Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 6, 2023 at 09:20 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 unsettled on April 5, most likely due to effects from CH1139. Solar wind speed at SOHO ranged between 399 and 519 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 136.6 - decreasing 42.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 138.48). The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 10.8). Three hour interval K indices: 32223332 (planetary), 33334422 (Boulder), 44223445 (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 17 active regions using 2K resolution (SN: 277) and in 11 active regions using 1K resolution (SN: 161) SDO/HMI images.

Region 13266 [N10W53] was quiet and stable.
Region 13267 [S18W48] decayed slowly and quietly.
Region 13269 [S28E13] was quiet and stable.
Region 13270 [S23W44] lost spots and some area. The region still has minor polarity intermixing. Although the region was mostly quiet, an M class flare is possible. C1 flares: C1.0  @ 04:18 UT
Region 13271 [S17W32] decayed slowly and quietly.

Spotted regions not observed (or interpreted differently) by SWPC:
S8408 [N13W25] was quiet and stable.
S8418 [S10W09] reemerged with tiny spots.
S8422 [N12W37] reemerged with tiny spots.
S8423 [S32W09] reemerged with tiny spots.
S8424 [S17W60] developed slowly and was quiet.
S8426 [N31W03] was quiet and stable.
S8427 [N11W03] was quiet and stable.
S8429 [S26E41] was quiet and stable.
New region S8430 [N28E50] emerged with a tiny spot.
New region S8431 [S21W01] emerged before noon with tiny spots, then decayed slowly.
New region S8433 [S21E84] rotated partly into view. This region was the source of an M3.0 flare at 05:54 UT on April 6. Further M class flares are possible. C1 flares: C1.0 @ 03:29, C1.1 @ 05:22, C1.3 @ 10:20, C1.8 @ 12:17, C1.0 @ 17:11, C1.7 @ 17:52, C1.4 @ 18:09, C1.2 @ 19:01, C1.2 @ 21:02, C1.4 @ 21:19, C1.2 @ 22:06 UT
New region S8434 [S07E69] emerged with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment

Coronal mass ejections (CMEs)

April 3-5: 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 conditions are likely on April 6-9. Quiet to active conditions are possible on April 10-11 due to effects from CH1140.

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
      N17W88        

 

13266 2023.03.26
2023.03.29
2 11 6 N11W54 0030 CRO CRO location: N10W53
13267 2023.03.27
2023.03.29
  1   S17W50 0001   AXX location: S18W48
S8408 2023.03.28   12 4 N13W25 0020   BXO  
13268 2023.03.28
2023.03.29
      S24W75           location: S23W68
13269 2023.03.30
2023.04.02
  8 4 S25W00 0013   BXO location: S28E13
S8418 2023.04.01   3 1 S10W09 0007   BXO    
13270 2023.04.02 15 40 25 S23W45 0140 DAI EAI beta-gamma

location: S23W44

area: 0480

S8419 2023.04.02       N35W54            
13271 2023.04.02
2023.04.04
  4   S16W33 0005   BXO location: S17W32
S8422 2023.04.02   5 3 N12W37 0010   BXO    
S8423 2023.04.02   3 3 S32W09 0010 BXO      
S8424 2023.04.03   3 1 S17W60 0010   HRX  
S8425 2023.04.03       S05W43            
S8426 2023.04.03   5   N31W03 0008   BXO  
S8427 2023.04.04   2 2 N11W03 0010   BXO  
S8428 2023.04.04       N19E10          
S8429 2023.04.04   5   S26E41 0007   BXO  
S8430 2023.04.05   1 1 N28E50 0004   AXX    
S8431 2023.04.05   2   S21W01 0002   AXX  
S8432 2023.04.05       S14E21          
S8433 2023.04.05   1 1 S21E84 0110   HAX    
S8434 2023.04.05   1   S07E69 0001   AXX    
Total spot count: 17 107 51  
Sunspot number: 37 277 161  (total spot count + 10 * number of spotted regions)
Weighted SN: 25 123 67  (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): 41 152 129  

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) 14.42
2023.04 131.6 (1)   7.1 (2A) / 42.8 (2B) / 129.0 (2C) (126.4 projected, +5.4) (12.5)
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.