Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 5, 2024 at 09:45 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 4. The high latitude magnetometer at Andenes recorded quiet to major 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 166.6 - increasing 42.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 158.47. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.71 on October 28, 2023). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.0). Three hour interval K indices: 11001113 (planetary), 11021213 (Boulder), 11012136 (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 13 active regions using 2K resolution (SN: 316) and in 10 active regions using 1K resolution (SN: 196) SDO/HMI images.

Region 13661 [N23W01] was quiet and stable.
Region 13662 [N29W44] decayed slowly and quietly.
Region 13663 [N26W17] has a strong magnetic delta with a very long east-west winding inversion line. Further major flares are very likely and there's a chance of a significant proton flare. Two major flares have been recorded so far on May 5: M8.4 @ 01:27 and X1.3 @ 06:01 UT
Region 13664 [S20E27] saw the most significant development of any of the current visible groups. The magnetic delta in the large southernmost penumbra is strengthening and a major flare is possible.
Region 13665 [S05E43] was quiet and stable.
Region 13666 [N07E01] matured and was quiet.
New region 13667 [N27E71] rotated into view on May 4 and was numbered the next day by SWPC.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9660 [N10E16] decayed slowly and quietly.
S9661 [S19W19] was quiet and stable.
S9667 [S09E57] was quiet and stable.
S9669 [S16E38] was quiet and stable.
New region S9673 [S11E03] emerged with a tiny spot.
New region S9674 [N01E01] emerged with a tiny spot.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C8.4 00:06   13664 GOES16  
C8.1 00:10   13663 GOES16  
M1.6 00:36 N26W06 13663 GOES16 simultaneous flare in AR 13664
C5.9 00:51   13664 GOES16  
C5.2 01:08   13663 GOES16  
C6.2 01:30   13663 GOES16  
C6.8 01:43   13663 GOES16  
C3.2 02:12   13664 GOES16  
C4.9 02:25   13663 GOES16  
C5.8 02:35   13664 GOES16  
C4.0 03:14   13663 GOES16  
C2.6 03:48   13663 GOES16  
C5.5 03:54 N25W05 13663 GOES16  
C2.2 04:48   13663 GOES16  
C3.1 05:17 N26W02 13663 GOES16  
C2.6 05:43   13663 GOES16  
C4.2 06:08   13663 GOES16  
M9.1/1B 06:19 N26W08 13663 GOES16 weak type II and IV radio sweeps
C8.5 07:00   13663 GOES16  
M1.5 07:07   13663 GOES16  
C4.3 07:25   13664 GOES16  
C4.0 07:31   13664 GOES16  
C3.9 07:41   13664 GOES16  
C3.6 08:11   13663 GOES16  
C4.5 08:36   13663 GOES16  
C2.7 09:19   13663 GOES16  
C3.2 09:50   13663 GOES16  
C3.3 10:38   13663 GOES16  
C3.6 11:27   13663 GOES16  
C3.5 11:51   13663 GOES16  
C4.2 12:05 N26W10 13663 GOES16  
C2.8 12:49   13663 GOES16  
C3.5 13:04   13663 GOES16  
C3.4 13:20   13663 GOES16  
C2.4 13:53   13663 GOES16  
C3.0 14:02   13663 GOES16  
C2.9 14:10   13663 GOES16  
C3.8 15:00   13663 GOES16  
C2.3 15:31   13664 GOES16  
C2.8 15:53   13663 GOES16  
C6.3 16:07 N26W14 13663 GOES16  
C6.4 16:14   13663 GOES16  
C9.1 17:19   13663 GOES16  
C4.0 17:49   13663 GOES16  
M1.3 18:20   13663 GOES16  
C5.6 19:23   13663 GOES16  
C6.0 19:43   13663 GOES16  
C4.4 20:41   13663 GOES16  
C2.3 21:27   13664 GOES16  
C4.7 21:56   13663 GOES16  
C4.2 22:06   13663 GOES16  
M3.2 22:37   13663 GOES16  
M6.6/1B 23:42   13663 GOES16  
M9.0/1B 23:48   13663 GOES16 simultaneous flare in AR 13664

Coronal mass ejections (CMEs)

May 4: LASCO imagery was unavailable. Due to the large amount of M flares from spot groups not far from the central meridian, it is likely there were some CMEs with Earth directed components.
May 3
: A partial halo CME was observed after the X1.6 flare in AR 13663. The CME could reach Earth between late on May 5 and noon on May 6. A partial halo CME was observed in LASCO imagery after a filament eruption in the eastern hemisphere (across the equator) that began at 20:17 UT in SDO/AIA imagery and was centered on AR S9660. This CME could reach Earth on May 6.
May 2: No obviously Earth directed CMEs were 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 positive polarity northern hemisphere coronal hole (CH1219) was Earth facing on May 1-2. A positive polarity trans equatorial coronal hole (CH1220) will rotate across the central meridian on May 3. A large positive polarity northern hemisphere coronal hole (CH1221) will likely become Earth facing on May 9-10.

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 quiet to major storm on May 5-7 due to CME effects and effects related to CH1219 and CH1220.

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
S9637 2024.04.25       S15W46          
13660 2024.04.26
2024.04.27
      N11W33         location: N10W30
13662 2024.04.27
2024.04.29
3 8 4 N29W40 0050 CSO CSO

location: N29W44

13661 2024.04.28
2024.04.29
1 6 3 N23W01 0050 HSX DAO area: 0060
S9651 2024.04.28       N06W56            
13663 2024.04.29
2024.04.30
30 72 41 N26W16 0580 EKC EKC beta-gamma-delta

area: 1030

S9653 2024.04.29       S04W38            
13664 2024.04.30
2024.05.01
20 63 35 S19E28 0310 EKC EKC beta-gamma-delta

area: 0710

location: S20E27

S9658 2024.04.30       N12W54            
S9660 2024.04.30   4 1 N10E16 0008   AXX  
S9661 2024.04.30   3   S19W19 0004   BXO  
S9662 2024.05.01       N20W20            
13665 2024.05.01
2024.05.02
1 3 2 S05E44 0010 HRX HRX area: 0020

location: S05E43

13666 2024.05.02
2024.05.03
10 16 6 N07E02 0130 CAI CSO

 

area: 0220

S9667 2024.05.02   2 1 S09E57 0015   HRX  
S9668 2024.05.02       N12W11            
S9669 2024.05.03   6 2 S16E38 0012   CRO  
S9670 2024.05.03       N04E41          
13667 2024.05.03
2024.05.04
1 1 1 N28E73 0080 HSX HHX location: N27E71

area: 0270

S9672 2024.05.03       S33E44          
S9673 2024.05.04   1   S33E44 0002   AXX    
S9674 2024.05.04   1   N01E01 0002   AXX    
Total spot count: 66 186 96  
Sunspot number: 136 316 196  (total spot count + 10 * number of spotted regions)
Weighted SN: 107 240 150  (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): 150 174 157  

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)
(SC25 solar max candidate)
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) 9.5
2024.05 150.1 (1)   15.7 (2A) / 121.5 (2B) / 176.3 (2C) (118.3 projected, +1.2) (16.0)
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.