11:15 AM - 11:30 AM
[PEM14-20] Seasonal and solar wind control of the reconnection line location at the Earth’s dayside magnetopause
Keywords:magnetopause, magnetic reconnection
Among full magnetopause crossing events, flows with a speed tangential to the magnetopause exceeding 150 km/s, which is of the order of the Alfvén speed in the magnetosheath, are chosen as candidates of the reconnection jets. The Walén relation is used to test whether the flow was generated by reconnection, and a total of 715 jets were identified. We estimated the X-line location by the direction and position of the identified jets. The present analysis assume that the northward jets are observed on the northern side of the X-line and the southward jets are observed on the southern side. The average X-line location was estimated by determining a linear discriminant function that minimizes the occurrence probability of the southward jets on the northern side of the estimated X-line or the northward jets on the southern side. It was found that the X-line location shifts about 6 Earth radii from the subsolar point toward the winter hemisphere under the largest dipole tilt. This is also the first study that reveals that the X-line location shifts about 2.5 Earth radii from the subsolar point when the IMF BX component is large. The results demonstrate that the effect of dipole tilt on the X-line position is larger than that of the IMF BX component. To summarize, the dipole tilt dependence of the X-line location suggests that efficiency of energy transport into the magnetosphere by dayside magnetic reconnection during southward IMF may decrease when the dipole tilt is large. This suggests that the well-known geomagnetic activity decrease under larger dipole tilts may be partially due to the X line position displaced from the subsolar point for large dipole tilt.