Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 29, 2024 at 08:55 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 (March 2, 2024)
Solar cycle Solar cycles 23-25 (March 2, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (March 2, 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 (March 2, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (March 2, 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 quiet on March 278 The high latitude magnetometer at Andenes recorded quiet to unsettled levels. The above 10 MeV proton flux was at 0.5 pfu at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 172.7 - increasing 19.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.19. 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 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.4). Three hour interval K indices: 21112122 (planetary), 11223323 (Boulder), 31112223 (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 8 active regions using 2K resolution (SN: 187) and in 8 active regions using 1K resolution (SN: 135) SDO/HMI images.

Region 13614 [N17W72] decayed slowly and quietly.
Region 13615 [S12W61] developed early in the day, then decayed significantly in the leading and intermediate spot sections with several penumbrae fragmenting into smaller penumbrae. The magnetic delta structures in the southern part of the huge trailing penumbra decreased in size after the X1 flare. Further major flares are possible as the spot group approaches and begins to rotate over the southwest limb.
Region 13617 [S13W34] decayed slowly and quietly.
Region 13619 [N18W37] decayed slowly and quietly.
Region 13620 [S10W03] decayed slowly and quietly.
Region 13622 [N20E12] was quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9528 [N19W17] was quiet and stable.
S9543 [N09W21] reemerged with tiny spots.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.4 01:16   13615 GOES16  
C2.6 02:10   13615 GOES16  
C2.5 02:30   13615 GOES16  
C2.7 02:52   13615 GOES16  
C3.9 02:58   13615 GOES16  
C3.4 03:30   13615 GOES16  
C3.0 04:18   13615 GOES18  
C7.5 04:27 S13W50 13615 GOES18  
C2.4 05:03   13615 GOES18  
M7.1/1N 06:29 S14W51 13615 GOES16  
C3.4 08:07   13615 GOES16  
C3.3 08:38   13615 GOES16  
C8.4 09:43   13615 GOES16 multiple flare centers
SWPC incorrectly attributes this flare to AR 13623
C3.3 10:21   13615 GOES16  
C4.5 11:28   13615 GOES16  
C4.2 11:51   13615 GOES16  
C5.5 12:27   13615 GOES16  
C4.1 13:50   13615 GOES16  
C7.9 14:03   13615 GOES16  
C8.3 14:08   13615 GOES16  
C5.6 14:59   13615 GOES16  
C7.2 15:35   13615 GOES16  
M6.1/1N 15:56 S13W58 13615 GOES16  
C8.4 17:07 S13W55 13615 GOES16  
C4.3 18:18 southeast limb   GOES16 simultaneous flare in AR 13615
C5.6 19:11   13615 GOES16  
M1.1/1F 19:31   13615 GOES16  
X1.1/3B 20:56 S14W61 13615 GOES16  
C2.8 23:17   13617 GOES16  
C2.8 23:49   13615 GOES16  

Coronal mass ejections (CMEs)

March 26-28: 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 trans equatorial coronal hole (CH1209) was Earth facing on March 27. A positive polarity southern hemisphere coronal hole (CH1208) was Earth facing on March 27-28. Anorthern hemisphere negative polarity coronal hole (CH1210) will likely become Earth facing on March 31.

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 quiet on March 29. Quiet to unsettled is possible on March 30-31 due to effects from CH1208 and CH1209.

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
13614 2024.03.16
2024.03.17
1 1 1 N18W75 0060 HSX HSX

area: 0200

location: N17W72

13615 2024.03.17
2024.03.18
40 65 40 S13W69 0990 FKC FKC beta-gamma-delta

area: 1900

location: S12W61

13617 2024.03.19
2024.03.20
3 4 2 S14W38 0030 CSO CAO

location: S13W34

area: 0040

13619 2024.03.20
2024.03.21
5 8 3 N19W39 0060 HAX CSO

location: N18W37

area: 0190

S9528 2024.03.21   5 1 N19W17 0010   BXO  
13623 2024.03.21
2024.03.25
      S19W76          

location: S18W72

13620 2024.03.22
2024.03.22
2 10 4 S08W10 0010 AXX BXO

location: S10W03

area: 0020

13622 2024.03.23
2024.03.24
  8 1 N11E03 0010   BXO location: N20E12
S9537 2024.03.23       S10W52            
S9538 2024.03.23       S28W42            
S9539 2024.03.24       S15W14          
S9540 2024.03.24       S11E07            
S9542 2024.03.26       S23W08            
S9543 2024.03.26   6 3 N09W21 0015   AXX    
S9544 2024.03.26       N05W58            
Total spot count: 51 107 55  
Sunspot number: 101 187 135  (total spot count + 10 * number of spotted regions)
Weighted SN: 76 132 80  (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): 111 103 108  

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
2022.08 114.2 117.1 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  153.7 157.6 114.8 124.0 (-0.3) 7.19
2023.09  154.4 156.0 134.2 (124.2 projected, +0.2) 14.26
2023.10  142.8 141.9 99.4 (125.0 projected, +0.8) 8.16
2023.11 153.5 150.2 105.4 (125.0 projected, -0.0) 12.20
2023.12 151.1 146.4 114.2 (121.7 projected, -3.3) 9.60
2024.01 164.6 159.3 123.0 (118.3 projected, -3.4) 5.46
2024.02 172.5 168.3 124.6 (117.5 projected, -0.8) 5.31
2024.03 155.2 (1)   97.5 (2A) / 107.9 (2B) / 128.3 (2C) (116.9 projected, -0.6) (11.7)
2024.04       (116.9 projected, -0.0)  
2024.05       (118.1 projected, +1.2)  
2024.06       (117.3 projected, -0.8)  
2024.07       (115.6 projected, -1.7)  
2024.08       (113.7 projected, -1.9)  
2024.09       (112.0 projected, -1.7)  

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 March 10, 2024

Solar activity saw a significant decrease during the latter half of February and the first part of March. While there is still a chance that there could be another and higher peak in October or November 2023, chances that June 2023 was solar max has increased. After November 2023 there is currently no other obvious candidate solar max month. Taking into account the state of the solar polar fields another major peak during SC25 is becoming less likely.

--------------------------------------------------------------------------------------

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.