Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 21, 2014 at 06:50 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 to minor storm on April 21. Solar wind speed at SOHO ranged between 524 and 968 km/s. The CME associated with the M7 flare on April 18 was observed at SOHO at 10:46 UTC (solar wind increase, solar wind density increased at 10:20 UTC).

Solar flux at 20h UTC on 2.8 GHz was 162.5 (increasing 3.9 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 154.0. The Potsdam WDC planetary A index was 21 (STAR Ap - based on the mean of three hour interval ap indices: 20.9). Three hour interval K indices: 32145444 (planetary), 32134434 (Boulder).

The background x-ray flux is at the class B7 level.

At the time of counting spots (see image time), spots were observed in 17 active regions in 2K resolution (SN: 380) and 17 active regions in 1K resolution (SN: 276) SDO images on the visible solar disk.

Region 12033 [N11W84] was mostly quiet and stable. SWPC attributed the largest flare of the day to this region, however, the flare location appears to have been in AR 12032, just behind the northwest limb.
Region 12034 [N04W67] developed in the southwestern section and produced low level C flares.
Region 12035 [S16W43] decayed slowly and was mostly quiet.
Region 12036 [S18W67] decayed, however, there is a weak magnetic delta structure in the leading spot section. An M flare is possible.
 
Region 12037 [S09W70] decayed slowly and lost the trailing spots.
Region 12038 [S11W04] was quiet and stable.
Region 12040 [N17W41] decayed and could soon become spotless.
Region 12042 [N18E13] was quiet and stable.
Region 12044 [S21E41] was quiet and stable.
Region 12045 [S23E62] was quiet and stable.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3323 [S14W25] was mostly quiet and stable.
S3339 [N07E20] was quiet and stable.
New region S3343 [S09E12] was observed with penumbra spots.
New region S3344 [S18E37] emerged to the northwest of AR 12044.
New region S3345 [N10E48] was observed with penumbra spots.
New region S3346 [N04W06] emerged with penumbra spots.
New region S3347 [S11W48] emerged quickly with several spots to the northwest of AR 12035.

Flares (SDO/EVE):

Magnitude Time (UTC) Location AR
C1.4 00:22 S12W15 S3323
C1.2 00:36 S16W28 12035
C1.0 00:54 S14W56 12036
C1.9 03:03 N02W57 12034
C2.2 03:05 S17W56 12036
C2.2 04:27 S15W59 12036
C2.0 05:18 N02W58 12034
C1.6 06:10 N12W87 12032
C1.0 06:43 N02W60 12034
C1.2 07:06 S21E53 12044
C1.2 07:16 S24E90  
C1.0 07:34 S24E90  
C4.7 08:13 N13W90 12032
C1.3 11:36 S16W63 12036
C1.5 11:40 N11W80 12033
C2.1 12:08 S15W34 12035
C1.5 13:45 N11W84 12033
C1.8 14:47 N02W66 12034
C1.1 15:44 S19W65 12036
C1.0 15:57 N02W67 12034

Coronal mass ejections (CMEs)

April 19-20: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
April 18: A filament eruption began just after 09h UTC to the south of AR 12036 and extended towards another center to the south of AR S3323 and appears to have been associated with a halo CME. The M8 flare after noon in AR 12036 was associated with a full halo CME which reached Earth on April 20.

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.

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 fair.

Forecast

The geomagnetic field is expected to be quiet to active on April 21 due to CME effects and quiet to unsettled on April 22 becoming quiet on April 23.

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
12033 2014.04.09 1 1 1 N11W84 0060 HSX HSX area: 0090
12034 2014.04.10 16 20 9 N04W66 0270 EKO EKC area: 0430
12035 2014.04.10
2014.04.11
30 36 21 S16W43 0200 EAI DAI beta-gamma
12037 2014.04.12
2014.04.13
4 1 1 S10W67 0040 CAO HRX

 

12036 2014.04.12
2014.04.13
20 22 7 S17W68 0180 DAC DAI beta-gamma-delta

area: 0270

S3317 2014.04.13       S09W15           plage
12040 2014.04.13
2014.04.15
  3 1 N15W42 0010   BXO  
12038 2014.04.14
2014.04.15
12 39 19 S11W05 0080 DAI DAI

area: 0160

S3323 2014.04.14   5 3 S14W25 0015   BXO  
12039 2014.04.15       N24W56         plage
12041 2014.04.15
2014.04.16
      S19W85           spotless
12042 2014.04.16 4 13 8 N19E15 0170 CSO DAO area: 0290
S3330 2014.04.16       N10W05         plage
12043 2014.04.16
2014.04.17
      S11W59           plage
S3333 2014.04.17       S07W48           plage
12044 2014.04.18
2014.04.19
11 17 7 S20E37 0030 DRO CRI area: 0060
12045 2014.04.18
2014.04.19
4 4 3 S22E62 0050 CAO CAO location: S23E62

area: 0080

S3338 2014.04.18       S09W12           plage
S3339 2014.04.19   5 3 N07E20 0025   BXO  
S3341 2014.04.19       S09E35         plage
S3342 2014.04.19       S03W25         plage
S3343 2014.04.20   6 3 S09E12 0018   AXX    
S3344 2014.04.20   12 6 S18E37 0040   CRI    
S3345 2014.04.20   2 1 N10E48 0007   AXX    
S3346 2014.04.20   2 2 N04W06 0007   BXO    
S3347 2014.04.20   22 11 S11W48 0100   CAI    
Total spot count: 102 210 106  
Sunspot number: 192 380 276  (total spot count + 10 * number of spotted regions)
Weighted SN: 150 264 160  (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): 115 133 152 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)   98.6 (2A) / 148.0 (2B) / 110.8 (2C) (77.7 projected, -0.8) (7.9)

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.