Solar Terrestrial Activity Report

Last major update issued on February 24, 2006 at 04:55 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 inactive to quiet on February 23. Solar wind speed ranged between 449 and 554 (all day average 494) km/sec under the decreasing influence of a high speed stream from CH212.

Solar flux measured at 20h UTC on 2.8 GHz was 75.1. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.3).
Three hour interval K indices: 12210000 (planetary), 13211110 (Boulder).

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

At midnight the visible solar disk was spotless (number of consecutive days as spotless: 5). The solar flare activity level was very low. No C class events were recorded during the day.

Coronal mass ejections (CMEs)

February 21-23: 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, poorly defined, coronal hole (CH213) in the southern hemisphere was in an Earth facing position on February 20. A recurrent coronal hole (CH214) in the southern hemisphere will rotate into an Earth facing position on February 24-25.

Processed SOHO/EIT 284 image at 19:07 UTC on February 23. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 24 due to coronal hole effects and quiet on February 25-26. A minor increase in geomagnetic activity is possible on February 27-28 as a low speed stream from CH214 sweeps over Earth.

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

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. 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 (Venezuela). Nighttime propagation was mostly unchanged from the previous night with the most common east coast North American stations audible at poor to fair signal levels.

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.

Monthly solar cycle data

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.