Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 30, 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 on March 29. The high latitude magnetometer at Andenes recorded quiet to unsettled levels. The above 10 MeV proton flux was at 0.2 pfu at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 167.3 - increasing 15.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 157.26. 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 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.9). Three hour interval K indices: 22222101 (planetary), 21221211 (Boulder), 33112101 (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 8 active regions using 2K resolution (SN: 148) and in 8 active regions using 1K resolution (SN: 115) SDO/HMI images.

Region 13615 [S12W73] continued to produce many C and M flares, although at a slightly lower level than during the previous days. The leader spots rotated out of view. The huge trailing penumbra became less complex as the magnetic delta structure disappeared. There are still magnetic deltas in the easternmost parts of that penumbra. Major flares are possible as the spot group is rotating over the southwest limb.
Region 13617 [S12W47] decayed slowly and quietly.
Region 13619 [N18W51] was quiet and stable.
Region 13620 [S10W15] was quiet and stable.
Region 13622 [N20W00] was quiet and stable.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9528 [N19W33] was quiet and stable.
New region S9546 [S13W28] emerged with tiny spots before noon, then decayed slowly.
New region S9547 [S10E23] emerged with tiny spots.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C3.0 00:40   13615 GOES16  
C4.6 00:54   13615 GOES16  
C4.0 01:40   13615 GOES16  
C9.4 02:06   13615 GOES16  
M3.2 02:30 S15W63 13615 GOES16  
C2.7 04:07   13617 GOES16  
C3.1 04:46   13615 GOES18  
C2.7 05:13   13615 GOES18  
C3.0 05:41   13615 GOES18  
C3.4 07:31   13615 GOES16  
C2.7 08:16   13615 GOES16  
C4.1 09:41   13615 GOES16  
C5.4 10:07   13615 GOES16  
C8.7 10:22   13615 GOES16  
C9.0 10:44   13615 GOES16  
C6.0 11:31   13615 GOES16  
C5.7 11:41   13615 GOES16  
C8.0/1F (estimated) 13:02   13615 GOES16  
C5.1 13:39   13615 GOES16  
C3.7 14:05   13615 GOES16  
C3.4 15:20   13615 GOES16  
C3.3 15:29   13615 GOES16  
C7.8 16:01   13615 GOES16  
C9.4 16:36   13615 GOES16  
C7.2 17:24   13615 GOES16  
M1.0 18:43   13615 GOES16  
M1.2 19:34 S12W78 13615 GOES16  
C7.8 20:34   13615 GOES16  
C5.5 21:08   13615 GOES16  
C4.0 22:03   13615 GOES16  
C3.7 22:26   13615 GOES16  
C2.8 23:06   13615 GOES16  
C3.5 23:23   13615 GOES16  
C3.2 23:35   13615 GOES16  

Coronal mass ejections (CMEs)

March 27-29: 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) was Earth facing on March 27-28. A trans equatorial negative polarity coronal hole (CH1210) will likely become Earth facing on March 31-April 1.

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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on March 30-31 due to effects from CH1208 and CH1209. Quiet conditions are likely on April 1-2. April 3-4 could see unsettled to minor storm conditions due to effects from CH1210.

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     N17W88 0050 HSX     rotated out of view
13615 2024.03.17
2024.03.18
34 34 21 S13W81 0960 FKC FKC beta-gamma-delta

area: 1600

location: S12W73

13617 2024.03.19
2024.03.20
2 7 3 S13W51 0030 CSO CRO

location: S12W47

13619 2024.03.20
2024.03.21
2 2 2 N17W52 0050 HSX HSX

location: N18W37

area: 0180

S9528 2024.03.21   6 2 N19W33 0010   BXO  
13620 2024.03.22
2024.03.22
  7 2 S08W24 0015   BXO

location: S10W15

13622 2024.03.23
2024.03.24
  6 1 N11W11 0010   BXO location: N20W00

SWPC position is way off

S9538 2024.03.23       S28W55            
S9539 2024.03.24       S15W27            
S9540 2024.03.24       S11W06            
S9542 2024.03.26       S23W21            
S9543 2024.03.26       N09W34          
S9546 2024.03.29   4 3 S13W28 0007   AXX    
S9547 2024.03.29   2 1 S10E23 0007   AXX    
Total spot count: 39 68 35  
Sunspot number: 79 148 115  (total spot count + 10 * number of spotted regions)
Weighted SN: 64 86 53  (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): 87 81 92  

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
2024.03 155.6 (1)   100.0 (2A) / 106.9 (2B) / 126.7 (2C) (116.9 projected, -0.6) (11.5)
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.