Magnetic-Field Variations in the Active Region NOAA 10486 and Their Relationship to X-Ray Flares and Coronal Mass Ejectionsстатья
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Аннотация:SOHO/MDI magnetograms are used to analyze the time variations in the magnetic parameters
of the active region (AR) NOAA 10486, which was part of a large activity complex that passed over the
solar disk from October 26 to 31, 2003, during solar cycle 23. The results are compared with X-ray flares
in the AR and the parameters of coronal mass ejections associated with the AR. The time variations in the
distributions of themagnetic-field strengths associated with the total magnetic flux (Fa), the flux imbalance
between the northern and southern polarities (Im), the complexity of the field, as a measure of the mutual
overlapping of the opposite polarities (Co), and the tilt angle of the magnetic axis (An) are considered. The
time variations in the free energy accumulated in current sheets of ARs were traced using a parameter
introduced for this purpose (Sh). The following results were obtained. First, the parameters Fa, Im, Co,
An, and Sh quantitatively describe the current state of the AR and can be used to trace and analyze the
dynamical evolution of its magnetic field. Second, variations in the magnetic-field-strength distributions
and the mean values of Fa, Im, Co, An, and Sh are associated with flares and coronal mass ejections, and
the variations have considerable amplitudes. Third, the parameter Sh characterizing the degree to which
the magnetic field is non-potential in regions adjacent to the main neutral line increases before eruptive
events, and is thus particular interest for monitoring the states of ARs in real time. Fourth, the magnetic
field of the AR manifests a sort of quasi-elasticity, so that the field structure is restored after active events,
on average, within 1–3 h.