Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 26, 2024 at 10:05 UT.

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 25, very weakly under the influence of a low speed stream from CH1223 after noon. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. 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 152.1 - increasing 12.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 161.13. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 161.13 on November 25, 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: 21111212 (planetary), 12212312 (Boulder), 23211435 (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: 263) and in 13 active regions using 1K resolution (SN: 181) SDO/HMI images.

Region 13684 [S06W80] decayed slowly and quietly.
Region 13685 [S14W48] decayed slowly and was mostly quiet.
Region 13686 [S08W40] decayed slowly and was mostly quiet.
Region 13689 [S08E04] decayed slowly and quietly.
Region 13690 [N17E49] was quiet and stable.
New region 13691 [N24E63] rotated into view on May 24 and was numbered the next day by SWPC. The region is compact, has a magnetic delta configuration and could produce M flares. C1 flares: C1.7 @ 13:40 UT
New region 13692 [S09E18] was observed with tiny spots on May 24, then new flux emerged and the region was numbered by SWPC.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9715 [N24E63] lost the leader spot and gained tiny trailing spots.
S9730 [S17W42] decayed further and lost the leader spots.
New region S9738 [N04E50] emerged with tiny spots.
New region S9739 [N31E18] was observed with tiny spots in an old plage area.
New region S9740 [N18W06] emerged with tiny spots.
New region S9741 [N08E81] rotated into view with a small spot.
New region S9742 [N25W24] was observed with a tiny spot in an old plage area.
New region S9743 [S27W19] was observed with tiny spots in an old plage area.

AR S9733 behind the northwest limb produced a C1.8 flare at 10:15 UT.
AR S9729 behind the southwest limb was the source of a C1.7 flare at 14:45 UT

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.7 01:19   13691 GOES16  
C3.2 01:30   S9729 GOES16  
C2.1 02:16   13691 GOES16  
C3.6 04:42 behind southwest limb S9729 GOES16  
C4.5 05:04 behind southwest limb S9729 GOES16  
C2.3 08:18 S04W35 13686 GOES16  
C2.0 09:05 behind northwest limb S9733 GOES16  
C2.0 10:24 behind southwest limb S9729 GOES16  
C2.2 10:32 behind southwest limb S9729 GOES16  
C5.8 17:26 behind southwest limb S9729 GOES16  
C2.2 22:11 behind southwest limb S9729 GOES16  
C2.2 22:51   13685 GOES16  

Coronal mass ejections (CMEs)

May 22-24: No obviously Earth directed CME observed.

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 negative polarity northern hemisphere coronal hole (CH1222) - an extension of the northern polar coronal hole - was in an Earth facing position on May 21-22. A small negative polarity southern hemisphere coronal hole (CH1223) will likely rotate across the central meridian on May 26.

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 26 due to weak effects from CH1222. Quiet conditions are likely on May 27-28.

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
13682 2024.05.12
2024.05.14
      N19W83          

SWPC location on May 22 was N13W50, the next day the spotless region was inexplicably at N18W67, and yet another day later the region was repositioned to N19W69

location: N14W86

13684 2024.05.15
2024.05.16
1 2 1 S06W74 0050 HSX HAX

location: S06W80

area: 0100

13685 2024.05.15
2024.05.16
9 12 5 S13W49 0210 ESO DHO

location: S14W48

area: 0410

S9715 2024.05.15   2 1 N23W64 0005   AXX  
13686 2024.05.16
2024.05.17
8 16 6 S08W38 0110 CAO CAO

location: S08W40

S9721 2024.05.17       S19W52            
13687 2024.05.19       N17W84           part of AR 13682
13688 2024.05.19       S12W27            
S9724 2024.05.19       S14W33            
13689 2024.05.19 5 13 7 S07E05 0010 BXO CRO

location: S08E04

area: 0030

S9726 2024.05.19       S19W55            
S9730 2024.05.21   10 2 S17W42 0020   AXX  
S9731 2024.05.21       S24W02            
13690 2024.05.23
2024.05.23
1 1 1 N17E49 0030 HSX HSX

area: 0080

13691 2024.05.24
2024.05.25
8 27 13 N25E60 0300 DKC DKC location: N24E63

area: 0450

S9736 2024.05.24       N09W50          
13692 2024.05.24
2024.05.25
4 17 10 S09E18 0020 CRO DRI area: 0120
S9738 2024.05.25   3 1 N04E50 0010   BXO    
S9739 2024.05.25   3 1 N31E18 0005   BXO    
S9740 2024.05.25   3 2 N18W06 0007   AXX    
S9741 2024.05.25   1 1 N08E81 0008   HRX    
S9742 2024.05.25   1   N25W24 0001   AXX    
S9743 2024.05.25   2   S28W19 0003   BXO    
Total spot count: 36 113 51  
Sunspot number: 106 263 181  (total spot count + 10 * number of spotted regions)
Weighted SN: 69 157 95  (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): 117 145 145  

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
2024.05 192.3 (1)   119.4 (2A) / 148.0 (2B) / 180.9 (2C) (118.3 projected, +1.2) (27.6)
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.