Solar Terrestrial Activity Report

Last update issued on May 12, 2003 at 02:40 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 1, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update May 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update May 12, 2003)]

Recent activity

The geomagnetic field was unsettled to major storm on May 11. Solar wind speed ranged between 552 and 712 km/sec under the influence of a high speed stream from coronal hole CH38.

Solar flux measured at 20h UTC on 2.8 GHz was 91.5. The planetary A index was 31 (STAR Ap - based on the mean of three hour interval ap indices: 31.8).
Three hour interval K indices: 53655333 (planetary), 43554433 (Boulder).

The background x-ray flux is at the class A8 level.

At midnight there were 3 spotted regions on the visible disk. Solar flare activity was very low.

Region 10351 decayed slowly and quietly.
Region 10356 decayed slowly early in the day, later on a few new spots emerged.
New region 10357 rotated into view at the southeast limb.

Coronal mass ejections (CMEs)

May 9-11: No obviously geoeffective CMEs observed. A large CME was observed above the north pole and the northern limbs late on May 11. Its source appears to have been backsided.

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 huge recurrent coronal hole (CH38) in the southern hemisphere was in a geoeffective position on May 2-10.

Processed SOHO EIT 284 image at 19:06 UTC on May 11. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm until May 13 and unsettled to active on May 14-15. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor and will likely be very poor until at least May 16. Propagation along north-south paths is fair and is likely to be at least fair until May 15. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay.]

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 SEC/NOAA. 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 (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.