузой, их длительность ~ десятков секунд, рост их динамического давления на фоне невозмущенного солнечного ветра

- до 2-3 раз. - Примерно 20% струй пронизывают высокоширотную магнитопаузу,

вызывая вторичное пересоединение и пролетая в межпланетное пространство через плазменную мантию или низкоширотный погранслой.

- Некоторые их них отражаются геомагнитным полем независимо от межпланетного магнитного поля.

- Одной из функций струй в магнитослое является «сброс» вниз по потоку до 40% импульса как в стационарном случае, так и при динамическом росте

или падении внешнего динамического давления. При этом локальный баланс энергии поддерживается квази-покоящимися электромагнитными

структурами в магнитослое.

- Одним из источников ускорения струй является Альвеновский коллапс, в котором взрывообразный рост магнитного поля опрокидывающихся

силовых линий вытесняет плазму вдоль силовых линийвытесняет плазму вдоль силовых линий