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Ann. Geophys., 18, 1054-1066, 2000
www.ann-geophys.net/18/1054/2000/
© European Geosciences Union 2000
Simultaneous optical and radar signatures of poleward-moving auroral forms
A. Thorolfsson1, J.-C. Cerisier1,2, M. Lockwood3,4, P. E. Sandholt5, C. Senior1, and M. Lester6
1Centre d'étude des Environments Terrestre et Planétaires, 4 avenue de Neptune, 94107 Saint-Maur CEDEX, France
2Université Pierre et Marie Curie, 4 place Jussieu, 75005 Paris, France
3Department of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
4Space Science Department, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, United Kingdom
5Department of Physics, University, University of Oslo, P.O. Box 1048, Blindern, Norway
6Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, United Kingdom
Correspondence to: A. Thorolfsson
e-mail: thorolfs@cetp.ipsl.fr
Abstract. Dayside poleward moving auroral forms (PMAFs)
were detected between 06:30 and 07:00 UT on December 16, 1998, by the meridian
scanning photometer and the all-sky camera at Ny Ålesund, Svalbard.
Simultaneous SuperDARN HF radar measurements permitted the study of the
associated ionospheric velocity pattern. A good general agreement is observed
between the location and movement of velocity enhancements (flow channels) and
the PMAFs. Clear signatures of equatorward flow were detected in the vicinity of
PMAFs. This flow is believed to be the signature of a return flow outside the
reconnected flux tube, as predicted by the Southwood model. The simulated
signatures of this model reproduce globally the measured signatures, and
differences with the experimental data can be explained by the simplifications
of the model. Proposed schemes of the flow modification due to the presence of
several flow channels and the modification of cusp and region 1 field-aligned
currents at the time of sporadic reconnection events are shown to fit well with
the observations.
Key words: Ionosphere (auroral ionosphere; plasma
convection) - Magnetospheric physics
(magnetopause; cusp and boundary layers)
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