Solar Terrestrial Activity Report

Last update issued on April 18, 2003 at 01:45 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update April 2, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April 2, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update April 14, 2003)]

Recent activity

The geomagnetic field was unsettled to minor storm on April 17. Solar wind speed ranged between 608 and 768 km/sec under the influence of a high speed stream from coronal hole CH32. Wind speed slowly decreased during the latter half of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 101.5. The planetary A index was 30 (STAR Ap - based on the mean of three hour interval ap indices: 30.9).
Three hour interval K indices: 35554533 (planetary), 35544432 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 3 spotted regions on the visible disk. Solar flare activity was low. Only 1 C class event was recorded during the day.

Region 10334 developed a trailing spot and was otherwise quiet and stable.
Region 10335 developed slowly adding several small spots.
New region 10336 rotated into view at the northeast limb.

An active region behind the southeast limb should soon rotate into view. Flare: C4.4 at 22:16 UTC.

Coronal mass ejections (CMEs)

April 15-17: 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 large trans equatorial southern hemisphere coronal hole (CH32) was in a geoeffective position on April 11-13. A small coronal hole (CH33) in the southern hemisphere will likely rotate into a geoeffective position on April 18. A recurrent coronal hole (CH34) in the northern hemisphere will rotate into a geoeffective position on April 18-19. A recurrent coronal hole (CH35) in the southern hemisphere is likely to be in a geoeffective position on April 21-22.

Processed SOHO EIT 284 image at 19:06 UTC on April 17. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled is likely on April 18-20 while high speed coronal hole streams will cause unsettled to active conditions on April 21-22. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is likely to remain very poor until at least April 19. Propagation along north-south paths is fair and is expected to remain fair until at least April 18. [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)
Coronal hole indicator CME indicator M and X class flare indicator

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 SEC/NOAA. 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.

Solar region Date numbered SEC
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10332 2003.04.07     N12W73     plage
10334 2003.04.10 4 3 S08W24 0060 DSO  
10335 2003.04.10 2 8 S22E06 0010 BXO  
10336 2003.04.17 1 1 N12E75 0100 HSX  
S138 emerged on
2003.04.16
    S07W15     now spotless
S139 emerged on
2003.04.16
    N18E59     now spotless
Total spot count: 7 12
SSN: 37 42

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)
2002.03 179.5 98.4 113.3 (-1.3)
2002.04 189.8 120.7 110.5 (-2.9)
2002.05 178.4 120.8 108.8 (-1.7)
2002.06 148.7 88.3 106.2 (-2.6)
2002.07 173.5 99.6 102.7 (-3.5)
2002.08 183.6 116.4 98.7 (-4.0)
2002.09 175.8 109.6 94.6 (-4.1)
2002.10 167.0 97.5 (91.0 predicted, -3.6)
2002.11 168.7 95.0 (85.7 predicted, -5.3)
2002.12 157.2 81.6 (81.3 predicted, -4.4)
2003.01 144.0 79.5 (78.3 predicted, -3.0)
2003.02 124.5 46.2 (73.3 predicted, -5.0)
2003.03 131.4 61.5 (67.6 predicted, -5.7)
2003.04 119.5 (1) 48.9 (2) (62.7 predicted, -4.9)

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 (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% 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.


[DX-Listeners' Club]