Evolution of two highly flare- and CME-productive emerging ARs. Top panels (a)–(d): representative snapshot LOS magnetograms showing the evolution of AR 11158 as observed by SDO/HMI. Both bipoles emerge simultaneously, with their conjugated polarities (annotated; N1 P1 and N2 P2) naturally separating from each other at their respective self-PILs (sPIL1 and sPIL2). As a result of the natural separation and orientation of the bipoles, a collision occurred between the negative polarity of the westward flux tube (N1) and the leading polarity of the eastward flux tube (P2). Due to their opposite-polarity signs, a collisional PIL (cPIL; yellow curve) is formed. Thus, the overall PIL of AR 11158 is composed of the integral system of sPIL2/cPIL/sPIL1. The apparent self-separation distance for each bipole is shown with a green and blue line, respectively. Note that a smaller parasitic bipole emerged later on (panel (c); dashed circle). Bottom panels (e)–(h): selected snapshot LOS magnetograms for AR 12017. Here the emergence of the two flux tubes is sequential (N1 P1 and N2 P2 emergence onsets separated by 4 days). A cPIL develops between P2 and N1. The grayscale magnetograms in all panels are saturated at ±1000 G. An animation of this figure is available. The videos begin on 2011-02-10T21:58:11.80 for the simultaneous emergence and on 2014-03-23T22:58:15.90 for the sequential emergence. The videos end 32 s later at 2011-02-17T13:58:12.50 and 2014-03-30T17:34:16.80, respectively.

(An animation of this figure is available.)

The video/animation of this figure is available in the online journal.