Systemic solar wind condition causing distortion of the predicted magnetic reconnection location at the dayside magnetopause as observed by MMS

Abstract

Across the Earth’s magnetopause, magnetic reconnection has been observed as either the anti-parallel and/or component reconnection scenarios. The magnetic reconnection location prediction model known as the Maximum Magnetic Shear model combines these two scenarios and predicts long reconnection lines crossing the dayside magnetopause along a ridge of maximum magnetic shear. The model has been tested and validated and predicts the dayside reconnection location correctly for 84% of the events. Observed magnetic reconnection events for which the model fails share common characteristics, which indicates that for these conditions additional factors have an influence on the location of the dayside reconnection line. One of these specific conditions results in a set of so-called Knee events for which the anti-parallel reconnection region lines up along the draped Interplanetary Magnetic Field (IMF) lines. For these events, magnetic reconnection remains in the anti-parallel reconnection region as long as it is crossed by the draped IMF. Compared to the usual events, this effect results in a deflection of the connection points between the anti-parallel and component reconnection regions (known as anchor points). This study investigates if the location of the entire component reconnection line or only the anchor points are affected by this deflection.  Using two Knee events with confirmed magnetic reconnection location observed by MMS, this study describes how the entire component reconnection line across the dayside magnetopause is deflected if the relative magnetic shear between the maximum magnetic shear location and the deflected magnetic shear location is less than ~5°.