Solar Terrestrial Activity Report

Last major update issued on July 17, 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 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 2, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on July 16. Solar wind speed ranged between 360 and 460 (all day average 429) km/sec. A minor solar wind shock was observed at 00:50 UTC at ACE (01:23 UTC at SOHO) on July 17. This was likely the arrival of the CME observed on July 14.

Solar flux measured at 20h UTC on 2.8 GHz was 76.3. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 8.9).
Three hour interval K indices: 22211333 (planetary), 33412333 (Boulder).

The background x-ray flux is at the class A7 level.

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

Spotted regions not numbered or wrongly numbered by NOAA/SEC:
[S570] This region emerged in the southwest quadrant on July 13 just west of region 10790. The region developed further on July 15-16 with no or poor separation between the opposite polarity areas in the trailing part of the region. The leading part of the region rotated out of view during the latter half of July 16. Location at midnight: S11W81. Flares: C1.3 at 02:52, M1.0 at 03:38, C1.8 at 06:34, C2.2 at 07:14 and C4.8 at 11:21 UTC.

Coronal mass ejections (CMEs)

July 14: A large, fast and very wide full halo CME was observed in LASCO C3 images after the X1 event in region 10786.
July 15-16: No obvious partly or fully Earth directed 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 recurrent trans equatorial coronal hole (CH175) will rotate into an Earth facing position on July 17-19.

Processed SOHO/EIT 284 image at 01:06 UTC on July 17. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on July 17 due to CME effects. Quiet to unsettled is likely on July 18-19. Late on July 19 or early on July 20 a high speed stream from CH175 is likely to arrive and could cause unsettled to minor storm conditions until July 21 or 22.

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 poor. Propagation along long distance north-south paths is poor to fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela). Weak signals from Argentina were observed on a number of frequencies including 1620 (Radio Vida), 1630 (AM Restauración), 1650, 1680 and 1690 kHz. From North America the Newfoundland stations on 590, 710 and 930 kHz had 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.