Solar Terrestrial Activity Report

Last major update issued on June 26, 2005 at 05:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update June 4, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 4, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 4, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update June 21, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on June 25. Solar wind speed ranged between 464 and 743 (all day average 598) km/sec under the influence of a high speed stream.

Solar flux measured at 20h UTC on 2.8 GHz was 76.7. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 10.9).
Three hour interval K indices: 33122323 (planetary), 23122323 (Boulder).

The background x-ray flux is at the class A3 level.

At midnight the the visible solar disk was spotless. The solar flare activity level was low. A single C class event was recorded during the day, a C1.3 flare in region 10780 at 03:46 UTC.

Coronal mass ejections (CMEs)

June 23-24: No obvious fully or partly Earth directed CMEs were observed in available LASCO images.
June 25: A full halo CME was observed in LASCO C3 images beginning at 08:42 UTC. Although I wouldn't say that the evidence is conclusive at this time, there was quite a bit of coronal activity during the first half of the day and into the early hours of the afternoon. Several disappearing filaments were reported. In particular the disappearance of a 23 degrees long filament in the central southeastern quadrant could be associated with the CME. At the very least this CME may have had a frontside origin. 

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 recurrent coronal hole (CH171) in the northern hemisphere was in an Earth facing position on June 20-22. A coronal hole (CH172) in the southern hemisphere (and with a trans equatorial extension) was in an Earth facing position on June 24-25. A large trans equatorial coronal hole (CH173) will likely be in an Earth facing position on June 28-29.

Processed SOHO/EIT 284 image at 01:06 UTC on June 26. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on June 26 with a chance of an active interval due to a high speed stream.  Another high speed stream, this time  from CH172, will likely reach Earth on June 27 and cause unsettled to active conditions that day and on June 28. The forecast for the latter half of June 27 and all of June 28 is uncertain due to a possible CME impact. If the full halo CME observed on June 25 had a frontside origin, the CME could reach Earth late on June 27 or early on June 28 and cause active to major 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 fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Rafaela Argentina. Lots of thunderstorm activity over France made it difficult to listen to weaker stations, however, there were quite a few stations from both Brazil and Argentina to be heard.

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.