Mystery of frequently-appeared cavities in 1999

Long lasting cavity, September to December, 1999.

There was a period (Sep through Dec, 1999), in which filament cavities appears from time to time on the SE or SW limb. Are those cavities the same entity (long-lasting cavity) or not (several different cavities)?

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)

Is there any way to figure this out?

Differential rotations.

(a) synodic values based on small magnetid structures (Howard, Harvey, and Forgach, Solar Physics, 130, 295, 1990).
(b) synodic values by Allen, Astrophysical Quantities (1973).
(c) Carrington rotation (27.2753 days period, rigid rotation)

latitude (deg) 0 30 60 days taken for 1/4 rotation
(a) deg/day 13.3407 12.6966 10.7214 8.4 days at 60 deg.
(b) deg/day 13.4544 12.7044 11.2044 8.0 days at 60 deg.
(c) deg/day 13.1988 13.1988 13.1988 6.8 days at all latitudes.

Cavity's lotation on synoptic maps.

Assuming that cavities are steady for 90-deg rotation, their Central Meridian passage time can be predicted by adding/subracting 8.x days. That way, the locations of the cavitis on the nearby synoptic maps are calculated.

number & location (1) SE (2) SE (3) SW (4) SE (5) SE (6) SW (7) SE (8) SE (9) SW (10) SE (11) SW
best-looked day on the limb 2-Sep 19:00 6-Sep 20:00 20-Sep 23:00 30-Sep 19:00 8-Oct 11:00 20-Oct 18:20 3-Nov 03:30 10-Nov 23:20 14-Nov 07:40 5-Dec 01:05 21-Dec 03:40
nearby CM passage 11-Sep 05:00 15-Sep 06:00 12-Sep 13:00 08-Oct 05:00 16-Oct 21:00 12-Oct 08:20 11-Nov 13:30 19-Nov 09:00 5-Nov 21:40 13-Dec 11:00 12-Dec 17:40

CR1953

CR1954

CR1955

CR1956

CR1957

SXT intensity with KittPeak magnetic field synoptic map is here.