analysis methods for magnetopause & boundary layer studies
DESCRIPTION
Analysis Methods for Magnetopause & Boundary Layer Studies. Hiroshi Hasegawa ISAS/JAXA In collaboration with B. U. Ö . Sonnerup & W.-L. Teh. Outline. Wavelet analysis (cascade in KH vortices) Reconstruction of 2D structures in a plasma fluid - PowerPoint PPT PresentationTRANSCRIPT
Analysis Methods for Magnetopause & Boundary Layer Studies
Hiroshi Hasegawa
ISAS/JAXA
In collaboration with B. U. Ö. Sonnerup & W.-L. Teh
Outline
• Wavelet analysis (cascade in KH vortices)
• Reconstruction of 2D structures in a plasma fluid
1. Grad-Shafranov (magneto-hydrostatic) reconstruction of magnetic field lines
2. Grad-Shafranov-like reconstruction of streamlines
3. MHD reconstruction (ideal & resistive)
4. Hall-MHD reconstruction
Wavelet analysis can be used to revealto what extent the KH instability grows
Roles of Kelvin-Helmholtz instability• Momentum and/or mass transport (Miura,
1984; Fujimoto & Terasawa, 1994)
• Generation of ULF waves that may accelerate radiation belt electrons (e.g., Elkington, 2006)
• Generation of vortical auroral forms via M-I coupling (e.g., Lui et al., 1989)
Nakamura et al., 2004
Matsumoto & Hoshino, 2004
(Inverse-) cascade
Miura, PoP, 1997
C1 electron
C1 ion
density
Cluster event on 20 Nov 2001 (19 LT)(Hasegawa et al., 2004; Chaston et al., 2007; Foullon et al., 2008)
temperature
velocity
magnetic field
TotalPvv
)(
streamline
Force balance
Total-P perturbation in the vortex
• Dominant-mode period ~200 s: Wavelength ~6 Re.• Power also at ~400 s: Beginning of vortex pairing?
• Wavelet analysis (cascade in vortices)
• Reconstruction of 2D structures in a plasma fluid
1. Grad-Shafranov (magneto-hydrostatic) reconstruction of magnetic field lines
2. Grad-Shafranov-like reconstruction of streamlines
3. MHD reconstruction (ideal & resistive)
4. Hall-MHD reconstruction
Outline
Flux Transfer Event
2D map of an FTE
Time series data to 2D image
X
A 2D structure
X
Y
Z (invariant axis)
Reconstruction frame
YReconstruction plane
Lx = VST_X* T (analyzed interval)
X axis: SC trajectory in the x-y plane
VST_X
VST (VHT)(in the x-z plane)
Integration as a spatial initial value problem
pBj
Assumptions: magneto-hydrostatic (time-independent) structures
PBJVVt
V
)(× ×
)(002
2
2
2
AjAd
Pd
y
A
x
Az
t
)2( 02 zt BpP
zAA
2-D (no spatial gradient in z direction)Grad-Shafranov (GS) equation (e.g., Sturrock, 1994)
1. Grad-Shafranov (GS) reconstruction
Hasegawa et al., 2006
B & p recovered(Hau & Sonnerup, 1999)
V, n, & T recovered(Sonnerup et al., 2006)
Assumptions: MHD, 2D, time-independent, & B along z axis
GS-like equation for the stream function
2. GS-like reconstruction of streamlines
Hasegawa et al., 2007
TotalPvv
)(
Dominant-mode wavelength ~6 Re
Vortex structurefrom GS-like reconstruction of streamlines
C1
C3
• Two vortices within one dominant-mode wavelength.
Breakup of a parent MHD-scale vortex (cascade)?
All MHD parameters recovered, e.g., in the X-line rest frame(Sonnerup & Teh, 2008)
Assumptions: MHD, 2D, time-independent
3. MHD reconstruction (ideal)
isentropic flow
perp. to invariant axis
Eriksson et al., 2009
MHD reconstruction of an FTESeen by THEMIS-A on the MP surface wave
sheath side
LLBL side
Streamline
Field line
All MHD parameters, E, & electron velocity recoveredSonnerup & Teh, 2009
Assumptions: Hall-MHD, 2D, time-independent
4. Hall-MHD reconstruction (ideal)
isentropic flow
perp. to invariant axis0 v
BjPPvv ei
)(
),(0 eisSv ss
0 B
)(nePBjBvE e
Benchmarking (Sonnerup & Teh, in press, 2009)
What could be analyzed?• Behavior of coalescence/breakup (inverse-
cascade/cascade) of KH vortices
• Structural properties (shape, size/width/amplitude, & orientation) of FTEs, KH waves/vortices, magnetic islands in/around the vortices, reconnection jets, & ion diffusion regions.
• Reconnection rate/electric field.
Drawback…
• The reality may rarely be 2D & d/dt~0.