Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 13, 2014 at 06:30 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 March 16, 2014]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to minor storm on April 12. Solar wind speed at SOHO ranged between 308 and 380 km/s.

Solar flux at 20h UTC on 2.8 GHz was 135.9 (increasing 0.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 150.7. 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: 54433233 (planetary), 43534423 (Boulder).

The background x-ray flux is at the class B5 level.

At the time of counting spots (see image time), spots were observed in 8 active regions in 2K resolution (SN: 153) and 7 active regions in 1K resolution (SN: 108) SDO images on the visible solar disk.

Region 12032 [N10E11] lost a few spots and was quiet.
Region 12033 [N11E22] was quiet and stable.
Region 12034 [N04E42] appears to be maturing and was quiet.
Region 12035 [S17E63] displayed no major changes. There is polarity intermixing and further C class flaring is likely. A minor M class flare is possible.
C5+ flares: long duration C5.0 event peaking at 07:27 UTC.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3309 [S21W23] was quiet and stable.
S3310 [S15W03] was quiet and stable.
New region S3315 [S09E44] was observed with a penumbra spot.
New region S3316 [S18E38] emerged with a few spots.

Coronal mass ejections (CMEs)

April 10-12: 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

An extension of a northern hemisphere coronal hole (CH611) was in a potentially geoeffective position on April 10.

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 to good.

Forecast

The geomagnetic field is expected to be quiet to unsettled on April 13 and quiet on April 14-15.

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
12027 2014.03.30
2014.03.31
1     N13W91 0060 HSX     rotated out of view
12028 2014.03.31
2014.04.01
      S08W83           plage
12030 2014.04.01       N12W76           plage
S3300 2014.04.03       S13W44           plage
S3301 2014.04.04       N14W38           plage
S3304 2014.04.06       S13W56           plage
S3305 2014.04.06       N11W26           plage
12032 2014.04.07
2014.04.08
6 12 8 N13E12 0150 CSO CHO beta-gamma

area: 0280

location: N10E11

S3308 2014.04.07       S02W30           plage
S3309 2014.04.07   4 2 S20W37 0013   BXO images/AR_S3309_20140412_2345.png images/AR_S3309_20140411_2345.png  
S3310 2014.04.08   3 2 S15W15 0010   BXO images/AR_S3310_20140411_2345.png  
12033 2014.04.09 1 1 1 N12E20 0090 HSX HSX area: 0140

location: N11E22

S3311 2014.04.09       S14E03         plage
12034 2014.04.10 9 17 10 N04E44 0220 DAI DKO area: 0340
12035 2014.04.10
2014.04.11
7 31 14 S16E62 0190 EAI EAI beta-gamma

area: 0350

S3314 2014.04.10       S22W59           plage
S3315 2014.04.12   1   S09E44 0003   AXX    
S3316 2014.04.12   4 1 S18E38 0020   CRO    
Total spot count: 24 73 38  
Sunspot number: 74 153 108  (total spot count + 10 * number of spotted regions)
Weighted SN: 49 106 71  (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): 44 54 59 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 (74.9 projected, +1.8) 7.71
2013.11  148.3 145.1 77.6 (74.9 projected, -0.0) 5.68
2013.12 147.7 143.1 90.3 (74.4 projected, -0.5) 4.68
2014.01 157.4 152.4 82.0 (74.3 projected, -0.1) 5.44
2014.02 170.3
(cycle peak)
166.3 102.8 (cycle peak) (73.7 projected, -0.6) 10.70
2014.03 149.9 148.5 92.2 (73.8 projected, +0.1) 4.88
2014.04 142.4 (1)   49.0 (2A) / 113.1 (2B) / 103.7 (2C) (73.0 projected, -0.8) (7.2)

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.