The characteristics of the magnetopause reconnection X-line deduced from low-altitude satellite observations of cusp ions
Lockwood, M., Onsager, T. G., Davis, C. J., Smith, M. F. and Denig, W. F. (1994) The characteristics of the magnetopause reconnection X-line deduced from low-altitude satellite observations of cusp ions. Geophysical Research Letters, 21 (24). pp. 2757-2760. ISSN 0094-8276
To link to this article DOI: 10.1029/94GL02696
We present an analysis of a “quasi-steady” cusp ion dispersion signature observed at low altitudes. We reconstruct the field-parallel part of the Cowley-D ion distribution function, injected into the open LLBL in the vicinity of the reconnection X-line. From this we find the field-parallel magnetosheath flow at the X-line was only 20 ± 60 km s−1, placing the reconnection site close to the flow streamline which is perpendicular to the magnetosheath field. Using interplanetary data and assuming the subsolar magnetopause is in pressure balance, we derive a wealth of information about the X-line, including: the density, flow, magnetic field and Alfvén speed of the magnetosheath; the magnetic shear across the X-line; the de-Hoffman Teller speed with which field lines emerge from the X-line; the magnetospheric field; and the ion transmission factor across the magnetopause. The results indicate that some heating takes place near the X-line as the ions cross the magnetopause, and that sheath densities may be reduced in a plasma depletion layer. We also compute the reconnection rate. Despite its quasi-steady appearance on an ion spectrogram, this cusp is found to reveal a large pulse of enhanced reconnection rate.