Given by Walter Gekelman (UCLA Physics department)
University of Central Arkansas, Conway Arkansas, Feb 6, 2000
Baylor University , Waco, Texas, April 7, 2000
Dartmouth University, New Hampshire, April, 21, 2000.
University of New Hampshire, New Hampshire , April, 24, 2000.
Howard University, Washington D.C., march 29, 2000
University of New Mexico, March 24, 2000
Stevens Institute of Technology, Hoboken New Jersey, Oct 28, 1999
Work supported by NSF, ONR and DOE
The auroral ionosphere is highly structured. It is filled
with field aligned density cavities and plasma wave
activity
The interaction of whistler
waves and density
striations can be modeled
in carefully scaled
laboratory experiments
The experiment must be carefully scaled:
"Whistler Wave
Interaction with a Density Striation: A Laboratory Investigation of an Auroral Process,"
J.F. Bamber, J.E. Maggs, W. Gekelman, Jour. Geophys. Research, 1 0 0, 23,795 - 2 3 , 8 10 (1995).
TABLE 1. Typical whistler wave – striation interaction parameters
and ratios in the ionosphere and the LAPD
ionosphere
parameter
(~ 1000 km)
ionosphere(~
LAPD
ratio
1000 km)
LAPD
f
5-30 kHz
101 MHz
f/fLH
1-7
6.7
fLH
4.5-6 kHz
15 MHz
f/fce
0.005-0.030
0.077
fce
1 MHz
1.3 GHz
fpe/fce
0.6-1.0
6.5
fpe
0.6-1 MHz
8.5 GHz
d/rci
2-150
15
rci
6.5 m
0.4 cm
d/L∇
1-10
4.6
d
10-1000 m
6 cm
λ||/d
1-650
2.7
L∇
10-300 m
1.3 cm
λ||/L∇
2-650
12.3
λ||
0.5-6.5 km
16 cm
λ⊥,LH/L∇
0.1-3.5
1.1
20-35 m
1.4 cm
λ||/λ⊥,LH
15-300
11
λ⊥,LH
kT
T
∝ e
2
4πne
n
λD =
µTI
vthermal − ion
∝
B
ω ci
δ=
c
me
∝
ω pe
n
λw = (2πc)
LI =
(ω − ω ce cosθ )
ω 2 − ω 2pe
c
∝
ω pi
MI
n
ω
= VA =
k||
B
B
= 2.2 X1011
µn
4πnM
VA ≈ 108 cm / sec (LAPD)
δBwave
⊥ B0
B0
−λ+
2
2
ω 2pe 2
ω
1
−
(
e
I 0 (λ + ))
ω
p+
2
2
ζ Z ′(ζ )( k || − 2 ε ⊥ ) = − k ⊥ 2
2
c
ω
ω − ω ci2
λ+
where :
ω
ξ=
, a+ =
k ||a
 k a
KTi
, λ+ =  ⊥ 
Mi
 ω ci 
[
2
2π
k=
λ
r r r
k = k|| + k⊥
] Complex error function
Z ' (ξ ) = −2 1 + ξZ (ξ )
1
Z (ξ ) ≡
π
∞
e − ε dε
∫−∞ ε − ξ (here ω = ω r + iω im )
2
π
1
I0 (λ ) ≡ ∫ e λ cos θ cosθdθ
π0
Modified Bessel Function
ω = 2π f
Shear Alfvén waves
fe (v)
ω2
k ||2
where a =
and ϖ =
ω
ω ci
=
v 2A (1 − ϖ 2 )
(1 + k 2⊥ δ 2 )
a
( v 2A >> a 2 )
kTe
= 4.2 X10 7 Te ≈ 6 X10 7 Te = 2 e.V.
me
fci =
ω ci
B
= 1520
2π
µ
vA
Shear Alfvén waves
fe (v)
a
vA
ω2
k ||2
ρs =
= v 2A ( 1 − ϖ 2 + k 2⊥ ρs2 )
kTe / Mi
µTe
= 102
B
ω ci
( v 2A << a 2 )
≈ 7 mm, He, 12 e.V., 1.0 kGauss
•
•
•
•
•
•
•
•
128 ports
40 cm dia plasma
10 meter long
Quiescent δnn ≈ 3%
400G ≤ Bz ≤ 1.7kG
Fully ionized
Reproducible
1 Hz rep rate
Experimental wave launching setup
Tone burst at three axial positions
1
Bx (arbitrary units)
δ x=1.75cm
0.5
0
-0.5
z=151cm
z=252 cm
z=346cm
- 1
0.0
5.0
1 0
7
vphase = 8.4 x10 cm/s
1 5
2 0
2 5
3 0
3 5
4 0
time ( µ s)
1D information
Dispersion relation (uniform field )
400
n
frequency
(kHz)
350
1 2
= 1.0X10
e
f
c i
cm
- 3
= 418 kHz
300
250
200
150
100
100
200
300
400
500
600
700
Parallel Wavelength (cm)
800
900
Antenna
is 1.5 m
out of
this plane
Wave current…
perpendicular
to B
Disk exciter (kinetic regime)
3D Data
:
The shear wave Kinetic in center of the column,
inertial on edge causes the “illusion” of an inward
propagating spherical wave (blue rings)
Magnetic Field Line Resonances
LAPD data
“High
Current
Antenna”
Antenna is insulated
from plasma. I = 600A
pp
No Plasma
Plasma
λ|| = 10 m
δBwave
≈ 10 −3
B
LIF ArII 611.492 nm
•Ions are observed to move in
the wave field
• In center vdrift/vthermal≈20%
• “DC” component ( fig b)
shows ion drift from the cavity
• Perturbed ion motion is
localized to regions where wave
is intense.