The geomagnetic field was at quiet to unsettled levels on May 21. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was near background levels at the end of the day.
Solar flux density measured at 20h UT on 2.8 GHz was 190.8 - decreasing 8.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 160.94. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 160.94 on November 21, 2023). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.4). Three hour interval K indices: 21133222 (planetary), 21133321 (Boulder), 21133433 (Andenes).
The background x-ray flux is at the class C1 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 14 active regions using 2K resolution (SN: 313) and in 12 active regions using 1K resolution (SN: 212) SDO/HMI images.
Region
13674 [S14W69] was quiet and stable.
Region
13679 [S07W50] became complex as small magnetic delta configurations
developed along the northern part of the main penumbra. The region produced
several C and one M class flare during the day and an M1.5 flare at 03:13 UT
on May 22. A major flare is possible. The former trailing spot section was
split off into AR S9729. C1 flares: C1.7 @ 09:06, C1.8 @ 11:14, C1.9 @ 11:42
UT
Region
13682 [N14W34] was quiet and stable.
Region 13684 [S06W21]
decayed slowly in the trailing spot section and was quiet.
Region 13685 [S13E05] decayed slowly
and was mostly quiet. C1 flares: C1.9 @ 17:51 UT
Region 13686 [S08E12] decayed slowly and was mostly quiet.
New region 13688 [S12E28] emerged on May 19 and was numbered 2 days
later by SWPC as the region began to decay.
New region 13689 [S09E55] rotated into view on May 19 and received
its NOAA number 2 days later.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9715 [N23W22] was quiet and stable.
S9721 [S19W13] reemerged with tiny spots.
S9728 [S20W80] decayed slowly and produced several flares. An M2.3 flare was
was recorded at 04:04 UT on May 22 from neighboring AR 13683 just behind the
southwest limb. C1 flares: C1.9 @ 12:08 UT
New region S9729 [S10W43] was split off from AR 13679.
New region S9730 [S17E08] emerged with several spots.
New region S9731 [S24E49] emerged with a tiny spot.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.5 | 00:10 | S9728 | GOES16 | ||
| C3.5 | 01:04 | 13686 | GOES16 | ||
| C3.2 | 01:38 | 13685 | GOES16 | ||
| C2.4 | 03:32 | 13674 | GOES16 | ||
| C4.3 | 06:16 | 13683 | GOES16 | ||
| C2.3 | 07:12 | S9728 | GOES16 | ||
| C4.8 | 07:32 | S9728 | GOES16 | ||
| C2.3 | 10:24 | 13685 | GOES16 | ||
| C7.0 | 13:36 | S9728 | GOES16 | ||
| C2.2 | 13:51 | 13686? | GOES16 | ||
| C6.6 | 14:13 | 13683 | GOES16 | ||
| C6.9 | 16:05 | 13679 | GOES16 | ||
| C2.1 | 17:32 | S9728 | GOES16 | ||
| M1.9/1N | 19:31 | 13679 | GOES16 | ||
| C2.8 | 21:03 | 13683 | GOES16 | ||
| C2.3 | 22:25 | 13674 | GOES16 | ||
| C3.9 | 22:40 | 13674 | GOES16 | ||
| C2.3 | 23:56 | 13685 | GOES16 |
May 19-21: No obviously Earth directed CME observed.
[Coronal hole history (since October 2002)]
[Compare today's report to the situation one solar rotation ago:
28 days ago
27 days ago
26 days ago]
A negative polarity northern hemisphere coronal hole (CH1222) - an extension of the northern polar coronal hole - was in an Earth facing position on May 21-22.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be at quiet to unsettled levels on May 20-22.
| Coronal holes (1) | Coronal mass ejections (2) | M and X class flares (3) |
1) Effects from a coronal hole
could reach Earth within the next 5 days. When the high speed
stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.
Green: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% probability.
(Click on image for 2K resolution).
4K resolution.
Compare to the previous
day's image. 0.5K image
When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue is positive.
