Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 12, 2023 at 09:50 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 11. Solar wind speed at SOHO ranged between 379 and 472 km/sec. The high latitude magnetometer at Andenes recorded quiet to unsettled levels.

Solar flux density measured at 20h UT on 2.8 GHz was 143.4 - increasing 7.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.00). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 01311120 (planetary), 11322311 (Boulder), 10101322 (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 15 active regions using 2K resolution (SN: 351) and in 12 active regions using 1K resolution (SN: 201) SDO/HMI images.

Region 13272 [S21E09] could be splitting into a northern and a southern spot group. As it is the region still has polarity intermixing and M class flare potential. C1 flares: C1.2 @ 01:33, C1.1 @ 07:12, C1.2 @ 07:38, C1.1 @ 09:47 UT
Region 13273 [N09W01] decayed slowly after losing area and spots. C1 flares: C1.1 @ 13:51 UT
Region 13274 [S07W14] developed slowly in the leading spot section and produced a low level flare at 19:56 UT.
Region 13275 [N19E49] was quiet and stable.
Region 13276 [S22E61] was mostly quiet and stable. SWPC apparently considers AR S8452 as part of this region. If that was the case the total longitudinal extension of the group would be 21 degrees. C1 flares: C1.3 @ 11:55 UT
New region 13277 [N10E23] emerged on April 10 and was numbered by SWPC the next day.

Spotted regions not observed (or interpreted differently) by SWPC:
S8429 [S19W35] developed slowly in the northern section and was quiet.
S8439 [S29W18] reemerged with tiny spots.
S8442 [N13W21] decayed slowly and quietly.
S8445 [N24E20] was quiet and stable.
S8446 [N27W02] was quiet and stable.
S8452 [S20E77] rotated fully into view and produced a few C flares. C1 flares: C1.2 @ 01:33, C1.5 @ 01:45, C1.3 @ 01:58, C1.6 @ 03:31, C1.4 @ 05:25, C1.6 @ 08:15, C1.0 @ 12:55 UT
S8455 [N23E34] was quiet and stable.
New region S8459 [N08E31] emerged with a few spots.
New region S8460 [S10E01] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.6 00:05   S8452 GOES16  
C6.3 03:07 S19E20 13272 GOES16  
M1.3/1N 10:16 S20E17 13272 GOES16  
C2.1 14:41 N10E05 13273 GOES16  
C5.9/1B 22:42 S20E09 13272 GOES16  

Coronal mass ejections (CMEs)

April 11: No obviously Earth directed CMEs were observed.
April 10: A filament eruption in the northeast quadrant began just after 06h UT and lasted until after 09h UT. Coronal dimming was observed over a fairly large area to the south of the eruption. Due to the absence of LASCO imagery for the hours after the event, it is uncertain if a CME was produced.
April 9
: A filament eruption in the southwest quadrant was observed beginning in SDO/AIA imagery at 19:06 UT and peaked 40 minutes later. A partial halo CME was observed in LASCO C2 imagery from 20:00 UT. There is a chance components of this CME will reach Earth on April 12 or 13.

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 recurrent northern hemisphere coronal hole (CH1140) was 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 fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

Quiet conditions are likely on April 12. There's a chance components of the April 9 and 10 CMEs could reach Earth on April 12-14 and cause unsettled to minor storm conditions. If that doesn't happen, conditions will likely remain quiet.

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
13269 2023.03.30
2023.04.02
      S25W82           location: S24W73
S8429 2023.04.04   13 5 S19W35 0030   BXO  
S8432 2023.04.05       S14W57            
13272 2023.04.05
2023.04.06
36 81 36 S21E10 0250 FKC FAI beta-gamma

area: 0280

location: S21E09

S8434 2023.04.05       S07W09            
S8435 2023.04.06       S27W43            
S8437 2023.04.06       S13W39          
S8438 2023.04.06       N14W36            
S8439 2023.04.07   8 2 S29W18 0015   BXO    
13274 2023.04.08
2023.04.10
  5 2 S07W17 0014 AXX BXO  
S8442 2023.04.08   9 2 N13W21 0015   BXO  
13273 2023.04.09
2023.04.09
12 31 14 N09W01 0100 DSI DAI

area: 0160

13275 2023.04.09
2023.04.10
1 4 3 N20E48 0050 HSX HSX area: 0100

location: N19E49

S8445 2023.04.09   4   N24E20 0008   BXO  
S8446 2023.04.09   3   N27W02 0004   AXX    
S8447 2023.04.09       S09E07            
S8448 2023.04.09       N13W39            
13276 2023.04.10
2023.04.10
3 3 2 S20E63 0080 DAO CAO area: 0080

location: S22E61

13277 2023.04.10
2023.04.11
1 8 5 N10E20 0010 CRO CRO location: N10E23

area: 0030

S8451 2023.04.10       N29W28          
S8452 2023.04.10   20 6 S20E77 0350   EAI  
S8453 2023.04.10       S18W57          
S8454 2023.04.10       S01W22          
S8455 2023.04.10   3   N23E34 0005   BXO  
S8456 2023.04.10       S09E24          
S8457 2023.04.10       S33W11          
S8458 2023.04.10       S04W56          
S8459 2023.04.11   7 3 N08E31 0015   CRO    
S8460 2023.04.11   2 1 S10E01 0004   BXO    
Total spot count: 53 201 81  
Sunspot number: 103 351 201  (total spot count + 10 * number of spotted regions)
Weighted SN: 81 232 112  (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): 113 193 161  

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
2023.04 135.5 (1)   19.4 (2A) / 52.8 (2B) / 122.4 (2C) (126.4 projected, +5.4) (9.6)
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.