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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L17101, doi:10.1029/2005GL023355, 2005

Reconnection at the dayside low-latitude magnetopause and its nonrole in low-latitude boundary layer formation during northward interplanetary magnetic field

Tai-D. Phan

Space Science Laboratory, University of California, Berkeley, California, USA


Marit Oieroset

Space Science Laboratory, University of California, Berkeley, California, USA


Masaki Fujimoto

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan


Abstract

On 2001-12-02 Wind crossed the dayside magnetopause (MP) at ∼15 MLT and traversed the adjacent low-latitude boundary layer (LLBL) over a period of 2 hours. The IMF was steady (northward and dawnward) during the MP/LLBL encounter. Reconnection flows were observed in the MP that were directed 130° away from the magnetosheath flow direction. In contrast, the LLBL flow was aligned with the magnetosheath flow. The counterstreaming field-aligned and anti-field-aligned electrons have different energies and their fluxes are unbalanced in the open MP whereas they are precisely balanced throughout most of the LLBL indicative of a closed LLBL. These observations indicate that reconnection occurs at the low-latitude MP during northward IMF (with a significant By), but low-latitude reconnection is not responsible for the creation of the LLBL. Instead, reconnection appears to be in the process of eroding a pre-existing LLBL that was created either by diffusive entry or by non-simultaneous double-cusp reconnection.

Received 27 April 2005; accepted 4 August 2005; published 2 September 2005.

Index Terms: 2706 Magnetospheric Physics: Cusp; 2724 Magnetospheric Physics: Magnetopause and boundary layers; 7526 Solar Physics, Astrophysics, and Astronomy: Magnetic reconnection (2723, 7835); 7859 Space Plasma Physics: Transport processes.

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Citation: Phan, T.-D., M. Oieroset, and M. Fujimoto (2005), Reconnection at the dayside low-latitude magnetopause and its nonrole in low-latitude boundary layer formation during northward interplanetary magnetic field, Geophys. Res. Lett., 32, L17101, doi:10.1029/2005GL023355.