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1 CLUSTER SATELLITE OBSERVATIONS OF FIELD LINE RESONANCES IN THE DAYSIDE MAGNETOSPHERE P. T. I. Eriksson, L. G. Blomberg Alfvén Laboratory, Royal Institute of Technology, Stockholm, Sweden
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CLUSTER SATELLITE OBSERVATIONS OF FIELDLINE RESONANCES IN THE DAYSIDEMAGNETOSPHERE
P. T. I. Eriksson, L. G. Blomberg
Alfvén Laboratory, Royal Institute of Technology, Stockholm, Sweden
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Background
Assume wave propagation on the form
)3(1
)2(1
)1(1
2
2
2
22
2
0
2
2
0
2
r
uimBrE
ri
BBirE
BrrB
rm
r
ur
r
BbB
bBBBB
bBBB
)exp( tiim
The hydrodynamic equations in a cylindrical geometry then gives
Two limit cases: mm ;0 Toroidal and poloidal mode resp.In general (finite m) the two modes are coupled
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Background cont.Background
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Spacecraft orbit
•Plot in GSM-coordinates•Snapshot taken at 16:00 UT
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Fieldline footprint
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Electric field
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Spectral characteristics
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•Data bandpass-filtered 2-10 mHz•Background magnetic field defined by•20 min running average•r~radial; e~eastward; p~parallell
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Phase relationships
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Phase relationships cont.
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Summary of observations
•On 17 August 2002 a FLR event is observed in the dayside magnetosphere.
•The oscillations occur at one stable frequency, 4.2 mHzin the satellite frame.
•Radial polarisation of the magnetic field indicates thepoloidal mode.
