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Sunspots and active regions
The following active regions with sunspot groups were visible on the Sun on April 21, 1999. Coordinates are given as of the end of the day.
| Group ID | Location | Number of sunspots | Area (msh) | Type | CM Passage | Disappearance (W90) | Reappearance (W270) | |
|---|---|---|---|---|---|---|---|---|
| № 8521 | N32 | W19 | 01 | 0000 | ALPHA | Apr 20, 1999 | Apr 28, 1999 | May 12, 1999 |
| № 8520 | N19 | W00 | 06 | 0010 | BETA | Apr 22, 1999 | Apr 29, 1999 | May 13, 1999 |
| № 8518 | S15 | E29 | 16 | 0160 | BETA | Apr 24, 1999 | May 1, 1999 | May 15, 1999 |
| № 8517 | N22 | W77 | 03 | 0100 | BETA | Apr 16, 1999 | Apr 23, 1999 | May 7, 1999 |
| № 8516 | S19 | W11 | 03 | 0040 | BETA | Apr 21, 1999 | Apr 28, 1999 | May 12, 1999 |
Solar cycle progression
The average monthly sunspot number (SSN) from January 1970 to April 1999. The gray background is the average SSN index.
