Solar Terrestrial Activity Report

Last update issued on July 13, 2003 at 03:25 UTC.

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

Recent activity

The geomagnetic field was unsettled to severe storm on July 12. Solar wind speed ranged between 567 and 777 km/sec, mostly under the influence of a high speed stream from coronal hole CH47. Having been quite variable early in the day, solar wind density dropped to the low levels usually associated with high speed streams after 09h UTC. This coincided with a fairly sudden decrease in the total field of the interplanetary magnetic field and the end of the strong southwards excursions of the IMF. After 19h UTC solar wind speeds began to decrease and has dropped to the 550 km/sec level as I write this.

Solar flux measured at 20h UTC on 2.8 GHz was 121.5. The planetary A index was 46 (STAR Ap - based on the mean of three hour interval ap indices: 46.5).
Three hour interval K indices: 67643343 (planetary), 56543253 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 7 spotted regions on the visible disk. Solar flare activity was moderate. A total of 8 C and 1 M class events was recorded during the day.

Region 10401 decayed quickly and lost nearly half of the penumbral area.
Region 10405 developed slowly and quietly.
Region 10406 added a few trailing spots while only minor changes was noted in the leading penumbra.
Region 10407 developed a few small trailing spots and was quiet.

Spotted regions not numbered by SEC:
[S201] A new region emerged early on July 12 in the northeast quadrant. Location at midnight: N15E37.
[S202] A new region rotated into view at the southeast limb early on July 12. Location at midnight: S13E73.
[S203] A new region rotated partly into view at the northeast limb. This region has at least two active centers with the southern center having rotated fully into view. The more active northern center is still rotating into view. Further M class flares are possible. Location at midnight: N15E80. Flares: C3.1 at 02:48, C2.9 at 06:30, C1.9 at 09:57, C1.4 at 13:22, C1.2 at 13:44, C1.5 at 14:28, C2.9 at 16:16, M1.4 at 19:06 and C4.6 at 20:50 UTC.

Coronal mass ejections (CMEs)

July 10 and 12: No LASCO images available due to a problem with the SOHO high gain antenna.

July 11: The long duration C3 event in the morning near the center of the solar disk appears to have been associated with a slow CME. While best defined over the north pole, material outflow was observed over both the southeast and southwest limbs. The CME could reach Earth on July 14.

July 13: A filament eruption beginning at 00:32 UTC in spotless region 10404 and along the southern border of CH48 visibly affected the corona as far north as N20 (on the other side of coronal hole CH48) and areas well into the northwest quadrant. A CME was likely associated with this event. With an origin near the center of the solar disk the CME could easily become geoeffective.

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

Another recurrent and developing coronal hole (CH48) in the northern hemisphere and with a significant trans equatorial extension will rotate into a geoeffective position on July 12-15.

Processed GOES SXI coronal structure image at 20:00 UTC on July 12. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on July 13 due to a high speed stream from coronal hole CH47. A CME observed on July 11 could reach Earth on July 14 and cause unsettled to minor storm conditions. A likely CME associated with a near center disk filament eruption early on July 13 could reach Earth late on July 15. The high speed stream from coronal hole CH48 will cause unsettled to minor storm conditions on July 15-17.

Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor to 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 with a weak signal. ]

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 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.