Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 16, 2024 at 08:05 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 15 due to weakening effects from CH1204. Solar wind speed at SOHO ranged between 387 and 439 km/sec. The high latitude magnetometer at Andenes recorded quiet to major storm levels. The above 10 MeV proton flux was at 10 pfu at the end of the day due to long duration events from AR 13599 behind the southwest limb.

Solar flux density measured at 20h UT on 2.8 GHz was 129.0 - decreasing 40.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.28. 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: 6.5). Three hour interval K indices: 32211101 (planetary), 43211210 (Boulder), 63312101 (Andenes).

The background x-ray flux is at the class B7 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 9 active regions using 2K resolution (SN: 144) and in 8 active regions using 1K resolution (SN: 106) SDO/HMI images.

Region 13606 [N08W12] was quiet and stable.
Region 13607 [S17E03] decayed slowly and quietly.
Region 13610 [S16E41] decayed slowly and quietly.
Region 13611 [N28E48] was quiet and stable.
New region 13612 [N23W58] emerged on March 14 and was numbered the next day as the spot group began to decay.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9484 [S20W28] was quiet and stable.
S9499 [N14W15] was quiet and stable.
New region S9503 [S22W03] emerged with tiny spots.
New region S9504 [N23E03] emerged with tiny spots.

AR 13599 behind the southwest limb produced several C1 flares: C1.3 @ 00:06, C1.9 @ 01:47, C1.7 @ 12:10 UT
An active region behind the northeast limb was the source of a C1.3 flare at 20:36 UT

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.9 04:05   13599 GOES16 LDE, CME
C5.5 05:15   13599 GOES18  
C6.0 06:10   13599 GOES16 LDE, proton event

Coronal mass ejections (CMEs)

March 13-15: 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 small negative polarity southern hemisphere coronal hole (CH1205) was Earth facing on March 13. A positive polarity northern hemisphere coronal hole (CH1206) was in an Earth facing position on March 14.

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 to unsettled on March 16-17 due to effects from CH1205 and on March 18 due to effects from CH1206.

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
13604 2024.03.04
2024.03.05
      N08W69        

location: N08W62

13605 2024.03.07
2024.03.07
      S13W86        

location: S15W80

S9484 2024.03.07   8   S20W28 0012   BXO  
13606 2024.03.10
2024.03.12
  8 4 N09W13 0015   BXO

location: N08W12

13608 2024.03.10
2024.03.13
      N11E14         location: N15E14
S9491 2024.03.11       N06W14            
13609 2024.03.11       N06E22           location: N05E22
13607 2024.03.11
2024.03.13
6 18 11 S17E06 0040 DRO DRO area: 0050

location: S17E03

S9494 2024.03.11       N26W22            
S9495 2024.03.12       N32W51            
13610 2024.03.12
2024.03.13
1 3 1 S16E42 0010 AXX AXX location: S16E41
S9497 2024.03.13       S09W52            
13611 2024.03.13
2024.03.14
1 3 2 N28E48 0020 HRX HAX area: 0040
S9499 2024.03.13   3 1 N14W15 0006   BXO  
13612 2024.03.14
2024.03.15
1 2 1 N23W57 0010 AXX HRX location: N23W58
S9502 2024.03.14       N25W04          
S9503 2024.03.15   6 4 S22W03 0015   BXO    
S9504 2024.03.15   3 2 S23E31 0007   BXO    
Total spot count: 9 54 26  
Sunspot number: 49 144 106  (total spot count + 10 * number of spotted regions)
Weighted SN: 15 65 37  (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): 54 79 85  

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
2024.03 135.8 (1)   43.6 (2A) / 90.2 (2B) / 114.3 (2C) (116.9 projected, -0.6) (8.7)
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.

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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.