Data for all officially numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC, all other regions are numbered sequentially as they emerge using the STAR spot number. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers. SWPC data considered to be not sufficiently precise (location, area, classification) are colored red.
| Active region | SWPC date numbered STAR detected |
Spot count | Location at midnight | Area | Classification | SDO / HMI 4K continuum image with magnetic polarity overlays |
Comment | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| SWPC/ USAF |
Magnetic (SDO) |
SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 13673 | 2024.05.09 2024.05.11 |
S08W81 |
location: S09W77 |
||||||||
| 13674 | 2024.05.10 | 1 | 3 | 1 | S14W69 | 0080 | HSX | CAO |
 |
 |
area: 0140 |
| 13683 | 2024.05.11 2024.05.15 |
4 | S23W87 | 0070 | DSO |
 |
rotated out of view | ||||
| 13678 | 2024.05.11 2024.05.12 |
N09W62 | location: N09W56 | ||||||||
| 13679 | 2024.05.12 | 13 | 21 | 13 | S09W46 | 0250 | EKI | DKC |
 |
 |
beta-delta area: 0340 location: S07W50 split into AR S9729 |
| 13680 | 2024.05.12 2024.05.13 |
N18W48 |
 |
location: N15W42 |
|||||||
| 13682 | 2024.05.12 2024.05.14 |
2 | 12 | 4 | N13W36 | 0000 | AXX | BXO |
 |
 |
location: N14W34 area: 0020 |
| 13684 | 2024.05.15 2024.05.16 |
8 | 24 | 15 | S06W19 | 0080 | DAO | DAI |
 |
 |
location: S06W21 area: 0190 |
| 13685 | 2024.05.15 2024.05.16 |
17 | 36 | 18 | S12E02 | 0380 | EHC | DHO |
 |
 |
beta-gamma location: S13E17 area: 0550 |
| S9715 | 2024.05.15 | 4 | N23W22 | 0006 | AXX |
 |
 |
||||
| S9716 | 2024.05.15 | N30W46 | |||||||||
| 13686 | 2024.05.16 2024.05.17 |
5 | 22 | 10 | S07E12 | 0120 | CAO | DAO |
 |
 |
area: 0250 location: S08E12 |
| S9720 | 2024.05.16 | S30W11 | |||||||||
| S9721 | 2024.05.17 | 2 | 1 | S19W13 |
 |
||||||
| 13687 | 2024.05.19 | N15W26 | part of AR 13682 | ||||||||
| 13688 | 2024.05.19 | 3 | 6 | 3 | S12E28 | 0010 | BXO | CRO |
 |
 |
area: 0020 |
| S9724 | 2024.05.19 | S17E22 |
 |
||||||||
| 13689 | 2024.05.19 | 3 | 9 | 6 | S08E55 | 0030 | CRO | DRI |
 |
 |
location: S09E55 area: 0050 |
| S9726 | 2024.05.19 | S19W03 |
 |
||||||||
| S9728 | 2024.05.20 | 5 | 3 | S20W80 | 0040 | CRO |
 |
 |
|||
| S9729 | 2024.05.21 | 19 | 12 | S10W43 | 0420 | DAI |
 |
split off from AR 13679 | |||
| S9730 | 2024.05.21 | 9 | 6 | S17E08 | 0040 | DRO |
 |
||||
| S9731 | 2024.05.21 | 1 | S24E49 | 0001 | AXX |
 |
|||||
| Total spot count: | 56 | 173 | 92 | ||||||||
| Sunspot number: | 146 | 313 | 212 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 99 | 225 | 144 | (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10) | |||||||
| Relative sunspot number (Wolf number): | 161 | 172 | 170 | ||||||||
| Month | Average solar flux | International sunspot number (WDC-SILSO) |
Smoothed sunspot number (4) | Average ap (3) |
|
|---|---|---|---|---|---|
| Measured | 1 AU | ||||
| 2014.02 | 170.3 (cycle peak) |
166.3 | 146.1 (SC24 peak) | 110.5 | 10.70 |
| 2014.04 | 143.9 | 144.8 | 112.5 | 116.4 (SC24 solar max) | 7.88 |
| 2017.09 | 91.3 | 92.3 | 43.6 | 18.2 (-1.3) | 18.22 (SC24 peak) |
