venerdì 28 giugno 2019

Propagation News – 30 June 2019

Last week saw a continued quiet Sun with zero sunspots at the end of the week and a settled geomagnetic field. A feature in Nature magazine has suggested that we may be heading for a Maunder Minimum in the next three decades. The report cites a study of long-term oscillations of the solar background magnetic field associated with double dynamo waves generated in the inner and outer layers of the Sun, which indicate that the solar activity is heading for a grand minimum.

Another report says an international panel of experts coordinated by the NOAA and NASA have released its preliminary solar cycle 25 forecast, predicting that cycle 25 will peak no earlier than 2023 and no later than 2026, with a minimum peak sunspot number of 95 and a maximum of 130. This would make it similar to cycle 24, which was predicted to reach a maximum smoothed sunspot number of 90 in May 2013. In fact, solar cycle 24’s maximum was reached in April 2014 and peaked at an average sunspot number of 82. Meanwhile, we continue to head towards sunspot minimum, which is predicted no earlier than July 2019, and no later than September 2020.

The HF doldrums continue, although evenings and night times seem to be best for DX, with 20m remaining open until very late indeed. OD5TX in Lebanon was romping in at around 1930UTC on Wednesday. 40m is also very active with Roger, G3LDI reporting many stations from the USA on the band around 0330UTC.

Next week, NOAA predicts the solar flux index will be in the range 67-69 with settled geomagnetic conditions and a maximum Kp index of two or three.

VHF and up:
This coming week, tropo should be fairly productive at times, especially across nearby sea paths over the North Sea and English Channel. High pressure remains a primary feature of the weekend and part of next week, although the centre of the high being close-by will mean that the inversion is quite close to the ground, so paths may suffer if this gets too low. That said, it looks like a good week to get those beams and some CW/SSB going on VHF bands.

Moving on to sporadic E now, which relies indirectly upon the presence of jet stream flow. This can make gravity waves that propagate up to the E region and play a role in the formation of sporadic E propagation.

The location of jet stream winds recently has been driven by an upper low west of Biscay, which has favoured paths to Spain and Portugal, but this is about to change as the pattern shifts to a jet stream across Scandinavia into eastern Europe. This will favour paths to Scandinavia, the Baltic and Ukraine. There is an outside chance of an upper ridge over western Europe, which could introduce a chance of sporadic E into Italy or Spain, but this is not a clear signal this far ahead.

The Moon reaches peak declination on Tuesday and perigee on Friday, so EME conditions will be at their best all week with low path losses and long Moon windows. There are no major meteor showers this week so continue to look for best DX opportunities via random meteors around dawn.