Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 18, 2023 at 08:40 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 on April 17. Solar wind speed at SOHO ranged between 343 and 412 km/sec. The high latitude magnetometer at Andenes recorded quiet to active levels.

Solar flux density measured at 20h UT on 2.8 GHz was 166.6 - increasing 15.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.93. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.5). Three hour interval K indices: 11111201 (planetary), 11222211 (Boulder), 21113403 (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 11 active regions using 2K resolution (SN: 302) and in 9 active regions using 1K resolution (SN: 193) SDO/HMI images.

Region 13272 [S24W62] decayed slowly and quietly.
Region 13275 [N19W29] was quiet and stable.
Region 13276 [S22W18] decayed slowly and quietly.
Region 13279 [S20W01] decayed slowly and was mostly quiet.
Region 13280 [S07W85] decayed slowly and produced a few flares.
Region 13281 [S23E14] decayed slowly and was mostly quiet.
Region 13282 [N11E10] decayed in the trailing spot section while the leading penumbra became larger. The region has weak polarity intermixing and an M class flare is possible. C1 flares: C1.6 @ 21:04 UT
Region 13283 [S22E33] was somewhat unstable and produced several C flares.
New region 13284 [S09E74] rotated into view.

Spotted regions not observed (or interpreted differently) by SWPC:
S8463 [N20E18] decayed slowly and quietly.
New region S8471 [N22W09] emerged with tiny spots.

A C1.9 flare was recorded at 09:52 UT from a location near the northeast limb, the same location produced a C1.6 flare at 21:48 UT.
A C1.9 flare was recorded at 13:09 UT from AR 13273 at the northwest limb.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.2 00:59 N10E18 13282 GOES16  
C2.2 03:31   13283 GOES16 incorrectly attributed to AR 13281 by SWPC
C4.1 04:16 S10W70 13280 GOES16  
C7.0 06:33   13283 GOES16 incorrectly attributed to AR 13281 by SWPC
C2.1 07:40   13279 GOES16  
C2.3 08:37   13280 GOES16  
C2.4 14:24   13282 GOES16  
C6.9 14:31   13283 GOES16 incorrectly attributed to AR 13282 by SWPC
C2.9 15:48   13283 GOES16  
C2.4 16:29   13282 GOES16  
C2.1 19:07   13282 GOES16  

Coronal mass ejections (CMEs)

April 16-17: No obviously Earth directed CMEs were observed.
April 15: An extensive filament eruption in the northwest quadrant was observed beginning in SDO/AIA imagery at 22:47 UT. A relatively faint partial halo CME was observed early on April 16  and could reach Earth on April 19 or 20 and cause unsettled to minor storm conditions.

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]

No obvious coronal holes are currently in or near Earth facing positions.

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 15-17.

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
13272 2023.04.05
2023.04.06
4 9 4 S22W71 0010 BXO CRO

location: S24W62

SWPC position is way off

13273 2023.04.09
2023.04.09
      N10W80        

location: N08W83

13275 2023.04.09
2023.04.10
1 6 3 N19W32 0010 AXX CRO

location: N19W29

13276 2023.04.10
2023.04.10
4 7 2 S22W19 0010 AXX CRO location: S22W18
13277 2023.04.10
2023.04.11
      N10W58            
13279 2023.04.10
2023.04.12
15 61 34 S19W05 0080 FAO EAO

location: S20W01

S8455 2023.04.10       N24W46            
S8456 2023.04.10       S09W54            
S8459 2023.04.11       N09W46            
13280 2023.04.11
2023.04.13
3 5 2 S08W80 0160 CSO CKO

location: S07W85

area: 0280

13281 2023.04.12
2023.04.13
16 36 22 S22E14 0160 EKI EAO

location: S23E14

13282 2023.04.13
2023.04.13
21 35 22 N11E11 0390 EKI FHI

area: 0590

location: N11E10

S8463 2023.04.13   1   N20E18 0001   AXX  
S8464 2023.04.13       S14W14          
13283 2023.04.13
2023.04.16
6 22 10 S20E37 0040 CRO DAO  
S8466 2023.04.13       S19E32            
S8467 2023.04.14       N08W13          
S8468 2023.04.14       N39W12          
S8469 2023.04.15       S15W47            
13284 2023.04.17
2023.04.17
2 6 4 S08E71 0030 CAO DAO   was AR S8470

area: 0070

location: S09E74

S8471 2023.04.17   4   N22W09 0005   AXX    
Total spot count: 72 192 103  
Sunspot number: 162 302 193  (total spot count + 10 * number of spotted regions)
Weighted SN: 110 241 152  (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): 178 166 154  

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
2023.04 146.8 (1)   48.8 (2A) / 86.1 (2B) / 141.0 (2C) (126.4 projected, +5.4) (7.9)
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.