Solar Terrestrial Activity Report

Last update issued on October 22, 2003 at 04:00 UTC. Minor update posted at 10:21 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update October 4, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2003)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update October 15, 2003)]
[Archived reports (last update October 22, 2003)]

Recent activity

The geomagnetic field was active to minor storm on October 21. Solar wind speed ranged between 577 and 765 km/sec under the influence of a high speed stream from coronal hole CH63. ACE EPAM data indicate that a solar storm will arrive within a few hours, this would be the expected arrival of the CME observed in connection with an X1 flare in region 10484 on October 19.

Solar flux measured at 20h UTC on 2.8 GHz was 151.5. The planetary A index was 39 (STAR Ap - based on the mean of three hour interval ap indices: 39.9).
Three hour interval K indices: 55555445 (planetary), 45555434 (Boulder).

The background x-ray flux is at the class C5 level.

At midnight there were 4 spotted regions on the visible disk. Solar flare activity was moderate. A total of 11 C and 3 M class flares was recorded during the day. Two regions just behind the southeast limb produced several events during the day including a C7.9 long duration event peaking at 03:45 (associated with a strong type II radio sweep and a large CME), A C6.0 flare at 04:59, a long duration M1.2 event peaking at 21:50 (CME observed off of the southeast limb) and an M2.5 flare at 23:29 UTC (CME observed again, this time the corona on the visible disk near the southeast limb was affected). The regions are very active and could produce major flares.

Two M class flares have been observed early on October 22, an M1.0 event at 02:27 and an M3.7 event at 03:51 UTC. Further STAR updates are likely to be posted during the day as events occur.

Region 10482 decayed slowly and quietly.
Region 10483 developed early in the day, then began to decay. Flare: C3.4 at 12:45 UTC.
Region 10484 developed further, particularly in the eastern section, but not as rapidly as over the last few days. The northern penumbra now spans an impressive 10 degrees longitude. The presence of several magnetic delta structures are likely to cause major flares over the next week, X class proton flares are possible. Flares: C2.5 at 02:53, M1.0 at 08:27, C2.5 at 18:00 and C3.3 at 19:20 UTC.
New region 10485 emerged in the southeast quadrant on October 20 and was numbered by SEC the next day. The region was mostly unchanged on October 21 with the leading and trailing spots increasing their separation.

Comment added at 10:21 UTC on October 22: Region 10484 is still developing and the eastern ends of the southern and northern penumbrae have merged completely. We are still waiting for a possibly huge flare from this region.
At the southeast limb the first part of a bright positive polarity field is rotating into view and spots should become visible soon. The extremely active region(s) at the southeast limb have contributed strongly to the increase in the background x-ray flux to the class M1 level. Since 0330 UTC today the x-ray level has been at or above the M1.0 level.

After having reexamined ACE data it appears as if a new disturbance arrived at about 03h UTC. Solar wind parameters indicate that the high speed stream ended at that time. The CME expected to arrive today probably caught up with the tail end of the high speed stream. The geomagnetic field is currently at minor to major storm levels. 

Coronal mass ejections (CMEs)

October 21: A large full halo CME was observed beginning at 03:54 UTC at the southeast limb. The source of this CME is a region one or two days behind the southeast limb. Further CMEs were observed late in the day from two sources at and just behind the southeast limb.

October 20: No potentially geoeffective CMEs observed.

October 19: A full halo CME was observed in LASCO C3 images after the X1 flare in region 10484. Although most of the ejected material was observed off of the northeast limb and the CME was faint in the southwest, this CME could cause a significant geomagnetic disturbance on October 22.

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 hole (CH63) was in a geoeffective position on October 12-19.

Processed SOHO/EIT 284 image at 01:06 UTC on October 22. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be active to major storm on October 22, at first due to a high speed stream from coronal hole CH64, then because of the arrival of a CME associated with the X1 flare in region 10484 on October 19. Unsettled to minor storm is likely on October 23 with quiet to active possible on October 24.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is useless. 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].

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