Solar Terrestrial Activity Report

Last major update issued on May 10, 2006 at 04:30 UTC.

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

Recent activity

The geomagnetic field was quiet on May 9. Solar wind speed ranged between 367 and 477 (all day average 443) km/sec, slowly decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 82.6. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.8).
Three hour interval K indices: 00121112 (planetary), 10122012 (Boulder).

The background x-ray flux is at the class A4 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 10880 lost some penumbral area as the single penumbra is splitting into two smaller penumbrae.
Region 10882 decayed slowly and quietly.

Coronal mass ejections (CMEs)

May 7-9: No partly or fully Earth directed CMEs were observed in LASCO imagery.

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

Recurrent coronal holes (CH223A and CH223B) in the northern hemisphere will rotate into an Earth facing position on May 8-11.

Processed SOHO/EIT 284 image at 01:06 UTC on May 10. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet most of May 10. Unsettled and active intervals are possible late in the day when the high speed stream from CH223A arrives. Unsettled to minor storm conditions are likely on May 11-14 due to high speed streams from CH223A and CH223B, isolated major storm intervals are possible.

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 very poor. Propagation on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Tonight Radio Cristal del Uruguay had, at times,  company from CPN Radio (Perú) and an Argentinian station. Propagation was best to Argentina near LSR with 1400 Cumbre AM noted among others. The strongest TA signals were from 1380 Radio Corporación (Chile) and 1030 Radio del Plata (Argentina).

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.