The geomagnetic field was quiet to unsettled on May 31. Solar wind speed at SOHO ranged between 380 and 432 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels.
Solar flux density measured at 20h UT on 2.8 GHz was 161.4 - decreasing 0.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 141.65. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 8.9). Three hour interval K indices: 21212233 (planetary), 22410323 (Boulder), 42224344 (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: 273) and in 15 active regions using 1K resolution (SN: 223) SDO/HMI images.
Region 13313 [N22W80] decayed slowly and quietly.
Region 13315 [S17W61] decayed slowly and was mostly quiet. A weak
magnetic delta configuration is still present in the southern part of a
trailing penumbra.
Region 13316 [N09W33] decayed slowly and quietly.
Region 13317 [N27W69] decayed slowly and quietly.
Region 13318 [N24W57] decayed slowly and quietly.
Region 13319 [S19W29] developed early in the day and developed a
magnetic delta in the intermediate spot section. This delta disappeared
later in the day. Another M
class flare is possible.
Region 13320 [N09E45] was quiet and stable.
Region 13321 [S17E55] was quiet and stable. There's a minor chance of
an M class flare.
Region 13322 [N16W52] decayed slowly and quietly.
New region 13323 [S08E75] rotated partially into view on May 30 and
was numbered the next day by SWPC. The region was very active and has a
magnetic delta in the central part. Further M class flares are likely and
there's a small chance of an X class event.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S8595 [N22W37] was quiet and stable.
S8600 [S12W21] developed early in the day, then decayed slowly.
S8606 [N09E55] was quiet and stable.
S8610 [N29E51] was quiet and stable.
S8611 [N13E17] was quiet and stable.
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C2.3 | 00:02 | 13323 | GOES16 | ||
| C4.3 | 01:02 | 13323 | GOES16 | ||
| C7.5 | 02:09 | 13323 | GOES16 | ||
| C2.9 | 02:56 | 13323 | GOES16 | ||
| C2.8 | 03:20 | 13323 | GOES16 | ||
| C3.8 | 03:47 | 13323 | GOES16 | ||
| M1.0 | 04:34 | 13323 | GOES16 | ||
| M1.3 | 04:38 | 13323 | GOES16 | ||
| M1.1 | 04:47 | 13323 | GOES16 | ||
| C5.7 | 05:25 | S18W16 | 13319 | GOES16 | |
| C5.7 | 06:09 | 13323 | GOES16 | ||
| C3.3 | 07:00 | 13319 | GOES16 | ||
| C3.0 | 07:32 | 13323 | GOES16 | ||
| C4.6 | 07:43 | 13323 | GOES16 | ||
| C6.1 | 08:31 | 13323 | GOES16 | ||
| C3.5 | 09:16 | 13319 | GOES16 | ||
| C2.7 | 10:20 | 13323 | GOES16 | ||
| C5.4 | 11:03 | 13323 | GOES16 | ||
| C3.7 | 11:45 | 13323 | GOES16 | ||
| C3.5 | 12:10 | 13323 | GOES16 | ||
| M1.0 | 12:26 | 13319 | GOES16 | ||
| C2.9 | 13:33 | 13323 | GOES16 | ||
| C4.8 | 13:48 | 13323 | GOES16 | ||
| C2.0 | 14:19 | 13319 | GOES16 | ||
| C2.0 | 14:24 | 13315 | GOES16 | ||
| C2.4 | 14:52 | 13319 | GOES16 | ||
| C2.8 | 15:00 | 13323 | GOES16 | ||
| C2.5 | 15:21 | 13323 | GOES16 | ||
| C2.1 | 15:47 | 13319 | GOES16 | ||
| C2.6 | 16:20 | S8606 | GOES16 | incorrectly attributed to AR 13315 by SWPC | |
| C2.9 | 16:27 | 13319 | GOES16 | ||
| C3.3 | 16:38 | 13315 | GOES16 | ||
| C3.5 | 16:49 | 13319 | GOES16 | ||
| C2.8 | 17:09 | 13323 | GOES16 | ||
| C2.5 | 17:24 | 13319 | GOES16 | ||
| C2.3 | 17:49 | 13323 | GOES16 | ||
| C2.4 | 18:22 | 13315 | GOES16 | ||
| C2.0 | 18:45 | 13319 | GOES16 | ||
| C9.6 | 20:10 | 13323 | GOES16 | ||
| C6.8 | 20:48 | S07E81 | 13323 | GOES16 | |
| C2.4 | 21:21 | 13323 | GOES16 | ||
| M1.0 | 22:08 | S07E81 | 13323 | GOES16 | |
| M4.2 | 22:52 | S07E79 | 13323 | GOES16 |
May 29-31: No obviously Earth directed CMEs were 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 trans equatorial coronal hole (CH1150) will rotate across the central meridian on May 31 - June 1. A southern hemisphere coronal hole (CH1151) will be Earth facing on May 29 - June 1.
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.
