Solar Terrestrial Activity Report

Last update issued on August 1, 2003 at 04:00 UTC. No updates are planned August 2-17 while I am on vacation. All images for that interval should become available on August 18.

[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 August 1, 2003)]

Recent activity

The geomagnetic field was unsettled to minor storm on July 31. Solar wind speed ranged between 752 and 962 km/sec under the influence of a high speed stream from coronal hole CH49.

Solar flux measured at 20h UTC on 2.8 GHz was 102.1. The planetary A index was 32 (STAR Ap - based on the mean of three hour interval ap indices: 33.4).
Three hour interval K indices: 45454434 (planetary), 45554434 (Boulder).

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

At midnight there were 5 spotted regions on the visible disk. Solar flare activity was low. A single C class event was recorded during the day.

Region 10420 was quiet and stable.
Region 10421 developed quietly with the leading penumbra increasing its area considerably.
Region 10422 decayed quietly and began to rotate over the northwest limb.
New region 10423 emerged in the southeast quadrant near the central meridian early in the day.

Spotted regions not numbered by NOAA/SEC:
[S218] A new region emerged on July 31 to the northwest of region 10421. Location at midnight: S04E20.

A region just behind the southeast limb is displaying quite a bit of activity and may be capable of minor M class flaring. Flare: C1.9 at 22:21 UTC. A C5.8 flare was recorded at 01:26 UTC on August 1.

Coronal mass ejections (CMEs)

July 29-31: 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: 29 days ago 28 days ago 26 days ago

A large coronal hole (CH49) in the southern hemisphere - an extension of the southern polar coronal hole - was in a geoeffective position on July 24-29. A coronal hole (CH50) in the northern hemisphere will likely be in a geoeffective position on August 4-5. Recurrent coronal hole CH48 will likely rotate to a geoeffective position on August 9-12.

Processed GOES SXI coronal structure image at 22:25 UTC on July 31. 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 minor storm until August 1 due to a high speed stream from coronal hole CH49, quiet to active is likely on August 2 becoming quiet to unsettled on August 2-6. A high speed stream from coronal hole CH50 will likely cause unsettled to active conditions on August 7-8 followed by mainly quiet to unsettled on August 9-11. Recurrent coronal hole CH48 could cause unsettled to minor storm conditions on August 12-16.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is useless and will likely remain useless to very poor until August 2. Propagation along north-south paths is poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a weak signal.]

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 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.