Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 27, 2015 at 02:45 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 (September 1, 2015)
Solar cycle Solar cycles 23-24 (September 1, 2015) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (September 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 (September 1, 2015) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12, 13, 14, 16 and 24 (September 1, 2015) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs solar cycles (September 16, 2015)  

Recent activity

The geomagnetic field was quiet on September 26. Solar wind speed at SOHO ranged between 385 and 493 km/s.

Solar flux at 20h UTC on 2.8 GHz was 120.2 (increasing 28.6 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 106.1. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.8). Three hour interval K indices: 10000121 (planetary), 11112321 (Boulder).

The background x-ray flux is at the class B4 level.

At the time of counting spots (see image time), spots were observed in 9 active regions using 2K resolution (SN: 260) and 7 active regions using 1K resolution (SN: 153) SDO images on the visible solar disk.

Region 12420 [N10W06] decayed slowly and quietly.
Region 12421 [N16W21] was quiet and developed slowly. The region has polarity intermixing.
Region 12422 [S20W01] developed further and has a magnetic delta in a leading penumbra. M class flaring is possible even if the region so far has only produced low level C flares.
Region 12423 [S09W50] developed slowly. The region is still being considered for splitting.
Region 12424 [N11W43] was quiet and stable.
Region 12425 [S05W14] decayed slowly and quietly.
Region 12426 [N16E36] decayed slowly and quietly.

Spotted regions not numbered (or interpreted differently) by SWPC:
New region S4781 [S18E51] was observed with a tiny spot.
New region S4782 [N25W08] was observed with penumbra spots.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
           

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

Coronal mass ejections (CMEs)

September 24-26: No obviously Earth directed CMEs were observed in available LASCO 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 recurrent northern hemisphere coronal hole (CH692) could rotate into an Earth facing position on September 29. A small coronal hole between ARs 12425 and 12422 was in a potentially geoeffective position on September 26 and could cause a brief disturbance on September 29.

Propagation

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

Forecast

The geomagnetic field is expected to be mostly quiet on September 27-29.

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
S4766 2015.09.18       N20W54         images/AR_S4766_20150925_2345.png  
12420 2015.09.19
2015.09.20
15 52 22 N10W04 0140 FAI EAI beta-gamma

area: 0250

12421 2015.09.20
2015.09.22
12 32 17 N17W21 0110 DAC DAC beta-gamma
S4773 2015.09.21       S18W37            
12423 2015.09.21
2015.09.23
5 15 8 S09W51 0020 CRI DRI

beta-gamma

area: 0035

12422 2015.09.22 28 53 28 S20W03 0410 EKC EKC beta-gamma-delta

area: 0700

location: S20W01

S4776 2015.09.22       S14W56            
12425 2015.09.23
2015.09.25
3 6 3 S05W15 0010 BXO DRO  
12426 2015.09.24
2015.09.25
2 4 2 N16E34 0010 CRO CRO  
S4780 2015.09.24       N30E23          
12424 2015.09.25 3 4 3 N12W44 0020 DRO DRO  
S4781 2015.09.26   1   S18E51 0001   AXX    
S4782 2015.09.26   3   N25W08 0006   AXX    
Total spot count: 68 170 83  
Sunspot number: 138 260 153  (total spot count + 10 * number of spotted regions)
Weighted SN: 97 202 115  (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): 152 143 130 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
2014.04 143.9 144.8 112.5 116.4 (+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 86.6 (-3.2) 9.92
2015.03 125.9 124.6 54.5 (82.1 projected, -4.5) 16.14
2015.04 128.8 129.7 78.0 (78.0 projected, -4.1) 10.73
2015.05 120.0 122.6 90.0 (75.3 projected, -2.7) 8.29
2015.06 122.3 126.1 68.3 (71.6 projected, -3.7) 13.15
2015.07 107.0 110.8 66.4 (67.9 projected, -3.7) 8.83
2015.08 105.4 108.0 64.6 (66.7 projected, -1.2) 14.58
2015.09 (97.6)   56.7 (2A) / 65.5 (2B) / 79.2 (2C) (67.0 projected, +0.3) (17.7)

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.