Solar Terrestrial Activity Report

Last major update issued on February 17, 2004 at 05:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update February 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update February 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update February 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update February 9, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on February 16. Solar wind speed ranged between 496 and 676 km/sec, generally decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 98.7. The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 8.0).
Three hour interval K indices: 31133221 (planetary), 31122221 (Boulder).

The background x-ray flux is at the class A8 level.

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was low. A total of 1 C class events was recorded during the day. 

Region 10554 decayed further and was quiet.
Region 10559 decayed and will likely become spotless today.
Region 10561 was quiet and stable.

Spotted regions not numbered by NOAA/SEC:
[S354] This region emerged in the northwest quadrant late on February 14 west of spotless region 10556. The region developed quickly initially, then decayed on February 15-16. The region will likely become spotless today. Location at midnight: N16W55. Please note that SEC has this as region 10556. Flare: C1.6 at 02:58 UTC.

Coronal mass ejections (CMEs)

February 14-16: No partly or fully earth directed CMEs 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

There is a small coronal hole (CH81) in the southern hemisphere. CH81 will rotate into a potentially geoeffective position on February 17.

Processed SOHO/EIT 284 image at 01:06 UTC on February 17. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 17-19. On February 20 there is a possibility of a weak high speed stream arriving from coronal hole CH81, this could cause unsettled to active conditions during parts of that day.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation along long distance north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). On other frequencies a few stations from Newfoundland and Nova Scotia were noted with weak signals].

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) Material from a CME is likely to impact 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.

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% less.

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