Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 21, 2024 at 04:25 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 20. Solar wind speed at SOHO ranged between 323 and 409 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at background levels at the end of the day. A weak solar wind shock was observed at ACE at 01:49 UT on March 21, the arrival of the March 17 CME.

Solar flux density measured at 20h UT on 2.8 GHz was 175.5 - increasing 2.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.51. 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 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.9). Three hour interval K indices: 20110012 (planetary), 10212312 (Boulder), 40010125 (Andenes).

The background x-ray flux is at the class C1 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 278) and in 11 active regions using 1K resolution (SN: 199) SDO/HMI images.

Region 13607 [S18W61] decayed slowly and quietly.
Region 13608 [N09W52] decayed slowly and quietly.
Region 13613 [S22W70] decayed slowly and quietly.
Region 13614 [N17E32] decayed slightly and was mostly quiet. The main penumbra has a magnetic delta structure and a major flare is possible.
Region 13615 [S12E39] gained spots and has many magnetic delta structures. Another major flare is likely. C1 flares: C1.7 @ 05:34, C1.7 @ 11:38, C1.7 @ 19:30 UT
Region 13616 [N02W62] decayed further and was quiet.
New region 13617 [S13E70] rotated into view on March 19 and was numbered by SWPC the next day as the spot group decayed slowly. C1 flares: C1.9 @ 03:16 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9522 [S19W48] developed slowly and quietly.
New region S9524 [S08W52] emerged with tiny spots.
New region S9525 [N17E03] emerged with a few spots.
New region S9526 [N19E74] rotated into view with small and tiny spots.
New region S9527 [N05E17] emerged with tiny spots.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C5.5 01:08 northeast limb S9526 GOES16  
C6.1 01:12   13615 GOES16  
C4.5 01:33   13615 GOES16  
C4.0 02:25   13615 GOES16  
C2.0 06:37   13615 GOES16  
M7.4/3B 07:36 S10E51 13615 GOES16  
C2.1 09:30   13615 GOES16  
C6.3 09:53   13615 GOES16  
C2.4 12:09   13615 GOES16  
C2.6 12:23   13615 GOES16  
C3.2 13:31 S11E43 13615 GOES16  
C3.2 13:36   13615 GOES16  
C3.3 14:53 S16E50 13615 GOES16  
C2.6 15:56   13615 GOES16  
C2.8 16:25   13615 GOES16  
C2.1 17:54   13617 GOES16  
C2.2 18:44   13615 GOES16  
C2.0 18:55   13615 GOES16  
C2.1 19:57   S9526 GOES16  
C2.2 20:43   13617 GOES16  
C2.8 20:57   13615 GOES16  
C3.3 21:34   13607 GOES16  
C3.5 21:47   13615 GOES16  
M1.8 22:56   13615 GOES16  
C8.7 23:18   13615 GOES16  

Coronal mass ejections (CMEs)

March 18-20: 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 negative polarity southern hemisphere coronal hole (CH1207) will rotate 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to active on March 21 due to effects from the March 17 CME. Quiet conditions are likely on March 22. A high speed stream associated with CH1207 could reach Earth on March 23 and cause unsettled to minor storm conditions lasting until March 25.

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
13606 2024.03.10
2024.03.12
      N09W82          

 

13608 2024.03.10
2024.03.13
2 8 4 N10W52 0010 AXX BXO location: N09W52

area: 0020

13609 2024.03.11       N06W53           location: N05W43
13607 2024.03.11
2024.03.13
10 12 7 S18W62 0070 DAI DAO

location: S18W62

area: 0150

13610 2024.03.12
2024.03.13
      S16W28           location: S15W20
13611 2024.03.13
2024.03.14
      N28W17        

location: N28W15

13613 2024.03.15
2024.03.16
5 5 4 S22W70 0060 DAO DAO

area: 0100

13616 2024.03.16
2024.03.18
6 4 3 N02W59 0030 CAO CRO

location: N02W62

13614 2024.03.16
2024.03.17
4 24 10 N17E32 0200 DAO DKC beta-delta

area: 0300

S9509 2024.03.16       S06W43            
S9510 2024.03.17       S22W34            
13615 2024.03.17
2024.03.18
20 68 41 S12E39 0300 EKC EAC beta-gamma-delta

area: 0450

S9512 2024.03.17       N20W43            
S9513 2024.03.17       S15W22            
S9514 2024.03.17       S30W10            
S9515 2024.03.17       N09E32            
S9518 2024.03.18       N26W30          
S9519 2024.03.18       N09E07            
S9522 2024.03.19   17 10 S19W48 0060   DRI  
13617 2024.03.19
2024.03.20
3 5 4 S15E70 0060 HAX HAX area: 0260

location: S13E70

S9524 2024.03.20   3 1 S08W52 0012   CRO    
S9525 2024.03.20   4 2 N17E03 0015   CRO    
S9526 2024.03.20   6 3 N19E74 0020   CRO    
S9527 2024.03.20   2   N05E17 0003   BXO    
Total spot count: 50 158 89  
Sunspot number: 120 278 199  (total spot count + 10 * number of spotted regions)
Weighted SN: 85 203 134  (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): 132 153 159  

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
2024.03 142.3 (1)   61.0 (2A) / 94.6 (2B) / 117.9 (2C) (116.9 projected, -0.6) (7.3)
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.