HF News
Last weekend’s Commonwealth Contest got off to a bad start, thanks to a Kp index of six that really affected the ionosphere. As a result, HF conditions were not good with the MUF over a 3,000km path below 21MHz until 1700hrs UTC.
Luckily, things improved a little on Sunday, but overall scores were down compared with previous events.
The Kp index increase was due to a coronal hole stream which reached 600-700 km/s and a Bz that pointed south. The equinox period hasn’t helped due to the Russell-McPherron effect, a phenomenon where Earth’s magnetic field aligns with the Sun’s magnetic field during equinoxes (March and September), creating “cracks” in the magnetosphere.
Otherwise, the week has been unremarkable. The solar flux index has remained firmly in the 110s and there have been no X-class solar flares, only a few M and lesser C-class events.
Next week, HF propagation may be dominated again by the solar wind. Coronal hole number 33 will begin to face Earth and a high speed stream is predicted to reach Earth this weekend, the 21st and 22nd. A coronal mass ejection is also due to arrive around the 19th.
Although at the time of writing, the Kp index has been below two for many days, that is likely to change. NOAA predicts the Kp index will rise to five at the weekend and not decline to three until March 26th. Meanwhile, the SFI is predicted to remain in the range 105-120 until March 27. It may then increase slightly to be in the 120s until the end of the month.
As a result, expect lower maximum usable frequencies and poorer HF conditions until around next Thursday/Friday.
VHF and up
The high pressure that has developed during the second half of the week just ending, formed on the warmer side of the front and as a result produced slightly better Tropo conditions than looked possible last week.
It is probably going to try to change to a colder air high after this weekend, so expect conditions to decline into next week. However, that’s not the only reason for a decline since as the main high centre displaces west of Britain, we will find a colder and unsettled west or north-westerly pattern affecting the UK next week… so less Tropo, but more chance of some rain scatter for the upper GHz bands.
Meteor scatter remains in the random activity domain, although we are edging closer to the next major shower of the late April Lyrids. It’s not to say that exciting things can’t happen; since just after a HamSCI workshop on the subject of meteor scatter last weekend, a multi-ton meteoroid was reported from Cleveland, Ohio, on the HamSCI Google groups around 1300UTC on March 17th, which produced a sonic boom and was visible in broad daylight.
All is quiet on the Sporadic-E front although we are slowly moving towards a period when the first glimmers of activity show themselves, particularly on digital modes.
Lastly, a comment on the chances of aurora ,which are usually enhanced due to solar-terrestrial alignment around the equinoxes and with two CMEs flagged to arrive for the tail end of the week just ending, on the 19th and 21st of March as we said earlier, As usual, checking for an increasing Kp index above Kp=5.
For EME, the weekend starting on the 21st sees the 5.7GHz section of the Dubus CW/SSB EME contest and associated all-mode activity weekend. With Moon declination positive and rising, and path losses still low it should produce some nice contacts. On VHF, 144 MHz sky noise is low in the coming week.