Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 30, 2015 at 03:45 UT

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data 2003.01 - now (April 1, 2015)
Solar cycle Solar cycles 23-24 (April 1, 2015) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (April 1, 2015) Noon SDO sunspot count 1K Reference: 4K (large file) (*)
  Solar cycles 1-20 POES auroral activity level October 2009 - December 2012
  Comparison of cycles 21, 22, 23 and 24 (April 1, 2015) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 10, 12, 13, 14, 16 and 24 (April 1, 2015) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs solar cycles (April 10, 2015)  

Recent activity

The geomagnetic field was very quiet on April 29. Solar wind speed at SOHO ranged between 271 and 350 km/s.

Solar flux at 20h UTC on 2.8 GHz was 104.0 (decreasing 17.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 127.5. The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.4). Three hour interval K indices: 10011111 (planetary), 00012212 (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 5 active regions using 2K resolution (SN: 71) and 3 active regions using 1K resolution (SN: 40) SDO images on the visible solar disk.

Region 12333 [N21W27] decayed slowly and could soon become spotless.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4414 [S15W19] reemerged with penumbra spots.
S4420 [S19E25] was quiet and stable.
New region S4422 [N19W67] emerged with a few spots.
New region S4423 [S27E07] was observed with a penumbra spot.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
           

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

Coronal mass ejections (CMEs)

April 27-29: 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) was in an Earth facing position on April 27-28. A recurrent trans equatorial coronal hole (CH666) will likely rotate into a potential geoeffective position on May 2.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to active on April 30 and May 1 due to effects from CH655 and associated northern hemisphere coronal holes, quiet to unsettled is likely on May 2.

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
12327 2015.04.16
2015.04.17
2     S08W90 0020 HSX     rotated out of view
S4404 2015.04.21        N09W43          
12333 2015.04.21
2015.04.22
4 1 1  N22W27 0010 BXO AXX area: 0003
S4407 2015.04.22        N22W42          
S4409 2015.04.22        N02W47            
S4411 2015.04.24        S17W18            
S4414 2015.04.26   5   S15W19 0010   AXX    
S4415 2015.04.26       N02W14            
S4417 2015.04.26       N16W54            
S4419 2015.04.27       S05W24            
S4420 2015.04.27   11 7 S19E25 0030   BXI  
S4421 2015.04.27       S10E34          
S4422 2015.04.29   3 2 N19W67 0012   BXO    
S4423 2015.04.29   1   S27E07 0002   AXX    
Total spot count: 6 21 10  
Sunspot number: 26 71 40  (total spot count + 10 * number of spotted regions)
Weighted SN: 11 21 10  (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): 16 29 22 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 (129.7)   71.7 (2A) / 74.1 (2B) / 78.8 (2C) (53.4 projected, -2.7) (10.6)

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.