HMI Active Region Tracks (Test 1)

Michael Turmon, JPL, 29 Sept. 2010

The movies below are made with the current masks, which use magnetogram information only (no intensity information). The masks are believed to be of good quality. The tracking parameters are carried over from MDI, and might stand some improvement. These test movies are one way to check on how well they're working.

Movie Layout

The movies have 1024x1024 frames; they may be cropped by the inline movie player in your browser. If this is getting in the way, download the movie and play it locally.

The disk is gray, and pixels labeled as "active" within the gray disk are black. The colored blobs represent the full content of different HARPs; small clumps of black pixels that are outside the HARP's are below-threshold. The color of the HARP-blob is related to its track number (counting up from one).

The white bounding box surrounding the HARP encircles all within-HARP pixels. Sometimes a white bounding box can enclose two separated blobs. (The blobs within a box should always be the same color.) This happens when, at a later frame, these two regions were merged. A small white square hangs inside the white box to remind us that this is a merged region.

New regions are shown with a white square hanging *outside * the bounding box.

Sometimes the bounding box is dotted. This means that the corresponding HARP was not seen in that frame, but is being kept around in case it reappears.

For display purposes, I rotated the images (which have p-angle 180) to make north appear up, and rotation from left-to-right, as expected.

Text Insets

All four corners of the movie have text insets.

Top left: frame number in overall image sequence.

Bottom left: Number of HARPs in this frame, and time and date of T_REC.

Top right: For the top half of the image, shows the HARP ID of the current region sets. A "^" next to the ID means it is the largest on the disk, and a "v" means it is the smallest. A "!" means it is new. A "+" means it will later be merged.

Bottom right: Region list for the bottom half of the image, in format just described. Next to the track number appears a colored square corresponding to the track shown.

Files Here

Tag Size Starts at Ends at Notes
25h 1.3M 2010/07/02_12:48 2010/07/03_13:36 Notes
96h 3.1M 2010/07/01_12:00 2010/07/03_23:48 (No Notes)
10d 17M 2010/08/10_00:00 2010/08/19_23:48 Notes

Times of Interest

Notes on 25h movie

There is slender new HARP at 2010/07/03_02:36 (frame 70) on the east limb. It looks like two boxes; the small square box underneath is just a graphical "flag" announcing that it is a new track in this frame.

(For a couple of frames afterwards, there is a graphical hiccup causing some large dotted lines that is now fixed in the code.)

This is not a real AR. It appears to be a cosmic ray strike. A detail from the image mask, shown below, shows the characteristic linear shape. (The image mask was not flipped for p-angle, sorry.)

Cosmic ray strike

In MDI, after various screening procedures had eliminated bogus data, scan line artifacts, and limb anomalies (no minor task), the largest single category of bad tracks was due to CRs. I used the 4/day photograms, matched with magnetograms, so it was not sensible to use temporal filtering to eliminate CR-induced tracks. That is, something really could have appeared and disappeared in a 6-hour interval. With the higher cadence of HMI, we should be able to use temporal filtering even if CR suppression is not part of the image pipeline (yet?).

There is an example of a merged track in frame 109. It is HARP ID 9, which goes back and forth between being a small blob and two connected blobs. On frame 109, a small, separate patch of flux (upper left) has been merged into the lower right patch due to connection in later frames (frame 110-120, say).

We would have to track a longer sequence to determine what happens to the larger area.

Notes on 10d movie

The green AR tagged #1 is two distinct regions in frame 1. Around frame 130 the two regions merge, which is the reason the two separated regions are grouped together in the first frame. After that, the regions merge again at several times, including in the mid 400s, and around frame 700. This behavior is correct.

The large yellow AR (ID #5) stays pretty consistent throughout the disk passage. It stays separated from the red AR (ID #6) even though #6 is inside the bounding box of #5.

There are several brief anomalies. One at frame 45 (at the limb) results in two new HARPs (#8 and #9). The data there look like this (mask and mag; again flipped, sorry):

mask magnetogram

So, the activity is real; this does not look like a CR. It should not have been split into two tracks, but the objects at the extreme limb are difficult because of foreshortening. Noticing these problems is how we can improve the tracks and the masks.

Around frame 465, there is a small AR (#19) at the limb. This seems to be real because it continues for six frames. However, there is a lot of noise at that longitude in the magnetograms. (It may not be visible in the compressed video here.) This noise persists thru the emergence of another small AR there (#22, in red) and a much larger one (#23, orange). Perhaps the small ARs are actually faculae. If so, adding intensity to the masks could improve the classification.

The most problematic issue in these tracks can be observed with HARP #7, in light blue, around frame 450, where its remnants split into another AR, labeled #18, in lavender. HARP #18 is actually a remnant that separated off HARP #7. These should be one track.

This also occurred in a more complex way with HARP #5 (yellow). Its remnants separate out, and are eventually tracked as HARPs #17 and #20. Because of the different cadence, this was not a problem for MDI.