Solar Terrestrial Activity Report

Last major update issued on June 20, 2004 at 03:40 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 19. Solar wind speed ranged between 406 and 464 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 112.7. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 6.6).
Three hour interval K indices: 22222221 (planetary), 23222220 (Boulder).

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

At midnight there were 5 spotted regions on the visible disk. The solar flare activity level was low. A total of 7 C class events was recorded during the day.

Region 10632 was quiet and stable.
Region 10634 decayed further in the trailing spot section. Development was observed near the southern edge of the large leading penumbra. A new penumbrae formed and currently has a magnetic delta structure. A minor M class flare is possible.
Region 10635 developed further with many spots emerging in the western part of the trailing spot section. The region has at least two magnetic delta structures and an M class flare is likely. Flares: C1.8 at 06:23, C1.0 at 08:16, C2.4 at 08:28, C1.2 at 10:41, C1.0 at 11:32, C3.0 at 19:37 and C1.3 at 21:38 UTC.

Spotted regions not numbered by NOAA/SEC:
[S420] This region was split off from region 10635 as magnetograms strongly suggest that this is a bipolar region by itself. The region has many small spots. Location at midnight: S15E18.
[S421] A new region emerged in the southeastern quadrant on June 19. Location at midnight S10E42.

Coronal mass ejections (CMEs)

June 17-19: No fully or partly Earth directed CMEs 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

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 quiet to unsettled on June 20-22.

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 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). Radio Rafaela (Argentina) was noted at times as well. On other frequencies several stations from Brazil were heard with reasonably good signals: 740, 760, 980, 1430 and 1440 kHz. From North America some of the usual Newfoundland and Nova Scotia stations were noted with mostly poor signals, as were a few US stations: 1030 WBZ, 1130 WBBR, 1440 WJAE, 1510 WWZN and an unidentified station on 1660 kHz.

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.