Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 20, 2014 at 05:50 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 active on April 20. Solar wind speed at SOHO ranged between 445 and 641 km/s.

Solar flux at 20h UTC on 2.8 GHz was 169.3 (increasing 12.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 153.6. The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.4). Three hour interval K indices: 43222331 (planetary), 34333321 (Boulder).

The background x-ray flux is at the class B8 level.

At the time of counting spots (see image time), spots were observed in 18 active regions in 2K resolution (SN: 408) and 17 active regions in 1K resolution (SN: 297) SDO images on the visible solar disk.

Region 12032 [N11W84] was mostly unchanged and produced a few low level C flares.
Region 12033 [N11W70] was quiet and stable.
Region 12034 [N04W53] decayed slowly and was mostly quiet.
Region 12035 [S16W27] decayed slowly and was quiet.
Region 12036 [S17W54] has a weak magnetic delta structure in the central spot section. An M flare is possible.
 
Region 12037 [S09W53] decayed slowly and quietly.
Region 12038 [S11E09] merged with AR S3337 and was quiet.
Region 12039 [N23W41] decayed slowly and could soon become spotless.
Region 12040 [N15W27] developed slowly and quietly.
Region 12042 [N18E28] was quiet and stable.
New region 12044 [S20E53] rotated into view on April 18 and was numbered by SWPC the next day as the region developed slowly.
New region 12045 [S23E75] rotated partly into view on April 18 and produced a few low level C flares.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3323 [S18W06] was quiet and stable.
S3330 [N10E08] was quiet and stable.
New region S3339 [N07E33] emerged with a few spots.
New region S3340 [S21W65] emerged early in the day with a penumbra spot and decayed slowly during the latter half of the day.
New region S3341 [S09E48] emerged with a penumbra spot.
New region S3342 [S03W12] emerged with a penumbra spot.

Flares (SDO/EVE):

Magnitude Time (UTC) Location AR
C2.0 03:26 S21E72 12044
C1.0 06:00 N02W43 12034
C1.4 09:39 S24E90 12045
C1.6 12:30 S23E90 12045
C1.5 12:52 S20E63 12044
C1.3 15:41 N12W86 12032
C1.4 16:51 N02W50 12034
C1.5 17:19 S16W52 12036
C4.1 19:33 N11W90 12032
C1.6 23:37 N11W90 12032

Coronal mass ejections (CMEs)

April 17, 19: 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 could reach 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 poor to fair.

Forecast

The geomagnetic field is expected to be quiet to minor storm on April 20-21 due to CME effects and quiet on April 22.

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
12032 2014.04.07
2014.04.08
2 1 1 N12W83 0130 HSX HSX

area: 0200

12033 2014.04.09 1 1 1 N12W71 0080 HSX HSX area: 0100

location: N11W70

12034 2014.04.10 16 26 13 N05W52 0400 EKC EKO area: 0460
12035 2014.04.10
2014.04.11
33 60 30 S16W31 0300 DKC EAC beta-gamma

area: 0330

location: S16W27

12037 2014.04.12
2014.04.13
8 8 4 S10W54 0090 CSO DAO

area: 0080

12036 2014.04.12
2014.04.13
35 33 21 S17W54 0300 DKC EAC beta-gamma-delta
S3317 2014.04.13       S09W02           plage
12040 2014.04.13
2014.04.15
6 12 7 N15W28 0020 CRO CRO area: 0040
12038 2014.04.14
2014.04.15
15 36 21 S11E09 0100 DSI DAC

merged with AR S3337

S3323 2014.04.14   5 4 S18W06 0020   BXO  
S3324 2014.04.14       N14W51           plage
12039 2014.04.15 4 3 1 N24W42 0010 BXO BXO area: 0006
12041 2014.04.15
2014.04.16
      S19W71           spotless
12042 2014.04.16 11 15 8 N19E27 0270 EKO DAO area: 0320
S3330 2014.04.16   2 1 N10E08 0006   AXX  
12043 2014.04.16
2014.04.17
      S11W45           plage
S3333 2014.04.17       S07W35           plage
12044 2014.04.18
2014.04.19
6 14 8 S20E52 0010 BXO CRI area: 0070
12045 2014.04.18
2014.04.19
2 4 2 S25E78 0050 HAX CAO location: S23E75
S3337 2014.04.18       S09E09         merged with AR 12038
S3338 2014.04.18       S09E01         plage
S3339 2014.04.19   5 3 N07E33 0015   CRO    
S3340 2014.04.19   1   S21W65 0003   AXX    
S3341 2014.04.19   1 1 S09E48 0003   AXX    
S3342 2014.04.19   1 1 S03W12 0003   AXX    
Total spot count: 139 228 127  
Sunspot number: 259 408 297  (total spot count + 10 * number of spotted regions)
Weighted SN: 207 287 186  (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): 155 143 163 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
2014.04 150.3 (1)   92.2 (2A) / 145.6 (2B) / 110.6 (2C) (77.7 projected, -0.8) (7.3)

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.