Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 31, 2024 at 06:15 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 30. The high latitude magnetometer at Andenes recorded quiet to active levels. A disturbance was observed reaching ACE near 21:20 UT, it is uncertain if this is another transient or the arrival of effects associated with  CH1223. 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 172.9 - increasing 16.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 161.27. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 161.23 on November 30, 2023). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.8). Three hour interval K indices: 11122323 (planetary), 12222323 (Boulder), 21023444 (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 10 active regions using 2K resolution (SN: 277) and in 10 active regions using 1K resolution (SN: 191) SDO/HMI images.

Region 13690 [N16W17] decayed slowly and quietly.
Region 13691 [N25W04] decayed further losing spots and area. The region is still compact and has minor polarity intermixing. An M class flare is possible.
Region 13692 [S09W51] decayed slowly and was mostly quiet.
Region 13693 [N04W19] decayed slowly and was mostly quiet.
Region 13695 [N27E10] gained several tiny spots and was mostly quiet.
Region 13696 [N08E19] was quiet and stable.
Region 13697 [S18E48] produced several C flares. Currently there is only one significant magnetic delta configuration in a leading penumbra. A major flare remains a possibility.
New region 13698 [N21E37] emerged on May 28 and was numbered 2 days later by SWPC as slow development persisted. The region has polarity intermixing.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9750 [N19E07] was quiet and stable.
New region S9755 [N20W03] emerged with a few spots to the south of AR 13691.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.5 00:35   13697 GOES16  
C2.8 01:12   13697 GOES16  
C3.7 03:24   13697 GOES16  
C4.9 03:36   13691 GOES16 attributed to AR 13697 by SWPC
C3.0 05:34 behind southwest limb 13686 GOES16  
M1.0/1F 07:13   13691 GOES16  
C2.9 10:59   13697 GOES16  
C2.8 11:59   13697 GOES16  
C2.2 13:48   13697 GOES16  
C2.1 15:53   13697 GOES16  
C2.0 16:42   13697 GOES16  
C2.5 17:26   13697 GOES16  
C2.0 17:59   13697 GOES16  
C2.1 18:11   13697 GOES16  
C6.8 18:46   13697 GOES16  
C3.1 19:05   13697 GOES16  
C2.4 19:19   13697 GOES16  
C2.2 19:31   13697 GOES16  
C2.1 19:47   13697 GOES16  
C2.1 20:25   13697 GOES16  
C2.0 22:18   13691 GOES16  
C2.1 22:40   13697 GOES16  
C2.3 23:17   13691 GOES16  
C2.4 23:25   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, 30
: 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 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 active levels on May 31-June 1, possible with minor storm intervals due to CME and coronal hole effects. Quiet conditions are likely on June 2

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
13689 2024.05.19       S07W69          

location: S08W57

13690 2024.05.23
2024.05.23
1 2 2 N17W19 0030 HSX HAX

location: N16W17

13691 2024.05.24
2024.05.25
27 54 26 N27W06 0300 DKC DAC beta-gamma

location: N25W04

area: 0400

13692 2024.05.24
2024.05.25
3 4 2 S08W52 0010 AXX BXO location: S09W51
13693 2024.05.25
2024.05.26
5 13 7 N04W18 0030 CSO CAO location: N04W19

area: 0040

S9739 2024.05.25       N31W47            
13696 2024.05.25
2024.05.26
1 4 1 N08E14 0010 AXX AXX

location: N08E19

area: 0006

13694 2024.05.26       S12W12           location: S15W04
13695 2024.05.26
2024.05.26
8 19 10 N27E08 0010 BXO BXI

location: N27E10

area: 0040

13697 2024.05.27
2024.05.28
14 47 27 S18E49 0420 EKI EKC beta-gamma-delta

location: S18E49

area: 0740

S9748 2024.05.27       S22W04          
S9750 2024.05.28   4 2 N19E07 0010   BXO  
S9751 2024.05.28       N11W52            
13698 2024.05.28
2024.05.30
5 22 9 N22E36 0050 CSO CRI location: N21E37
S9753 2024.05.28       S30W14            
S9754 2024.05.29       S28W50          
S9755 2024.05.30   8 5 N20W03 0030   DRO    
Total spot count: 64 177 91  
Sunspot number: 144 277 191  (total spot count + 10 * number of spotted regions)
Weighted SN: 99 208 122  (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): 158 152 153  

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
2024.05 188.1 (1)   141.0 (2A) / 145.7 (2B) / 180.7 (2C) (118.3 projected, +1.2) (24.0)
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.