Solar Terrestrial Activity Report

Last major update issued on June 28, 2006 at 03:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update June 7, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 7, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 7, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update June 5, 2006)]

Recent activity

The geomagnetic field was quiet to unsettled on June 27. Solar wind speed ranged between 270 and 369 km/s (all day average 301 km/s - increasing 27 km/s over the previous day). Wind speed increased slowly after 10 UTC as a moderately high speed stream from CH229 reached Earth.

Solar flux measured at 20h UTC on 2.8 GHz was 78.5. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.1).
Three hour interval K indices: 11112223 (planetary), 11113333 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10897 developed new spots, primarily in the dominant negative polarity area. A magnetic delta structure could be forming in the northernmost section. Two spots in the southwestern section could be a separate bipolar region. C flares are possible.

Spotted regions not numbered by NOAA/SEC:
[S665] This region rotated into view at the southeast limb at noon on June 27. Location at midnight: S05E79

Coronal mass ejections (CMEs)

June 25-27: No partly or fully Earth directed CMEs were detected in LASCO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent trans equatorial coronal hole (CH229) was in an Earth facing position June 24-26.

Processed SOHO/EIT 284 image at 21:04 UTC on June 27. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on June 28-29 and quiet to unsettled on June 30 due to effects from CH229.

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) Effects from a CME are likely to be observed at 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 fair to good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Cristal del Uruguay had company from two weaker stations, both probably from Argentina. At 01h UTC several stations from Brazil had good signals. Later on there were many signals from Argentina (best on 950, 1030, 1070, 1190 and 1480 kHz), Uruguay (930, 1400?, 1410)  and Paraguay (780, 920, 1020 kHz). 830.06 kHz had Radio Provincia (Argentina), while 1220 Rádio Globo was very strong after LSR.

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.