Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 18, 2015 at 03:30 UT.

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data from 2003.01 (August 1, 2015)
Solar cycle Solar cycles 23-24 (August 1, 2015) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (August 1, 2015) Noon SDO sunspot count 1K Reference: 4K (large file) (*)
  Solar cycles 1-24 (July 17, 2015) POES auroral activity level October 2009 - December 2012
  Comparison of cycles 21, 22, 23 and 24 (August 1, 2015) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12, 13, 14, 16 and 24 (August 1, 2015) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs solar cycles (August 18, 2015)  

Recent activity

The geomagnetic field was unsettled to active on August 17 under the influence of a high speed stream (source uncertain, maybe CH682, however, CH682 has previously only caused weak geomagnetic effects. A co-rotating interaction region associated with CH683 is another candidate as the source). Solar wind speed at SOHO ranged between 468 and 567 km/s.

Solar flux at 20h UTC on 2.8 GHz was 87.0 (decreasing 4.0 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 113.5. The Potsdam WDC planetary A index was 21 (STAR Ap - based on the mean of three hour interval ap indices: 21.0). Three hour interval K indices: 34444343 (planetary), 45544322 (Boulder).

The background x-ray flux is at the class B1 level.

At the time of counting spots (see image time), spots were observed in 4 active regions using 2K resolution (SN: 74) and 3 active regions using 1K resolution (SN: 47) SDO images on the visible solar disk.

Region 12401 [S10W02] gained a few spots and remains a reversed polarity region. The northernmost positive polarity area may belong to a separate region with a normal polarity layout.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4694 [N07W22] was quiet and stable.
New region S4695 [S13E80] rotated into view with a few spots and was slightly active during the day.
New region S4696 [S44E09] emerged at a high latitude as a bipolar region. Only a tiny spot was visible at the end of the day.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
           

Flare activity (SDO/EVE/ESP XRS-B proxy)

Coronal mass ejections (CMEs)

August 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]

An extension of a northern hemisphere coronal hole (CH683) will rotate across the central meridian on August 15-18. A co-rotating interaction region may be associated with CH683 and could cause a geomagnetic disturbance on August 17-19.

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 active on August 18-20 due to effects from coronal hole high speed 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 overlays
Comment
SWPC Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
12398 2015.08.06
2015.08.07
      N16W78           location: N18W64
12399 2015.08.10
2015.08.11
      S16W84            
12400 2015.08.11       N17W47          
12401 2015.08.12
2015.08.13
10 24 11 S10W03 0030 CRO DRI

reversed polarities

S4687 2015.08.13       S07E02            
S4688 2015.08.13       N20W34            
S4689 2015.08.13       S23W50            
S4690 2015.08.14       N09E29            
S4691 2015.08.14       N13W24         images/AR_S4691_20150816_2345.png  
S4692 2015.08.14       S07W38            
S4694 2015.08.16   3 3 N07W22 0012   BXO  
S4695 2015.08.17   6 3 S13E80 0040   CRO    
S4696 2015.08.17   1   S44E09 0001   AXX    
Total spot count: 10 34 17  
Sunspot number: 20 74 47  (total spot count + 10 * number of spotted regions)
Weighted SN: 13 40 23  (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): 22 41 40 k * (sunspot number)
As of July 1, 2015: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.85 for MSN 1K (MSN=Magnetic Sunspot Number)

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO) (4)
Smoothed sunspot number (4) Average ap
(3)
Measured 1 AU
2014.02 170.3
(cycle peak)
166.3 146.1 (cycle peak) 110.5 (+1.2) 10.70
2014.03 149.9 148.5 128.7 114.3 (+3.8) 4.88
2014.04 143.9 144.8 112.5 116.4 (+2.1) (solar max) 7.88
2014.05 129.7 132.9 112.5 115.0 (-1.4) 5.75
2014.06 122.0 125.8 102.9 114.1 (-0.9) 6.72
2014.07 137.4 141.8 100.2 112.6 (-1.5) 4.50
2014.08 124.7 127.9 106.9 108.3 (-4.3) 7.71
2014.09 146.6 148.1 130.0 101.9 (-6.4) 9.78
2014.10 153.4 152.9 90.0 97.4 (-4.5) 8.96
2014.11 154.8 151.4 103.6 95.0 (-2.4) 9.33
2014.12 158.7 153.8 112.9 92.6 (-2.4) 11.24
2015.01 141.9 137.3 93.0 89.8 (-2.8) 9.46
2015.02 129.1 126.0 66.7 (86.8 projected, -3.0) 9.92
2015.03 125.9 124.6 54.5 (83.1 projected, -3.7) 16.14
2015.04 128.8 129.7 78.0 (79.8 projected, -3.3) 10.73
2015.05 120.0 122.6 90.0 (77.4 projected, -2.4) 8.29
2015.06 122.3 126.1 68.3 (73.9 projected, -3.5) 13.15
2015.07 107.0 110.8 66.4 (70.2 projected, -3.7) 8.83
2015.08 (103.6)   34.8 (2A) / 63.5 (2B) / 71.8 (2C) (69.0 projected, -1.2) (11.8)

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).
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.
4) Updated to new data set from WDC-SILSO on July 1, 2015

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 Universal Time. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.