Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 18, 2024 at 05:55 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 inactive on March 17. Solar wind speed at SOHO ranged between 297 and 363 km/sec. The high latitude magnetometer at Andenes recorded inactive levels. The above 10 MeV proton flux was at 1 pfu at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 151.3 - decreasing 0.8 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.34. 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 0 (STAR Ap - based on the mean of three hour interval ap indices: 0.3). Three hour interval K indices: 00000000 (planetary), 00112321 (Boulder), 00000000 (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 15 active regions using 2K resolution (SN: 279) and in 11 active regions using 1K resolution (SN: 173) SDO/HMI images.

Region 13606 [N08W42] was quiet and stable.
Region 13607 [S18W18] decayed early in the day, then new flux emerged and many new spots formed.
Region 13608 [N10W11] developed slowly and quietly.
Region 13611 [N28E22] decayed slowly and quietly.
Region 13612 [N22W82] developed significantly as the spot group began to rotate out of view at the northwest limb. This region was the source of an M2.7 flare 03:32 UT on March 18.
Region 13613 [S22W31] developed further and could produce C flares and maybe a minor M class flare.
New region 13614 [N16E71] rotated into view on March 16 and was numbered the next day by SWPC. The spot group was mostly unchanged on March 17 and has a significant magnetic delta structure within the large main penumbra. A major flare is possible. An M1.0 flare was recorded at 04:14 UT on March 18. C1 flares: C1.7 @ 14:52 UT

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9484 [S16W41] decayed slowly and quietly.
S9505 [N03W17] developed slowly and quietly.
New region S9510 [N26E06] emerged with tiny spots before noon, then decayed slowly.
New region S9511 [S12E80] rotated into view with many small spots. The spot group has a small magnetic delta structure in the central spot section. M class flaring is likely. C1 flares: C1.9 @ 00:02, C1.9 @ 05:27, C1.8 @ 14:11, C1.8 @ 19:13, C1.9 @ 20:19 UT
New region S9512 [N20W04] was observed with tiny spots in an old plage area.
New region S9513 ]S10E15] emerged with tiny spots.
New region S9514 [S30E29] emerged with a tiny spot.
New region S9515 [N09E73] emerged with a tiny spot.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.9 00:42 southeast limb S9511 GOES16  
C2.5 02:36   13613 GOES16 LDE, associated with filament eruption
C2.1 03:25   13614 GOES16  
C6.6 03:59 southeast limb S9511 GOES16  
C3.9 04:27   13614 GOES16  
C3.5 04:36   13614 GOES18  
C3.8 05:47   13614 GOES18  
C2.1 06:32   S9511 GOES16  
C2.4 06:52   13614 GOES16  
C2.8 07:41 southeast limb S9511 GOES16  
C2.1 10:22   13612 GOES16  
C4.3 10:43 southeast limb S9511 GOES16  
C5.5 12:13 southeast limb S9511 GOES16  
C3.3 12:23 southeast limb S9511 GOES16  
C2.3 12:59 southeast limb S9511 GOES16  
C2.8 13:19   13614 GOES16  
C3.1 13:23   S9511 GOES16  
C2.7 13:43 southeast limb S9511 GOES16  
C4.9 15:43   13612 GOES16  
C3.3 15:58 southeast limb S9511 GOES16  
C3.3 16:09   13612 GOES16  
C2.4 17:46   13614 GOES16 simultaneous flare in AR S9511
C2.6 19:44 southeast limb S9511 GOES16  
C4.9 21:12   13612 GOES16  
C3.7 21:42   13612 GOES16  
C2.1 00:01   13614 GOES16  

Coronal mass ejections (CMEs)

March 15-16: 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 positive polarity northern hemisphere coronal hole (CH1206) was in an Earth facing position on March 14. A negative polarity southern hemisphere coronal hole (CH1207) will likely rotate across the central meridian on March 20-21.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on March 18-19 due to effects from CH1206. The March 17 CME could reach Earth on March 20 and cause unsettled to active conditions that day and on March 21.

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
S9484 2024.03.07   2   S16W41 0003   AXX  
13606 2024.03.10
2024.03.12
  2 1 N09W40 0005   BXO

location: N08W42

13608 2024.03.10
2024.03.13
10 14 8 N11W10 0030 DRO DRI location: N10W11

area: 0050

S9491 2024.03.11       N06W40            
13609 2024.03.11       N06W08           location: N05W04
13607 2024.03.11
2024.03.13
5 25 12 S17W21 0030 DRO DRI

location: S18W18

area: 0100

S9494 2024.03.11       N26W48            
13610 2024.03.12
2024.03.13
      S16E14         location: S15E19
13611 2024.03.13
2024.03.14
1 5 3 N28E21 0020 HRX HRX area: 0030

location: N28E22

S9499 2024.03.13       N17W39          
13612 2024.03.14
2024.03.15
2 5 2 N22W80 0010 AXX DRO location: N22W82

area: 0050

S9502 2024.03.14       N25W30            
13613 2024.03.15
2024.03.16
7 28 15 S22W30 0130 DAI DAI location: S22W31

area: 0270

S9505 2024.03.16   5 2 N03W17 0020   DRO  
13614 2024.03.16
2024.03.17
1 7 5 N16E70 0080 HAX DKC beta-delta

location: N16E71

area: 0400

S9509 2024.03.16       S06W04          
S9510 2024.03.17   3   S26E06 0005   BXO    
S9511 2024.03.17   23 10 S12E80 0150   ERI   beta-delta
S9512 2024.03.17   1   N20W04 0001   AXX    
S9513 2024.03.17   7 3 S10E15 0015   AXX    
S9514 2024.03.17   1 1 S30E29 0003   AXX    
S9515 2024.03.17   1   N09E73 0002   AXX    
Total spot count: 26 129 62  
Sunspot number: 86 279 172  (total spot count + 10 * number of spotted regions)
Weighted SN: 44 162 95  (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): 95 153 138  

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
2024.03 137.2 (1)   48.6 (2A) / 88.6 (2B) / 113.5 (2C) (116.9 projected, -0.6) (7.8)
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.