Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 27, 2014 at 04:35 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 26. Solar wind speed at SOHO ranged between 346 and 425 km/s.

Solar flux at 20h UTC on 2.8 GHz was 120.7 (decreasing 27.7 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 154.2. The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 12111112 (planetary), 13212211 (Boulder).

The background x-ray flux is at the class B3 level.

At the time of counting spots (see image time), spots were observed in 10 active regions in 2K resolution (SN: 152) and 10 active regions in 1K resolution (SN: 124) SDO images on the visible solar disk.

Region 12042 [N18W65] was quiet and stable.
Region 12044 [S21W41] decayed further and could soon become spotless.
Region 12045 [S23W14] was quiet and stable.
New region 12047 [S18E57] emerged with a few spots.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3349 [N19W24] reemerged rapidly with several spots. The region has polarity intermixing.
S3356 [S14E27] was quiet and stable.
S3360 [S22E08] was quiet and stable.
New region S3366 [N07E16] emerged with penumbra spots.
New region S3367 [S08E83] rotated into view.
New region S3368 [S28W51] emerged with a penumbra spot.

C2+ Flares (SDO/EVE):

Magnitude Time (UTC) Location AR
C2.3 15:00 S11W90 S3347

Coronal mass ejections (CMEs)

April 24-26: 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) was in an Earth facing position on April 24.

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 unsettled on April 27-28 due to a stream from CH613 and quiet on April 29-30.

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
12038 2014.04.14
2014.04.15
      S09W88        

rotated out of view

12042 2014.04.16 1 2 1 N18W67 0120 HSX CSO area: 0190
12044 2014.04.18
2014.04.19
  2 1 S21W41 0004   BXO  
12045 2014.04.18
2014.04.19
1 16 6 S24W16 0080 HAX CAO

area: 0110

S3339 2014.04.19       N10W54           plage
S3341 2014.04.19       S09W43           plage
S3348 2014.04.21       S20W24           plage
S3349 2014.04.23   15 4 N19W24 0060   CRI   beta-gamma
S3350 2014.04.23       S16W36           plage
S3353 2014.04.23       N10W31           plage
S3354 2014.04.23       S10W47           plage
S3355 2014.04.24       N18E21         plage
S3356 2014.04.24   3 2 S14E27 0017   BXO  
S3358 2014.04.24       S11W27           plage
S3359 2014.04.25       S28E39         plage
S3360 2014.04.25   4 2 S22E08 0012   BXO  
S3361 2014.04.25       S20W23         plage
S3362 2014.04.25       S11E52         plage
S3363 2014.04.25       S36W05         plage
S3364 2014.04.25       S08W56         plage
12047 2014.04.26 2 6 4 S19E56 0010 BXO CRO   location: S18E57

area: 0024

S3366 2014.04.26   2 2 N07E16 0007   AXX    
S3367 2014.04.26   1 1 S08E83 0190   HSX    
S3368 2014.04.26   1 1 S28W51 0003   AXX    
Total spot count: 4 52 24  
Sunspot number: 34 152 124  (total spot count + 10 * number of spotted regions)
Weighted SN: 14 73 45  (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): 20 53 68 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
2014.04 147.5 (1)   118.2 (2A) / 136.4 (2B) / 103.2 (2C) (77.7 projected, -0.8) (8.0)

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.