ULF Energy Transport Induced
by Magnetospheric Boundary Oscillations
Bill Lotko and Jeff Proehl Thayer School of EngineeringDartmouth College
Boundary oscillations induce internal MHD waves
Internal wave power is absorbed
Characterize:
Wave distribution
Energy transport
One-fluid, linear MHD
Cold plasma = 0 slow mode
Density
Dipole magnetic field
Boundaries L = 5, 10 and r = 2 RE
Radial boundary oscillation n = 1, m = 3, f = 6 mHz
Numerical solution, dissipation
Boundary-constrained, magnetic flux coordinates
Approach
mp E
3 6
0 L L R L rn(r,L)=n
v = 0
=
v
v
=
v = 0
Mode Structure v
v
b
b
b
1000
100
10
1
km/s
100
10
1
.1
nT
224
84
100
15
2
224
84
.5
.1
3
PHASE QUADRATURE
• Parallel – compare v and b
• Azimuthal – compare v and v
DIPOLE “LENS”
• Compressional signal
• Inner magnetosphere
• m 6
LARGE EQUATORIAL FLOWS
• v, 100 km/s at L = 7.5
Validation
100
50
0
GOES 7 – CANOPUS Mar 1990
% C
om
pA
zim
uth
, d
eg
90
-90
0 || B
φ
r
r
P +P
P +P +P
0 2 4 6
LFLR - LGOES
Ziesolleck et al. ’96
100 nT
b
b
2 nT
FLR
MP
Compressional dipole lensEvanescent decay is counteracted by magnetic focusing at low m Outer magnetospheric, dayside Pc 5 waves can drive plasmaspheric cavity modes
Collective energy transportMode distribution + relative phases power flow and group propagation
Wave intensity energy pathways
Conclusions
Theory Program