HF News
Last weekend’s geomagnetic disturbance didn’t turn out to be quite as bad as predicted. A high-speed solar wind stream from a massive coronal hole and a coronal mass ejection caused the Kp index to rise to 6.33 on Friday May 15th, but it subsided and we were soon back to more normal figures in the range of two to four.
The last week has seen more normal Kp figures in the range of two to three which bodes well for HF propagation. Unfortunately, the solar flux index has been stuck in the low one hundreds, ranging from 109 on the 16th, to 106 on the 20th. It did rise to 114 on the 21st, which may continue next week.
Meanwhile, ESA’s Solar Orbiter has been monitoring solar activity on the far side of the Sun, which continues to feature a number of large sunspot groups. A number of C-class Flares and one low-level M-Flare have been detected on the far side, but we will have to wait until next week for that activity to rotate to an Earth-facing position.
A lot of the activity on the higher HF bands is currently due to Sporadic E and Jim G3YLA reports several multi-hop paths showing up between Europe to the Caribbean and the USA on six metres. A quick check on 10m only revealed low power beacons out of Spain and Andorra unfortunately.
Next week NOAA predicts that the SFI may rise to 115 on May 25th and then increase to 135 by the end of the month. The start of next week should see settled geomagnetic conditions, but we are predicted to see a rise in the Kp index to four on the 27th.
VHF and up
The recent lengthy period of indifferent weather has now changed over to a predominantly high-pressure type, which should last through to the end of next week when a possible return to unsettled weather edges up from the south.
Starting with the large-scale pressure pattern, it will be a period of improving Tropo conditions for the VHF/UHF bands as the high builds over the country. The conditions should cover a large area across the North Sea and into the near continent. It is often the case that lift conditions may be improved by night-time cooling and fade slightly during the day, unless over a sea path, which doesn’t change much from day to night.
The late May and early June period is a reasonable time for meteor activity, although mostly minor, there is still the tail end of the Eta Aquarids to work through this month. The solar conditions have offered up some reasonable coronal holes recently and, although the light evenings don’t allow visual confirmation, the Kp index going above Kp=7 should make life more interesting for aurora. Needless to say, rain scatter will not feature in a predominantly high pressure period of weather.
Lastly a thought about sporadic-E which is coming into full bloom now and is typically at a peak around early to mid-June. There have been some successful openings on 6m with some multi-hop paths to the Far East and across to the States and Caribbean.
On the basis that jet streams may be useful indicators of where Es are more likely, then the coming week will see the main jet stream flow being pushed well north to a typical summer position from Iceland to Scandinavia and possibly making paths to Scandinavia and the Baltic a good option including northern multi-hop paths to the Far East.
EME now, and Moon declination is falling again, going negative on Monday. Combined with increasing path losses, conditions will worsen as the week progresses, but there is still plenty of time to make some QSOs, albeit with shorter Moon windows and lower peak elevation. 144 MHz sky temperature is low, but increasing to moderate by Friday the 29th.