Magnetic Reconnection Rate and Flux‐Rope Acceleration of Two‐Ribbon Flares

Abstract

Forbes & Lin derived simple equations to link the properties ofmagnetic reconnection in the corona to observed signatures of solarflares. We measured the photospheric magnetic fields and the flareribbon separation speeds then applied these equations to derive twophysical terms for the magnetic reconnection rates: the rate of magneticflux change ϕrec involved in magnetic reconnection inthe low corona and the electric field Erec inside thereconnecting current sheet (RCS) that is generated during magneticreconnection. The central interest in this work is to investigate andquantify the statistical correlation between the magnetic reconnectionrate and the corresponding flux-rope acceleration. From a sample of 13well-observed two-ribbon flares, which are associated with filamenteruptions or coronal mass ejections (CMEs), the acceleration of eruptingfilaments is found mainly in the range of 0.05-0.4 km s-2, upto 3 km s-2. Correspondingly, the maximum Erec andϕrec mostly occur in the range of 0.2-5 Vcm-1 and 0.5-6×1018 Mx s-1,respectively. A positive and strong correlation is found with across-correlation coefficient of 0.94-0.97 between the magneticreconnection rate and the acceleration of erupting filaments thatrepresents the early stages of flux-rope eruptions in the low corona.However, the inferred reconnection rate is not correlated to theacceleration of CME fronts measured by the Large Angle and SpectrometricCoronagraph (LASCO) observations in the range of 2-30 solar radii (thecorrelation coefficient is less than 0.2). A reasonable correlation isfound between the reconnection rate and the velocity of CMEs, whichindicates the cumulative acceleration of CMEs from the low corona to theLASCO C2 field of view. The temporal correlation between the magneticreconnection rate and the flare nonthermal emissions has also beenverified in this paper.