Post on 25-Jan-2016
description
Wave-particle interactions in the magnetosheath/magnetosphere
boundary layers
Alexandra Teste, G. K. Parks, M. Wilber, N. Lin
SSL, University of California, Berkeley
17th Cluster Workshop
Uppsala Universitet, Sweden
2nd Waves session
Thursday, May 14, 2009
Acknowledgement to D. Fontaine for providing access to the electron data and to Y. Voitenko for discussing the wave data
• BL = Msheath population accelerated ~ 300 eV & heated ~ 900 eV
Magnetospheric event within the magnetosheath: Magnetospheric event within the magnetosheath: May 2, 2003May 2, 2003
• Cluster 3 at ~ (6.6, -5.8, 11.1)gse Re• southward turning of IMF
A. Teste 17th Cluster Workshop May 14, 2009
01:30 01:32 01:34 01:36 01:38 01:40 01:42
Ene
rgy
(eV
)
102
103
104
101
ions
e- (anti-//)
Bx
ByBz
|B|
ExEy
Ez
Efie
ld (
mV
/m)
-5
5
10
0
Bfie
ld (
nT)
0
40
-40
Ene
rgy
(eV
)
102
103
104
ergs
/(cm
².s.
sr.e
V)
Xgse (Re)20 10 0 -10 -20
Zgs
e (R
e) 10
20
30
0
-10
-20
-30
Ene
rgy
(eV
)
e- (//)
e- (anti-//)
e- ()
ergs
/(m
².s.
sr.e
V)
Msheath
Msphere
outer inner
diffusion across inner & outer BL
direction
Internal structure and characteristics of the boundary layer Internal structure and characteristics of the boundary layer (BL)(BL)
diffusion across inner BL only
// & anti// directions
Msheath
Msphere
outer inner
Our study: characterization of these 2 regions from particle and wave points of view
Robert et al., 2005; Fear et al., 2005 & Owen et al., 2008: FA ct-streaming BL pop. & inner/outer BL
BL
A. Teste 17th Cluster Workshop May 14, 2009
-10 -5 0 5 10Velocity (1.e4 km/s)
f (s3/m6)
10-18
10-14
10-22iso. diff. msph. e-
-10 -5 0 5 10Velocity (1.e4 km/s)
diff. msph. e-
10-14
10-18
10-22
f (s3/m6)
//, anti//MsheathMsphere
Ene
rgy
(eV
)
e- (//)
e- (anti-//)
e- ()
01:30 01:32 01:34 01:36 01:38 01:40 01:42
ergs
/(m
².s.
sr.e
V)
01:30 01:32 01:34 01:36 01:38 01:40 01:42
High E: 1500-9000 eV
• Typical ES waves (Anderson et al., 1982):
Waves in the magnetospheric domainWaves in the magnetospheric domain
A. Teste 17th Cluster Workshop May 14, 2009
Pitc
h an
gle
(°)
cnts
/sec
101
102
103
104
100
10
1000 Mag.
Fre
quen
cy (
Hz)
V²/
(m².
Hz)
nT²/
Hz
Elec.
- Upper hybrid waves: f~fuH~6.6 kHz: conic-like e-
- ES e- cyclotron waves (f~fce ~1.1 kHz), 1st harmo. f ~2.2 kHz, Bernstein (n=2-5): 2 tenuous loss cones
• Magnetospheric e- with peaks at intermediate angles conic-like distributions
Ene
rgy
(eV
)
e- (//)
e- (anti-//)
e- ()
01:30 01:32 01:34 01:36 01:38 01:40 01:42
ergs
/(m
².s.
sr.e
V)
High E: 1500-9000 eV
• Typical EM waves (Anderson et al., 1982):
Waves in the magnetospheric domainWaves in the magnetospheric domain
A. Teste 17th Cluster Workshop May 14, 2009
101
102
103
104
100
10
1000 Mag.
Fre
quen
cy (
Hz)
V²/
(m².
Hz)
nT²/
Hz
Elec.
- EM e- cyclotron (EMEC) waves: f~400 Hz<fce, right-handed, (k,B)~10°-30°: conic-like e-
with broadband ES spikes
Ene
rgy
(eV
)
e- (//)
e- (anti-//)
e- ()
01:30 01:32 01:34 01:36 01:38 01:40 01:42
ergs
/(m
².s.
sr.e
V)
EMEC waves: f < fce, RH polarized, // to B
nT²/
Hz
Outer BL: anisotropic diffusion of Mspheric pop. EMEC waves
A. Teste 17th Cluster Workshop May 14, 2009
Waves in the boundary layerWaves in the boundary layer
100
10
1000 Mag.
V²/
(m².
Hz)
101
102
103
Fre
quen
cy (
Hz)
104Elec.
Fre
q. (
Hz)
-0.2
T/T
// -1
0.0
0.4
0.8
B (
nT²/
Hz)
10-11
10-9
10-7
10-5
• ~ 710 Hz• ce ~ 1.4 kHz
EMEC waves (outer BL)
• (k,B) ~10°- 30°
with N = 0 and v 3.2 keV = diffused Mspheric e-
ceNvk ////
01:30 01:32 01:34 01:36 01:38 01:40 01:42
1.2 < Ee- < 15 keV
at ~ 700 Hz
Ene
rgy
(eV
)e- (anti-//)
e- ()
ergs
/(m
².s.
sr.e
V)
Msheath
Msphere
outer inner
diffusion across inner & outer BL
direction
SUMMARY SKETCHSUMMARY SKETCH
diffusion across inner BL only
// & anti// directions
Msheath
Msphere
outer inner
BL
A. Teste 17th Cluster Workshop May 14, 2009
-10 -5 0 5 10Velocity (1.e4 km/s)
f (s3/m6)
iso. diff. msph. e-
-10 -5 0 5 10Velocity (1.e4 km/s)
diff. msph. e-
10-14
10-18
10-22
f (s3/m6) //, anti//MsheathMsphere
-10 -5 0 5 10Velocity (1.e4 km/s)
10-14
10-18
10-22
f (s3/m6)
-10 -5 0 5 10Velocity (1.e4 km/s)
10-14
10-18
10-22
f (s3/m6)
EM e- cycl. waves
Conclusion:Conclusion:
The boundary layer is composed of:
• outer BL: - Msheath plasma: FA, counter-streaming and only accelerated - anisotropic diffusion of Mspheric plasma distribution unstable to EMEC waves
• inner BL: - Msheath plasma: FA, counter-streaming, accelerated & heated and denser than outer BL
- isotropic diffusion of Mspheric plasma - weak wave activity if any
Questions:Questions:
• what is the heating process of low E e- in inner BL & why isn’t at work in the outer BL too?
• why is diffusion anisotropic in the outer BL?
• why do the spikes gather together when EM e- cyclotron waves are observed?
• …