Embedded current sheet in the Earth’s magnetotail A.A. Petrukovich, A.V. Artemyev, L.M. Zelenyi Space Research Institute, Moscow R. Nakamura Space Research Institute, Graz Outline 1. Thin embedded sheets are frequently observed 2. How sheets can be quantified ? 3. Embedded sheets in the magnetotail context 4. Implications for substorms
Embedded current sheet in the Earth’s magnetotail A.A. Petrukovich , A.V. Artemyev , L.M. Zelenyi Space Research Institute, Moscow R. Nakamura Space Research Institute, Graz. Outline 1. Thin embedded sheets are frequently observed 2. How sheets can be quantified ? - PowerPoint PPT Presentation
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Embedded current sheet in the Earth’s magnetotail
A.A. Petrukovich, A.V. Artemyev, L.M. Zelenyi Space Research Institute, Moscow
R. NakamuraSpace Research Institute, Graz
Outline
1. Thin embedded sheets are frequently observed
2. How sheets can be quantified ?
3. Embedded sheets in the magnetotail context
4. Implications for substorms
Вложенный токовый слой в хвосте магнитосферы
A.A. Petrukovich, A.V. Artemyev, L.M. Zelenyi Space Research Institute, Moscow
R. NakamuraSpace Research Institute, Graz
1. Тонкие вложенные слои – характерный объект в хвосте
2. Количественное описание вложенных слоев
3. Вложенные слои в контексте плазменного слоя
4. Вложенные слои в контексте суббури
Runov et al., 2006, AnGeo
Embedding: spatial scale of current is smaller than
spatial scale of density
Asano et al 2005, GRL
ISEE-1,2: thin current sheet (with small Bz) is embedded in a thicker plasma sheet
Mitchell et al, 1990, Sergeev et al, 1993
Cluster:
Observations
Embedded sheet profile
Harris sheet: Be and Je: He=Be/Je
Embedded sheet: J0 and B0: H0=B0/J0
Total: Jmax, B0, BeJe<<J0 , Je is not resolved by Cluster
at distances 15-20 Re
Jmax ~J0
Jmax=J0+Je, Je<<J0
B0 Be
Harris profile
Je
Embedded sheet in theory
essentially embedded sheet in thin anisotropic current sheet
model by Zelenyi et al.
B0 is less definite:
embedding is often created just adding background plasmas.
Thin current sheets have typical thickness ~ Larmor radiusin boundary magnetic field B0
Leaving more space for increase of open magnetic flux even when Be=const
3. Total cross-tail current I grows towards Earth and during growth phase, but local current density J is controlled by embeddingwhere and why current density peaks (at onset)?
4. During growth phase embedded sheet intensifies.Flux is removed or plasma is removed to allow larger B0
Sergeev et al, 1993
Implications for substorms
Petrukovich et al, 2007
5. Stability
Burkhart, 1992, suggestedfor an embedded sheet
The growth rate scales asB0/Be *(1- (B0/Be)2)
Zelenyi et al model predicts instabilityzone related with Bz
Implications for substorms
Conclusions
Thin ion scale embedded sheets are frequent especially during substorms
Thickness is controlled by local larmor (as in theory) and plasma properties
Crucial internal parameter is B0, magnetic flux is constant.
Sheet in the magnetotail is controlled by B0/Be and F0/Fe
Quiet sheets have deep embedding B0<< Be (at 15-20 Re) and slowly
evolve with increase of B0 during growth phase
Largest embedding B0~Be requires plasma sheet magnetic flux drop –
after onset or in the distant tail
Plasma sheet is thinner when embedded and less stable.
Embedding should be taken into account in analyses of ion kinetics,global convection, stability, etc.