Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 23, 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 (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 22. Solar wind speed at SOHO ranged between 336 and 438 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was at background levels at the end of the day. After the major flares in ARs 13914 and 13915 early on March 23, proton levels began to increase after 03:50 UT and the above 10 MeV proton flux is currently close to event levels. A corotating interaction region associated with CH1207 was observed reaching DSCOVR at 22:56 UT and a disturbance began early on March 23.

Solar flux density measured at 20h UT on 2.8 GHz was 197.6 - increasing 18.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.70. 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 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.5). Three hour interval K indices: 33331100 (planetary), 33332311 (Boulder), 43231001 (Andenes).

The background x-ray flux is at the class C5 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 14 active regions using 2K resolution (SN: 342) and in 12 active regions using 1K resolution (SN: 231) SDO/HMI images.

Region 13607 [S19W84] decayed slowly and quietly.
Region 13608 [N09W81] decayed slowly and quietly.
Region 13614 [N16E06] decayed slowly losing area and spots. A major long duration X1.1 event was recorded peaking at 01:33 UT on March 23. A large asymmetrical full halo CME was observed after this event.
Region 13615 [S12E12] gained spots and area becoming one of the largest spot groups of SC25. The region is very complex and could easily produce further major flares. A major M5.0 flare was recorded at 02:36 UT.
Region 13617 [S13E44] produced a few C flares and decayed slowly.
Region 13618 [S19W76] was mostly quiet and stable as the spot group rotated to the southwest limb.
Region 13619 [N19E44] was mostly quiet and stable.
New region 13620 [S09E74] rotated into view.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9525 [N17W23] was quiet and stable.
S9528 [N19E60] was quiet and stable.
New region S9531 [N09W01] emerged with tiny spots.
New region S9533 [N05W09] emerged with a tiny spot.
New region S9534 [S04W14] emerged with tiny spots.
New region S9535 [S08E26] was observed with tiny spots in an old plage area.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C3.2 00:19   13615 GOES16  
C3.5 00:55   13615 GOES16  
C3.3 01:17 N14E19 13614 GOES16  
C2.6 02:17   13615 GOES16  
C2.2 02:40   13615 GOES16  
C2.4 03:43   13615 GOES16  
C2.5 03:59   13615 GOES16  
C2.8 04:34   13615 GOES18  
C3.6 04:55 S13E27 13615 GOES18  
C5.7 05:16 S15E26 13615 GOES18  
C5.4 05:21   13619 GOES18  
C3.6 05:54   13614 GOES16  
C3.6 06:42 behind northeast limb   GOES16  
C3.5 07:14 behind northeast limb   GOES16  
C2.5 08:14   13615 GOES16  
C2.4 08:51   13618 GOES16  
C2.3 09:27   13615 GOES16  
C3.2 10:53   13615 GOES16  
C4.3 11:16 S17E49 13617 GOES16  
C3.0 12:15   13615 GOES16  
C6.0/1F 13:27 N14E09 13614 GOES16  
C6.2 13:35   13614 GOES16  
C8.4 13:58   13614 GOES16  
C6.4 14:41 N20E14 13614 GOES16  
C3.6 15:30 behind northeast limb   GOES16  
C3.5 16:13   13615 GOES16 simultaneous flare in AR 13618
C4.1 16:29   13615 GOES16  
C4.9 16:57   13617 GOES16  
C3.5 17:44   13617 GOES16  
C3.8 18:21   13615 GOES16  
C3.6 19:09   13615 GOES16  
C3.4 19:38   13615 GOES16  
C5.2 20:04   13615 GOES16  
C5.9 20:12   13615 GOES16  
M4.3/2B 20:32   13615 GOES16  
M1.1 21:22 S14E18 13615 GOES16  
C5.9 21:40   13615 GOES16  
C7.4 22:55   13615 GOES16  
C8.5 23:24 behind northeast limb   GOES16 LDE
C8.3 23:58 S15E15 13615 GOES16  

Coronal mass ejections (CMEs)

March 20-22: No obviously Earth directed CMEs were observed.
March 23: An asymmetrical full halo CME was observed after the X1.1 flare in AR 13614 early in the day. The CME could reach Earth sometime between late on March 24 and noon on March 25 and cause active to severe storm conditions.

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 negative polarity southern hemisphere coronal hole (CH1207) rotated across the central meridian on March 20-22.

Propagation

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

Forecast

The geomagnetic field is expected to be quiet to minor storm on March 23-24 due to effects associated with CH1207 due to CME effects. The March 23 CME could reach Earth between late on March or noon on March 25 and cause active to severe storm conditions lasting until March 26 or 27.

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
13608 2024.03.10
2024.03.13
2 2   N11W81 0010 BXO AXX  
13609 2024.03.11       N06W82           location: N05W69
13607 2024.03.11
2024.03.13
2 2 1 S18W91 0150 DSO AXX

location: S19W84

area: 0020

13610 2024.03.12
2024.03.13
      S16W57           location: S15W46
13611 2024.03.13
2024.03.14
      N28W46        

location: N29W40

13616 2024.03.16
2024.03.18
1     N03W88 0010 BXO    

rotated out of view

mismatch between SWPC spot count and classification

13614 2024.03.16
2024.03.17
4 27 14 N17E03 0210 DSO DSO

area: 0270

location: N16E06

13615 2024.03.17
2024.03.18
52 110 62 S13E10 0370 EKC FKC beta-gamma-delta

area: 1270

location: S12E12

S9513 2024.03.17       S15W48            
S9514 2024.03.17       S30W36            
S9515 2024.03.17       N09E06            
S9518 2024.03.18       N26W56            
S9519 2024.03.18       N09W19            
13618 2024.03.19
2024.03.21
6 7 5 S19W77 0100 CAO DAO location: S19W76
13617 2024.03.19
2024.03.20
6 14 7 S14E41 0100 CAO CAO

location: S13E44

S9525 2024.03.20   9 3 N17W23 0020   BXO  
13619 2024.03.20
2024.03.21
5 12 6 N20E46 0100 CAO CAO location: N19E44

area: 0150

S9528 2024.03.21   3 2 N19E60 0010   AXX  
S9529 2024.03.21       S22E06          
S9530 2024.03.21       N37W07          
S9531 2024.03.22   7 5 N09W01 0015   BXO    
13620 2024.03.22
2024.03.22
3 4 3 S10E74 0030 CRO CAO   was AR S9532

area: 0060

S9533 2024.03.22   1   N05W09 0002   AXX   was AR S9527
S9534 2024.03.22   2 2 S04W14 0005   BXO    
S9535 2024.03.22   2 1 S08E26 0005   AXX    
Total spot count: 81 202 111  
Sunspot number: 171 342 231  (total spot count + 10 * number of spotted regions)
Weighted SN: 119 237 146  (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): 188 188 185  

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
2024.03 146.6 (1)   71.1 (2A) / 100.2 (2B) / 126.4 (2C) (116.9 projected, -0.6) (8.1)
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.