venerdì 28 ottobre 2016

Propagation News – 30 October 2016

Last week was characterised by low sunspot activity, but very unsettled geomagnetic conditions. The solar flux index was in the mid to high 70s, but the K index was five or six for days on end, and even peaked at seven. This was high enough for automatic visible aurora e-mail warnings to be sent out by Lancaster University.

The noon Chilton Digisonde plot from Harwell suggested that only 20 metres would be open, with the higher bands closed. These poor conditions were caused by a massive coronal hole on the sun. This hole is recurring and brought the same conditions 27 days ago. Rest assured, we can probably expect a repeat performance again around November 22nd.

With regards to LF/MF propagation, the Dst index was depressed to -80nT on the 25th but is rising slowly. It would seem from reports that LF/MF propagation on paths over 2,000km has suffered but not as much as might be expected. It seems that though the solar wind velocity had increased, the plasma density is low. This suggests there may be lower levels of electron precipitation and a faster recovery of conditions than would be expected after a coronal mass ejection.

Next week looks set to continue with the poor geomagnetic conditions. NOAA suggests the K index will remain at around five until a much-needed respite beginning around the 2nd of November.

VHF and up propagation news:

Most of this week will be dominated by high pressure and this is likely to continue to provide slightly-enhanced Tropo opportunities for many areas although, like last week, the better conditions will be when there is moist air near the surface, which quite often means those typical foggy autumnal nights and mornings.

The longer range models do, unfortunately, suggest that the high weakens and is replaced by low pressure in the second half of the week, so it won’t last forever.

As for operating tips, it’s simple; don’t restrict yourself to FM and repeaters, and do remember to try the other modes on VHF/UHF because SSB and CW can produce surprising results – and there’s plenty of spectrum space down there.

For meteor scatter enthusiasts, we are now approaching the peak of the Taurids meteor shower, a diffuse shower that lasts from late September until late November. Don’t get too excited though, as the meteor rate is low. It does though, have a reputation for some fireballs. Look for a peak overnight around the 4th and 5th of November.

The Moon is close to the Sun today so noise will be high, especially on the low bands with wider antenna beamwidths. Combined with a low declination and high losses at apogee on Monday, it’s a week for EME system maintenance only.