The geomagnetic field was quiet to unsettled on May 28. Solar wind speed at SOHO ranged between 409 and 504 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.
Solar flux density measured at 20h UT on 2.8 GHz was 151.3 - increasing 3.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 141.13. 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: 9.3). Three hour interval K indices: 33223112 (planetary), 34324322 (Boulder), 45345233 (Andenes).
The background x-ray flux is at the class B9 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 15 active regions using 2K resolution (SN: 275) and in 13 active regions using 1K resolution (SN: 195) SDO/HMI images.
Region 13310 [S20W70] was quiet and stable.
Region 13311 [N20W53] decayed slowly and was mostly quiet.
Region 13312 [S25W45] decayed slowly and quietly.
Region 13313 [N22W40] was quiet and stable.
Region 13315 [S17W21] lost a few spots and still has small magnetic delta configurations
within western parts of the trailing spot section. A major
flare is still possible. The region is less compact as the main opposite polarity areas
continued to drift apart. C1 flares: C1.4 @ 01:17, C1.3 @ 03:28, C1.3 @
09:25, C1.6 @ 12:24, C1.2 @ 13:15, C1.4 @ 13:52, C1.2 @ 14:27, C1.3 @ 15:24,
C1.1 @ 16:15, C1.0 @ 16:59, C1.1 @ 19:54, C1.2 @ 20:40, C1.1 @ 21:58 UT.
Region 13316 [N08E08] decayed slowly and was mostly quiet. C1 flares:
C1.4 @ 03:46 UT
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S8590 [N15W72] decayed slowly and lost the
magnetic delta. C1 flares: C1.1 @ 00:55, C1.8 @ 01:52, C1.0 @ 18:28, C1.2 @
21:32 UT
S8595 [N20E07] was quiet and stable.
S8597 [N24W18] developed slowly and was quiet.
S8599 [S19E13] was quiet and stable.
S8600 [S12E25] was quiet and stable.
New region S8601 [N26W35] emerged before noon, then decayed slowly.
New region S8602 [N11E19] emerged with tiny spots.
New region S8603 [N09E86] rotated partly into view.
A C1.6 flare was recorded at the northeast limb at 15:41 UT
C2+ flares:
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| M1.0/1N | 10:36 | S15W11 | 13315 | GOES16 | |
| C2.0 | 14:55 | S17W15 | 13315 | GOES16 |
May 26-28: 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 likely rotate across the central meridian on May 31 - June 1. A southern hemisphere coronal hole (CH1151) will be Earth facing on May 29, however, it is uncertain if CH1151 is too far to the south to be the source of a geoeffective disturbance.
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 unsettled conditions are expected for May 28-30.
| 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 | ||||||||||
| 13310 | 2023.05.16 2023.05.17 |
2 | 3 | 2 | S20W71 | 0260 | HHX | HKX |
 |
 |
area: 0410 |
| 13311 | 2023.05.17 2023.05.18 |
9 | 20 | 11 | N18W59 | 0200 | EAO | ESO |
 |
 |
beta-gamma location: N20W53 |
| 13312 | 2023.05.18 2023.05.19 |
2 | 4 | 2 | S25W46 | 0010 | AXX | AXX |
 |
 |
location: S25W45 |
| 13313 | 2023.05.18 2023.05.19 |
1 | 3 | 1 | N23W42 | 0080 | HSX | CSO |
 |
 |
area: 0130 location: N22W40 |
| 13314 | 2023.05.19 2023.05.20 |
4 | N15W72 | 0160 | DAO |
merged with AR 13311 on 2023.05.22 SWPC resurrected the region on 2023.05.24 see AR S8590 |
|||||
| 13315 | 2023.05.22 2023.05.23 |
26 | 39 | 26 | S17W22 | 0800 | EKC | EKI |
 |
 |
beta-gamma-delta location: S17W21 |
| S8584 | 2023.05.22 | S19W39 | |||||||||
| S8589 | 2023.05.24 | S20W38 |
 |
||||||||
| S8590 | 2023.05.24 | 4 | 4 | N15W72 | 0150 | DAC |
 |
 |
|||
| S8591 | 2023.05.24 | 3 | 1 | N14W05 | 0008 | BXO |
 |
||||
| 13316 | 2023.05.24 2023.05.26 |
5 | 16 | 7 | N08E08 | 0030 | DRO | DRO |
 |
 |
area: 0040 |
| S8593 | 2023.05.25 | N26W26 | |||||||||
| S8594 | 2023.05.26 | N08W06 | |||||||||
| S8595 | 2023.05.26 | 6 | N20E07 | 0008 | BXO |
 |
 |
||||
| S8596 | 2023.05.27 | N01W04 |
 |
||||||||
| S8597 | 2023.05.27 | 5 | 5 | N24W18 | 0030 | CRO |
 |
 |
|||
| S8598 | 2023.05.27 | S09E01 |
 |
||||||||
| S8599 | 2023.05.27 | 11 | 3 | S19E13 | 0020 | BXO |
 |
 |
|||
| S8600 | 2023.05.27 | 7 | 1 | S12E25 | 0010 | BXO |
 |
 |
|||
| S8601 | 2023.05.28 | 1 | 1 | N26W25 | 0002 | AXX |
 |
||||
| S8602 | 2023.05.28 | 2 | 1 | N11E19 | 0006 | BXO |
 |
||||
| S8603 | 2023.05.28 | 1 | N09E86 | 0050 | HSX |
 |
|||||
| Total spot count: | 49 | 125 | 65 | ||||||||
| Sunspot number: | 119 | 275 | 195 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 87 | 171 | 111 | (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): | 131 | 151 | 156 | ||||||||
| 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 | (100.4 projected, +1.7) | 9.33 |
| 2022.12 | 147.9 | 143.4 | 112.8 | (104.1 projected, +3.7) | 10.99 |
| 2023.01 | 182.4 | 176.6 | 143.6 | (110.1 projected, +6.0) | 8.73 |
| 2023.02 | 167.2 | 163.2 | 110.9 | (115.2 projected, +5.1) | 14.48 (current SC25 peak) |
| 2023.03 | 157.2 | 155.6 | 122.6 | (118.3 projected, +3.1) | 14.42 |
| 2023.04 | 145.4 | 146.4 | 96.4 | (123.7 projected, +5.4) | 13.40 |
| 2023.05 | 155.2 (1) | 111.4 (2A) / 123.3 (2B) / 152.9 (2C) | (129.3 projected, +5.6) | (11.5) | |
| 2023.06 | (132.5 projected, +3.2) | ||||
| 2023.07 | (132.0 projected, -0.5) | ||||
| 2023.08 | (133.0 projected, +1.0) | ||||
| 2023.09 | (136.4 projected, +3.4) | ||||
| 2023.10 | (138.3 projected, +1.9) | ||||
| 2023.11 | (141.4 projected, +3.1) | ||||
| 2023.12 | (142.5 projected max SC25) | ||||
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: SIDC-SILSO.
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.
