The geomagnetic field was at quiet levels on May 20. The high latitude magnetometer at Andenes recorded quiet to unsettled levels. The above 10 MeV proton flux was at 0.3 pfu at the end of the day, slightly above background levels. Both the above 50 and above 100 MeV proton flux became slightly enhanced after 14h UT, most likely due to a very large backsided eruption (and subsequent full halo CME) from what was likely old AR S9676.
Solar flux density measured at 20h UT on 2.8 GHz was 199.7 - decreasing 19.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 160.86. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 160.86 on November 20, 2023). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 13123222 (planetary), 13233322 (Boulder), 13222123 (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: 329) and in 13 active regions using 1K resolution (SN: 230) SDO/HMI images.
Region
13674 [S14W55] was quiet and stable.
Region
13679 [S09W33] saw new flux emerge in the trailing spot section. The
region is being considered for a split into 2 groups. C1 flares: C1.7 @
14:10 UT
Region 13680 [N15W29]
decayed slowly and quietly.
Region
13682 [N14W19] decayed slowly and quietly.
Region 13683 [S23W73]
decayed slowly and was mostly quiet. C1 flares: C1.9 @ 14:26, C1.7 @ 17:43,
C1.8 @ 18:14 UT
Region 13684 [S06W07]
developed slowly and quietly.
Region 13685 [S13E17] was less
active than during the previous day, however, M class flares are still
likely. C1 flares: C1.6 @ 05:01, C1.8 @ 08:37, C1.7 @ 13:12, C1.8 @ 17:16 UT
Region 13686 [S07E26] developed a weak magnetic delta configuration
to the south of the main penumbra. M class flaring is possible. C1 flares:
C1.5 @ 16:16 UT
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9715 [N22W11] reemerged with tiny spots.
S9723 [S12E42] developed slowly and quietly.
S9724 [S17E35] reemerged with tiny spots.
S9725 [S08E69] was mostly quiet and stable.
S9726 [S19E10] was quiet and stable.
New region S9728 [S20W67] emerged to the northeast of AR 13683 with
several spots. C1 flares: C1.6 @ 17:33 UT
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.3 | 05:39 | 13686 | GOES16 | ||
| C6.7 | 05:54 | 13683 | GOES16 | ||
| C2.2 | 07:39 | 13685 | GOES16 | ||
| C2.0 | 09:57 | 13685 | GOES16 | ||
| C2.0 | 10:08 | 13685 | GOES16 | ||
| C2.8 | 10:36 | 13686 | GOES16 | ||
| C2.1 | 12:51 | 13685 | GOES16 | ||
| C4.6 | 19:50 | southeast quadrant | near 13685, 13686 | GOES16 | LDE, filament eruption |
| C2.3 | 22:20 | 13679 | GOES16 | ||
| C2.5 | 22:49 | 13683 | GOES16 |
May 18-20: 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) will likely rotate into 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 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 | ||||||||||
| 13672 | 2024.05.08 2024.05.09 |
N19W87 |
 |
|
|||||||
| 13673 | 2024.05.09 2024.05.11 |
S08W67 |
location: S09W64 |
||||||||
| 13674 | 2024.05.10 | 5 | 9 | 4 | S13W55 | 0100 | CSO | CSO |
 |
 |
area: 0160 location: S14W55 |
| 13683 | 2024.05.11 2024.05.15 |
15 | 12 | 5 | S24W72 | 0100 | DAI | CAO |
 |
 |
area: 0110 location: S23W73 |
| 13678 | 2024.05.11 2024.05.12 |
N09W48 |
 |
location: N09W43 | |||||||
| 13679 | 2024.05.12 | 11 | 31 | 23 | S08W31 | 0150 | ESI | ESI |
 |
 |
beta-gamma area: 0320 location: S09W33 split being considered |
| 13680 | 2024.05.12 2024.05.13 |
6 | 2 | N18W34 | 0013 | BXO |
 |
 |
location: N15W29 |
||
| 13682 | 2024.05.12 2024.05.14 |
16 | 5 | N15W26 | 0030 | CRO |
 |
 |
location: N14W19 |
||
| S9708 | 2024.05.12 | N19W58 | |||||||||
| 13684 | 2024.05.15 2024.05.16 |
5 | 19 | 14 | S07W04 | 0020 | CAO | DAI |
 |
 |
location: S06W07 area: 0150 |
| 13685 | 2024.05.15 2024.05.16 |
20 | 47 | 27 | S12E15 | 0350 | EHC | DHI |
 |
 |
beta-gamma location: S13E17 area: 0620 |
| S9715 | 2024.05.15 | 6 | 1 | N22W11 | 0012 | AXX |
 |
||||
| S9716 | 2024.05.15 | N30W33 |
 |
||||||||
| 13686 | 2024.05.16 2024.05.17 |
8 | 20 | 10 | S06E25 | 0120 | CAO | DAO |
 |
 |
beta-delta area: 0270 location: S07E26 |
| S9720 | 2024.05.16 | S30E02 | |||||||||
| S9721 | 2024.05.17 | S22W11 |
 |
||||||||
| 13687 | 2024.05.19 | N15W13 | part of AR 13682 | ||||||||
| S9723 | 2024.05.19 | 3 | 2 | S12E42 | 0020 | CRO |
 |
 |
|||
| S9724 | 2024.05.19 | 4 | S17E35 | 0004 | BXO |
 |
|||||
| S9725 | 2024.05.19 | 5 | 3 | S08E69 | 0030 | DRO |
 |
 |
|||
| S9726 | 2024.05.19 | 4 | 1 | S19E10 | 0008 | BXO |
 |
 |
|||
| S9727 | 2024.05.19 | S24W57 |
 |
||||||||
| S9728 | 2024.05.20 | 7 | 3 | S20W67 | 0030 | CRO |
 |
||||
| Total spot count: | 64 | 189 | 100 | ||||||||
| Sunspot number: | 124 | 329 | 230 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 99 | 236 | 147 | (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): | 136 | 181 | 184 | ||||||||
| 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 | 196.4 (1) | 99.9 (2A) / 154.9 (2B) / 200.3 (2C) | (118.3 projected, +1.2) | (34.0) | |
| 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.
