Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 23, 2014 at 05:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2014)] [Cycle 24 progress (last update April 1, 2014) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2014)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2014)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 2, 2014)]

[POES auroral activity level October 2009 - December 2012]
[Solar polar fields vs solar cycles - updated April 17, 2014]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on April 22. Solar wind speed at SOHO ranged between 448 and 509 km/s.

Solar flux at 20h UTC on 2.8 GHz was 144.8 (decreasing 8.4 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 154.3. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.8). Three hour interval K indices: 12110101 (planetary), 12222211 (Boulder).

The background x-ray flux is at the class C1 level.

At the time of counting spots (see image time), spots were observed in 10 active regions in 2K resolution (SN: 200) and 10 active regions in 1K resolution (SN: 159) SDO images on the visible solar disk.

Region 12035 [S16W71] decayed slowly and quietly.
Region 12038 [S11W33] developed, has polarity intermixing and produced a few low level C flares.
Region 12042 [N18W12] decayed slowly and quietly.
Region 12044 [S20E13] decayed slowly and quietly.
Region 12045 [S23E38] was quiet and stable.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3323 [S19W38] was quiet and stable.
S3339 [N07W06] was quiet and stable.
S3343 [S16W12] was quiet and stable.
S3347 [S12W73] produced many C flares. The region has a magnetic delta structure in the trailing spot section and has M class flare potential. SWPC failed to notice this region when it emerged a few days ago and seems to count the spots with nearby AR 12035.
S3348 [S20E28] was quiet and stable.

Flares (SDO/EVE):

Magnitude Time (UTC) Location AR
C1.8 01:04 S12W60 S3347
C1.0 02:11 S13W60 S3347
C1.5 02:42 S16W90 12036
C2.2 04:20 S14W60 S3347
C3.9 05:51 S11W22 12038
C2.6 08:03 S13W64 S3347
C2.6 08:21 S15W90 12036
C3.5 08:50 S10W24 12038
C2.3 09:39 S11W64 S3347
C7.8 11:37 S11W67 S3347
C2.3 12:34 S13W70 S3347
C3.5 15:23 S18W90 12036
C3.1 15:35 N04W90 12034
C2.1 16:07 S12W69 S3347
C2.8 18:43 S13W71 S3347
C2.1 20:18 N03W90 12034
C2.5 20:51 N03W90 12034
C1.4 23:51 S13W78 S3347

Coronal mass ejections (CMEs)

April 20-22: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

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 southern hemisphere coronal hole (CH613) will likely rotate into an Earth facing position on April 24-25.

Coronal hole map

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on April 23-26. Quiet to unsettled conditions are likely on April 27-28 due to effects from CH613.

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) 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 numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. 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.

Active region Date numbered
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
Comment
SWPC Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
12034 2014.04.10 1     N06W92 0080 ESO     rotated out of view

SWPC's ESO classification is impossible with 1 spot

12035 2014.04.10
2014.04.11
18 4 2 S13W71 0240 EAC DSO area: 0150

real location: S16W71

SWPC failed to observe new AR S3347

12036 2014.04.12
2014.04.13
3     S17W92 0090 ESO    

rotated out of view

S3317 2014.04.13       S09W41           plage
12040 2014.04.13
2014.04.15
      N15W70           plage
12038 2014.04.14
2014.04.15
24 26 14 S12W33 0080 DAC DAC

area: 0230

S3323 2014.04.14   1 1 S19W38 0004   AXX  
12039 2014.04.15       N24W84           plage
12042 2014.04.16 5 13 8 N18W11 0170 CAO CSO area: 0220
12043 2014.04.16
2014.04.17
      S11W87           plage
12044 2014.04.18
2014.04.19
5 13 8 S21E24 0030 CSO BXO merged with AR S3344
12045 2014.04.18
2014.04.19
10 12 8 S23E36 0080 DAO CAO

area: 0140

S3338 2014.04.18       S09W38           plage
S3339 2014.04.19   3 2 N07W06 0010   AXX  
S3341 2014.04.19       S09E09           plage
S3342 2014.04.19       S03W51           plage
S3343 2014.04.20   8 5 S16W12 0030   AXX images/AR_S3343_20140422_2345.png images/AR_S3343_20140421_2345.png  
S3344 2014.04.20       S18E08         merged with AR 12044
S3345 2014.04.20       N10E22           plage
S3346 2014.04.20       N18W35         plage
S3347 2014.04.20   15 8 S12W73 0330   EAC beta-gamma-delta
S3348 2014.04.21   5 3 S20E28 0013   AXX  
Total spot count: 66 100 59  
Sunspot number: 136 200 159  (total spot count + 10 * number of spotted regions)
Weighted SN: 101 125 84  (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): 82 70 87 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for MSN 2K, k = 0.55 for MSN 1K (MSN=Magnetic Sunspot Number)

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO)
Smoothed sunspot number Average ap
(3)
Measured 1 AU
2013.01 127.1 123.1 62.9 58.7 (-0.9) 4.69
2013.02 104.3 101.8 38.0 58.4 (-0.3) 6.11
2013.03 111.3 110.2 57.9 57.5 (-0.9) 10.56
2013.04 124.8 125.9 72.4 57.9 (+0.4) 5.40
2013.05 131.4 134.3 78.7 59.9 (+2.0) 9.73
2013.06 110.1 113.7 52.5 62.6 (+2.7) 12.60
2013.07 115.5 119.3 57.0 65.5 (+2.9) 9.47
2013.08 114.6 118.3 66.0 69.0 (+3.5) 8.27
2013.09 102.6 103.7 36.9 73.1 (+4.1) 5.23
2013.10  132.1 131.2 85.6 (75.3 projected, +2.1) 7.71
2013.11  148.3 145.1 77.6 (76.3 projected, +1.0) 5.68
2013.12 147.7 143.1 90.3 (77.3 projected, +1.0) 4.68
2014.01 157.4 152.4 82.0 (78.3 projected, +1.0) 5.44
2014.02 170.3
(cycle peak)
166.3 102.8 (cycle peak) (78.1 projected, -0.2) 10.70
2014.03 149.9 148.5 92.2 (78.5 projected, +0.4) 4.88
2014.04 151.0 (1)   108.8 (2A) / 148.3 (2B) / 108.8 (2C) (77.7 projected, -0.8) (8.1)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official WDC-SILSO international sunspot number is typically 30-50% lower. 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.

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 the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.