Solar Terrestrial Activity Report

Last major update issued on August 6, 2005 at 06:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update August 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update August 3, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on August 5. Solar wind speed ranged between 367 and 569 (all day average 439) km/sec. A high speed stream from CH178B arrived at ACE at about 17h UTC and caused minor geomagnetic storming early on August 6.

Solar flux measured at 20h UTC on 2.8 GHz was 98.8. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.1).
Three hour interval K indices: 22112333 (planetary), 32333313 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day.

Region 10792 decayed further. The region has reversed polarities and could redevelop. Flare: C2.6 long duration event peaking at 08:05 UTC.
Region 10794 decayed in the northwestern section while some development was observed in the southwestern part. Flare: C1.1 at 20:46 UTC.
Region 10795 decayed slowly and quietly.

Coronal mass ejections (CMEs)

August 3-4: No obvious partly or fully Earth directed CMEs were observed.
August 5: A filament eruption across the central meridian in the northern hemisphere was triggered by the C2 LDE in region 10792 during the morning. At least a partial halo CME was observed after this event.

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 extension (CH178B) of the southern polar coronal hole was in an Earth facing position on August 2. A small trans equatorial coronal hole (CH178) became less obvious on August 4 when it would have been in an Earth facing position. This was probably due to coronal outflow from nearby region 10796. A small, elongated coronal hole in the northern hemisphere was in an Earth facing position on August 5-6.

Processed SOHO/EIT 284 image at 01:54 UTC on August 6. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on August 6 due to coronal hole effects and quiet to unsettled on August 7. THE CME observed on August 5 could arrive early on August 8 and cause unsettled to minor storm conditions. Additionally effects from CH179 are possibly on August 8. 

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.

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 to fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and Radio Cristal del Uruguay. After LSR a few stations from Argentina were noted with good signals; Radio del Plata on 1030, Radio El Mundo on 1070 and Radio América on 1190 kHz. Several stations from Venezuela were audible as well (880, 1130, 1140, 1420, 1500 kHz to mention the strongest signals), event Puerto Rico was present with 1480, 1520 and 1660 kHz having the best signals. Before local sunrise a few stations from Newfoundland (590, 620 and 930 kHz) had weak to fair signals.

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.