Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 24, 2024 at 07:40 UT. Minor update posted at 15:30 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 unsettled to major storm on March 23 under the influence of effects from CH1207 most of the day. At 17:29 UT there was a sudden increase in solar wind temperature and solar wind speed at DSCOVR, possibly due to a CME combining with the coronal holehigh speed stream. Solar wind speed at SOHO ranged between 341 and 513 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at 294 pfu at the end of the day having peaked at 956 pfu at 18:20 UT and is likely to stay at moderate levels until the arrival of the March 23 CME late in the day or early on March 25.

Solar flux density measured at 20h UT on 2.8 GHz was 210.7 - increasing 29.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.84. 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 32 (STAR Ap - based on the mean of three hour interval ap indices: 32.5). Three hour interval K indices: 35444456 (planetary), 25434544 (Boulder), 15433555 (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: 299) and in 10 active regions using 1K resolution (SN: 190) SDO/HMI images.

Region 13614 [N17W07] decayed slowly losing area and spots. Apart from the major X1 flare early in the day, the region was mostly quiet.
Region 13615 [S12E01] developed further in the southern spot section. Fairly long neutral lines between opposite polarity spot sections have formed and an X class flare would be no surprise.
Region 13617 [S13E31] decayed slowly and was mostly quiet.
Region 13618 [S20W83] rotated mostly out of view and was quiet.
Region 13619 [N18E30] was mostly quiet and stable.
Region 13620 [S09E60] was mostly quiet and stable.
New region 13621 [N17W40] emerged on March 20 and was was numbered by SWPC 3 days later as the spot group began to decay.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9528 [N19E48] was quiet and stable.
S9529 [S19W09] reemerged with tiny spots.
New region S9536 [N19E77] rotated into view with a few spots.
New region S9537 [S10E13] emerged with tiny spots.
New region S9538 [S28E23] emerged with a tiny spot.

Minor update posted at 15:30 UT: The leading edge of the March 23 CME was observed at DSCOVR at approximately 14:02 UT, a transit time of just over 36 hours. Solar wind speed has reached 800 km/sec. The Bz component of the interplanetary magnetic field is currently very strongly southwards. K index intervals peaking at 8 or 9 are possible.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.9 00:22   13615 GOES16  
C4.9 00:48   13621 GOES16  
X1.1/2F 01:33 N27E08 13614 GOES16 LDE, moderate type II radio sweep
asymmetrical full halo CME
M5.0 02:36   13615 GOES16  
M1.4 04:27   13615 GOES16  
M1.5 04:54   13615 GOES18  
C8.9/1F 05:38   13615 GOES18  
M1.1 06:55 S13E04 13615 GOES16  
M2.4/1B 07:09   13615 GOES16  
M3.1 07:38   13615 GOES16  
M1.1 08:18   13615 GOES16  
C7.2 08:58   13615 GOES16  
C8.0 09:07   13615 GOES16  
C8.0 09:12   13615 GOES16  
C4.1 10:11   13615 GOES16  
C4.7 10:28   13617 GOES16  
C5.2 11:01   13615 GOES16  
C6.7 11:18 S15E05 13615 GOES16  
M1.0 11:29   13615 GOES16  
C5.9 12:03   13615 GOES16  
C5.8 12:15   13615 GOES16 simultaneous flare behind the southwest limb
M1.3 12:47   13615 GOES16  
M1.1 13:11   13615 GOES16  
M1.9 13:37   13615 GOES16  
M5.3/1B 14:02   13615 GOES16  
M1.8 14:33   13615 GOES16  
M1.5 14:53   13615 GOES16  
M3.8 15:13   13615 GOES16  
M2.8 16:51   13615 GOES16  
C3.9 17:48   13615 GOES16  
C4.2 18:20   13615 GOES16  
C9.9 18:57   13615 GOES16  
C9.0 19:42   13615 GOES16  
C8.5 20:08   13615 GOES16  
C9.9 20:21   13615 GOES16  
C9.3 20:28   13615 GOES16  
C6.4 20:56   13615 GOES16  
C6.1 21:05   13615 GOES16  
C6.2 21:25   S9536 GOES16  
C6.1 21:32   13615 GOES16  
C5.1 22:26   13615 GOES16  
C4.2 22:39   13615 GOES16  
C5.8 22:50   13615 GOES16  
C7.9 22:59   13615 GOES16  
M2.4/2N 23:49 S12E01 13615 GOES16  

Coronal mass ejections (CMEs)

March 21-22: 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 24 until the arrival of the March 23 CME. Active to severe storm conditions are likely from the onset of the CME disturbance until March 26.

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
13610 2024.03.12
2024.03.13
      S16W71           location: S15W59
13611 2024.03.13
2024.03.14
      N28W60          

location: N29W53

13614 2024.03.16
2024.03.17
5 28 8 N17W07 0170 DSO DSO

area: 0260

13615 2024.03.17
2024.03.18
53 100 59 S13W01 0730 FKC FKC beta-gamma-delta

area: 1760

location: S12E01

S9514 2024.03.17       S30W49            
S9515 2024.03.17       N09W07            
S9519 2024.03.18       N09W32            
13618 2024.03.19
2024.03.21
4 1 1 S18W90 0120 CAO AXX location: S20W83

area: 0004

13617 2024.03.19
2024.03.20
4 13 7 S14E29 0090 CAO CAO

location: S13E31

13621 2024.03.20
2024.03.23
4 5 2 N17W38 0020 CRO CAO location: N17W40

area: 0040

13619 2024.03.20
2024.03.21
3 15 5 N19E31 0120 CAO CAO location: N18E30

area: 0160

S9528 2024.03.21   2 1 N19E48 0005   AXX  
S9529 2024.03.21   5 3 S19W09 0020   CRO    
S9530 2024.03.21       N37W20            
S9531 2024.03.22       N09W14          
13620 2024.03.22
2024.03.22
3 3 2 S10E61 0030 HRX CAO

area: 0050

S9533 2024.03.22       N05W22         was AR S9527
S9534 2024.03.22       S04W27          
S9535 2024.03.22       S08E13          
S9536 2024.03.23   4 2 N19E77 0110   HAX    
S9537 2024.03.23   2   S10E13 0002   AXX    
S9538 2024.03.23   1   S28E23 0001   AXX    
Total spot count: 76 179 90  
Sunspot number: 146 299 190  (total spot count + 10 * number of spotted regions)
Weighted SN: 112 222 133  (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): 161 164 152  

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
2024.03 149.3 (1)   75.8 (2A) / 102.2 (2B) / 127.3 (2C) (116.9 projected, -0.6) (9.2)
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.