On the use of directional derivatives of SuperDARN convection flow for estimating open-closed field line boundary during the intervals of substorm activity on 14 October 2001

Abstract

The maximum peak of the directional derivative of the SuperDARN convection flow has been proposed as a proxy for the open/closed magnetic field line boundary (OCB) and this has been evaluated using data from the ultraviolet imagers collected during the steady southward Interplanetary Magnetic Field (IMF) condition. However, the technique ignores the contribution of ionospheric vorticity in determining the peak of the directional derivative of SuperDARN convection flow. In this paper these effects have been considered when identifying the OCB in the night sector, calculated using the directional derivatives of SuperDARN convection flow during the active substorm interval which occurred on October 14, 2001. Statistical comparison of the latitudes of the OCB, as estimated from the peaks of the directional derivative of the SuperDARN convection flow, determined with and without considering the relative maxima and minima vorticity, and as provided by images taken by the two Far Ultraviolet (FUV) Spectral Imagers onboard the IMAGE spacecraft (SI-12 and SI-13) indicates that the modified approach of the directional derivative of the SuperDARN convection flow may be used as an OCB proxy during active geomagnetic activity.