Solar Terrestrial Activity Report

Last major update issued on June 21, 2004 at 04:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update June 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update June 14, 2004)]

Recent activity

The geomagnetic field was quiet on June 20. Solar wind speed ranged between 378 and 429 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 119.1. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 4.4).
Three hour interval K indices: 11112211 (planetary), 11112111 (Boulder).

The background x-ray flux is at the class B2-B3 level.

At midnight there were 6 spotted regions on the visible disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day.

Region 10632 decayed slowly and quietly, the region will rotate to the southwest limb late today.
Region 10634 decayed with the trailing penumbra disintegrating. There is still a magnetic delta structure in a penumbra just south of the large, leading penumbra. A minor M class flare is possible.
Region 10635 developed slowly in the trailing spot section. There is a magnetic delta structure in the main trailing penumbra. An M class flare is possible. Flares: C2.0 at 13:32 and C1.0 at 16:37 UTC.
New region 10636 emerged in the southeast quadrant late on June 19 and was numbered the next day by SEC. The region developed slowly on June 20.

Spotted regions not numbered by NOAA/SEC:
[S420] This region was split off from region 10635 on June 19 as magnetograms suggested that this is a bipolar region by itself. The region has many small spots. The region decayed slightly on June 20. Location at midnight: S15E06.
[S422] A new region emerged in the southeast quadrant between regions 10636 and 10635 on June 20. Location at midnight S10E18.

Coronal mass ejections (CMEs)

June 18-20: No fully or partly Earth directed CMEs observed. The available data set on June 20 was very limited. Little or no new LASCO data is expected to become available over the next week or so.

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

No obvious coronal holes are currently at or near geoeffective positions.

Processed SOHO/EIT 284 image at 13:05 UTC on June 15. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on June 21-23.

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 to very poor. Propagation along long distance north-south paths is fair to good. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela). Despite the quiet geomagnetic conditions propagation to North America was worse than during the previous night with only a few weak signals observed. Surprisingly propagation towards Brazil, Argentina and Uruguay became good after local sunrise. A very stable and clear signal was heard from Floresta AM (Joinville, Santa Catarina, Brazil) on 1589.99 kHz. The Uruguay station on 1480 kHz was there again and an unidentified Argentinean station on 1620.04 kHz was noted with a fairly clear signal and religious programming.

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.