Solar Terrestrial Activity Report

Last major update issued on February 27, 2007 at 05:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update January 11, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 11, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update January 11, 2007)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update February 6, 2007)]

Recent activity

The geomagnetic field was quiet to unsettled on February 26. Solar wind speed ranged between 337 and 528 km/s (average speed was 395 km/s, increasing 101 km/s from the previous day) under the influence of a stream from CH258. The interplanetary magnetic field was northwards almost all the time causing only very a minor geomagnetic disturbance.

Solar flux measured at 20h UTC on 2.8 GHz was 75.4. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.5). Three hour interval K indices: 23111000 (planetary), 23111100 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10944 was quiet and stable.
New region 10945 rotated into view at the southeast limb on February 25 and was numbered the next day by NOAA/SEC.

Coronal mass ejections (CMEs)

February 24-26: No obvious partly or fully Earth directed CMEs were detected in LASCO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent coronal hole (CH258) in the southern hemisphere was in an Earth facing position on February 22-25.

Processed SOHO/EIT 195 image at 21:37 UTC on February 13. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 27-28 due to effects from CH258, occasional active intervals are possible. Mostly quiet conditions are likely on March 1-3.

Coronal holes (1) Coronal mass ejections (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: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Propagation

Daily monitoring will not resume until a local noise problem (related to construction work on a neighboring property) has been fixed. Occasional monitoring reports will be submitted when propagation is good.

February 18, 2007: Strong signals were noted from a number of USA east coast stations as well as from stations located in the Canadian Atlantic provinces. CFDR on 780 kHz was particularly strong.

Active solar regions (Recent map)

Compare to the previous day's image.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SEC. 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 SEC or where SEC has observed no spots. SEC active region numbers in the table below and in the active region map above are the historic SEC/USAF numbers.

Active region Date numbered SEC
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10942 2007.02.16     S11W65     plage
10944 2007.02.22 1 1 S07E22 0110 HKX classification was HSX at midnight, area 0080
10945 2007.02.26 1 1 S06E60 0020 HSX formerly region S696
Total spot count: 2 2  
SSN: 22 22  

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2005.12 90.7 41.1 23.0 (-1.9)
2006.01 83.4 15.3 20.8 (-2.2)
2006.02 76.5 4.9 18.6 (-2.2)
2006.03 75.4 10.6 17.3 (-1.3)
2006.04 89.0 30.2 17.1 (-0.2)
2006.05 80.9 22.2 17.3 (+0.2)
2006.06 76.5 13.9 16.3 (-1.0)
2006.07 75.7 12.2 15.3 (-1.0)
2006.08 79.0 12.9 (15.6 predicted, +0.3)
2006.09 77.8 14.5 (15.7 predicted, +0.1)
2006.10 74.3 10.4 (14.5 predicted, -1.2)
2006.11 86.3 21.5 (12.8 predicted, -1.7)
2006.12 84.5 13.6 (12.1 predicted, -0.7)
2007.01 83.3 16.9 (12.0 predicted, -0.1)
2007.02 77.9 (1) 15.7 (2) (12.1 predicted, +0.1)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (NOAA/SEC) sunspot number. The official international sunspot number is typically 30-50% lower.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.


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