The geomagnetic field was at quiet to active levels on May 23. A disturbance with unknown origin was in progress 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 176.2 - increasing 23.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 161.09. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 161.09 on November 23, 2023). The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.4). Three hour interval K indices: 12222224 (planetary), 12222334 (Boulder), 01135445 (Andenes).
The background x-ray flux is at the class C2 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 11 active regions using 2K resolution (SN: 249) and in 9 active regions using 1K resolution (SN: 156) SDO/HMI images.
Region
13679 [S07W77] in conjunction with AR S9729 produced C and M flares as it approached the southwest
limb.
Region 13684 [S06W53]
was mostly quiet and stable.
Region 13685 [S14W22] decayed slowly
and was mostly quiet.
Region 13686 [S08W13] was mostly quiet and stable and has minor
polarity intermixing.
Region 13689 [S09E29] decayed slowly and was mostly quiet.
New region 13690 [N17E77] rotated into view with a mature spot. A
larger spot group at N26 is rotating into view early on May 24.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9715 [N19W53] was quiet and stable.
S9729 [S09W70] lost the magnetic delta as well as some area.
S9730 [S17W18] gained a small magnetic delta configuration centrally
and could produce a minor M class flare.
New region
S9733 [N27W75] emerged with tiny spots.
New region S9734 [S16W05] emerged with a tiny spot.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C4.1 | 01:10 | 13679 | GOES16 | ||
| C4.1 | 01:24 | S9729 | GOES16 | ||
| C8.5 | 01:51 | 13679 | GOES16 | ||
| M4.2/1N | 02:16 | S09W64 | 13679 | GOES16 | |
| M1.7 | 04:29 | S9729 | GOES16 | ||
| C6.8 | 05:23 | S9729 | GOES16 | ||
| C4.7 | 06:08 | S08W63 | S9729 | GOES16 | |
| C9.7 | 06:42 | behind southwest limb | S9728 | GOES16 | |
| C5.5 | 07:18 | S9729 | GOES16 | ||
| C3.3 | 07:45 | S9729 | GOES16 | ||
| C5.5 | 08:09 | S08W65 | S9729 | GOES16 | |
| C2.2 | 08:46 | S9729 | GOES16 | ||
| C2.5 | 09:04 | S9729 | GOES16 | ||
| C8.3 | 09:21 | S08W65 | S9729 | GOES16 | |
| C8.5 | 09:34 | behind southwest limb | S9728 | GOES16 | |
| C6.8 | 10:01 | S9729 | GOES16 | ||
| M1.0 | 10:08 | behind southwest limb | 13674 | GOES16 | simultaneous flare in AR S9729 |
| C7.8 | 10:40 | S08W65 | S9729 | GOES16 | |
| C6.0 | 11:10 | S9729 | GOES16 | ||
| C4.1 | 12:11 | S9729 | GOES16 | ||
| C4.5 | 12:24 | S9729 | GOES16 | ||
| C5.8 | 12:36 | S9729 | GOES16 | ||
| M2.5 | 13:26 | S9729 | GOES16 | ||
| C5.9 | 14:31 | S9729 | GOES16 | ||
| C4.5 | 14:50 | behind northeast limb | GOES16 | ||
| C4.4 | 14:58 | 13685 | GOES16 | ||
| C4.3 | 15:17 | S9729 | GOES16 | ||
| C4.7 | 15:28 | 13689 | GOES16 | ||
| C6.8/1N | 15:48 | 13689 | GOES16 | simultaneous flare in AR S9729 | |
| M1.0 | 15:58 | 13689 | GOES16 | ||
| C5.6 | 16:27 | behind southwest limb | S9728 | GOES16 | |
| C5.5 | 16:40 | behind southwest limb | 13674 | GOES16 | |
| C5.6 | 17:12 | S9729 | GOES16 | ||
| C3.3 | 17:42 | S9729 | GOES16 | ||
| C2.7 | 18:23 | S9729 | GOES16 | ||
| C2.5 | 19:19 | S9729 | GOES16 | ||
| C6.0 | 19:46 | S9729 | GOES16 | ||
| C6.5 | 20:34 | S08W69 | S9729 | GOES16 | |
| C4.1 | 21:25 | S9729 | GOES16 | simultaneous flare in AR 13685 | |
| C4.1 | 21:39 | S9729 | GOES16 | simultaneous flare in AR S9733 | |
| C3.8 | 22:05 | S9733 | GOES16 | ||
| C3.5 | 22:22 | S9733 | GOES16 | ||
| C5.6/1F | 22:58 | S07W70 | S9729 | GOES16 | |
| C5.2 | 23:09 | S9729 | GOES16 | ||
| C5.5 | 23:28 | 13685 | GOES16 | ||
| C4.9 | 23:49 | S9729 | GOES16 |
May 21-23: 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. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be at quiet to active levels on May 24-25, first due to effects from the ongoing disturbance, then from a high speed stream originating in CH1222. Quiet conditions are possible on May 26.
