Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 5, 2023 at 06:00 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 (April 1, 2023)
Solar cycle Solar cycles 23-25 (April 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (April 1, 2023) 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 (April 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (April 1, 2023) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (April 5, 2023) 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

Recent activity

The geomagnetic field was quiet to active on April 4, most likely due to effects from CH1139. Solar wind speed at SOHO ranged between 483 and 566 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 135.7 - decreasing 46.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 138.44). The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.5). Three hour interval K indices: 44222133 (planetary), 33323322 (Boulder), 54322254 (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 12 active regions using 2K resolution (SN: 227) and in 8 active regions using 1K resolution (SN: 129) SDO/HMI images.

Region 13264 [N16W72] decayed slowly and quietly.
Region 13266 [N09W39] was quiet and stable.
Region 13267 [S18W30] decayed slowly and quietly.
Region 13269 [S27E20] developed slowly and quietly.
Region 13270 [S23W30] developed further gaining area and spots. Magnetically the region became simpler as the magnetic deltas disappeared and only minor polarity intermixing remains. An M class flare is still possible. C1 flares: C1.4 @ 01:24, C1.7 @ 02:49, C1.3 @ 03:40, C1.2 @ 03:52, C1.3 @ 04:05, C1.5 @ 04:13 UT
New region 13271 [S17W18] emerged on April 2 and was numbered by SWPC 2 days later.

Spotted regions not observed (or interpreted differently) by SWPC:
S8408 [N13W15] was quiet and stable.
S8424 [S18W45] was mostly quiet and stable. C1 flare: C1.4 @ 04:47 UT
S8426 [N37E10] was quiet and stable.
New region S8427 [N12E10] emerged with tiny spots.
New region S8428 [N19E23] emerged with tiny spots.
New region S8429 [S24E55] was observed with tiny spots in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.1 03:08   S8429 GOES16  

Coronal mass ejections (CMEs)

April 2-4: 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 southern hemisphere coronal hole (CH1139) rotated across the central meridian on April 1. A recurrent northern hemisphere coronal hole (CH1140) will likely become Earth facing on April 7-8.

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

Quiet to unsettled conditions are expected April 5 due to effects from CH1139. Quiet conditions are likely on April 6-7.

Coronal holes (1) Coronal mass ejection (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
13264 2023.03.23
2023.03.24
1 2 1 N16W72 0000 AXX AXX

area: 0008

13266 2023.03.26
2023.03.29
  10 4 N10W39 0030   DRO location: N09W39
13267 2023.03.27
2023.03.29
  2   S17W36 0004   AXX location: S18W30
S8408 2023.03.28   13 4 N13W15 0025   BXO  
13268 2023.03.28
2023.03.29
      S24W61           location: S23W55
13269 2023.03.30
2023.04.02
  10 2 S25E28 0020   BXO location: S27E20
S8417 2023.03.31       S14W56            
S8418 2023.04.01       S11E16            
13270 2023.04.02 11 49 31 S23W32 0140 DSI DKI beta-gamma

location: S23W30

area: 0540

S8419 2023.04.02       N35W41          
13271 2023.04.02
2023.04.04
2 6 4 S17W18 0000 AXX BXO area: 0020
S8422 2023.04.02       N11W22          
S8423 2023.04.02       S29E08          
S8424 2023.04.03   1   S18W45 0002   AXX  
S8425 2023.04.03       S05W30          
S8426 2023.04.03   6   N37E10 0008   BXO  
S8427 2023.04.04   3 2 N12E10 0012   CRO    
S8428 2023.04.04   2   N19E23 0003   BXO    
S8429 2023.04.04   3 1 S24E55 0006   BXO    
Total spot count: 14 107 49  
Sunspot number: 44 227 129  (total spot count + 10 * number of spotted regions)
Weighted SN: 19 123 65  (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): 48 125 103  

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
2021.09 87.0 88.2 51.3 40.2 (+4.8) 6.33
2021.10 88.9 88.3 37.4 45.2 (+5.0) 7.38
2021.11 86.2 84.4 34.8 50.8 (+5.6) 9.83
2021.12 103.0 99.8 67.5 55.9 (+5.1) 6.40
2022.01 103.8 100.5 55.3 60.1 (+4.2) 8.92
2022.02 109.1 106.5 60.9 64.7 (+4.6) 10.46
2022.03 117.0 115.8 78.6 68.7 (+4.0) 10.20
2022.04 130.8 131.7 84.0 73.0 (+4.3) 11.79
2022.05 133.8 136.8 96.5 77.4 (+4.4) 7.48
2022.06 116.1 119.8 70.3 81.1 (+3.7) 8.20
2022.07 125.4 129.5 91.4 86.7 (+5.6) 9.51
2022.08 114.2 117.1 74.6 92.5 (+5.8) 10.92
2022.09 135.1 136.5 96.0 96.4 (+3.9) 12.18
2022.10 133.5 132.7 95.5 (99.0 projected, +2.6) 11.16
2022.11 123.4 120.7 80.5 (102.0 projected, +3.0) 9.33
2022.12 147.9 143.4 112.8 (106.8 projected, +4.8) 10.99
2023.01 182.4 176.6 143.6 (112.9 projected, +6.1) 8.73
2023.02 167.2 163.2 110.9 (117.9 projected, +5.0) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 122.6 (121.0 projected, +3.1) 14.5
2023.04 130.4 (1)   5.9 (2A) / 44.3 (2B) / 131.8 (2C) (126.4 projected, +5.4) (12.9)
2023.05       (132.1 projected, +5.7)  
2023.06       (135.2 projected, +3.1)  
2023.07       (134.7 projected, -0.5)  
2023.08       (135.7 projected, +1.0)  
2023.09       (139.2 projected, +3.5)  
2023.11       (142.5 projected max SC25)  

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: SIDC-SILSO.

Solar cycles 24-25

Smoothed SF and sunspot numbers

 

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.