Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 18, 2015 at 07:00 UT

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2015)] [Cycle 24 progress (last update April 1, 2015) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2015)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2015)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 1, 2015)]

[Noon SDO sunspot count 1K Reference: 4K (large file) (updated daily)]

[POES auroral activity level October 2009 - December 2012]
[Solar polar fields vs solar cycles - updated April 10, 2015]
[Presentations: 3rd SSN Workshop, Tucson, 2013 (pdf) / 4th SSN Workshop, Locarno, 2014]

Recent activity

The geomagnetic field was quiet to minor storm on April 17 under the influence of effects from a co-rotating interaction region and an extension of the southern polar coronal hole. Solar wind speed at SOHO ranged between 566 and 771 km/s.

Solar flux at 20h UTC on 2.8 GHz was 149.6 (increasing 36.0 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 127.3. The Potsdam WDC planetary A index was 20 (STAR Ap - based on the mean of three hour interval ap indices: 20.4). Three hour interval K indices: 55433232 (planetary), 45433332 (Boulder).

The background x-ray flux is at the class B6 level.

At the time of counting spots (see image time), spots were observed in 20 active regions using 2K resolution (SN: 361) and 14 active regions using 1K resolution (SN: 225) SDO images on the visible solar disk.

Region 12321 [N11W12] decayed slowly and quietly.
Region 12322 [N12W39] decayed slowly and quietly.
Region 12324 [N19E21] gained a few spots and produced low level C flares.
Region 12325 [N04E29] was mostly unchanged and produced a few C flares.
Region 12326 [N15W01] was quiet and stable.
New region 12327 [S09E70] rotated into view on April 16 and was numbered the next day by SWPC.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4367 [N08W03] was quiet and has weak polarity intermixing.
S4369 [S03W71] was quiet and stable.
S4380 [S15E16] was quiet and stable.
S4381 [N18W08] was quiet and stable.
S4382 [N12W59] decayed slowly and quietly.
S4383 [S11E55] was quiet and stable.
S4385 [S19W12] developed slowly and quietly.
New region S4387 [S02W53] emerged with several spots.
New region S4388 [N7W18] emerged with penumbra spots.
New region S4389 [S22E78] rotated into view.
New region S4390 [S12E65] emerged with penumbra spots.
New region S4391 [S08W19] emerged with several penumbra spots.
New region S4392 [N10W31] emerged with a few spots.
New region S4393 [S20W52] emerged with a penumbra spot.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
C2.6 01:37   12325 GOES15  

Flare activity according to SDO/EVE/ESP XRS-B proxy

Coronal mass ejections (CMEs)

April 15-17: No obviously Earth directed CMEs were observed.

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 (CH664) will rotate across the central meridian on April 16-18.

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 18-21. On April 19-20 there is a chance of occasional active intervals due to effects from CH664.

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
12322 2015.04.10
2015.04.11
  1   N12W39 0002   AXX

 

12321 2015.04.10
2015.04.11
17 36 23 N11W08 0320 EKC DAI  
S4367 2015.04.11   10 7 N08W03 0200   CAO  
12326 2015.04.11
2015.04.16
6 16 8 N15W02 0030 CRI CRI  
S4369 2015.04.12   3 1 S03W71 0010   AXX  
12324 2015.04.13
2015.04.14
9 28 13 N19E23 0250 CKI CKO area: 0430
S4372 2015.04.13       S18W12            
12325 2015.04.13
2015.04.14
8 18 14 N04E32 0140 DAI DHO area: 0330
S4375 2015.04.13       N10W17            
S4377 2015.04.14       N11W34            
S4379 2015.04.15       N22W28            
S4380 2015.04.15   3   S15E16 0003   BXO  
S4381 2015.04.15   3 1 N18E03 0008   AXX  
S4382 2015.04.16   1   N12W59 0002   AXX  
S4383 2015.04.16   1 1 S11E55 0004   AXX  
12327 2015.04.16
2015.04.17
3 7 3 S10E70 0140   CAO  
S4385 2015.04.16   7 2 S19W12 0020   CRO  
S4386 2015.04.16        N27W53          
S4387 2015.04.17   10 5  S02W53 0035   CRI    
S4388 2015.04.17   3 2  N17W18 0007   BXO    
S4389 2015.04.17   1    S22E78 0001   AXX    
S4390 2015.04.17   3    S12E65 0007   BXO    
S4391 2015.04.17   6 3  S08W19 0015   BXO    
S4392 2015.04.17   3 2  N10W31 0012   CRO    
S4393 2015.04.17   1    S20W52 0001   AXX    
Total spot count: 43 161 85  
Sunspot number: 93 361 225  (total spot count + 10 * number of spotted regions)
Weighted SN: 76 208 132  (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): 56 126 124 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
2013.11  148.3 145.1 77.6 75.4 (+0.4) 5.68
2013.12 147.7 143.1 90.3 76.0 (+0.6) 4.68
2014.01 157.4 152.4 81.8 77.3 (+1.3) 5.44
2014.02 170.3
(cycle peak)
166.3 102.3 (cycle peak) 78.4 (+1.1) 10.70
2014.03 149.9 148.5 91.9 80.8 (+2.4) 4.88
2014.04 143.9 144.8 84.7 81.9 (+1.1)
(likely solar max)
7.88
2014.05 129.7 132.9 75.2 80.5 (-1.4) 5.75
2014.06 122.0 125.8 71.0 79.7 (-0.8) 6.72
2014.07 137.4 141.8 72.5 78.6 (-1.1) 4.50
2014.08 124.7 127.9 74.7 75.6 (-3.0) 7.71
2014.09 146.6 148.1 87.6 70.9 (-4.7) 9.78
2014.10 153.4 152.9 60.6 (67.3 projected, -3.6) 8.96
2014.11 154.8 151.4 70.1 (64.7 projected, -2.6) 9.33
2014.12 158.7 153.8 78.0 (62.4 projected, -2.3) 11.24
2015.01 141.9 137.3 67.0 (60.2 projected, -2.2) 9.46
2015.02 129.1 126.0 44.8 (58.4 projected, -1.8) 9.92
2015.03 125.9 124.6 38.4 (56.1 projected, -2.3) 16.14
2015.04 (127.6)   35.2 (2A) / 62.2 (2B) / 76.2 (2C) (53.4 projected, -2.7) (12.6)

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.