Solar Terrestrial Activity Report

Last update issued on July 11, 2003 at 03:15 UTC. Minor update posted at 09:51 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, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 2, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 2, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update July 11, 2003)]

Recent activity

The geomagnetic field was quiet to unsettled on July 10. Solar wind speed ranged between 327 and 383 km/sec. The solar wind disturbance which began after 18h UTC on July 9 intensified after 16h UTC and the interplanetary magnetic field has since been moderately strongly southwards.

Solar flux measured at 20h UTC on 2.8 GHz was 122.9. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 9.5).
Three hour interval K indices: 22223233 (planetary), 21224323 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was moderate. A total of 10 C and 1 M class events was recorded during the day.

Region 10397 rotated out of view at the northwest limb and was quite active most of the day. A minor M class flare is still possible while the region is just behind the limb. Flares: C2.8 at 00:51, C2.1 at 02:34, C2.9 at 03:42, C3.1 at 04:41, C1.8 at 06:09, C5.2 at 06:45, C1.2 at 07:52, C1.3 at 08:54, M3.6 (associated with a strong type II radio sweep) at 14:12 and C1.4 at 16:30 UTC.
Region 10400 decayed quickly and lost about two thirds of its penumbral area.
Region 10401 developed quickly with a large increase in penumbral area. The region is magnetically fairly simple with the exception of a section in the northeast where the positive and negative polarities are not well separated. Further development could cause the formation of a magnetic delta structure in that part of the region.
Region 10402 decayed slowly and rotated partly out of view at the southwest limb. Flare: C1.2 at 11:40 UTC.
Region 10403 decayed further and had only a couple of tiny spots left late in the day, the region will likely soon become spotless.
Region 10404 decayed and lost its trailing spots.

Spotted regions not numbered by SEC:
[S200] A new region is rotating into view at the southeast limb. Location at midnight: S10E82.

Comment added at 09:51 UTC on July 11: The solar wind disturbance mentioned above finally caused a geomagnetic disturbance. The interplanetary magnetic field strengthened further and was strongly southwards after 06h UTC. From 08 to 09h UTC major storm conditions were observed with the planetary A index reaching 93 for the 06-09h UTC interval. Some high latitude magnetometers recorded severe and even very severe (K=8) storm conditions. Taking into account the low solar wind speed and events over the recent days, the disturbance could be related either to a large filament eruption (and CME) near the northwest limb, or an M flare with an associated CME in region 10400, both events occured on July 6.

A long duration C3 event peaked at about 07:38 UTC. The source of this event was a flare in region 10401 and a nearby erupting filament. Coronal movement was observed afterwards a significant distance from the source of the event and it is likely that there was a CME. With the event center near the center of the disk the CME has a high likelihood of becoming geoeffective and could reach Earth on July 14.

Coronal mass ejections (CMEs)

July 8-10: No LASCO images available. There is a problem with the SOHO high gain antenna. Until the high gain antenna is in a favorable position starting from approximately July 14, SOHO science data will be transmitted over a low gain antenna and only a limited amount of data will be available.

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 (CH47) was in a geoeffective position on July 8-9, this coronal hole appeared to be decaying on July 9 and 10. Another coronal hole (CH48) in the northern hemisphere and with a trans equatorial extension will rotate into a geoeffective position on July 12-14.

Processed GOES SXI coronal structure image at 16:24 UTC on July 10. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to active conditions on July 11-13 due to a high speed stream from coronal hole CH47 while the high speed stream from coronal hole CH48 will cause unsettled to minor storm conditions on July 15-17.

Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along north-south paths is fair to good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. Otherwise quite a few stations from Brazil were noticed, mostly on frequencies above 1350 kHz.]

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.