| 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 | ||||||||||
| 13678 | 2024.05.11 2024.05.12 |
N09W76 | location: N09W69 | ||||||||
| 13679 | 2024.05.12 | 10 | 4 | 3 | S09W73 | 0480 | EKC | CAO |
 |
 |
area: 0220 location: S07W77 |
| 13680 | 2024.05.12 2024.05.13 |
N18W76 |
location: N15W68 |
||||||||
| 13682 | 2024.05.12 2024.05.14 |
N18W67 |
SWPC location on May 22 was N13W50, then the next day the spotless region was inexplicably moved 5 degrees northwards and further west than it have been. location: N14W60 |
||||||||
| 13684 | 2024.05.15 2024.05.16 |
8 | 20 | 8 | S06W48 | 0100 | CSO | DAI |
 |
 |
beta-gamma location: S06W50 area: 0190 |
| 13685 | 2024.05.15 2024.05.16 |
23 | 27 | 14 | S13W22 | 0400 | EHC | DHO |
 |
 |
beta-gamma location: S14W22 area: 0450 |
| S9715 | 2024.05.15 | 3 | 2 | N19W53 | 0015 | CRO |
 |
 |
|||
| 13686 | 2024.05.16 2024.05.17 |
11 | 23 | 10 | S07W15 | 0100 | CAO | DAO |
 |
 |
beta-gamma area: 0180 location: S08W13 |
| S9720 | 2024.05.16 | S30W37 | |||||||||
| S9721 | 2024.05.17 | S19W26 | |||||||||
| 13687 | 2024.05.19 | 1 | N17W56 | 0010 | AXX |
part of AR 13682 SWPC moved this AR to the location of AR S9715 on May 23 |
|||||
| 13688 | 2024.05.19 | S12W00 | |||||||||
| S9724 | 2024.05.19 | S14W07 |
 |
||||||||
| 13689 | 2024.05.19 | 6 | 19 | 8 | S08E31 | 0030 | CRO | CRI |
 |
 |
beta-gamma location: S09E29 area: 0050 |
| S9726 | 2024.05.19 | S19W29 | |||||||||
| S9729 | 2024.05.21 | 16 | 8 | S09W70 | 0380 | DAC |
 |
 |
beta-gamma | ||
| S9730 | 2024.05.21 | 21 | 12 | S17W18 | 0070 | DRI |
 |
 |
beta-delta | ||
| S9731 | 2024.05.21 | S24E24 |
 |
||||||||
| 13690 | 2024.05.23 2024.05.23 |
1 | 1 | 1 | N17E75 | 0030 | HSX | HSX |
 |
was AR S9732 location: N17E77 area: 0090 |
|
| S9733 | 2024.05.23 | 4 | N27W75 | 0010 | BXO |
 |
|||||
| S9734 | 2024.05.23 | 1 | S16W65 | 0002 | AXX |
 |
|||||
| Total spot count: | 60 | 139 | 66 | ||||||||
| Sunspot number: | 130 | 249 | 156 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 98 | 183 | 110 | (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): | 143 | 137 | 125 | ||||||||
| 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 | 195.3 (1) | 112.7 (2A) / 151.9 (2B) / 186.7 (2C) | (118.3 projected, +1.2) | (29.4) | |
| 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.
