Solar Terrestrial Activity Report

Last major update issued on February 7, 2006 at 05:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update February 4, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update February 4, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update February 4, 2006)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update February 7, 2006)]

Recent activity

The geomagnetic field was quiet to active on February 6. Solar wind speed ranged between 305 and 365 (all day average 337) km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 74.9. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.3).
Three hour interval K indices: 14223233 (planetary), 24333323 (Boulder).

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

At midnight the visible solar disk was spotless. The solar flare activity level was very low. No C class events were recorded during the day.

Coronal mass ejections (CMEs)

February 4-6: No obviously fully or partly Earth directed CMEs were observed.

Coronal holes

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

A small coronal hole (CH209) in the northern hemisphere was in an Earth facing position on February 4. A recurrent coronal hole (CH210) in the northern hemisphere will rotate into an Earth facing position on February 8-9.

Processed SOHO/EIT 284 image at 01:06 UTC on February 7. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on February 7-10, becoming quiet to unsettled on February 11-12 due to effects from CH210.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
Coronal hole indicator CME indicator M and X class flare indicator

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

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezueal). At 05 UTC on February 7 there were few stations audible below 1400 kHz. Propagation was improving at the high end of the AM band with KVNS on 1700 kHz noted with a fair to good signal

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
S620 2006.02.04     N05W42     plage
Total spot count: 0 0  
SSN: 0 0  

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)
2004.12 94.5 17.9 35.2 (-0.1)
2005.01 102.2 31.3 34.6 (-0.6)
2005.02 97.2 29.2 33.9 (-0.7)
2005.03 89.9 24.5 33.5 (-0.4)
2005.04 86.0 24.4 31.6 (-1.9)
2005.05 99.3 42.6 28.9 (-2.7)
2005.06 93.7 39.6 28.8 (-0.1)
2005.07 96.4 39.9 29.1 (+0.3)
2005.08 90.5 36.4 (27.6 predicted, -1.5)
2005.09 91.1 22.1 (25.8 predicted, -1.8)
2005.10 77.0 8.5 (24.0 predicted, -1.8)
2005.11 86.3 18.0 (21.6 predicted, -2.4)
2005.12 90.7 41.2 (18.7 predicted, -2.9)
2006.01 83.4 15.4 (15.6 predicted, -3.1)
2006.02 77.0 (1) 0.0 (2) (12.5 predicted, -3.1)

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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