|
|
 |
|
|
Ann. Geophys., 24, 3115-3129, 2006
www.ann-geophys.net/24/3115/2006/
© European Geosciences Union 2006
The auroral and ionospheric flow signatures of dual lobe reconnection
S. M. Imber1, S. E. Milan1, and B. Hubert2
1Department of Physics and Astronomy, University of Leicester, Leicester, UK
2Institut d'Atmospherique et de Geophysique, Université de Liège, Liège, Belgium
Abstract. We present the first substantial evidence for the occurrence of dual lobe
reconnection from ionospheric flows and auroral signatures. The process of
dual lobe reconnection refers to an interplanetary magnetic field line
reconnecting with lobe field lines in both the northern and southern
hemispheres. Two bursts of sunward plasma flow across the noon portion of
the open/closed field line boundary (OCB), indicating magnetic flux closure
at the dayside, were observed in SuperDARN radar data during a period of
strongly northward IMF. The OCB is identified from spacecraft, radar
backscatter, and auroral observations. In order for dual lobe reconnection
to take place, we estimate that the interplanetary magnetic field clock
angle must be within ±10° of zero (North). The total flux crossing
the OCB during each burst is small (1.8% and 0.6% of the flux
contained within the polar cap for the two flows). A brightening of the noon
portion of the northern auroral oval was observed as the clock angle passed
through zero, and is thought to be due to enhanced precipitating particle
fluxes due to the occurrence of reconnection at two locations along the
field line. The number of solar wind protons captured by the flux closure
process was estimated to be ~2.5×1030 (4 tonnes by mass),
sufficient to populate the cold, dense plasma sheet observed following this
interval.
Full Article in PDF (2919 KB) |
|
|
