Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 24, 2015 at 04:35 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 unsettled on April 23. Solar wind speed at SOHO ranged between 425 and 491 km/s.

Solar flux at 20h UTC on 2.8 GHz was 140.5 (increasing 2.7 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 129.2. The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.0). Three hour interval K indices: 23111001 (planetary), 14121221 (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 13 active regions using 2K resolution (SN: 231) and 11 active regions using 1K resolution (SN: 163) SDO images on the visible solar disk.

Region 12324 [N19W60] decayed slowly and was mostly quiet.
Region 12325 [N04W52] decayed slowly and quietly.
Region 12327 [S09W09] was quiet and stable.
Region 12330 [N15W07] was quiet and stable.
Region 12331 [S10W21] decayed in the trailing spot section.
Region 12333 [N20E51] gained a few spots and was mostly quiet.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4383 [S10W32] was quiet and stable.
S4398 [N10W25] decayed slowly and quietly.
S4400 [N07W05] was quiet and stable.
S4404 [N07E43] was quiet and stable.
S4407 [N18E25] decayed slowly and quietly.
S4408 [N20W82] developed further and produced some C flares. SWPC has, for reasons unknown, failed to number a new region and moved spotless AR 12326 5 degrees northwards to include the spots of this region.
S4409 [S07E34] was quiet and stable.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
C2.2 02:09   S4408 GOES15  
M1.1 (LDE) 10:07 behind NW limb S4392 GOES15 CME
C7.3 12:03   S4408 GOES15  
C3.1 15:20   12325 GOES15  
C2.6 17:46   S4408 GOES15  
C3.0 19:59   S4408 GOES13 attributed to AR 12333 by SWPC

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

Coronal mass ejections (CMEs)

April 21-23: 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 recurrent southern hemisphere coronal hole (CH665) will likely rotate into an Earth facing position on April 26-27.

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 24-26.

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
12321 2015.04.10
2015.04.11
1     N08W84 0030 HSX    

location: N13W86

SWPC data is for AR S4367

12326 2015.04.11
2015.04.16
7     N20W83 0080 CAO       spotless

real location: N15W69

SWPC data is for AR S4408

12324 2015.04.13
2015.04.14
5 7 3 N19W59 0060 HAX CAO  
12325 2015.04.13
2015.04.14
1 8 5 N05W52 0240 HSX CKO area: 0340
S4383 2015.04.16   5   S10W32 0025   AXX  
12327 2015.04.16
2015.04.17
1 16 12 S08W10 0090 HSX CAI area: 0170
S4389 2015.04.17        S22W03          
12331 2015.04.17
2015.04.21
11 22 12  S10W21 0090 DAI DAI area: 0200
12332 2015.04.18
2015.04.21
2      S13W43 0010 BXO     spotless
12330 2015.04.19
2015.04.20
  3 1  N15W10 0010   BXO  
S4398 2015.04.19   5 2  N10W25 0010   BXO  
S4400 2015.04.20   4 2  N07W05 0015   AXX images/AR_S4400_20150422_2345.png  
S4404 2015.04.21   10 5  N07E43 0025   BXI images/AR_S4404_20150423_2345.png  
12333 2015.04.21
2015.04.22
2 11 6  N20E51 0030 HAX DRI area: 0060

location: N20E65

S4406 2015.04.21        S11W52          
S4407 2015.04.22   2    N18E25 0006   BXO  
S4408 2015.04.22   6 4  N20W82 0300   DKO  
S4409 2015.04.22   2 1  S07E34 0007   AXX  
S4410 2015.04.22        N23W00          
Total spot count: 30 101 53  
Sunspot number: 110 231 163  (total spot count + 10 * number of spotted regions)
Weighted SN: 65 139 119  (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): 66 81 90 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 (133.2)   61.2 (2A) / 79.8 (2B) / 85.3 (2C) (53.4 projected, -2.7) (12.5)

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.