Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 22, 2024 at 06:10 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 to unsettled levels on May 21. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was near background levels at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 190.8 - decreasing 8.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 160.94. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 160.94 on November 21, 2023). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.4). Three hour interval K indices: 21133222 (planetary), 21133321 (Boulder), 21133433 (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 14 active regions using 2K resolution (SN: 313) and in 12 active regions using 1K resolution (SN: 212) SDO/HMI images.

Region 13674 [S14W69] was quiet and stable.
Region 13679 [S07W50] became complex as small magnetic delta configurations developed along the northern part of the main penumbra. The region produced several C and one M class flare during the day and an M1.5 flare at 03:13 UT on May 22. A major flare is possible. The former trailing spot section was split off into AR S9729. C1 flares: C1.7 @ 09:06, C1.8 @ 11:14, C1.9 @ 11:42 UT
Region 13682 [N14W34] was quiet and stable.
Region 13684 [S06W21] decayed slowly in the trailing spot section and was quiet.
Region 13685 [S13E05] decayed slowly and was mostly quiet. C1 flares: C1.9 @ 17:51 UT
Region 13686 [S08E12] decayed slowly and was mostly quiet.
New region 13688 [S12E28] emerged on May 19 and was numbered 2 days later by SWPC as the region began to decay.
New region 13689 [S09E55] rotated into view on May 19 and received its NOAA number 2 days later.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9715 [N23W22] was quiet and stable.
S9721 [S19W13] reemerged with tiny spots.
S9728 [S20W80] decayed slowly and produced several flares. An M2.3 flare was was recorded at 04:04 UT on May 22 from neighboring AR 13683 just behind the southwest limb. C1 flares: C1.9 @ 12:08 UT
New region S9729 [S10W43] was split off from AR 13679.
New region S9730 [S17E08] emerged with several spots.
New region S9731 [S24E49] emerged with a tiny spot.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.5 00:10   S9728 GOES16  
C3.5 01:04   13686 GOES16  
C3.2 01:38   13685 GOES16  
C2.4 03:32   13674 GOES16  
C4.3 06:16   13683 GOES16  
C2.3 07:12   S9728 GOES16  
C4.8 07:32   S9728 GOES16  
C2.3 10:24   13685 GOES16  
C7.0 13:36   S9728 GOES16  
C2.2 13:51   13686? GOES16  
C6.6 14:13   13683 GOES16  
C6.9 16:05   13679 GOES16  
C2.1 17:32   S9728 GOES16  
M1.9/1N 19:31   13679 GOES16  
C2.8 21:03   13683 GOES16  
C2.3 22:25   13674 GOES16  
C3.9 22:40   13674 GOES16  
C2.3 23:56   13685 GOES16  

Coronal mass ejections (CMEs)

May 19-21: 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.

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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be at quiet to unsettled levels on May 20-22.

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
13673 2024.05.09
2024.05.11
      S08W81          

location: S09W77

13674 2024.05.10 1 3 1 S14W69 0080 HSX CAO

area: 0140

13683 2024.05.11
2024.05.15
4     S23W87 0070 DSO     rotated out of view
13678 2024.05.11
2024.05.12
      N09W62           location: N09W56
13679 2024.05.12 13 21 13 S09W46 0250 EKI DKC beta-delta

area: 0340

location: S07W50

split into AR S9729

13680 2024.05.12
2024.05.13
      N18W48        

location: N15W42

13682 2024.05.12
2024.05.14
2 12 4 N13W36 0000 AXX BXO

location: N14W34

area: 0020

13684 2024.05.15
2024.05.16
8 24 15 S06W19 0080 DAO DAI location: S06W21

area: 0190

13685 2024.05.15
2024.05.16
17 36 18 S12E02 0380 EHC DHO beta-gamma

location: S13E17

area: 0550

S9715 2024.05.15   4   N23W22 0006   AXX  
S9716 2024.05.15       N30W46            
13686 2024.05.16
2024.05.17
5 22 10 S07E12 0120 CAO DAO

area: 0250

location: S08E12

S9720 2024.05.16       S30W11            
S9721 2024.05.17   2 1 S19W13          
13687 2024.05.19       N15W26           part of AR 13682
13688 2024.05.19 3 6 3 S12E28 0010 BXO CRO area: 0020
S9724 2024.05.19       S17E22          
13689 2024.05.19 3 9 6 S08E55 0030 CRO DRI location: S09E55

area: 0050

S9726 2024.05.19       S19W03          
S9728 2024.05.20   5 3 S20W80 0040   CRO  
S9729 2024.05.21   19 12 S10W43 0420   DAI   split off from AR 13679
S9730 2024.05.21   9 6 S17E08 0040   DRO    
S9731 2024.05.21   1   S24E49 0001   AXX    
Total spot count: 56 173 92  
Sunspot number: 146 313 212  (total spot count + 10 * number of spotted regions)
Weighted SN: 99 225 144  (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): 161 172 170  

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
2024.05 196.2 (1)   104.6 (2A) / 154.5 (2B) / 196.7 (2C) (118.3 projected, +1.2) (31.6)
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.