Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 19, 2024 at 07:30 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 to unsettled on February 18. Solar wind speed at SOHO ranged between 297 and 388 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was at 0.8 pfu at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 156.5 - decreasing 39.6 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.17. 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: 5.3). Three hour interval K indices: 32121000 (planetary), 22111110 (Boulder), 43100021 (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 12 active regions using 2K resolution (SN: 205) and in 9 active regions using 1K resolution (SN: 124) SDO/HMI images.

Region 13581 [S21W58] decayed slowly and quietly.
Region 13583 [N08W71] decayed slowly and produced several C flares. C1 flares: C1.6 @ 11:42, C1.9 @ 13:42, C1.5 @ 16:33, C1.7 @ 23:34 UT
Region 13584 [S14W33] decayed slowly and quietly.
Region 13585 [N12W09] was quiet and stable.
Region 13586 [N27E20] developed slightly and was quiet.
Region 13587 [S21W02] decayed slowly and quietly.
Region 13588 [S03W12] was quiet and stable.
New region 13590 [N19E76] rotated partly into view with large spots.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9428 [S11W06] was mostly quiet and stable. C1 flares: C1.7 @ 10:52 UT
S9433 [S11E07] was quiet and stable.
New region S9435 [N08E02] emerged with a tiny spot.
New region S9436 [S08E16] emerged with tiny spots.

AR 13589 behind the southwest limb was the source of a C1.9 flare at 13:02, a C1.6 flare at 22:47 and a C1.7 flare recorded at 23:51 UT.
AR S9418 behind the northwest limb was the likely source of a C1.9 flare at 08:14 UT

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.7 00:16   13583 GOES16  
C2.4 00:37   13583 GOES16  
C2.2 01:16   13590 GOES16  
C2.3 02:11   13583 GOES16  
C3.5 02:42   13590 GOES16  
C3.8 02:53   13583 GOES16  
C5.0 04:05 behind southwest limb 13589 GOES16  
C4.6 04:21   13590 GOES16  
C2.7 05:37   13583 GOES16  
C2.6 12:08   13583 GOES16  
C2.2 18:37   13590 GOES16  

Coronal mass ejections (CMEs)

February 16-18: 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 recurrent southern hemisphere coronal hole (CH1202) will likely rotate into an Earth facing position on February 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on February 19-21.

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
13581 2024.02.07
2024.02.08
1 1 1 S21W59 0020 HSX HAX location: S21W58
13583 2024.02.08
2024.02.10
11 18 10 N09W67 0250 FKI FSI

area: 0320

location: N08W71

 
13584 2024.02.09
2024.02.10
6 14 7 S15W33 0020 BXO CRO  
13585 2024.02.12
2024.02.13
  9   N13W09 0013   BXO location: N12W09
S9421 2024.02.12       N27W40            
13587 2024.02.13
2024.02.15
3 7 4 S20W02 0010 BXO BXO  
13586 2024.02.13
2024.02.15
2 11 4 N27E20 0140 HSX CSO

area: 0190

13588 2024.02.14
2024.02.15
  6 1 S03W15 0010   BXO location: S03W12
S9428 2024.02.15   7 2 S11W06 0020   BXO  
S9431 2024.02.16       S28W24            
S9432 2024.02.17       S21E29          
S9433 2024.02.17   7 4 S11E07 0020   BXO  
13590 2024.02.18
2024.02.18
1 2 1 N19E78 0250 HHX EHO   was AR S9434

area: 0900

location: N19E76

S9435 2024.02.18   1   N08E02 0002   AXX    
S9436 2024.02.18   2   S08E16 0003   AXX    
Total spot count: 24 85 34  
Sunspot number: 84 205 124  (total spot count + 10 * number of spotted regions)
Weighted SN: 54 113 62  (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): 92 113 99  

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
2024.02 175.0 (1)   82.1 (2A) / 132.2 (2B) / 149.7 (2C) (116.3 projected, -0.8) (5.1)
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.