The geomagnetic field was quiet on May 24. The high latitude magnetometer at Andenes recorded quiet to unsettled conditions.
Solar flux density measured at 20h UT on 2.8 GHz was 72.7 - decreasing 6.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 75.57). The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.1). Three hour interval K indices: 20010000 (planetary), 20021101 (Boulder), 31101000 (Andenes).
The background x-ray flux is at the class B1 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 4 active regions using 2K resolution (SN: 81) and in 4 active regions using 1K resolution (SN: 67) SDO/HMI images.
Region 12824 [N19W12]
decayed slowly and was mostly quiet.
Region 12825 [N17E41] was quiet and stable.
Spotted regions not observed (or interpreted
differently) by SWPC:
New region
S6874 [N24W37] emerged early in the day with tiny spots and peaked
after noon. Slow decay was observed late in the day.
New region S6875 [N22W29] emerged with tiny spots late in the day.
Minor update added at 19:25 UT on May 25: AR S6874 has developed quickly today and could produce C flares and perhaps an M class flare. The background x-ray flux is increasing as well.
C2+ flares:
| Magnitude | Peak time (UT) | Location | AR | Recorded by | Comment |
May 24: No obviously Earth directed CMEs
were observed in available LASCO imagery.
May 23: Another faint halo CME was observed in LASCO imagery after
the M1.1 flare in AR 12824 at 11:08 UT. This CME could reach Earth on May
26.
May 22: Faint halo CMEs were observed in LASCO imagery following a
C1.3 long duration event peaking at 08:44 and an M1.1 flare at 17:11 UT.
These CMEs could reach Earth during the latter half of May 25 or the first
half of May 26.
[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]
No obvious coronal holes are currently in or near Earth facing positions.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet during the first half of May 25. Several CMEs could reach Earth on May 25 and 26 and cause unsettled to major storm conditions until May 27.
| 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 red colored.
| 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 | ||||||||||
| S6863 | 2021.05.15 | S15W51 | |||||||||
| S6864 | 2021.05.16 | S15W57 | |||||||||
| 12824 | 2021.05.17 2021.05.18 |
8 | 34 | 24 | N19W13 | 0180 | CSI | CSI |
 |
 |
beta-gamma |
| S6866 | 2021.05.17 | S21W34 | |||||||||
| S6870 | 2021.05.20 | N08W47 | |||||||||
| 12825 | 2021.05.21 2021.05.23 |
1 | 1 | 1 | N17E39 | 0010 | AXX | AXX |
 |
 |
location: N17E41 area: 0006 |
| S6872 | 2021.05.21 | N20W44 | |||||||||
| S6873 | 2021.05.21 | S26W08 |
 |
||||||||
| S6874 | 2021.05.24 | 4 | 1 | N24W37 | 0007 | BXO |
 |
||||
| S6875 | 2021.05.24 | 2 | 1 | N22W29 | 0006 | BXO |
 |
||||
| Total spot count: | 9 | 41 | 27 | ||||||||
| Sunspot number: | 29 | 81 | 67 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 14 | 46 | 32 | (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): | 32 | 45 | 54 | k * (sunspot number) As of May 7, 2016: k = 1.1 for SWPC, k = 0.55 for STAR 2K, k = 0.80 for STAR 1K |
|||||||
| 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 (cycle peak) | 110.5 | 10.70 |
| 2014.04 | 143.9 | 144.8 | 112.5 | 116.4 (solar max) | 7.88 |
| 2017.09 | 91.3 | 92.3 | 43.6 | 18.2 (-1.3) | 18.22 (cycle peak) |
| 2019.10 | 67.4 | 67.0 | 0.4 | 2.6 (-0.5) | 7.53 |
| 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 |
| 2020.01 | 72.2 | 69.9 | 6.4 | 2.2 (+0.4) | 4.39 |
| 2020.02 | 71.0 | 69.3 | 0.4 | 2.7 (+0.5) | 6.16 |
| 2020.03 | 70.2 | 69.5 | 1.5 | 3.0 (+0.3) | 5.63 |
| 2020.04 | 69.5 | 70.0 | 5.4 | 3.6 (+0.6) | 5.32 |
| 2020.05 | 69.0 | 70.6 | 0.2 | 5.6 (+2.0) | 3.80 |
| 2020.06 | 69.5 | 71.7 | 5.8 | 7.9 (+2.3) | 3.75 |
| 2020.07 | 69.5 | 71.8 | 6.3 | 9.0 (+1.1) | 4.28 |
| 2020.08 | 71.6 | 73.4 | 7.6 | 9.5 (+0.5) | 5.68 |
| 2020.09 | 70.7 | 71.4 | 0.7 | 10.5 (+1.0) | 8.59 |
| 2020.10 | 74.6 | 74.2 | 14.6 | 11.9 (+1.4) | 6.13 |
| 2020.11 | 89.9 | 88.0 | 34.5 | (13.8 projected, +1.9) | 4.77 |
| 2020.12 | 86.9 | 84.2 | 23.1 | (16.2 projected, +2.4) | 4.72 |
| 2021.01 | 76.0 | 73.6 | 10.4 | (19.5 projected, +3.3) | 4.39 |
| 2021.02 | 74.3 | 72.4 | 8.3 | (22.8 projected, +3.3) | 9.50 |
| 2021.03 | 76.0 | 75.2 | 17.3 | (26.2 projected, +3.4) | 10.17 |
| 2021.04 | 75.9 | 76.4 | 24.5 | (30.3 projected, +4.1) | 8.40 |
| 2021.05 | 73.8 (1) | 13.1 (2A) / 16.9 (2B) / 30.7 (2C) | (33.0 projected, +2.7) | (6.7) | |
| 2021.06 | (36.2 projected, +3.2) | ||||
| 2021.07 | (40.8 projected, +4.6) | ||||
| 2021.08 | (45.5 projected, +4.7) | ||||
| 2021.09 | (51.2 projected, +5.7) | ||||
| 2021.10 | (55.6 projected, +4.4) | ||||
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.
