NW7US Propagation Bulletin, 5-XII-2003

Post your observations about the day's conditions - like hot Sporadic-E openings, or perhaps the complete shutdown of the HF spectrum due to a solar flare. This is the place to share your reports on the "real world" conditions.

NW7US Propagation Bulletin, 5-XII-2003

Postby NW7US » Fri Dec 05, 2003 5:17 pm

This weekend is quite active on the Amateur Radio bands. The ARRL 160-Meter Contest starts at 2200 on 5-XII-2003 UTC to 1600, 7-XII-2003 UTC, while the PSK Death Match starts at 0000, 6-XII-2003 and runs until 2400 7-XII-2003 on 80, 40, 20, 15, 10, and 6 meters. The TARA RTTY Melee runs from 0000 to 2400 on 6-XII-2003 on 80, 40, 20, 15, and 10 meters. There's also the TOPS Activity 80m Contest, which starts at 1800 on 6-XII-2003 and runs to 1800 on 7-XII-2003 in CW only on 80 meters. Finally, there's the QRP ARCI Holiday Spirits Homebrew Sprint that runs from 2000 to 2400 on 7-XII-2003 in CW mode only on 160, 80, 40, 20, 15, and 10 meters.

What is the propagation outlook on the High Frequency (HF) bands during this weekend?

Earlier, today (5-XII-2003 UTC), between 0100 and 0300, a weak shock wave was detected that indicated the arrival of the glancing blow from the coronal mass ejection from the prominence eruption on 2-XII-2003. The geomagnetic field activity increased to minor storm levels with a planetary K index reaching 6. Since, the geomagnetic field activity is remaining at the active (Kp of 5) level. After about 1200 UTC, the solar wind speed further increased, and the interplanetary magnetic field has remained moderately to strongly southward in its orientation. This will continue to keep the geomagnetic field active to somewhat stormy.

There has been no clear influence of the small coronal hole that is now situated moving closer to the western limb of the sun. However, another large coronal hole is moving into a position that will directly increase the solar wind speed and therefore possibly influence the geomagnetic activity starting today. This coronal hole, originally numbered CH66 and now numbered CH71 by Jan Alvestad, was geo-effective in previous 27-day solar cycles. The leading edge of the coronal hole is now at the central meridian. Soon, the solar wind speed will become even stronger, with the possibility of strongly negative (southward) interplanetary field orientation as this coronal hole moves fully into a geo-effective position.

The geomagnetic field is expected to be quiet to active on 6-XII-2003, increasing to minor storm levels, off and on, from 7-XII-2003 through 15-XII-2003. This will cause the highest HF bands to become degraded and unreliable. At the same time, we don't expect much flare activity, so the middle to low HF bands will be in fair to good condition.

That means that conditions on HF this weekend will be fair to good for most of the contests and for general HF activity, except on the highest bands. Long distance low frequency HF, below 2 MHz, propagation along east-west paths over high and upper middle latitudes will remain poor, while propagation along long distance north-south paths will be fair. Above 2 MHz, to about 18 MHz, should be fair to good over most low- to mid-latitude paths, but somewhat degraded over the polar paths. Frequencies above 18 MHz will be degraded, with at least a fifteen-percent depression of normal maximum usable frequencies.
73, de NW7US (Tomas David Hood)
.. Contributing editor, Propagation Columns in:
.... CQ Magazine, CQ VHF Quarterly, Popular Communications Magazine

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