We study the physical mechanism of a major X-class solar flare that occurred in the super NOAA active region (AR) 12192 using a data-driven numerical magnetohydrodynamic (MHD) modeling complemented with observations. With the evolving magnetic fields observed at the solar surface as bottom boundary input, we drive an MHD system to evolve self-consistently in correspondence with the realistic coronal evolution. During a two-day time interval, the modeled coronal field has been slowly stressed by the photospheric field evolution, which gradually created a large-scale coronal current sheet, i.e., a narrow layer with intense current, in the core of the AR. The current layer was successively enhanced until it became so thin that a tether-cutting reconnection between the sheared magnetic arcades was set in, which led to a flare. The modeled reconnecting field lines and their footpoints match well the observed hot flaring loops and the flare ribbons, respectively, suggesting that the model has successfully "reproduced" the macroscopic magnetic process of the flare. In particular, with simulation, we explained why this event is a confined eruption-the consequent of the reconnection is the shared arcade instead of a newly formed flux rope. We also found much weaker magnetic implosion effect comparing to many other X-class flares.

This paper investigates the statistical features of equatorial plasma bubbles (EPBs) using airglow images from 2012 to 2014 from a ground‐based network of four imagers in the equatorial region of China. It is found that (1) EPBs mainly occur during 21:00–00:00 local time (LT) in equinoxes. There is an asymmetry in occurrence rates between March (June) and September equinoxes (December solstices). (2) Most EPBs occur in groups of two to six depletions. The distance between adjacent EPB depletions is ~100–700 km, and the average is 200–300 km. The zonal extension of an EPB group is usually less than 1500 km but can reach 3000 km. (3) EPBs usually have a maximum drift velocity near 100 m/s at 21:00–22:00 LT in 9.5° ± 1.5° geomagnetic latitude and then decrease to 50–70 m/s toward sunrise. (4) The averaged westward tilt angle of most EPBs (with respect to the geographic north‐south) increased from 5°–10° to 23°–30° with LT between 20:00 and 03:00 LT, then decreasing to 10°–20° toward sunrise. (5) When 90 < F10.7 < 140, the maximum magnetic latitudinal extension (PMLE) is usually lower than 15.0° (apex height ~725 km), but it can reach 23.0° (apex height ~1330 km) when F10.7 > 140. The maximum PMLE increases by 3.4°–5.5° when F10.7 changes from 90 to 190. (6) The EPB occurrence patterns and zonal drift velocities are significantly different from those at Kolhapur, India, which locates west to our stations by 20.0°–32.0° in longitude.