Last major update issued on September 20, 2013 at 05:05 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update September 1, 2013)] [Cycle 24 progress (last update September 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update September 5, 2013)]
[POES auroral activity level since October
2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated September 5, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet to unsettled on September 19. Solar wind speed at SOHO ranged between 463 and 559 km/s under the influence of a high speed stream.
Solar flux measured at 20h UTC on 2.8 GHz was 107.9 (decreasing 16.2 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 114.6. The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 10.8). Three hour interval K indices: 33332122 (planetary), 23442322 (Boulder).
The background x-ray flux was at the class B3 level.
At the time of counting spots (see image time) there were 11 active regions in 2K resolution (SN: 150) and 7 active regions in 1K resolution (SN: 90) SDO images with spots on the visible solar disk.
Region 11841 [S03W37] decayed slowly and quietly.
Region 11843 [N01W21] decayed slowly and quietly.
Region 11845 [S17E36] decayed slowly and quietly.
Region 11846 [S18E49] was mostly unchanged and could produce occasional C flares.
Region 11847 [N11E47] decayed and could become spotless today.
New region 11848 [S10E36] emerged with spots. This area had spots on September 16-17, then became spotless on September 18.
New region 11849 [N20E32] emerged with several spots.
New region 11850 [N08E78] rotated into view and appears to have polarity intermixing. C flares are possible.
Spotted regions not numbered by SWPC:
New region S2700 [S20E24] emerged with a penumbra spot.
New region S2701 [N16W37] emerged with penumbra spots.
New region S2702 [S11W48] emerged with a penumbra spot.
September 16-18: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A coronal hole (CH587) in the northern hemisphere will likely rotate into an Earth facing position on September 19-20.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair.
The geomagnetic field is expected to be quiet to unsettled on September 20-23 due to 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
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: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.
(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
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with magnetic polarity overlay
|Total spot count:||15||40||20|
|Sunspot number:||85||150||90||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||28||61||41||(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):||51||53||50||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
|2011.11||153.5 (cycle peak)||96.7 (cycle peak)||61.1 (+1.2)||5.55|
likely cycle 24 max
|2013.03||111.3||57.9||(58.2 projected, -0.2)||10.56|
|2013.04||124.8||72.4||(57.9 projected, -0.3)||5.40|
|2013.05||131.4||78.7||(58.0 projected, +0.1)||9.73|
|2013.06||110.1||52.5||(58.3 projected, +0.3)||12.60|
|2013.07||115.5||57.0||(58.3 projected, 0.0)||9.47|
|2013.08||114.6||66.0||(58.2 projected, -0.1)||8.27|
|2013.09||99.3 (1)||31.7 (2A) / 50.1 (2B) / 39.7 (2C)||(57.8 projected, -0.4)||(5.89)|
1) Running average based on the daily 20:00 UTC observed solar flux value at
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC 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 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.