.jpg)
RSGB
GB2RS News Team | March 21, 2025
Last week was pretty unremarkable from an HF perspective. After the disturbed geomagnetic conditions on the 12 to the 14 when the Kp index rose to five, conditions were a little more settled.
The solar flux index hit 204 on the 17 March but then declined back to the 180s.
Having said that things were settled, the Kp index did exceed four for three periods on the 19 March, peaking at 4.67. This had the effect of reducing the MUF over a 3,000km path to 21-24MHz.
We also had two M-class solar flares on the 17 and the 19 March, with the latter causing a coronal mass ejection that may give Earth a glancing blow around the 22 March.
As spring progresses, we may find the F2-layer MUF dropping as we move to summer ionospheric conditions, perhaps to be replaced by enhanced sporadic-E conditions on 10 metres instead.
Next week, NOAA predicts that the solar flux index may drop further, perhaps hitting 150 on the 28 March. Unsettled geomagnetic conditions are forecast for the 25 to the 28 March, with a maximum Kp index of five.
As we said last week, this is now a peak period for auroral activity, given the angle that the Earth makes with the Sun. The ‘Russell-McPherron’ effect is down to the alignment of the Sun and Earth around the spring and autumn equinox and means that you are twice as likely to experience the aurora in spring and autumn than in winter and summer.
VHF and up :
The recent fine weather has provided some useful Tropo. This has been mainly towards the east and into the near continent, which seemed like nice timing for the 1.3GHz UK Activity Contest last Tuesday evening.
Despite this, many participants reported conditions as poor. The high is now moving away and by the time you hear this, it will be a predominantly low-pressure weather sequence from now on. This means limited Tropo in the coming week, and rain scatter comes to the fore as a mode of choice if you have a GHz band set up.
The solar conditions continue to provide a trickle charge of auroral alerts, but not enough for any significant operating advantage. As usual the message is to keep on top of things by monitoring the Kp index for values in excess of 5.
Meteor scatter remains largely in the gift of random meteors, so it’s an early start to catch the pre-dawn peak of random meteors if you are so persuaded.
Lastly, a mention of Sporadic-E which is still in its close season. We have a while to wait until later next month when we could expect the occasional stirrings on 10m.
EME path losses continue to improve until the Moon’s perigee (its closest point to Earth) on the morning of the 30 March. Moon declination has been falling, reaching a minimum yesterday, the 22 March.
So again, we have short Moon windows and reducing peak Moon elevation. 144MHz sky noise started high on Friday the 21 March but will drop back to low by the middle of next week.
(Mike Terry, UK/BDXC)
