Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 23, 2024 at 06:05 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 (February 4, 2024)
Solar cycle Solar cycles 23-25 (February 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (February 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 (February 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (February 1, 2024) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (January  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 quiet on February 22. Solar wind speed at SOHO ranged between 306 and 373 km/sec. The high latitude magnetometer at Andenes recorded quiet to unsettled 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 173.3 - increasing 16.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.18. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.71 on June 27, 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: 22221111 (planetary), 12222212 (Boulder), 32211331 (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 12 active regions using 2K resolution (SN: 227) and in 10 active regions using 1K resolution (SN: 159) SDO/HMI images.

Region 13586 [N27W31] was quiet and stable.
Region 13587 [S21W53] was quiet and stable.
Region 13590 [N18E26] decayed slowly in the trailing spot section while development was observed in the intermediate spot section. The region has multiple magnetic delta structures. Further X class flaring is obviously a possibility.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9432 [S18W34] reemerged with a tiny spot.
S9440 [N13W51] was quiet and stable.
S9442 [N22W41] was quiet and stable.
S9445 [S17E17] was quiet and stable.
New region S9446 [S06W53] emerged with several spots.
New region S9447 [S36E82] rotated into view with a mature spot. This is the return of AR 13575. M class flaring is possible based on flare history.
New region S9448 [S13E82] rotated into view with a few spots. C and minor M class flaring is possible.
New region S9449 [N04E81] rotated into view with small spots.
New region S9450 [N17E05] was observed with tiny spots in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C5.8 00:55   13590 GOES16  
C4.3 01:24   13590 GOES16  
C2.9 03:00   13590 GOES16  
C4.0 03:47 N18E36 13590 GOES16  
C2.7 04:27   13590 GOES16  
C2.2 05:10   13590 GOES16  
X1.7/2B 06:32 N16E35 13590 GOES16  
C3.0 09:25   13590 GOES16  
C3.4 11:39   S9449 GOES16  
C3.4 15:35   S9449 GOES16 incorrectly attributed to AR 13590 by SWPC
C9.4 16:29   S9449 GOES16 incorrectly attributed to AR 13590 by SWPC
C4.6 17:16   S9449 GOES16  
C4.5 17:57 N18E32 13590 GOES16  
C4.7 18:25   13590 GOES16  
C5.7 18:43   13590 GOES16  
C3.9 19:26   S9449 GOES16  
M4.8/2B 20:46 N18E29 13590 GOES16  
X6.3 22:34   13590 GOES18 largest flare of SC25

Coronal mass ejections (CMEs)

February 20, 22: No obviously Earth directed CMEs were observed.
February 21: A partial halo CME was observed after a filament eruption in the northwest quadrant during the evening. The CME was first seen in LASCO C3 imagery at 19:42 UT. There's a slight chance of a weak geomagnetic effects on February 25.

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 recurrent southern hemisphere coronal hole (CH1202) will rotate into an Earth facing position on February 21-24.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on February 23. Quiet to active conditions are possible on February 24-26 due to effects from CH1202. If the February 21 CME reaches Earth weak effects could be observed on February 25.

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
13584 2024.02.09
2024.02.10
      S15W89           location: S15W85
13585 2024.02.12
2024.02.13
      N13W65           location: N12W61
13587 2024.02.13
2024.02.15
  2   S20W58 0002   BXO location: S21W53
13586 2024.02.13
2024.02.15
2 4 3 N27W32 0080 HSX HSX

area: 0120

location: N27W31

13588 2024.02.14
2024.02.15
      S03W75           location: S03W69
S9428 2024.02.15       S11W58            
S9432 2024.02.17   1   S21W23 0002   AXX    
S9433 2024.02.17       S08W44          
13590 2024.02.18
2024.02.18
24 69 44 N18E26 0900 FKC FKC beta-gamma-delta

area: 1130

S9435 2024.02.18       N08W50            
S9436 2024.02.18       S08W36            
S9437 2024.02.19       N38W38            
S9438 2024.02.19       N11W10            
S9439 2024.02.19       S27W33            
S9440 2024.02.20   4 2 N13W51 0007   BXO  
S9441 2024.02.20       N02W23          
S9442 2024.02.21   3 1 N22W41 0005   BXO  
S9443 2024.02.21       N37W53          
S9444 2024.02.21       S19W06          
S9445 2024.02.21   5 1 S17E17 0010   BXO  
S9446 2024.02.22   9 3 S06W53 0030   DRO    
S9447 2024.02.22   1 1 S36E82 0120   HSX   old AR 13575
S9448 2024.02.22   3 2 S13E82 0180   DAO    
S9449 2024.02.22   3 1 N04E81 0040   CRO    
S9450 2024.02.22   3 1 N17E05 0007   AXX    
Total spot count: 26 107 59  
Sunspot number: 46 227 159  (total spot count + 10 * number of spotted regions)
Weighted SN: 41 138 90  (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): 51 125 127  

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
2022.07 125.4 129.5 91.4 86.7 (+5.6) 9.51
2022.08 114.2 117.1 74.6 92.6 (+5.9) 10.92
2022.09 135.1 136.5 96.0 96.5 (+3.9) 12.18
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
2023.05 155.6 159.2 137.4 124.1 (+1.2) 10.67
2023.06 161.7 166.8 160.5 125.2 (+1.1)
(SC25 solar max candidate)
8.95
2023.07  176.4 182.2 160.0 124.3 (-0.9) 8.15
2023.08  153.7 157.6 114.8 (123.4 projected, -0.9) 7.19
2023.09  154.4 156.0 134.2 (123.1 projected, -0.3) 14.26
2023.10  142.8 141.9 99.4 (123.9 projected, +0.8) 8.16
2023.11 153.5 150.2 105.4 (123.9 projected, +0.0) 12.20
2023.12 151.1 146.4 114.2 (120.5 projected, -3.4) 9.60
2024.01 164.6 159.3 123.0 (117.1 projected, -3.3) 5.46
2024.02 172.7 (1)   89.1 (2A) / 117.5 (2B) / 134.1 (2C) (116.3 projected, -0.8) (4.9)
2024.03       (115.8 projected, -0.5)  
2024.04       (115.7 projected, -0.1)  
2024.05       (117.0 projected, +1.3)  
2024.06       (116.2 projected, -0.8)  
2024.07       (114.5 projected, -1.7)  
2024.08       (113.1 projected, -1.4)  

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 February 11, 2024

The relatively high solar activity during the first weeks of 2024 has changed the outlook regarding solar max. The first peak in June 2023 currently has a less than 10% probability of being the actual solar max. The next candidate month is October 2023 (October 8-11 if zooming in on a specific date). The likelihood of October 2023 surpassing June 2023 is at least 50%. It is still likely that solar max will be sometime between October 2023 and March 2025.

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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.