Solar Terrestrial Activity Report

Last update issued on June 21, 2003 at 03:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update June 3, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 3, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 3, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update June 17, 2003)]

Recent activity

The geomagnetic field was quiet to unsettled on June 20. Solar wind speed ranged between 475 and 604 km/sec. A weak solar wind shock was observed at SOHO at 07:59 UTC. This was likely the arrival of the full halo CME observed on June 17. Just after the arrival of the CME the interplanetary magnetic field swung southwards for a short time but then returned northwards and stayed mostly northwards for the remainder of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 116.9. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.8).
Three hour interval K indices: 32333333 (planetary), 22322232 (Boulder - source USAF).

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

At midnight there were 5 spotted regions on the visible disk. Solar flare activity was low. A total of 3 C class events was recorded during the day.

Region 10385 decayed further and had only a couple of small spots left by the end of the day. The region will likely become spotless today.
Region 10386 decayed significantly losing penumbral area and quite a few small spots. There is still a magnetic delta structure. however, both the positive and negative polarity fields have weakened. A major flare is possible as long as the delta structure remains intact. Flares: C1.2 at 05:01, C1.2 at 14:41 and C1.0 at 22:31 UTC.
Region 10387 developed slowly with penumbral area increasing. The region is magnetically fairly simply structured.
Region 10388 developed moderately quickly. A small magnetic delta structure formed at the eastern edge of the intermediate spot section. If the region develops further minor M class flares will become likely.
New region 10389 emerged in the southeast quadrant on June 19 and was numbered by SEC the next day. The region decayed on June 20 and could soon become spotless.

Coronal mass ejections (CMEs)

June 18: A large CME was observed off of the west limb after 09h UTC and was likely associated with an eruption in region 10375 which rotated over the northwest limb a few days ago.

June 19-20: No obviously geoeffective 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

A new coronal hole (CH45) in the southern hemisphere was in a geoeffective position on June 18-19.

Processed SOHO EIT 284 image at 01:06 UTC on June 21. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to active on June 21-23 as a high speed stream from coronal hole CH45 dominates the solar wind.

Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor and will likely stay very poor until at least June 24. Propagation along north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay (weak signal) with Cadena Peruana de Noticias interfering near local sunrise.]

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.
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.

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.

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 interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.