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Ann. Geophys., 22, 2565-2575, 2004
www.ann-geophys.net/22/2565/2004/
© European Geosciences Union 2004
Cluster observations of mid-latitude hiss near the plasmapause
A. Masson1, U. S. Inan2, H. Laakso1, O. Santolík3, and P. Décréau4
1RSSD of ESA, ESTEC, Noordwijk, 2201AZ, The Netherlands
2STAR Laboratory, Stanford University, Stanford, CA 94305, USA
3Charles University, Prague, Czech Republic
4LPCE/CNRS and Université d’Orléans, Orléans, 45071, France
Abstract. In the vicinity of the plasmapause, around the geomagnetic
equator, the four Cluster satellites often observe banded hiss-like
electromagnetic emissions (BHE); below the electron gyrofrequency but above
the lower hybrid resonance, from 2kHz to 10kHz. We show that below 4kHz,
these waves propagate in the whistler mode. Using the first year of
scientific operations of WHISPER, STAFF and WBD wave experiments on Cluster,
we have identified the following properties of the BHE waves: (i) their
location is strongly correlated with the position of the plasmapause, (ii)
no MLT dependence has been found, (iii) their spectral width is generally 1
to 2kHz, and (iv) the central frequency of their emission band varies from
2kHz to 10kHz. All these features suggest that BHE are in fact
mid-latitude hiss emissions (MLH). Moreover, the central frequency was found
to be correlated with the Kp index. This suggests either that these banded
emissions are generated in a given f/fce range, or that there is a Kp
dependent Doppler shift between the satellites and a possible moving source
of the MLH.
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