Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 17, 2014 at 05:05 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 16. Solar wind speed at SOHO ranged between 272 and 345 km/s. A weak disturbance began late in the day and has caused unsettled conditions early on April 17.

Solar flux at 17h UTC on 2.8 GHz was 173.1 (increasing 21.8 over the last solar rotation, the measurement at 17h UTC was used due to an M1 flare enhancing the flux at 20h UTC). The 90 day 10.7 flux at 1 AU was 151.9. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 11111012 (planetary), 01122322 (Boulder).

The background x-ray flux is at the class B9 level.

At the time of counting spots (see image time), spots were observed in 14 active regions in 2K resolution (SN: 386) and 14 active regions in 1K resolution (SN: 270) SDO images on the visible solar disk.

Region 12032 [N11W42] decayed slowly and quietly.
Region 12033 [N11W31] was quiet and stable.
Region 12034 [N04W12] developed with new flux emerging in the central and trailing sections. C and minor M class flares are possible.
Region 12035 [S16E09] was fairly active with some decay observed, particularly in the central and trailing spot sections. Another minor M class flare is possible.
C5+ flares: C5.2 at 08:44, C7.5/1F at 12:51, M1.0/1N at 19:59 UTC.
Region 12036 [S18W13] decayed slowly and was remarkably quiet. An M class flare is still a possibility.
  
Region 12037 [S09W13] decayed and lost the magnetic delta structures. There is still polarity intermixing and a minor M class flare is possible.
Region 12038 [S13E52] was quiet and stable.
Region 12039 [N14E10] decayed slowly losing all umbrae on both polarities.
Region 12040 [N24W02] decayed slowly and quietly.
New region 12041 [S20W29] emerged on April 15 and was numbered by SWPC the next day.
New region 12042 [N19E68] rotated into view and developed quickly. The region produced a few low level C flares. A minor M class flare is possible.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3323 [S16E32] was quiet and stable.
New region S3330 [N17E30] emerged with a penumbra spot.
New region S3331 [S11W03] emerged with penumbra spots.

Coronal mass ejections (CMEs)

April 14-16: 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 small trans equatorial coronal hole (CH612) rotated across the central meridian on April 16.

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 unsettled with a chance of active intervals on April 17 and quiet on April 18. Weak effects from CH612 could cause unsettled intervals on April 19.

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
1 1 1 N11W41 0110 HAX HSX

area: 0190

12033 2014.04.09 2 1 1 N12W31 0080 HSX HSX images/AR_12033_20140415_2345.png area: 0150

location: N11W31

S3311 2014.04.09       S09W44           plage
12034 2014.04.10 19 32 20 N04W10 0250 EKI DSC area: 0480

location: N04W12

12035 2014.04.10
2014.04.11
45 62 36 S17E11 0320 EKC EHI beta-gamma

area: 0370

location: S16E09

12037 2014.04.12
2014.04.13
27 34 17 S10W13 0100 DAI DAI beta-gamma

area: 0210

location: S09W13

12036 2014.04.12
2014.04.13
22 47 22 S18W14 0450 DKC DKC beta-gamma

area: 0670

S3317 2014.04.13       S09E37           plage
12040 2014.04.13
2014.04.15
7 19 8 N15E11 0010 BXO BXO area: 0040

location: N14E10

NOAA swapped positions for ARs 12039 and 12040 on April 16.

S3319 2014.04.13       N25W53           plage
S3320 2014.04.13       N16W48           plage
12038 2014.04.14
2014.04.15
4 10 4 S14E51 0070 CSO DSO location: S13E52
S3323 2014.04.14   7 2 S16E32 0018   AXX  
S3324 2014.04.14       N14W12           plage
12039 2014.04.15 2 9 4 N23W02 0010 BXO BXO area: 0020

see AR 12040

12041 2014.04.15
2014.04.16
4 9 4 S21W30 0010 BXO CRO area: 0030

location: S20W29

12042 2014.04.16 2 11 8 N19E69 0070 CSO DAO   area: 0160
S3330 2014.04.16   1 1 N17E10 0005   AXX    
S3331 2014.04.16   3 2 S11W03 0012   BXO    
Total spot count: 135 246 130  
Sunspot number: 245 386 270  (total spot count + 10 * number of spotted regions)
Weighted SN: 190 299 183  (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): 147 135 149 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
2014.04 146.0 (1)   65.0 (2A) / 121.8 (2B) / 107.4 (2C) (73.0 projected, -0.8) (6.8)

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.