Observations of auroral broadband emissions by CLUSTER

• Published in: Geophysical research letters Vol. 30; no. 11; pp. 1563 - n/a
• Main Authors: Wahlund, J.-E., Yilmaz, A., Backrud, M., Sundkvist, D., Vaivads, A., Winningham, D., André, M., Balogh, A., Bonnell, J., Buchert, S., Carozzi, T., Cornilleau, N., Dunlop, M., Eriksson, A. I., Fazakerley, A., Gustafsson, G., Parrot, M., Robert, P., Tjulin, A.
• Format: Journal Article
• Language: English
• Published: American Geophysical Union 01-06-2003; Blackwell Publishing Ltd
• Subjects: Auroral phenomena; Earth Sciences; Electric fields; Geophysics; Magnetospheric Physics; Plasma waves and instabilities; Sciences of the Universe
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2002GL016335

We present the results of a study based on several events of broadband ULF/ELF emissions observed in the auroral region by the CLUSTER multi‐spacecraft at distances around 4–5 RE. These emissions, observed below the ion plasma frequency, are similar to the broadband emissions observed at lower altitudes (800–4000 km) by rockets (e.g. AMICIST) and satellites (e.g. FREJA and FAST). As successive passages of the four CLUSTER satellites through nearly the same regions show, the intensity of the emissions depend on the thermal properties of the plasma and gradients thereof. The total Poynting flux is downward and is comparable to energy fluxes observed at lower altitudes. We believe the broadband emissions are the result of dispersed Alfvén waves (DAW), which propagates down the magnetic field lines, and emits higher frequency ion plasma wave modes.