Solar Terrestrial Activity Report

Last major update issued on June 2, 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 15, 2005)]

Recent activity

The geomagnetic field was very quiet to unsettled on June 1. Solar wind speed ranged between 355 and 471 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 96.9. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.4).
Three hour interval K indices: 33121221 (planetary), 33122331 (Boulder).

The background x-ray flux is at the class B1-B2 level.

At midnight there were 5 spotted regions on the visible solar disk. The solar flare activity level was moderate. A tot6al of 8 C and 1 M class event was recorded during the day.

Region 10767 decayed slowly and quietly and will rotate over the southwest limb today.
Region 10769 lost the spots which emerged on May 31, instead new spots emerged further east..
Region 10771 decayed and could become spotless today.
Region 10772 developed further and has a magnetic structure in the trailing spot section. Further M class flares are possible. Flares: M1.7 at 02:43 (associated with a strong type II radio sweep), C1.2 at 04:42, C2.0 at 07:04, C2.3 at 10:51, C1.0 at 11:49, C1.0 at 12:46, C3.1 at 17:55, C5.9 at 18:11 and C7.2 at 22:18 UTC.
New region 10773 rotated into view at the southeast limb.

Coronal mass ejections (CMEs)

May 30- June 1: No obvious 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 small coronal hole (CH168) in the southern hemisphere was in an Earth facing position on May 29. A large, recurrent coronal hole (CH169) in the northern hemisphere will rotate into an Earth facing position on June 1-3.

Processed SOHO/EIT 284 image at 01:06 UTC on June 1. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on June 2 and quiet to unsettled on June 3. Sometime on June 4 a high speed stream from CH169 is likely to arrive causing unsettled to minor storm conditions.

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 excellent. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay was the most frequently heard station, however, there were several Argentinean and Brazilian stations in a huge mess. Conditions were exceptionally good towards southern Brazil, Uruguay and Argentina. Particularly on frequencies above 1350 kHz there were a large number of stations. 1590 kHz had Radio Real (Uruguay) in addition to two other Spanish language stations.

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.