| 2019.11 | 70.2 | 68.7 | 0.5 | 2.0 (-0.6) (Solar minimum using 365d smoothing: November 17, 2019) |
4.19 |
| 2019.12 | 70.8 | 68.6 | 1.6 | 1.8 (-0.2) (ISN 13 months smoothed solar minimum) |
3.22 |
| 2022.10 | 133.5 | 132.7 | 95.5 | 98.9 (+2.4) | 11.16 |
| 2022.11 | 123.4 | 120.7 | 80.5 | 101.2 (+2.3) | 9.33 |
| 2022.12 | 147.9 | 143.4 | 112.8 | 106.7 (+5.5) | 10.99 |
| 2023.01 | 182.4 | 176.6 | 144.4 | 113.3 (+6.6) | 8.73 |
| 2023.02 | 167.2 | 163.2 | 111.3 | 117.8 (+3.5) | 14.48 (current SC25 peak) |
| 2023.03 | 157.2 | 155.6 | 123.3 | 121.1 (+3.3) | 14.42 |
| 2023.04 | 145.4 | 146.4 | 97.6 | 122.9 (+1.8) | 13.40 |
| 2023.05 | 155.6 | 159.2 | 137.4 | 124.2 (+1.3) | 10.67 |
| 2023.06 | 161.7 | 166.8 | 160.5 | 125.3 (+1.1) | 8.95 |
| 2023.07 | 176.4 | 182.2 | 160.0 | 124.4 (-0.9) | 8.15 |
| 2023.08 | 153.7 | 157.6 | 114.8 | 124.1 (-0.3) | 7.19 |
| 2023.09 | 154.4 | 156.0 | 134.2 | 123.9 (-0.2) | 14.26 |
| 2023.10 | 142.8 | 141.9 | 99.4 | 124.8 (+0.9) | 8.16 |
| 2023.11 | 153.5 | 150.2 | 105.4 | (125.2 projected, +0.4) | 12.20 |
| 2023.12 | 151.1 | 146.4 | 114.2 | (121.9 projected, -3.3) | 9.60 |
| 2024.01 | 164.6 | 159.3 | 123.0 | (118.5 projected, -3.4) | 5.46 |
| 2024.02 | 172.5 | 168.3 | 124.7 | (117.7 projected, -0.8) | 5.31 |
| 2024.03 | 154.4 | 152.9 | 104.9 | (117.1 projected, -0.6) | 11.03 |
| 2024.04 | 161.3 | 162.6 | 136.5 | (117.1 projected, -0.0) | 9.69 |
| 2024.05 | 196.2 (1) | 104.6 (2A) / 154.5 (2B) / 196.7 (2C) | (118.3 projected, +1.2) | (31.6) | |
| 2024.06 | (117.4 projected, -0.9) | ||||
| 2024.07 | (115.7 projected, -1.7) | ||||
| 2024.08 | (113.8 projected, -1.9) | ||||
| 2024.09 | (112.5 projected, -1.3) | ||||
| 2024.10 | (111.1 projected, -1.4) | ||||
| 2024.11 | (108.6 projected, -2.5) | ||||
1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz
and any corrections applied to that measurement.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days).
2B) Boulder SN current month average to date.
2C) STAR SDO 1K Wolf number 30 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red
are based on the definitive international
GFZ Potsdam WDC ap indices.
4) Source: WDC-SILSO, Royal Observatory
Of Belgium, Brussels
The big increase in sunspot counts during the April 14-27 interval caused a major uptick in the smoothed SNs and solar flux. It's not yet clear when the next peak will be, anytime between October 28 and December 20, 2023 looks possible. The 365d smoothed solar flux exceeded the June 27 peak on October 28, while the 365d smoothed ISN and NOAA SN both exceeded the June 2023 peak in late October 2023. It should be noted that the current peak using 13-month smoothing is still in June 2023.
--------------------------------------------------------------------------------------
This report has been prepared by Jan Alvestad. It is based on the analysis of data from whatever sources are available at the time the report is prepared. All time references are to Universal Time. Comments and suggestions are always welcome.
SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.
