The geomagnetic field was at quiet levels on May 25, very weakly under the influence of a low speed stream from CH1223 after noon. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at background levels at the end of the day.
Solar flux density measured at 20h UT on 2.8 GHz was 152.1 - increasing 12.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 161.13. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 161.13 on November 25, 2023). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.3). Three hour interval K indices: 21111212 (planetary), 12212312 (Boulder), 23211435 (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 15 active regions using 2K resolution (SN: 263) and in 13 active regions using 1K resolution (SN: 181) SDO/HMI images.
Region 13684 [S06W80]
decayed slowly and quietly.
Region 13685 [S14W48] decayed slowly
and was mostly quiet.
Region 13686 [S08W40] decayed slowly and was mostly quiet.
Region 13689 [S08E04] decayed slowly and quietly.
Region 13690 [N17E49] was quiet and stable.
New region 13691 [N24E63] rotated into view on May 24 and was
numbered the next day by SWPC. The region is compact, has a magnetic delta
configuration and could produce M flares. C1 flares: C1.7 @ 13:40 UT
New region 13692 [S09E18] was observed with tiny spots on May 24,
then new flux emerged and the region was numbered by SWPC.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9715 [N23W64] lost the leader spot and gained tiny trailing spots.
S9730 [S17W42] decayed further and lost the leader spots.
New region S9738 [N04E50] emerged with tiny spots.
New region S9739 [N31E18] was observed with tiny spots in an old
plage area.
New region S9740 [N18W06] emerged with tiny spots.
New region S9741 [N08E81] rotated into view with a small spot.
New region S9742 [N25W24] was observed with a tiny spot in an
old plage area.
New region S9743 [S27W19] was observed with tiny spots in an old
plage area.
AR S9733 behind the northwest limb produced a C1.8
flare at 10:15 UT.
AR S9729 behind the southwest limb was the source of a C1.7 flare at 14:45
UT
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.7 | 01:19 | 13691 | GOES16 | ||
| C3.2 | 01:30 | S9729 | GOES16 | ||
| C2.1 | 02:16 | 13691 | GOES16 | ||
| C3.6 | 04:42 | behind southwest limb | S9729 | GOES16 | |
| C4.5 | 05:04 | behind southwest limb | S9729 | GOES16 | |
| C2.3 | 08:18 | S04W35 | 13686 | GOES16 | |
| C2.0 | 09:05 | behind northwest limb | S9733 | GOES16 | |
| C2.0 | 10:24 | behind southwest limb | S9729 | GOES16 | |
| C2.2 | 10:32 | behind southwest limb | S9729 | GOES16 | |
| C5.8 | 17:26 | behind southwest limb | S9729 | GOES16 | |
| C2.2 | 22:11 | behind southwest limb | S9729 | GOES16 | |
| C2.2 | 22:51 | 13685 | GOES16 |
May 22-24: 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. A small negative polarity southern hemisphere coronal hole (CH1223) will likely rotate across the central meridian on May 26.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be at quiet to unsettled levels on May 26 due to weak effects from CH1222. Quiet conditions are likely on May 27-28.
| 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 | ||||||||||
| 13682 | 2024.05.12 2024.05.14 |
N19W83 |
SWPC location on May 22 was N13W50, the next day the spotless region was inexplicably at N18W67, and yet another day later the region was repositioned to N19W69 location: N14W86 |
||||||||
| 13684 | 2024.05.15 2024.05.16 |
1 | 2 | 1 | S06W74 | 0050 | HSX | HAX |
 |
 |
location: S06W80 area: 0100 |
| 13685 | 2024.05.15 2024.05.16 |
9 | 12 | 5 | S13W49 | 0210 | ESO | DHO |
 |
 |
location: S14W48 area: 0410 |
| S9715 | 2024.05.15 | 2 | 1 | N23W64 | 0005 | AXX |
 |
 |
|||
| 13686 | 2024.05.16 2024.05.17 |
8 | 16 | 6 | S08W38 | 0110 | CAO | CAO |
 |
 |
location: S08W40 |
| S9721 | 2024.05.17 | S19W52 | |||||||||
| 13687 | 2024.05.19 | N17W84 | part of AR 13682 | ||||||||
| 13688 | 2024.05.19 | S12W27 | |||||||||
| S9724 | 2024.05.19 | S14W33 | |||||||||
| 13689 | 2024.05.19 | 5 | 13 | 7 | S07E05 | 0010 | BXO | CRO |
 |
 |
location: S08E04 area: 0030 |
| S9726 | 2024.05.19 | S19W55 | |||||||||
| S9730 | 2024.05.21 | 10 | 2 | S17W42 | 0020 | AXX |
 |
 |
|||
| S9731 | 2024.05.21 | S24W02 | |||||||||
| 13690 | 2024.05.23 2024.05.23 |
1 | 1 | 1 | N17E49 | 0030 | HSX | HSX |
 |
 |
area: 0080 |
| 13691 | 2024.05.24 2024.05.25 |
8 | 27 | 13 | N25E60 | 0300 | DKC | DKC |
 |
 |
location: N24E63 area: 0450 |
| S9736 | 2024.05.24 | N09W50 |
 |
||||||||
| 13692 | 2024.05.24 2024.05.25 |
4 | 17 | 10 | S09E18 | 0020 | CRO | DRI |
 |
 |
area: 0120 |
| S9738 | 2024.05.25 | 3 | 1 | N04E50 | 0010 | BXO |
 |
||||
| S9739 | 2024.05.25 | 3 | 1 | N31E18 | 0005 | BXO |
 |
||||
| S9740 | 2024.05.25 | 3 | 2 | N18W06 | 0007 | AXX |
 |
||||
| S9741 | 2024.05.25 | 1 | 1 | N08E81 | 0008 | HRX |
 |
||||
| S9742 | 2024.05.25 | 1 | N25W24 | 0001 | AXX |
 |
|||||
| S9743 | 2024.05.25 | 2 | S28W19 | 0003 | BXO |
 |
|||||
| Total spot count: | 36 | 113 | 51 | ||||||||
| Sunspot number: | 106 | 263 | 181 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 69 | 157 | 95 | (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): | 117 | 145 | 145 | ||||||||
| 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 | 192.3 (1) | 119.4 (2A) / 148.0 (2B) / 180.9 (2C) | (118.3 projected, +1.2) | (27.6) | |
| 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.
