Do Solar Winds from a Coronal Hole or CME only bring bad radio conditions?

WHEN they hit the K Index shoots up bringing up with it, the noise floor (as is the situation at the moment) BUT …

The two days before the winds hit (i.e. when they are still on their way here) HF radio conditions appear to improve - why is that? It also seems when these “pre-solar-wind-hit” conditions occur, not only are signals better in general but often I can hear stations closer-in to me than I normally can given the skip distance on the various bands.

This situation with improved day time radio conditions before the solar winds hit the Ionosphere seems to be consistent, as I have now witnessed it a few times this year.

It is also thought that the day after the winds subside, there is a short improvement of conditions for up to a day or so.

To this end, Mike 2E0YYY @2E0YYY , Jonathon VK7JON @vk7jon and I will try for HF contacts on this Wednesday morning (10th. Oct 2018) around 0700 UTC, to see if we have improved conditions as it is hoped that the last of the solar winds will have disolved by then. We could of course be a day early but as there’s no accurate way of knowing how long it will be before the current solar winds will subside, Wednesday morning is as likely a time as any and around 0700 UTC is the time that VK & ZL stations were being heard last week.

73 Ed.

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Hi Ed,
Good point. If you wait until wednesday, I fear you might loose the train, as I already experienced pretty good conditions yesterday, Sunday October 7th.
See the last 3 entries of my chaser log:

These 3 chases were made with my endfed in the balcony and 50 watts out from my IC-706.

I won’t be able to join you though but I wish you very good luck in your wednesday activations.



That would be a good question to ask Dr Skov

She is very active on Twitter and is usually happy to answer questions.

Been getting same here couple days prior to storm event.

I measure this over here by way Inter G is happening in UK. Prior to event at least 48hrs to Storm event. We get a what i call the black hole of RF on 40m normally about 400km to 500km. Then during the period we get burst of anything from Minutes to hrs of its reducing down as far as 180km and can work friend in Poole and get lot closer contacts with in England. BUT one draw back i have noticed the Scottish signals normal beyond 500km well heard normally tend to duck off into noise.

But first signs are noted when certain stations are being worked from northern England to Midlands and Eastern England 400km to 300km start coming up the scale.

You Know in 48 hrs bands are going to go bad.

My gut feeling is the first winds from Pre-storm events excite the ionosphere creating the CF to rise allowing closer and closer stations to be heard and worked instead of being in the black hole its reduced. And when the event does happen that;s its game over no longer excited and CF crashes going back to normal black hole of 400km. And Scottish stations are loud again on 40m being 400km plus from here.

Friday and Saturday heard G0FVH and worked 5/9 + he’s only 180Km east of me and certainly not rise in Es and as not in yesterday CF rose again 16:00hrs utc and prob worked him again if been home.

Remember when CF rises, better chances reaching more local stations in this case 7mhz and above Inter G kicks off. And the local black hole of 400km is reduced in size. During good solar times 7mhz ++ is well maintained and inter G is daily.

So we enter a inter G winter with the odd nice day when we can work each other cause of this pre-event of storm coming.


It’s a lottery on HF, with 20m particularly fickle right now, Ed.

During my two activations last week, I worked just 2 VK’s however, 8 ZL’s found my log…Go figure.

My activation from G/SP-010 Winter Hill on Thursday was totally baffling. 3 x ZL and one SV logged on 20m ssb. Then I couldn’t buy another contact on the band and so returned to 40m.


Hi Guru - yes yesterday and the day before were the two "good " days before the Solar Winds hit - what did you hear / work today? Not a lot I suspect as conditions are not good when the K Index is up at 5. The hope is that once the Solar Winds pass (hopefully by Wednesday morning), we should get one day of good conditions again, before dropping back into normality.

We’ll see - this could be all wrong abiout the one good day after a solar storm but the 2 good days before the storm hitting the earths atmosphere does seem to be the case.

73 Ed.

OK Ed, now I understand that we are suppossed to be hitted by the Solar Winds today or so and you expect the after Solar Winds conditions enhancement by Wednesday.
I made my comment because I was wrongly understanding that the Solar Winds had already hitted us some few days ago and thus, the good conditions I experienced yesterday were due to the conditions enhancement right after the hit. That’s why I was in doubt that those enhanced conditions would last until wednesday.
Now, “alles klar” :wink:

BTW, today, during my lunch time break I managed to chase 3 HB activators on 40m (2) and 20m (1) but conditions were very difficult.



Hi Guru,
Sorry if my first post wasn’t very clear but my feeling is that we might see the following sequence (as an example):

Day 1 Eruption on Earth facing side of Sun sending solar winds towards Earth.
Day 2 nothing different to normal.
Day 3 & 4 Improved radio conditions in general and some “closer-in” contacts possible - perhaps “scatter propogation”?
Day 5 & 6 Solar winds hit, K index goes up, contacts difficult.
Day 7 Solar winds have passed but ionosphere is still charged, so contacts easier (especially DX).
Day 8 HF bands back to as there were before the Solar storm.

If this hyposesis turns out to be correct, once we know an eruption has occured on the Earth facing side of the Sun we can look out for the improved conditions before the solar winds actually hit and hopefully the day after the winds have past as well.

We’ll see on Wednesday morning whether this sequence is the case (this time) or not. We’ve had the two days of improved band conditions before the impact of the Solar winds. Of course the winds might already have passed by tomorrow (Tuesday) or indeed not until Thursday.



