Kinematics of plasmoids and flux rope
This protocol is extracted from research article:
The birth of a coronal mass ejection
Sci Adv, Mar 6, 2019; DOI: 10.1126/sciadv.aau7004

We visually identified plasmoids that persist over a few frames in a series of AIA 131-Å unsharp masked images, obtained their projected heights above the solar limb, assuming a measurement error of 2 pixels (1″.2), and estimated the speed by linearly fitting the time-height profile of each plasmoid (Fig. 4). Similarly, we obtained the time-height profile of the current-sheet tip, and because of its smooth continuous extending, we derived the speed by numerical derivatives using the IDL (Interactive Data Language) procedure DERIV.pro. The appearance of a few plasmoids is temporally associated with HXR bursts, but there is no one-on-one correspondence (fig. S2), similar to previous studies [e.g., (10, 20, 36)].

We fitted the seed CME in AIA 131 Å by an ellipse, assigning a conservative four pixels as the uncertainties of the fitting parameters, i.e., the center and the two semi-axes. We considered the center as the axis of the seed CME and derived the rising speed of the axis and the expanding rate of the ellipse area by numerical derivatives.

We have also constructed time-distance diagrams by taking slices oriented along the current sheet (dotted line in the inset of fig. S2A) off the original or running-difference images and then stacking them up chronologically. Structures moving along the slit leave clear tracks on these diagrams.

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