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Solar flares in September 1999
C-class92
M-class2
X-class0
LargestM2.11999-09-17
Sunspot number107.4NOAA SWPC
Flares per day (C and above)
M/X flares per day
Same month a year earlier
| Month | C | M | X | Largest |
|---|---|---|---|---|
| September 1998 | 103 | 9 | 0 | M7.1 |
| September 1999 | 92 | 2 | 0 | M2.1 |
Top 15 flares
| Date | Begin | Peak | Min | Class | Location | Region |
|---|---|---|---|---|---|---|
| 1999-09-17 | 01:14 | 01:20 | 9 | M2.1 | N14W64 | 8690 |
| 1999-09-08 | 12:08 | 12:17 | 19 | M1.4 | N12E53 | 8690 |
| 1999-09-19 | 23:03 | 23:12 | 17 | C9.6 | N21W76 | 8699 |
| 1999-09-21 | 03:42 | 03:52 | 34 | C9.4 | N20E61 | 8706 |
| 1999-09-17 | 22:06 | 22:12 | 11 | C8.8 | N14E19 | – |
| 1999-09-16 | 03:23 | 03:31 | 12 | C7.7 | N13E46 | 8700 |
| 1999-09-01 | 18:52 | 18:59 | 13 | C6.6 | S28W75 | 8674 |
| 1999-09-21 | 09:39 | 10:47 | 101 | C6.4 | – | – |
| 1999-09-02 | 17:43 | 18:28 | 72 | C5.3 | N21W34 | 8675 |
| 1999-09-21 | 03:00 | 03:32 | 41 | C5.2 | N19W90 | 8699 |
| 1999-09-22 | 13:29 | 13:40 | 24 | C5.2 | N17E39 | – |
| 1999-09-13 | 08:05 | 08:46 | 87 | C4.9 | N22E10 | 8699 |
| 1999-09-19 | 14:07 | 14:40 | 54 | C4.9 | N21W71 | 8699 |
| 1999-09-17 | 11:47 | 12:06 | 33 | C4.5 | N18W81 | – |
| 1999-09-28 | 15:22 | 15:39 | 37 | C4.3 | – | – |
All times UTC. Until June 2017 classes are NOAA's reports of the time (GOES-15 and earlier included a 0.7 scaling factor); later classes come from calibrated GOES-16/18 data, so the same flare reads about 1.4× larger. Do not compare the two periods directly.
About this page
94 flares of class C or larger in September 1999; by M/X count it ranks 394 of 565 months.