Geomagnetic Storm G4

NOAA has predicted and now reported the start of a G4 geomagnetic storm. This storm will significantly affect our HF radio propagation, probably mostly adversely, for several days.

We’ll probably see a lot of HF absorption due to auroral activity in the polar regions, as well as QSB and other disruptive effects. CW signals may be modulated and sound weird, and other modes may be affected. It is likely that the aurora may be visible at night, if the geomagnetic storm continues.

There also is an S2 solar radiation event in progress, which usually means additional absorption of HF signals at high latitudes. Not good for SOTA or DX!

The solar flux is very high - 233 - which means the ionosphere is getting a very high level of EUV and X-ray radiation. Levels this high greatly increase the D-layer absorption on longer HF wavelengths - like 40M - but also may enhance propagation on bands with shorter wavelengths, like 10 and 6 meters.

Most of these effects are related to several recent major solar flares. A very large and complex sunspot group (NOAA # 3664) has developed into a formidable active region. This solar feature has plenty of energy and is likely to continue to create more major flares soon.

Please see these links for more details and updates - this is going to be quite a ride:

The SDO site has numerous near-real-time solar images from an orbiting solar observatory. If you select “Data Links”, you can get the higher-resolution images - these have great detail and reveal the complexity of the sun’s outer layers. Many of these images are in the EUV. The plain yellow image called “HMI Intensitygram - Flattened” shows the sunspot Region 3664 - be sure to go to Data Links and magnify the image to see the soul of this monster. This surely is one of sun’s largest spot groups this solar cycle, so far. The span of the group is on the order of 200,000 KM.

The image called “HMI Colorized Magnetogram” reveals the magnetic complexity of Region 3664. Most average sunspot groups are simple bipolar regions - this one is a tangle of strong magnetic fields in the solar plasma. It is growing and changing as I type!

Enjoy the ride - this is solar maximum, like it or not!



I don’t know when NOAA forecast this for - but it’s already here:


This is great … current webcam view to the highest summit of Austria OE/KT-001


Today I saw my very first northern lights. And at home in Hanover in Northern Germany.

73 Chris


I’m interested in hearing reports from activators on bands and conditions. The N0NBH chart of solar conditions and propagation shows poor Hf conditions on all bands. I do not have a permanent antenna installed so unsure if any sky wave QSOs are being made.


Right now there are a number of S9 stations on 10m, with rapid flutter making them hard to read, I am listening to a very fluttery OG1D, there is a very strong LY with tone A signals, I must walk the dog and will listen again when I get back!


I had an activation planned after work on 10m but got to the summit after the storm had started. No DX on 10m SSB but I was heard across Europe/Russia on 10m FT8 and several signals had a bit of an echo on them.

I jumped onto 6m FT8 to see if there was anything exciting happening but nothing special at my end (just UK and Ireland) but there were a lot of people on 6m FT8 so maybe they had the same idea as me.


Had a big outburst of aurora while walking the dog, around 2230UTC, rapidly changing rays and bands with splashes of red, about the third best display of my life!

The 10m activity seems to have ceased.


Great views from here, just south of Hamburg. Would have been even better from somewhere darker and above the mist covering most of the countryside.


Never mind the radio, I’m so pleased to have been able to see a nice display this far south.

This just outside Cambridge about an hour ago (photo pretty much straight out of camera with only minor level adjustments, no saturation changes):

Lovely to see easily visible curtains and colours this far south, probably a once in a lifetime event down here.


I activated today and couldn’t figure out what was wrong! Signals were distorted, and generally horrible conditions. The QSB was so bad most of us were walking on each other trying to find a free spot. Probably my most frustrating activation to date. Thanks to those few dedicated, patient chasers who allowed me to just get it done with 5 contacts after an hour’s work.


Thanks George for providing this information and links; very useful in helping us to understand this phenomenon.

Geoff vk3sq


I looked out last night when I knew this was happening but could see nothing - a combination of cloud cover and lights from the houses around here - I never thought to look for a webcam, somewhere out away from the metro lights.
This was DL/AM-001 Peissenberg around Midnight:

73 Ed.


I’m bummed!!

Ive never seen the Northern Lights and am currently in the Scottish Borders where I assume it must have been visible.

Maybe tonight!!


Looks like no radio today due to QRN but at least nice pictures. Here is aurora borealis as seen from IO83.




Thank you. Problem with my Q dictionary.


Apparently it’s large enough that you can see it with just eclipse glasses, but I couldn’t definitely see anything last night as I watched the sun set.


VHF/UHF/SHF it is then :slight_smile:


49 years that shot took me!

2024-05-11T07:26Z 45•S