Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 20, 2024 at 07:10 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 19, weakly under the influence of coronal hole effects. Solar wind speed at SOHO ranged between 362 and 421 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels. The above 10 MeV proton flux was slightly elevated above background levels at 0.3 pfu towards the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 168.9 - decreasing 1.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.45. 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: 6.3). Three hour interval K indices: 32221111 (planetary), 32333312 (Boulder), 33111224 (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 10 active regions using 2K resolution (SN: 249) and in 9 active regions using 1K resolution (SN: 175) SDO/HMI images.

Region 13607 [S18W46] decayed slowly and was mostly quiet.
Region 13608 [N10W37] decayed slowly and quietly.
Region 13611 [N28W02] decayed slowly and quietly.
Region 13613 [S22W58] decayed slowly and quietly.
Region 13614 [N17E45] was mostly quiet, however, there is still a significant magnetic delta structure within the large main penumbra. A major flare is possible.
Region 13615 [S12E53] developed slowly and was by a large margin the most active spot group on the visible disk. There is significant polarity intermixing and several small magnetic delta structures are visible. Further M class flaring is likely. C1 flares: C1.8 @ 14:43, C1.9 @ 14:50 UT
Region 13616 [N02W45] developed early in the day, then decayed after noon. The region produced several C flares.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9518 [N26W17] was quiet and stable.
New region S9522 [S19W34] emerged with tiny spots.
New region S9523 [S13E83] rotated into view with a large penumbra containing a few spots. A minor M class flare is possible.

Minor update at 07:55 UT: AR 13615 produced a major M7.4 flare at 07:36 UT on March 20. It is not yet known if there was a CME associated with this event.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.6 00:34 behind northwest limb   GOES16  
C3.7 01:16   13615 GOES16  
C2.4 01:40   13615 GOES16  
C2.7 01:48   13615 GOES16  
C3.5 01:59   13616 GOES16  
M1.4 02:29   13615 GOES16  
C2.3 03:09   13615 GOES16  
C5.2 03:47   13616 GOES16  
C5.3 05:16   13615 GOES18 simultaneous flare in AR S9523
C2.4 05:37   13615 GOES18  
C2.2 05:59   13614 GOES16  
C4.2 06:18   13615 GOES16  
C2.4 07:28   13615 GOES16  
C2.6 07:51   13614 GOES16  
C2.8 10:01   13615 GOES16  
C2.2 10:37   13616 GOES16  
C3.6 11:40 S12E60 13615 GOES16  
C3.1 11:53   13615 GOES16  
C2.8 12:40   13615 GOES16  
C5.9 12:53 S11E59 13615 GOES16  
C4.3 13:15 southeast limb S9523 GOES16 simultaneous flare in AR 13615
C2.1 13:51   13615 GOES16  
C2.3 14:57   13615 GOES16  
C2.5 15:09   13615 GOES16  
C2.7 15:59   13615 GOES16  
C2.9 16:29   13615 GOES16  
C7.1 17:26 S14E59 13615 GOES16  
C2.4 18:14   13615 GOES16  
C5.8 19:58   13615 GOES16  
C3.0 21:21   13615 GOES16  
C6.0 21:30 N05W44 13616 GOES16  
C2.1 22:32   13614 GOES16  
M2.1 23:27 S16E57 13615 GOES16  

Coronal mass ejections (CMEs)

March 18-19: No obviously Earth directed CMEs were observed.
March 17: A faint full halo CME was observed after a southern hemisphere filament eruption that began at approx. 02:16 UT. The CME was visible in LASCO C2 imagery from 03:36 UT

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 20-21 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
      N09W68          

location: N08W68

13608 2024.03.10
2024.03.13
5 9 5 N10W38 0020 CAO BXO location: N11W23

area: 0030

13609 2024.03.11       N06W36           location: N05W30
13607 2024.03.11
2024.03.13
11 18 12 S17W48 0080 DAO DAI

location: S18W46

area: 0120

13610 2024.03.12
2024.03.13
      S16W14           location: S15W07
13611 2024.03.13
2024.03.14
1 3 1 N28W03 0010 HRX AXX

location: N28W02

S9502 2024.03.14       N25W56            
13613 2024.03.15
2024.03.16
9 15 9 S22W58 0080 DAI DAI

area: 0130

13616 2024.03.16
2024.03.18
9 8 6 N02W45 0050 CAO CAI

area: 0130

13614 2024.03.16
2024.03.17
6 25 9 N16E43 0200 DAO DKC beta-delta

location: N17E45

area: 0300

S9509 2024.03.16       S06W30            
S9510 2024.03.17       S22W21          
13615 2024.03.17
2024.03.18
28 59 37 S12E48 0240 EAC EAC beta-gamma-delta

location: S12E53

area: 0350

S9512 2024.03.17       N20W30            
S9513 2024.03.17       S15W09          
S9514 2024.03.17       S30E03            
S9515 2024.03.17       N09E45          
S9518 2024.03.18   3   N26W17 0005   BXO  
S9519 2024.03.18       N09E20          
S9522 2024.03.19   6 4 S19W34 0012   BXO    
S9523 2024.03.19   3 2 S13E83 0310   HKX    
Total spot count: 69 149 85  
Sunspot number: 139 249 175  (total spot count + 10 * number of spotted regions)
Weighted SN: 102 189 125  (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): 153 137 140  

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
2024.03 140.5 (1)   57.2 (2A) / 93.3 (2B) / 115.8 (2C) (116.9 projected, -0.6) (7.5)
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.