Solar Terrestrial Activity Report

Last major update issued on June 25, 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 21, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on June 24. Solar wind speed ranged between 300 and 350 km/sec. There may have been a weak solar wind shock passing ACE at 04:20 UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 108.3. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.8).
Three hour interval K indices: 21312221 (planetary), 12311111 (Boulder).

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

At midnight there were 3 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 10634 was quiet and stable and is rotating over the northwest limb.
Region 10635 decayed significantly in the trailing spot section, however, there is still a magnetic delta structure in the main trailing penumbra. Flares: C1.4 at 05:59 and C1.7 at 06:21 UTC. There may have been a small CME associated with the latter event as a weak type II radio sweep was recorded.

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 separate bipolar region. Slow decay was observed on June 24. Location at midnight: S16W47.

Coronal mass ejections (CMEs)

June 22-24: Very few LASCO images available. A weak CME may have been associated with a C1 event in region 10635 on June 24.

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 (CH103) will rotate into a geoeffective position on June 26-27.

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 quiet to unsettled on June 25-27 and quiet to active on June 28-30 due to a high speed stream from coronal hole CH103.

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 fair. 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 Cristal del Uruguay and Radio Vibración (Venezuela). Brazilian stations had fair to good signals on some frequencies: 740, 760, 930, 980, 1350 and 1440 kHz. Stations from Uruguay were better than one day ago with signals noted on 930, 1440, 1540, 1560, 1570 and 1590 kHz. From North America most of the usual stations from Newfoundland and Nova Scotia were heard with weak to fair signals while 1510 WWZN Boston was the only US station.

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.