Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 28, 2024 at 08:00 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 to unsettled on March 27. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was at 1.2 pfu at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 174.6 - increasing 10.5 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.12. 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: 5.8). Three hour interval K indices: 31211111 (planetary), 31321211 (Boulder), 43112213 (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 9 active regions using 2K resolution (SN: 231) and in 7 active regions using 1K resolution (SN: 143) SDO/HMI images.

Region 13614 [N17W59] decayed slowly and quietly.
Region 13615 [S12W51] developed in the trailing spot section. The spot group has multiple magnetic delta structures with the most significant in the southern part of the trailing spots. A major M7.1 flare was recorded at 06:29 UT on March 28. X class flaring is possible. C1 flares: C1.9 @ 02:37 UT
Region 13617 [S13W21] was quiet and stable.
Region 13619 [N18W23] decayed slowly and quietly.
Region 13620 [S09E08] decayed slowly and quietly.
Region 13622 [N20E25] decayed slowly and quietly.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9528 [N20W04] decayed slowly and quietly.
S9539 [S15W01] reemerged with tiny spots.
New region S9545 [S24W49] emerged with a tiny spot.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C5.4 00:28   13615 GOES16  
C3.0 00:55   13615 GOES16  
C2.9 01:30   13615 GOES16  
M1.1/1F 01:44 S13W37 13615 GOES16  
C4.8 02:46 S13W37 13615 GOES16  
C2.9 03:11 S13W37 13615 GOES16  
C2.9 03:19   13615 GOES16  
C4.0 03:53   13615 GOES16  
C2.7 04:41   13615 GOES18  
C2.6 05:25   13615 GOES18  
C3.6 06:16 behind northwest limb 13621 GOES16  
C3.3 06:22   13615 GOES16  
M1.1/1N 06:41 S11W48 13615 GOES16  
C3.7 07:30   13615 GOES16  
C3.4 08:04   13615 GOES16  
C3.0 08:18   13615 GOES16  
C4.1 08:44 S15W39 13615 GOES16  
C3.8 08:52   13615 GOES16  
C4.2 09:37   13615 GOES16  
C4.2 09:41   13615 GOES16  
C3.0 10:27   13615 GOES16  
C3.4 10:46   13615 GOES16  
C3.4 11:04   13615 GOES16 simultaneous flare in AR 13621
C3.1 11:12   13615 GOES16  
C3.4 11:17   13615 GOES16  
C3.4 11:37   13615 GOES16  
C5.1 11:57   13615 GOES16  
C4.8 12:11   13615 GOES16  
C6.6 12:24   13615 GOES16  
C4.5 13:10   13615 GOES16  
C5.5 13:15   13615 GOES16  
C3.0 14:24   13615 GOES16  
C2.7 14:43   13615 GOES16  
C6.0 15:03   13615 GOES16  
C3.4 15:16   13615 GOES16  
C6.8 15:41   13615 GOES16  
C8.8 15:47   13615 GOES16  
C2.8 16:40   13615 GOES16  
C3.3 17:12   13615 GOES16  
C3.0 17:17   13615 GOES16  
C2.5 17:40   13615 GOES16  
C2.8 18:19   13615 GOES16  
C3.3 19:12   13615 GOES16  
C4.4 20:03   13615 GOES16  
C8.1 20:27   13615 GOES16  
C2.8 21:34   13615 GOES16  
C2.9 21:38   13615 GOES16 simultaneous flare in AR 13621
C3.0 21:55   13615 GOES16  
C4.1 22:17 S12W48 13615 GOES16  
C3.8 22:27   13615 GOES16  
C3.4 23:56   13615 GOES16  

Coronal mass ejections (CMEs)

March 25-27: 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) will be Earth facing on March 27-28.

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 28-29. 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 N16W62 0090 HSX HSX

area: 0220

location: N17W59

13615 2024.03.17
2024.03.18
41 81 53 S13W55 0960 FKC FKC beta-gamma-delta

area: 1970

location: S12W51

S9515 2024.03.17       N09W59            
13617 2024.03.19
2024.03.20
1 9 2 S14W24 0030 HSX CSO

location: S13W21

area: 0050

13621 2024.03.20
2024.03.23
3     N15W94 0030 CSO     rotated out of view
13619 2024.03.20
2024.03.21
6 15 8 N18W24 0140 DSO CAO

location: N18W23

area: 0190

S9528 2024.03.21   6 2 N20W04 0010   BXO  
13623 2024.03.21
2024.03.25
      S19W61        

location: S18W59

13620 2024.03.22
2024.03.22
2 12 5 S09E05 0020 HRX CRO

location: S09E08

13622 2024.03.23
2024.03.24
  6   N11E18 0010   BXO location: N20E25
S9537 2024.03.23       S10W39            
S9538 2024.03.23       S28W29            
S9539 2024.03.24   10 2 S15W01 0020   AXX    
S9540 2024.03.24       S11E20            
S9542 2024.03.26       S23E05          
S9543 2024.03.26       N09W00          
S9544 2024.03.26       N05W45          
S9545 2024.03.27   1   S24W49 0001   AXX    
Total spot count: 54 141 73  
Sunspot number: 114 231 143  (total spot count + 10 * number of spotted regions)
Weighted SN: 87 169 101  (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): 125 127 114  

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
2024.03 154.6 (1)   94.2 (2A) / 108.2 (2B) / 129.3 (2C) (116.9 projected, -0.6) (11.9)
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.

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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.