Solar Terrestrial Activity Report

Last major update issued on May 14, 2005 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 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 minor storm on May 13. Solar wind speed ranged between 467 and 562 km/sec. A weak coronal hole stream became the dominant solar wind source during the last hours of the day, earlier in the day the solar wind was more complex and it is difficult to determine its sources.

Solar flux measured at 23h UTC on 2.8 GHz was 113.0 (the measurements at both 17 and 20h UTC were influenced by the major flare). The planetary A index was 27 (STAR Ap - based on the mean of three hour interval ap indices: 27.1).
Three hour interval K indices: 55533432 (planetary), 55523433 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was high. A total of 2 C and 1 M class events was recorded during the day.

Region 10758 rotated partly out of view at the southwest limb. The region is still complex and could produce an M class flare while at and just behind the limb.
Region 10759 developed some new spots to the southeast of the main penumbra. Another M class proton flare is possible. Flares: C1.6 at 03:24, C1.5 at 13:04 and an M8.0/2B major long duration proton event peaking at 16:57 UTC. Strong type II and IV radio sweeps were recorded in association with the major event.
Region 10762 lost some penumbral area in the largest leading and trailing penumbrae, however, a few new intermediate spots developed.
Region 10763 decayed slowly, however, there is still a small magnetic delta structure in the trailing penumbra.

Coronal mass ejections (CMEs)

May 11: A slow full halo CME was observed after an M flare in region 10758 during the evening.
May 12: No obviously fully or partly potentially geoeffective CMEs were observed.
May 13: A bright and fast CME aimed directly at Earth was first observed in LASCO C2 images at 17:22 and in C3 at 17:42 UTC and was associated with the major M8 proton flare in region 10759. The propagation of the shock wave on and near the solar surface was extremely impressive in EIT 195 images. This CME will impact Earth, probably sometime between 20h UTC on May 14 and 15h UTC on May 15.

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 poorly defined coronal hole (CH164) in the northern hemisphere near the equator was in an Earth facing position on May 10-12.

Processed SOHO/EIT 284 image at 01:06 UTC on May 14. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected be quiet to minor storm on May 14 due to coronal hole effects and the arrival of a CME observed on May 11. Minor to extremely severe storm (Kp 5-9) conditions are likely on May 15 after the arrival of the CME observed on May 13. Unsettled to major storm is possible on May 16 becoming quiet to active on May 17.

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 stations tonight: Radio Cristal del Uruguay and Radio Rafaela (Argentina). Conditions were fair at 02h UTC, however, propagation weakened and there was no local sunrise enhancement.

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% 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.