Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 25, 2014 at 05:00 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 unsettled on April 24. Solar wind speed at SOHO ranged between 378 and 502 km/s under the influence of a low to moderately high speed coronal hole stream.

Solar flux at 20h UTC on 2.8 GHz was 130.1 (decreasing 16.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 154.3. The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.5). Three hour interval K indices: 32332333 (planetary), 22332422 (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 11 active regions in 2K resolution (SN: 179) and 9 active regions in 1K resolution (SN: 125) SDO images on the visible solar disk.

Region 12038 [S10W60] decayed fairly quickly and was quiet.
Region 12042 [N17W39] was quiet and stable.
Region 12044 [S21W13] decayed slowly and quietly.
Region 12045 [S24E11] was quiet and stable.
New region 12046 [S17W76] emerged on April 23 and was numbered the next day as the region continued to develop.

Spotted regions not numbered (or interpreted differently) by SWPC:
S3343 [S15W39] was quiet and stable.
S3349 [N19E04] was quiet and stable.
New region S3355 [N19E47] emerged with a penumbra spot.
New region S3356 [S17W62] emerged with a penumbra spot.
New region S3357 [S29W42] emerged with a penumbra spot.
New region S3358 [S11W01] was observed with penumbra spots.

C2+ Flares (SDO/EVE):

Magnitude Time (UTC) Location AR
C2.7 10:18 S14W90 S3347
C2.1 21:23 S14W90 S3347
C2.6 22:04 S14W90 S3347

AR S3347 behind the southwest limb produced a major X1.7 flare at 00:24 UT on April 25.

Coronal mass ejections (CMEs)

April 22-24: 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 poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on April 25-28 due to coronal hole streams.

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
7 9 4 S10W59 0070 DAO DRO

area: 0040

12042 2014.04.16 1 5 3 N18W40 0160 CSO CSO area: 0230
12044 2014.04.18
2014.04.19
7 17 7 S21W14 0030 CRO CRO  
12045 2014.04.18
2014.04.19
1 20 10 S25E09 0120 CSO DAO

area: 0170

S3339 2014.04.19       N10W28         plage
S3341 2014.04.19       S09W17           plage
S3343 2014.04.20   2 2 S15W39 0008   AXX  
S3345 2014.04.20       N10W04           plage
S3348 2014.04.21       S20E02           plage
S3349 2014.04.23   3 3 N19E04 0012   BXO  
S3350 2014.04.23       S16W10         plage
S3351 2014.04.23       N16W46         plage
12046 2014.04.23
2014.04.24
5 8 4 S17W78 0070 CAO DAO area: 0180
S3353 2014.04.23       N10W05         plage
S3354 2014.04.23       S10W21         plage
S3355 2014.04.24   1   N19E47 0002   AXX    
S3356 2014.04.24   1 1 S17E54 0003   AXX    
S3357 2014.04.24   1 1 S29W42 0003   AXX    
S3358 2014.04.24   2   S11W01 0004   AXX    
Total spot count: 21 69 35  
Sunspot number: 71 179 125  (total spot count + 10 * number of spotted regions)
Weighted SN: 44 90 56  (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): 43 63 69 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
2014.04 149.5 (1)   114.6 (2A) / 143.3 (2B) / 106.7 (2C) (77.7 projected, -0.8) (8.1)

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.