Simultaneous Cluster and IMAGE observations of cusp reconnection and auroral 
proton spot for northward IMF

T. Phan, H. U. Frey, S. Frey, and L. Peticolas
Space Science Laboratory,
Berkeley, California, USA

S. Fuselier
Lockheed Martin Adv. Tech. Cent.,
Palo Alto, California, USA

C. Carlson
Space Science Laboratory,
Berkeley, California, USA

H. Reme and J.-M. Bosqued
Centre d'Etude Spatiale des Rayonnements,
Toulouse, France

A. Balogh
Imperial College,
London, UK

M. Dunlop
Rutherford Laboratory,
Oxford, UK

L. Kistler and C. Mouikis
University of New Hampshire,
Durham, New Hampshire, USA

I. Dandouras and J.-A. Sauvaud
Centre d'Etude Spatiale des Rayonnements,
Toulouse, France

S. Mende, J. McFadden, and G. Parks
Space Science Laboratory,
Berkeley, California, USA

E. Moebius
University of New Hampshire,
Durham, New Hampshire, USA

B. Klecker and G. Paschmann
Max-Planck-Institut fur Extraterrestrische Physik,
Garching, Germany

M. Fujimoto
Tokyo Institute of Technology,
Meguro, Japan

S. Petrinec
Lockheed Martin Adv. Tech. Cent.,
Palo Alto, California, USA

M. F. Marcucci
Instituto di Fisica dello Spazio Interplanetario,
Rome, Italy

A. Korth
Max-Planck-Institut für Aeronomie,
Katlenburg-Lindau, Germany

R. Lundin
Swedish Institute of Space Physics,
Kiruna, Sweden


On March 18, 2002, under northward interplanetary magnetic field (IMF) and high 
(~15 nPa) solar wind dynamic pressure conditions, Cluster observed reconnection 
signatures and the passage of an X-line at the large (~175 deg) magnetic-shear 
high-latitude magnetopause (MP). The observations are consistent with the 
occurrence of a reconnection site tailward of the cusp and in the vicinity of 
the spacecraft. At the same time IMAGE observed a bright spot poleward of the 
dayside auroral oval resulting from precipitating protons into the atmosphere. 
The intensity of the proton spot is consistent with the energy flux contained in 
the plasma jets observed by Cluster. Using the Tsyganenko-01 magnetic field 
model with enhanced solar wind pressure, the Cluster MP location is mapped to 
the vicinity of the IMAGE proton spot. Mapping the auroral spot out to the MP 
implies an X-line of at least 3.6 RE in yGSM. In addition to confirming the 
reconnection source of the dayside auroral proton spot, the Cluster observations 
also reveal sub-Alfvenic flows and a plasma depletion layer in the magnetosheath 
next to the MP, in a region where gas dynamic models predict super-Alfvenic 
flows.

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Geophysical Research Letters, 30(10), 1509, p. 16-1, doi:10.1029/2003GL016885, 2003.