I should also say that the test will be better the more people from different summits take part so anyone who can get out tomorrow (Wednesday 10/10) around 0700 UTC to a summit and report back here what you found would be very welcome.

73 Ed.

PS. The K index dropped from 5 to 3 by last night and is presently at 2 - so it looks like Wednesday we should be down to 1, so the timing “looks” about right.

WRONG! The K Index is still high at 4 today.
My activation from DL/AL-179 Weichberg this morning got me only two contacts, albeit S2S contacts with Mike 2W0YYY and Herbert OE9HRV. These were on 40m. When we all moved to 20m, I heard Herbert making a very difficult contact with ZL1BYZ (I couldn’t hear John at all).
What I am surprised at is that I got no chaser calls at all! If anyone called me and didn’t get a response please let me know as that would indicate a receive problem at my end but having worked the other two portables, that seems unlikely.

I guess we were too early and the Solar winds haven’t as yet cleared. I wonder if there’s any website that tells us these things - i.e when a CME has passed??

73 Ed.

Hi Ed

I was using the NCRG Club Remote station this afternoon, it is a SteppIR Antenna at about 20 metres. Herbert OE9HRV/P was an easy contact but his signal was all over the place from about S3 to S9 at times. I heard him work John ZL1BYZ but I could not hear John, which is unusual as he is normally a good signal herein VK6. I also called you and Mike several times but no luck at all. The band seemed to close around 07:30 and I could not hear any signals after that.

There were some decent European signals earlier but the band died very quickly. I’m not sure if something caused a major fade out but i would have expected conditions to UK to improve around 07:30 but it totally faded out.

Conditions around 00:00 to 01:00 were excellent with good signals to eastern states and JA logged.

Hoping for better conditions for the VK-EU-JA whatever day :slight_smile:


John VK6NU


OK after some searching found this site:

And from what is displayed there, I would say we are still in the middle of the Solar winds hitting us, so there’s no wonder conditions were bad this morning!

Isn’t this exactly the type of problem that WSPR (Weak Signal Propagation Reporter) was designed to address?
In fact the data to answer the question could already be available on the WSPRnet web-site.


WSPRNet does not report on the physical state of the Ionosphere - i.e. in this case Solar Winds still hitting (or not).

WSPRNet is a very useful tool and it shows if signals are getting from A to B in real-time on the band you select.

What I am looking out for is when the winds stop. Once that happens see what is happening as regards the bands - does propagation improve the day after a solar storm passes over the Earth? WSPRNet would be one possible way of looking at conditions. Of course actually getting on the bands from a Summit and making contacts is a more fulfilling way.

73 Ed.

Hello Ed,
You mention that WSPRnet is good for real-time information on propagation of signals.
In fact it is possible to download WSPR data packaged in periods of one month, from the start of the program in 2008.

So if you have information about the date and time of past Solar wind events, it is possible to look at the WSPR data for the time around the event.

I certainly agree that getting out on the summits is a more fulfilling exercise!

Ian charts the band conditions in real time. It’s one of the things it was designed to do.

Hi Ian,
Unfortunately the one piece of data that I don’t have is when the previous Solar Winds occurred. I wonder if that might be available from one of the Space weather sites?
In any case before any big analysis, lets see if what has been suggested to me turns out to be true as regards the day AFTER the storm has past, having better propagation - this time.

I’m happy that the two days BEFORE a Solar storm hits do have improved propagation as I’ve seen that at least twice in the last couple of months. The question is whether this re-occurs as the storm subsides?

At the moment K is still up at 4, so it may be Friday before the storm passes. I’ll monitor the soalr wind values values shown at over the next couple of days.


Actually the wind never stops. The speed varies, as does the proton density, the wind from a coronal hole is about 50% faster than the wind in quiet conditions. The CME from a major flare is faster. At first sight the proton density appears to be an independant variable ranging from about 3 protons/cm^3 to in excess of 20 protons/cm^3 but there is a tendency for the proton count to rise before a gust of faster wind arrives. These figures are given daily on and anyone interested in studying the interactions between the wind and HF conditions can avail themselves of the archives.

Thats interesting - are the proton streams what cause the K Index to increase and hence bring up the background noise then?

After a Coronal hole opens it spews out something in an earthwards direction and we get visible auroras and (generally) bad conditions. That’s how I’ve understood it anyway.

Quote" but there is a tendency for the proton count to rise before a gust of faster wind arrives. " End-quote - so is the higher proton count cause the good conditions that we get before the faster winds arrive and cause the Auroras and bad RF conditions?

I have to say that I don’t know, Ed. I have been intending to dive into the literature and find out what is known but haven’t got around to it, I just watch the figures and the images on spaceweather as years ago I used to observe the sun and report my observations to the BAA Solar Section. I’m minded to mention the old saw about correlation not implying causation! However a vague hypothesis is that an advancing wind from a coronal hole, permeated as it is with a magnetic field, will be overtaking the quiet wind and compressing it, hence the increasing proton count. This may correlate with propagation but I haven’t tried to get some numbers together yet. Then there are the complications of solar sector boundary crossings and co-rotating interactive regions, do these impinge on propagation? I’m sure that there are researchers focussing on such questions, all we have to do is be patient with Google! :grinning: