Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 30, 2024 at 06:00 UT. Active region table to be updated.

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data since 2003.01 (May 1, 2024)
Solar cycle Solar cycles 23-25 (May 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (May 1, 2024) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (July 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (May 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (May 1, 2024) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (March 3, 2024) Cycle 25 spots (final update December 25, 2019)
  Solar cycles 24-25 transition using 365d smoothing Research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing
Calculating the Strength of Solar Cycle 25 Using 365-day Smoothing

Recent activity

The geomagnetic field was at quiet levels on May 29. The high latitude magnetometer at Andenes recorded quiet to active levels. A weak disturbance began after 05h UT possibly related to effects from the May 27 CME. 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 170.5 - increasing 28.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 161.23. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 161.23 on November 29, 2023). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.3). Three hour interval K indices: 11211122 (planetary), 12222322 (Boulder), 00121343 (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: 262) and in 10 active regions using 1K resolution (SN: 177) SDO/HMI images.

Region 13690 [N16W04] was quiet and stable.
Region 13691 [N26E09] decayed slowly with spots becoming smaller. Several C and M flares were recorded during the day.
Region 13692 [S08W39] decayed slowly and was mostly quiet.
Region 13693 [N03W05] decayed slowly and quietly.
Region 13695 [N27E22] decayed slowly, yet managed to produce a few M class flares.
Region 13696 [N08E28] was quiet and stable.
Region 13697 [S18E62] continued to produce lots of flares. A long duration X1.4 flare was the most interesting one due to the fast partial halo CME that was observed during the hours after the event. Further X class flaring is possible as the magnetic delta configurations are still present.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9748 [S22E09] was quiet and stable.
S9750 [N19E20] was quiet and stable.
S9752 [N21E52] developed slowly and quietly.
New region S9754 [S28W37] emerged with tiny spots.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.5 00:06   13697 GOES16  
C6.7 00:17   13697 GOES16  
C6.5 00:36   13697 GOES16  
M1.3 01:06 S18E71 13697 GOES16 simultaneous flare in AR 13695
C5.6 02:19   13697 GOES16  
C6.2 03:30   13697 GOES16  
C7.4 04:18   13697 GOES16  
C8.3 05:00   13697 GOES16  
M1.4 06:45 S20E68 13697 GOES16  
M1.0 07:05   13695 GOES16  
C4.2 08:14   13697 GOES16  
C8.3 09:32   13697 GOES16  
C5.8 09:55   13697 GOES16 simultaneous flare in AR 13691
C4.5 10:24   13691 GOES16  
C3.2 10:48   13697 GOES16  
M1.8/2N 11:21   13695 GOES16  
C3.9 12:11   13691 GOES16  
M2.5/1N 12:55   13697 GOES16  
X1.4/2B 14:37 S21E66 13697 GOES16 partial halo CME, moderate type II and weak type IV radio sweep
M5.9 16:21   13691 GOES16  
M2.0 17:39   13691 GOES16  
M1.6 17:50   13691 GOES16  
M2.7/2B 18:28 N28E12 13691 GOES16  
M5.7 18:41   13691 GOES16  
M2.6 18:53   13691 GOES16  
M1.2 19:09   13691 GOES16  
C7.2 20:13   13692 GOES16  
C4.8 21:03   13697 GOES16  
C5.6 21:36 behind southwest limb 13686 GOES16  
C5.4 22:47   13691 GOES16  

Coronal mass ejections (CMEs)

May 29: At least a partial halo CME was observed after the X1 long duration event in AR 13697. A flanking impact is possible on May 31 or June 1.
May 28
: No obviously Earth directed CME observed.
May 27: A full halo CME was observed after the X2.9 flare in AR S9747 from a flare site slightly behind the southeast limb.

Coronal holes

[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 small negative polarity southern hemisphere coronal hole (CH1223) rotated across the central meridian on May 26 and early on May 27.

Propagation

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.

Forecast

The geomagnetic field is expected to be at quiet to unsettled levels on May 30. On May 31 - June 1 there's a chance of effects from the May 29 CME, and we could possible see unsettled to minor geomagnetic storm levels.

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.

Active solar regions


(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
13685 2024.05.15
2024.05.16
3 2 1 S13W90 0110 DSO HHX

location: S13W85

area: 0320

13686 2024.05.16
2024.05.17
3 2 1 S09W81 0050 CAO HAX

location: S08W80

13688 2024.05.19       S12W71            
13689 2024.05.19       S07W39        

location: S08W31

S9731 2024.05.21       S24W41            
13690 2024.05.23
2024.05.23
1 5 2 N17E06 0030 HSX HSX

area: 0060

location: N16E09

13691 2024.05.24
2024.05.25
20 63 41 N27E20 0400 EKC DKC beta-gamma-delta

location: N26E23

area: 0690

13692 2024.05.24
2024.05.25
6 16 7 S08W24 0030 CRO CRO

location: S09W24

13693 2024.05.25
2024.05.26
8 18 14 N05E07 0050 DAO DAO location: N03E08

area: 0140

S9739 2024.05.25   5 1 N31W21     BXO  
S9740 2024.05.25       N18W44            
13696 2024.05.25
2024.05.26
1 3 2 N09E38 0010 HRX AXX

location: N08E42

S9743 2024.05.25       S31W45            
13694 2024.05.26       S12E16           location: S15E22
13695 2024.05.26
2024.05.26
4 17 5 N28E33 0020 CRO DRO

location: N27E35

area: 0030

13697 2024.05.27
2024.05.28
5 17 11 S18E69 0250 EHO FKC location: S18E77

area: 0750

S9748 2024.05.27   2   S24E26 0005   AXX  
S9750 2024.05.28   3 2 N19E33 0012   CRO    
S9751 2024.05.28   1   N11W26 0003   AXX    
S9752 2024.05.28   1   N21E63 0001   AXX    
S9753 2024.05.28   1   S30E12 0001   AXX    
Total spot count: 51 156 87  
Sunspot number: 141 306 197  (total spot count + 10 * number of spotted regions)
Weighted SN: 100 210 141  (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): 155 168 158  

Monthly solar cycle data

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
2024.05 189.2 (1)   132.4 (2A) / 146.6 (2B) / 178.7 (2C) (118.3 projected, +1.2) (25.3)
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

Solar cycles 24-25

Smoothed SF and sunspot numbers

Update on the progress of solar cycle 25 as of April 28, 2024

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.

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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.