Solar Terrestrial Activity Report

Last major update issued on May 12, 2005 at 04:10 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 6, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 6, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update May 6, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update May 2, 2005)]

Recent activity

The geomagnetic field was quiet to active on May 11. Solar wind speed ranged between 411 and 545 km/sec. 

Solar flux measured at 20h UTC on 2.8 GHz was 125.3. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.4).
Three hour interval K indices: 10232334 (planetary), 10212233 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight there were 5 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 8 C and 2 M class events was recorded during the day.

Region 10758 developed slowly in the leading spot section while most of the trailing spots disappeared. There is at least one magnetic delta structure within the leading penumbrae and M class flares are possible. Flares: C1.4 at 04:16, M1.2 at 06:41, C1.0 at 10:33, C1.0 at 11:37, C1.0 at 12:09, M1.1/1F at 19:38 and C5.9 at 23:37 UTC.
Region 10759 lost all penumbra on the trailing spots while the leader spots were mostly unchanged. There is a fair chance of an M class flare. Flare: C6.9 at 17:00 UTC.
Region 10762 developed moderately quickly. Flare: C1.8 at 13:08 UTC.

Spotted regions not numbered by NOAA/SEC:
[S545] A new region emerged in the southeast quadrant on May 9. The region decayed slowly on May 10 and 11. Location at midnight: S07W02.
[S547] This region was first observed at the southeast limb late on May 10. The trailing spot section appears to be complex and could contain a magnetic delta structure. Location at midnight: S16E68. Flares: C1.0 at 04:54 and C1.7 at 09:08 UTC.

Coronal mass ejections (CMEs)

May 9-11: No obviously fully or partly potentially geoeffective CMEs were 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 narrow elongated coronal hole (CH164) in the northern hemisphere near the equator will be in an Earth facing position on May 10-12.

Processed SOHO/EIT 284 image at 01:06 UTC on May 12. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected be quiet to unsettled on May 12. Quiet to active is possible on May 13-14 due to a low speed stream from CH164.

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 very poor. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a weak signal.

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.

SEC active region data for May 11 was unavailable at the time of this report.

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 some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.