Quiet to active conditions are expected for June 1. Quiet to minor storm conditions are possible on June 2-3 do to effects from CH1150 and CH1151.
| Coronal holes (1) | Coronal mass ejection (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 | ||||||||||
| 13312 | 2023.05.18 2023.05.19 |
S25W88 |
location: S23W85 |
||||||||
| 13313 | 2023.05.18 2023.05.19 |
1 | 1 | 1 | N21W79 | 0030 | HSX | HSX |
 |
 |
area: 0060 location: N22W80 |
| 13315 | 2023.05.22 2023.05.23 |
13 | 24 | 14 | S17W58 | 0510 | DKO | EKI |
 |
 |
beta-delta location: S17W61 |
| S8591 | 2023.05.24 | N14W44 | |||||||||
| 13316 | 2023.05.24 2023.05.26 |
1 | 2 | 2 | N07W34 | 0010 | AXX | AXX |
 |
 |
location: N09W33 |
| S8594 | 2023.05.26 | N08W45 | |||||||||
| S8595 | 2023.05.26 | 3 | 1 | N22W37 | 0005 | AXX |
 |
 |
|||
| S8596 | 2023.05.27 | N01W43 | |||||||||
| 13318 | 2023.05.27 2023.05.29 |
2 | 7 | 4 | N24W58 | 0120 | DSO | ESO |
 |
 |
location: N24W57 |
| S8598 | 2023.05.27 | S09W38 | |||||||||
| 13319 | 2023.05.27 2023.05.29 |
19 | 28 | 21 | S19W27 | 0300 | DHI | EKI |
 |
 |
area: 0500 location: S19W29 |
| S8600 | 2023.05.27 | 8 | 4 | S12W21 | 0020 | BXO |
 |
 |
|||
| 13317 | 2023.05.28 2023.05.29 |
2 | 4 | 1 | N27W65 | 0030 | CRO | CRO |
 |
 |
location: N27W69 |
| S8602 | 2023.05.28 | N11W21 |
 |
||||||||
| 13320 | 2023.05.28 2023.05.29 |
2 | 3 | 1 | N09E45 | 0120 | HSX | HSX |
 |
 |
area: 0080 |
| 13321 | 2023.05.29 2023.05.30 |
3 | 8 | 4 | S15E52 | 0260 | HHX | CKO |
 |
 |
area: 0310 location: S17E55 |
| S8606 | 2023.05.29 | 1 | 1 | N09E55 | 0020 | HRX |
 |
 |
|||
| 13322 | 2023.05.29 2023.05.30 |
1 | 9 | 5 | N17W52 | 0010 | BXO | DRI |
 |
 |
location: N16W52 area: 0040 |
| S8608 | 2023.05.29 | S33W03 |
 |
||||||||
| S8609 | 2023.05.30 | N19E27 |
 |
||||||||
| S8610 | 2023.05.30 | 4 | 2 | N29E51 | 0012 | CRO |
 |
 |
|||
| S8611 | 2023.05.30 | 8 | 2 | N13E17 | 0015 | AXX |
 |
 |
|||
| 13323 | 2023.05.30 2023.05.31 |
3 | 13 | 10 | S05E68 | 0200 | DAO | EAC |
 |
 |
beta-delta area: 0500 location: S08E75 |
| Total spot count: | 47 | 123 | 73 | ||||||||
| Sunspot number: | 147 | 273 | 223 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 100 | 185 | 135 | (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): | 162 | 150 | 178 | ||||||||
| 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 |
| 2021.09 | 87.0 | 88.2 | 51.3 | 40.2 (+4.8) | 6.33 |
| 2021.10 | 88.9 | 88.3 | 37.4 | 45.2 (+5.0) | 7.38 |
| 2021.11 | 86.2 | 84.4 | 34.8 | 50.8 (+5.6) | 9.83 |
| 2021.12 | 103.0 | 99.8 | 67.5 | 55.9 (+5.1) | 6.40 |
| 2022.01 | 103.8 | 100.5 | 55.3 | 60.1 (+4.2) | 8.92 |
| 2022.02 | 109.1 | 106.5 | 60.9 | 64.7 (+4.6) | 10.46 |
| 2022.03 | 117.0 | 115.8 | 78.6 | 68.7 (+4.0) | 10.20 |
| 2022.04 | 130.8 | 131.7 | 84.0 | 73.0 (+4.3) | 11.79 |
| 2022.05 | 133.8 | 136.8 | 96.5 | 77.4 (+4.4) | 7.48 |
| 2022.06 | 116.1 | 119.8 | 70.3 | 81.1 (+3.7) | 8.20 |
| 2022.07 | 125.4 | 129.5 | 91.4 | 86.7 (+5.6) | 9.51 |
| 2022.08 | 114.2 | 117.1 | 74.6 | 92.5 (+5.8) | 10.92 |
| 2022.09 | 135.1 | 136.5 | 96.0 | 96.4 (+3.9) | 12.18 |
| 2022.10 | 133.5 | 132.7 | 95.5 | 98.7 (+2.3) | 11.16 |
| 2022.11 | 123.4 | 120.7 | 80.5 | 101.0 (+2.3) | 9.33 |
| 2022.12 | 147.9 | 143.4 | 112.8 | (105.8 projected, +4.8) | 10.99 |
| 2023.01 | 182.4 | 176.6 | 143.6 | (112.2 projected, +6.4) | 8.73 |
| 2023.02 | 167.2 | 163.2 | 110.9 | (117.0 projected, +4.8) | 14.48 (current SC25 peak) |
| 2023.03 | 157.2 | 155.6 | 122.6 | (120.1 projected, +3.1) | 14.42 |
| 2023.04 | 145.4 | 146.4 | 96.4 | (125.5 projected, +5.4) | 13.40 |
| 2023.05 | 155.6 | 159.2 | 137.9 | (131.2 projected, +5.7) | 10.9 |
| 2023.06 | (1) | (2A/2B) / 156.5 (2C) | (134.3 projected, +3.1) | () | |
| 2023.07 | (133.8 projected, -0.5) | ||||
| 2023.08 | (134.8 projected, +1.0) | ||||
| 2023.09 | (138.2 projected, +3.4) | ||||
| 2023.10 | (140.1 projected, +1.9) | ||||
| 2023.11 | (142.7 projected max SC25) | ||||
| 2023.12 | (142.6 projected, 0.1) | ||||
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
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.
