Solar Terrestrial Activity Report

Last major update issued on July 20, 2005 at 03:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update July 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update July 19, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on July 19. Solar wind speed ranged between 351 and 429 (all day average 381) km/sec. A high speed stream from CH175 became the dominant solar wind source after 19h UTC and caused an increase in disturbance levels to the unsettled to active range towards the end of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 71.2 (the lowest solar flux since August 2, 1997). The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.6).
Three hour interval K indices: 32312223 (planetary), 32322223 (Boulder).

The background x-ray flux is at the class A1 level.

At midnight the visible solar disk was spotless. The solar flare activity level was very low. No C class events were recorded during the day.

Coronal mass ejections (CMEs)

July 18-19: No obvious partly or fully Earth directed CMEs were observed.
July 17: An impressive full halo CME was observed in LASCO C3 images starting at 12:18 UTC. Its source was in region 10786 well behind the northwest limb. A minor increase in proton levels was observed as well after this event.

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 well defined recurrent trans equatorial coronal hole (CH175) was in an Earth facing position on July 17-19.

Processed SOHO/EIT 284 image at 01:06 UTC on July 20. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on July 20-21 and quiet to active on July 22 due to a high speed stream from CH175.

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 to occasionally fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Rafaela Argentina on the antenna pointing towards the southwest, CPN Radio (Perú) on the westerly directed antenna. On that antenna a few interesting stations from Perú were noted with the best signals on 1200 and 1509.95 kHz in addition to Radio Santa Rosa on 1499.93 kHz. Those stations disappeared at local sunrise leaving only stations from Argentina and Uruguay on the main southwesterly antenna - on 1510 kHz both Radio Belgrano (Argentina) and Radio Rincón had weak to very weak signals.

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.