Solar Terrestrial Activity Report

Last major update issued on March 18, 2004 at 04:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update March 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update March 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update March 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update March 11, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on March 17. Solar wind speed ranged between 360 and 473 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 109.8. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 7.0).
Three hour interval K indices: 12122321 (planetary), 22113322 (Boulder).

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

At midnight there were 6 spotted regions on the visible disk. Solar flare activity was low. A total of 4 C class events was recorded during the day. 

Region 10570 was quiet and stable, the region is rotating out of view at the southwest limb.
Region 10572 decayed quickly and became spotless late in the day. Flare: C1.6 at 09:31 UTC. This event appears to have been associated with a small CME and a type II radio sweep.
Region 10573 decayed slowly and quietly.
Region 10574 developed quickly with both negative and positive polarity flux emerging. The region is complex with a high degree of polarity intermixing and possibly a magnetic delta structure in the largest (trailing) penumbra. M class flares are possible. Flares: C1.5 at 08:09, C2.5 at 14:27 and C1.3 at 18:12 UTC.
New region 10575 emerged in the southeast quadrant on March 16 and was numbered the next day by SEC. The region was decaying late in the day and early on March 18 no spots could be seen.
New region 10576 emerged in the southwest quadrant.
New region 10577 rotated into view at the southeast limb. The region may have some trailing spots further southeast, or maybe there is another region about to rotate into view at the southeast limb.

Coronal mass ejections (CMEs)

March 15 and 17: No partly or fully earth directed CMEs observed.
March 16: A CME was observed off of the northwest limb (first in LASCO C3 at 17:18 UTC) following a long duration event just south of region 10572. Within 3 hours faint ejecta was observed all around the disk, thus this could be a full halo CME. If it is a weak CME impact could be observed on March 19 or 20.

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, poorly defined coronal hole (CH85) in the northern hemisphere will rotate into a possibly geoeffective position on March 20.

Processed SOHO/EIT 284 image at 00:12 UTC on March 18. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet to unsettled on March 18-21. A weak CME impact is possible on March 19 or 20 and could cause unsettled to active conditions.

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 poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). Otherwise the best TA signal was from Rádio Uirapurú (Brazil) on 760 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. 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.

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.