Solar Terrestrial Activity Report

Last major update issued on February 4, 2004 at 04:10 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 3, 2004)]

Recent activity

The geomagnetic field was quiet to active on February 3. Solar wind speed ranged between 571 and 728 km/sec under the influence of a high speed stream from coronal hole CH78.

Solar flux measured at 20h UTC on 2.8 GHz was 99.4. The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 18.1).
Three hour interval K indices: 43433332 (planetary), 33433332 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was low. A total of 5 C class events was recorded during the day.

Region 10547 decayed further and could soon become spotless
Region 10549 simplified with the positive and negative polarity fields becoming well separated. Many small spots disappeared and the region lost a fair amount of penumbral area. Flare: C1.1 long duration event peaking at 21.45 UTC.
Region 10550 decayed and could become spotless later today.
Region 10551 developed slowly. The most interesting part of the region is where a thin patch of the leading negative polarity field is splitting parts of the trailing positive polarity field. Flares: C1.1 at 08:52, C3.2 at 13:40, C1.2 at 18:25 and C1.4 at 22:46 UTC.
Region 10552 lost some penumbral area, however, several new small spots emerged.

Spotted regions not numbered by NOAA/SEC:
[S347] This region emerged in the southeast quadrant on February 3 and displays some polarity intermixing in magnetograms. Further development is likely. Location at midnight: S05E25.

Coronal mass ejections (CMEs)

February 1-3: No partly or fully earth directed CME 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 recurrent coronal hole (CH78) in the northern hemisphere was in a geoeffective position on January 28 - February 2. Another coronal hole (CH79) in the southern hemisphere is the southern part of what was coronal hole CH74 during the previous rotation. CH79 decayed quickly on February 1-3 and could soon close if this development continues.

Processed SOHO/EIT 284 image at 01:06 UTC on February 4. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active February 4-5 under the influence of a high speed stream from coronal hole CH78 and quiet to unsettled on February 6-9.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor to very 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 Cristal del Uruguay. Otherwise WDHP on 1620 kHz had an unusually good signal for several hours].

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.