As compared with the Mount Wilson Magnetic Classification (MWMC), effective distance (d E ) is a useful parameter because it gives a quantitative measure of magnetic configuration in active regions. We have analyzed magnetograms of 24 active regions of different types with MWMC. We have studied the evolution of magnetic fields of five active regions using d E , total flux (F t ) and tilt angle (Tilt) quantitatively. Furthermore, 43 flare-associated and 25 CME-associated active regions have been studied to investigate and quantify the statistical correlation between flares/CMEs and the three parameters. The main results are as follows: (1) There is a basic agreement between d E and MWMC.(2) The evolution of magnetic fields can be described in three aspects quantitatively and accurately by the three parameters, in particular by d E on the analysis of δ-type active regions. (3) The high correlation between d E and flares/CMEs means that d E could be a promising measure to predict the flare-CME activity of active regions.
Aims. We study the properties of magnetic field of flare-coronal-mass-ejection (flare-CME) productive active regions and their statistic correlations with CME speed. Methods. We used a sample of 86 flare-CMEs in 55 solar active regions. Four measures, including the tilt angle (Tilt), total flux (Ft), length of the strong-field and strong-gradient main neutral line (Lsg) and effective distance (d E ), are used to quantify the properties of the magnetic field of flare-CME productive active regions. (4) The occurrence of 11 slow CMEs and 1 fast CME in β type regions with Lsg far below the threshold reminds us of some exceptions to be considered when Lsg with the threshold is used to predict the CME productivity of active regions.
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