Solar Terrestrial Activity Report

Last update issued on July 26, 2003 at 02:25 UTC. Any update on July 27 will be posted late in the day.

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

Recent activity

The geomagnetic field was quiet to active on July 25. Solar wind speed ranged between 311 and 388 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 111.6. The planetary A index is estimated at 11 (STAR Ap - based on the mean of three hour interval ap indices: (estimated at 14.0 based on 00-15h UTC data).
Three hour interval K indices: 22432332 (planetary), 22432222 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was low. Only 1 C class event was recorded during the day, this was a long duration C1.1 event peaking at 17:19 UTC from a source behind the southwest limb.

Region 10411 decayed slowly and quietly.
Region 10414 lost the trailing spots which had emerged on the previous day.
Region 10419 became spotless early in the day but began to develop slowly again after noon.
Region 10420 was quiet and stable.

Coronal mass ejections (CMEs)

July 23-25: No potentially geoeffective 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

A large coronal hole (CH49) in the southern hemisphere - an extension of the southern polar coronal hole - will be in a geoeffective position on July 24-31.

Processed GOES SXI coronal structure image at 20:48 UTC on July 25. Base SXI image courtesy of NOAA/SEC. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled most of July 26. A high speed stream from coronal hole CH49 will likely reach Earth late on July 26 and cause unsettled to minor storm conditions until August 3.

Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along north-south paths is fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay, several other stations were noted at times.]

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.
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.

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 interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.