magnetopause surface waves: a themis case...
TRANSCRIPT
F. Plaschke, V. Angelopoulos
IGPP, UCLA
March 23, 2012 - THEMIS SWT meeting, UCLA
Magnetopause surface waves: A THEMIS case
compared to MHD theory
MP surface waves: A THEMIS case compared to MHD theory
THEMIS configuration
3
MP
THEMIS
MP
THA THD THE
flow
wavewave
wave
MP
cross-correlationphase speed
comparison with MHD
wave formand structure
MP surface waves: A THEMIS case compared to MHD theory
MHD theory
4
evanescentwaves
MP
k2N =!2
V 2A + C2
S⌦2/!2
� k2t
⌦2 = !2 � (~k · ~VA)2
ptot,a = p
tot,b
⇠N,a = ⇠N,b
!a = !b � ~kt · ~v0,a
kN,a
⇢0,a⌦2a
=kN,b
⇢0,b⌦2b
vph =!b
kt=
⇢0,a(~nkt · ~v0,a)⇢0,a + ⇢0,b
±
s⇢20,a(~nkt · ~v0,a)2
(⇢0,a + ⇢0,b)2+
⇢0,a(~nkt · ~VA,a)2
⇢0,a + ⇢0,b+
⇢0,b(~nkt · ~VA,b)2
⇢0,a + ⇢0,b� ⇢0,a(~nkt · ~v0,a)2
⇢0,a + ⇢0,b
boundary conditions
magnetosonic dispersion relation
doppler shift
surface wave dispersion relation
solution for incompressible plasmas
MP surface waves: A THEMIS case compared to MHD theory
Comparison with MHD theory
5
PDL
LLBL
magnetosphere
magnetosheath ✔✘
parameters velocity wave modes
✘ ✔slow
stability
KHI✘
✔
wave
sheath
results of comparison
kN,a
⇢0,a⌦2a
=kN,b
⇢0,b⌦2b
surface wave dispersion relation
parameter study:balance sides of dispersion relation
magnetosheath and magnetospheric measurementspossible imaginary frequency component
MP surface waves: A THEMIS case compared to MHD theory
Wave form - plasma velocity
6
LLBL
PDL PDL
LLBL
wave
PDL
plasma flow in wave‘s frame of reference
sheath
LLBL
wave
wave
MP surface waves: A THEMIS case compared to MHD theory
Wave form - plasma velocity
6
LLBL
PDL PDL
LLBL
wave
PDL
plasma flow in wave‘s frame of reference
sheath
LLBL
wave
acceleration: Chen and Kivelson (1993)
wave
MP surface waves: A THEMIS case compared to MHD theory
Wave form - plasma velocity
6
LLBL
PDL PDL
LLBL
wave
PDL
plasma flow in wave‘s frame of reference
sheath
LLBL
wave
deceleration?
wave
MP surface waves: A THEMIS case compared to MHD theory
Phase vs. magnetosheath velocity
7
vph =!b
kt=
⇢0,a(~nkt · ~v0,a)⇢0,a + ⇢0,b
±
s⇢20,a(~nkt · ~v0,a)2
(⇢0,a + ⇢0,b)2+
⇢0,a(~nkt · ~VA,a)2
⇢0,a + ⇢0,b+
⇢0,b(~nkt · ~VA,b)2
⇢0,a + ⇢0,b� ⇢0,a(~nkt · ~v0,a)2
⇢0,a + ⇢0,b
solution for incompressible plasmas
MP surface waves: A THEMIS case compared to MHD theory
Phase vs. magnetosheath velocity
7
magnetosheath velocity
phas
e ve
loci
ty
KHI
vph =!b
kt=
⇢0,a(~nkt · ~v0,a)⇢0,a + ⇢0,b
±
s⇢20,a(~nkt · ~v0,a)2
(⇢0,a + ⇢0,b)2+
⇢0,a(~nkt · ~VA,a)2
⇢0,a + ⇢0,b+
⇢0,b(~nkt · ~VA,b)2
⇢0,a + ⇢0,b� ⇢0,a(~nkt · ~v0,a)2
⇢0,a + ⇢0,b
solution for incompressible plasmas
MP surface waves: A THEMIS case compared to MHD theory
Phase vs. magnetosheath velocity
7
magnetosheath velocity
phas
e ve
loci
ty
KHI
observed wave
vph =!b
kt=
⇢0,a(~nkt · ~v0,a)⇢0,a + ⇢0,b
±
s⇢20,a(~nkt · ~v0,a)2
(⇢0,a + ⇢0,b)2+
⇢0,a(~nkt · ~VA,a)2
⇢0,a + ⇢0,b+
⇢0,b(~nkt · ~VA,b)2
⇢0,a + ⇢0,b� ⇢0,a(~nkt · ~v0,a)2
⇢0,a + ⇢0,b
solution for incompressible plasmas