Double Star and Cluster Observations of Magnetic Reconnection at the Dayside 
Magnetopause

Pu, Z., Liu, Z., Dunlop, M.


Coordinate Double Star and Cluster measurements have brought new results
concerning the physics of the magnetopause. We can see for the first time, the
evolution of structures at small scales within the Cluster tetrahedron, and then
at large scales with Cluster and Double Star conjunction. This paper presents a
part of Double Star and Cluster observations of magnetic reconnection at the
dayside magnetopause by introducing a few interesting events. These include: (a)
TC-1 observations of the magnetic shear angle across the magnetopause near/at
the reconnection site which was considerably smaller than 180 degree and
observations of noticeable guide field near/in the diffusion region. (b) TC-1
observations of magnetic reconnection at the dayside low-latitude magnetopause
for northward IMF when a strong By component exists. (c) Observations of plasma
jets simultaneously at the subsolar point and near the cusp, suggesting that
reconnection is preferentially initiated near the subsolar point and then
propagates to the high-latitudes. (d) Almost simultaneous observations of an FTE
by Cluster and TC-1 at different positions of the flux rope. This allows us to
infer the large-scale configuration of the reconnected magnetic tube near the
dayside magnetopause. (e) Simultaneous multi-spacecraft observations of
reconnection signatures by Cluster at the northern high-latitude magnetopause,
TC-1 in the low-latitude region and TC-2 in the southern low-altitude cusp,
together with IMAGE in the southern hemisphere. The possible implications of
these observations are discussed. New challenges to the present theories of
magnetic reconnection and magnetopause reconnection models are addressed.

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Fall Meeting, American Geophysical Union, San Francisco, U.S.A., 
5-9 December 2005