Ten Years of Magnetic Reconnection Exhaust Observations by WIND at 1 AU

Using a sliding-window exhaust detection algorithm of various time durations (Δt) through WIND satellite observations in the solar wind, we have detected 4945 unique reconnection exhaust candidates in the period 2004-2014. The six windows detected 756 events at Δt=12 s, 847 events at Δt=18 s, 1194 events at Δt=2 min, 1353 events at Δt=4 min, 562 events at Δt=10 min and 233 events at Δt=20 min. To date, we have confirmed 1634 reconnection exhausts from a Walén prediction. These WIND events show a peak D_N=35 d_i exhaust normal width distribution, a D_N=75 d_i median, and a 95^th percentile of the distribution at D_N=725 d_i, where d_i is a local ion inertial length.

The D_N width obtained by a single spacecraft can be used to estimate a rough distance D_S to the upstream X-line source region, where the exhaust first formed. The assumptions are that the current sheet (CS) and the associated exhaust move away from the X-line source region at a radial solar wind speed V, and that the exhaust moves away from the X-line in this CS moving frame of reference at a constant Alfvén speed V_A in that same time t=D_S/V. The maximum distance covered by the observed exhaust since formation is D_L=V_At or D_L=V_AD_S/V. A fast reconnection rate (R=0.1) assumption, corresponding to D_L=5D_N, means D_S=5M_AD_N, where M_A=V/V_A is the Alfvén Mach number.

The median D_N=75 d_i value at 1 AU, and a typical solar wind M_A=7, suggest a common X-line source region D_S=2625 d_i upstream from the WIND satellite or D_S~40 R_E for a typical d_i=95 km value (1 R_E=6378 km). This is in stark contrast to an X-line source region at 0.3 AU (D_S=0.7 AU) from the Sun as this would result in an exhaust normal width D_N~0.02 AU at 1 AU for M_A=7 or D_N~470 R_E~30,000 d_i.