Solar Terrestrial Activity Report

Last major update issued on March 26, 2008 at 02:00 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, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update January 10, 2008)]

Recent activity

The geomagnetic field was quiet on March 25. Solar wind speed ranged between 342 and 409 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 88.6. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.5). Three hour interval K indices: 00011222 (planetary), 11012222 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was moderate. A single M class event was recorded during the day.

Region 10987 matured with the opposite polarity areas becoming better separated. There is still a chance of a C class flare.
Region 10988 developed in the trailing spot section and could produce C flares.
New region 10989 rotated into view at the southeast limb. Although this is a fairly small region, there's not much separating the opposite polarity areas in the center. The region will have to rotate into better view to determine if there's a magnetic delta structure. A C flare is possible and maybe even another M class flare. Flare: M1.7/1F at 18:36. This event was associated with a strong type II radio sweep and a CME off of the east limb.

Coronal mass ejections (CMEs)

March 23-25: No partially or fully Earth directed CMEs were observed.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A coronal hole (CH317) in the northern hemisphere was in an Earth facing position on March 22-23. A recurrent trans equatorial coronal hole (CH318) will be Earth facing on March 25-28.

Processed SOHO/EIT 195 image at 00:24 UTC on March 26. The darkest areas on the solar disk are likely coronal holes.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to active on March 26-31 due to effects from CH317 and CH318. There is a chance of minor storm intervals, particularly on March 28-29.

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) Effects from a CME are likely to be observed at 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/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region Date numbered SWPC
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10987 2008.03.23 10 15 S08E23 0130 DAC classification was DAI at midnight
10988 2008.03.24 11 17 S09E34 0200 DAO location: S08E32
10989 2008.03.25 1 3 S12E63 0050 HAX  
Total spot count: 22 35  
SSN: 52 65  

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2007.01 83.3 16.9 12.0 (-0.1)
2007.02 77.7 10.6 11.6 (-0.4)
2007.03 72.2 4.8 10.7 (-0.9)
2007.04 72.4 3.7 9.8 (-0.9)
2007.05 74.4 11.7 8.6 (-1.2)
2007.06 73.7 12.0 7.6 (-1.0)
2007.07 71.6 9.7 7.0 (-0.6)
2007.08 69.1 5.7 6.0 (-1.0)
2007.09 67.1 1.9 (5.7 predicted, -0.3)
2007.10 67.4 0.9 (5.9 predicted, +0.2)
2007.11 69.6 1.7 (6.2 predicted, +0.3)
2007.12 78.5 10.1 (6.4 predicted, +0.2)
2008.01 74.3 3.4 (6.9 predicted, +0.5)
2008.02 71.1 2.1 (7.9 predicted, +1.0)
2008.03 71.1 (1) 7.6 (2) (9.3 predicted, +1.4)

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/SWPC) sunspot number. The official international sunspot number is typically 30-50% lower.

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.


[DX-Listeners' Club]