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Ann. Geophys., 23, 2937-2942, 2005
www.ann-geophys.net/23/2937/2005/
© European Geosciences Union 2005
Radial variation of whistler-mode chorus: first results from the STAFF/DWP instrument on board the Double Star TC-1 spacecraft
O. Santolík1,2, E. Macúšová1, K. H. Yearby3, N. Cornilleau-Wehrlin4, and H. StC. K. Alleyne3
1Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, CZ-18000 Prague, Czech Republic
2also at: IAP, Czech Academy of Sciences, Boční II/1401, CZ-14131 Prague, Czech Republic
3University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK
4CETP/IPSL, 10-12 Av. de l’Europe, F-78140 Vélizy, France
Abstract. We use the first measurements of the STAFF/DWP instrument on the Double Star TC-1
spacecraft to investigate whistler-mode chorus.
We present initial results of a systematic study on radial variation of
dawn chorus. The chorus events
show an increased intensity at L parameter above 6.
This is important for the possible explanation of
intensifications of chorus, which were previously observed closer to the Earth
at higher latitudes.
Our results also indicate that the upper band of chorus at frequencies
above one-half of the electron cyclotron frequency
disappears for L above 8.
The lower band of chorus is observed at frequencies below
0.4 of the electron cyclotron frequency up to L of 11-12.
The maxima of the chorus power spectra are found at slightly lower frequencies
compared to previous studies. We do not observe
any distinct evolution of the position of the chorus frequency
band as a function of L. More data of the TC-1
spacecraft are needed to verify these initial
results and to increase the MLT coverage.
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