Solar Terrestrial Activity Report

Last update issued on May 1, 2003 at 03:15 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 28, 2003)]

Recent activity

The geomagnetic field was active to major storm on April 30. Solar wind speed ranged between 490 and 684 km/sec. The interplanetary magnetic field appeared to be under the combined influence of a high speed stream from coronal hole CH37 and the CME based disturbance which dominated the IMF on April 29.

Solar flux measured at 20h UTC on 2.8 GHz was 153.5. The planetary A index was 40 (STAR Ap - based on the mean of three hour interval ap indices: 40.8).
Three hour interval K indices: 56554445 (planetary), 56543444 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight there were 9 spotted regions on the visible disk. Solar flare activity was low. A total of 2 C class events was recorded during the day. A C1.0 long duration event peaking just after 18h UTC was associated with a filament eruption just west of region 10345. This event may have caused a small CME but I haven't been able to confirm that yet.

Region 10337 decayed quickly and is rotating over the southwest limb.
Region 10344 decayed further. The leading penumbra is about to split into two penumbrae.
Region 10345 was mostly unchanged and quiet.
Region 10346 was quiet and stable.
Region 10348 decayed slowly and lost the leader spots. The region could soon become spotless.
Region 10349 continued to add penumbral area and has become a huge region. The magnetic field layout is still relatively simple for such a large region. The only area showing any degree of complexity is in the central spots section where a weak delta structure could be developing. The region is capable of producing X class flares but will likely need to become more complex for that to happen. Any major flare over the next few days would likely be associated with a large geoeffective CME. Flare: C1.0 at 01:28 UTC.
New region 10350 emerged on April 28 and was numbered by SEC two days later, or rather, the region was initially numbered region 10340 on April 29. Realizing their mistake SEC renumbered the region. The region decayed slowly on April 30.
New region 10351 rotated into view at the northeast limb.

Spotted regions not yet numbered by SEC/NOAA:
[S148] A new region emerged early on April 30 in hot plage in the southeast quadrant. Location at midnight: S24E52.

Coronal mass ejections (CMEs)

April 28-30: 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 recurrent coronal hole (CH38) in the southern hemisphere will rotate into a geoeffective position on May 3-5.

Processed SOHO EIT 284 image at 19:06 UTC on April 30. Any black areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be unsettled to major storm on May 1 and quiet to active on May 2-3. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is useless and will likely remain useless to very poor until at least May 3. Propagation along north-south paths is good and will likely be fair to good until May 3. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: an unidentified station from Brazil with QRM from at least 2 other stations from the same country. Other frequencies were more interesting. 930 kHz was surprisingly dominated by Rádio Metropolitana, Fortaleza. At times 2 other stations from Brazil were heard as well as the usually dominant Radio Monte Carlo, Montevideo]

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
Location at midnight Area Classification Comment
10337 2003.04.18 4 2 S16W81 0080 DSO classification was HSX
at midnight, area 0050
10340 2003.04.21     S07W65
10341 2003.04.21     S10W41     plage
10343 2003.04.23     N07W36     plage
10344 2003.04.24 9 11 N15W41 0220 DKO classification was DAO
at midnight
10345 2003.04.24 9 11 S17W08 0110 DAO  
10346 2003.04.24 1 1 N16W02 0060 HSX  
10347 2003.04.26     S18W15     plage
10348 2003.04.26 5 1 S36E11 0020 CSO classification was AXX
at midnight, area 0010
10349 2003.04.26 45 74 S13E07 0740 EKI beta-gamma
classification was EKC
at midnight, area 1100
10350 2003.04.30 6 8 S12W58 0070 DAO formerly region S146
10351 2003.04.30 1 1 N06E76 0090 HSX  
S145 emerged on
    S21W79     now spotless
S147 emerged on
    S17W32     plage
S148 emerged on
  7 S24E52 0020 DSO  
Total spot count: 80 116
SSN: 160 206

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)
2003.04 126.4 (1) 114.3 (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]