Sporadic E and X-Ray bursts

Nobody knows exactly what causes Sporadic E. Yes, we know what the process of refracting the radio signals is (more or less), we know where it happens and the general pattern of when it occurs, but nobody can really say for sure what causes any specific event. Not even me.

It is not hard to see the problem. During the Summer, for instance, there are days with no Es, followed by days when there is lots of Es. Often on the higher VHF bands it will occur one day and not the next, and on the 2 metre band it might only occur on one day per year in any specific location.

So this mysterious process has been analysed looking for patterns and a theory has emerged that although most of the factors are present on many days, a certain "trigger" is needed to set off an Es event.

The RSGB website has a section devoted to maps of the "Jet Stream", following the idea that movements in the Jet Stream account for variation in Es occurrence. I have looked at all that stuff and I can find no evidence at all that the maps of the Jet Stream and the occurrence of Es at this location are linked. But good luck to them, they are sticking by their story.

I can see that the Jet Stream might have an influence on the atmospheric conditions, but their claim is more than that - that the Jet Stream is a trigger for something which happens in the ionosphere.

I find that during the Summer it is hard to see a pattern in Es events. Whilst on the one hand, on 10 metres there are so many events that the results are hidden by a vast sea of contacts, and at the same time, on the higher bands there is often nothing happening from day to day.

Basically my theory is that variations in the energy arriving from the Sun are the main trigger, and variations in the ionosphere and the Earth's magnetic field account for the regional variations. This is hard to see during the Summer as the general level of radiation from the Sun has a much higher effect on Earth.

The Sun does not know what season it is on Earth. The Sun just pumps out its variable stream of light, infra red, ultra violet (UV), X-rays, protons, ions, ... "stuff" made up partly of energy and partly of energetic charged material. The seasonal variation we see on Earth is due to the fact that the Earth's rotation is angled with respect to the path of rotation round the Sun. During the Summer the Earth is tilted towards the Sun, and the rays fall more vertically giving us longer warmer days. During the winter the Earth is at a steeper angle to the Sun's rays, and days are shorter, the energy reaching any part of the Earth is weaker and it gets colder. This effect is basically geometrical - angled rays strike a larger target than perpendicular ones.

Of course this effect is more pronounced at the Earth's poles. At the poles it is dark all day in Winter and bright all day in Summer. The effect lessens as you get further away from the poles towards the Equator. In the tropics there is not much seasonal variation, and surprise surprise there are places where you often find year-round Es ("Equatorial E-Skip"). Not much sign of the Jet Stream influence there.

So at any given level of output, the Sun's influence will be greater during the Summer. What takes a spike in activity to start an Es event in Winter might be triggered by the background level of radiation during the Summer. Simple geometry indicates that more radiation is needed from the Sun in Winter to create the same level of flux per volume unit of the Earth's ionosphere. So in Winter perhaps I can find conditions with no background Es, but a spike of radiation from the Sun might trigger an event.

Therefore I have been looking at 10 metres during the Winter. I have been looking for bursts of Es during periods when there is usually no Es at all, i.e. January. When I say "no Es at all" I mean - not if you don't look for it. The idea is that I am looking when otherwise there is no background Es. In Summer the band is often full of signals and no cause and effect can be found.

I have spent a long time comparing Es events with signs of spikes in activity from the Sun which would show a link. I watch all the available measures of Solar activity, but principally X-ray and proton levels, plus solar wind speed. Often these measures are linked, for example during a coronal mass ejection.

Can I find small pulses in the Solar activity which match small Es events? Yes, dozens of times but here is one (well, two actually).

As for my test over many days before this, nothing of note. No solar pulses, no Es. Sometimes pulses during the night which are not going to reach our side of the Earth. There was a small event on 27 January which I failed to record properly because it was tea time (I have to eat to live you know).

Try again on 28 January.

First of all, let me get rid of the background dx. Pain in the behind is that darned F layer stuff which just masks me looking at Es (hey, who does not want to hear VK on 10m?).

As usual, click to enlarge if you cannot read this stuff.

Ignoring the dx, I continue to look for Es and solar pulses. Let me show you the GOES satellite X-ray flux readings

There is a clear pulse just before 12:00, peaking at about 12:00. This will take a wee while longer to reach the Earth and do some ionising, so is there a sudden Es contact then?

Indeed there is, at 12:32.

Then there is another little pulse on the X-ray graph later. Not a big pulse, but enough to deviate the readout.

The blip at 13:00 was sufficient to raise the lower energy level rating (blue) quite a lot. Is there a sudden spike in Es after this?

Yes.

Rest of the day ... nothing of note. A bit of F layer propagation but no more Es.

These results, by themselves, prove nothing. It is just that I keep getting results like this, day after day, week after week.

It comes as no surprise that Es contacts and solar energy levels are related. Of course, during the Summer, the same radiation from the Sun causes much more Es, because it is more concentrated for us living in the North (or South) of our globe. We know that Solar energy causes Es. So what am I banging on about?

Well, I am fed up looking at graphs of weather charts and failing to find a relationship between Es events and the Jet Stream. I am fed up reading "VHF propagation predictions" rambling on about the Jet Sream and the likely effect it will have on Es next week. That may have some effect viewed from the Beautiful South, and me in the frozen North may not have that effect. Fair enough. I can only tell it like it is here.

Up here, I see every day a relationship between (even weak) Solar Pulses and Es events (even when Es is not expected). No solar pulses, no Es. Solar pulses, even in Winter, Es. During the Summer, the intensity of the solar energy is stronger overall and it is hard to pin down cause and effect. In Summer, no doubt the angle of the Sun also affects the Jet Stream, but that looks like a separate effect to me.

My belief that even weak solar pulses are the main triggers of Es is nothing new. You can see it happen with Auroral Es, you can see it with Polar Es. You can see it all Summer with the seasonal Es. I don't need a weather trigger explanation.

Surely I have now done this topic to death.

Next area of thought - In my experience Es incidence is not closely related to the Sun Spot cycle. Wikipedia states:-

No conclusive theory has yet been formulated as to the origin of Sporadic E. Attempts to connect the incidence of Sporadic E with the eleven-year Sunspot cycle have provided tentative correlations. There seems to be a positive correlation between sunspot maximum and Es activity in Europe. Conversely, there seems to be a negative correlation between maximum sunspot activity and Es activity in Australasia.

So that suggests that we are not looking at a sun spot number related effect. I need to look more closely at the various factors - protons, X-rays,  solar wind etc., to figure this out more clearly. It is probably too complex for my meagre resources and no doubt greater minds (and big number-crunching computers) than I have are working on it.

73

Jim
GM4FVM

Meteor Science and Engineering

Richard, GI4DOH, kindly loaned me a copy of the book "Meteor Science and Engineering" by D. W. R. McKinley.

As Richard pointed out, not much has changed in the science. That is true, but it has stuck me since reading the book that the technology has moved on.

This is an excellent text book. Published in 1961 it was probably one of the first fully encompassing books on the subject. That is certainly its strength, as McKinley seems to have been perfectly at home with the astrophysics, radio astronomy, optical astronomy and geometrical aspects of all of it. He ranges from descriptions of the radio systems to an interesting estimate of the dangers to space travellers of meteors. He draws from the research of many experts.

Some of it is beyond the area of my interest, but I read it all anyway. I have not yet seen a need to grasp the geometry of meteors. Their paths of approach are not something I think of as crucial, perhaps because so much of what I do is working with random meteorites. Yes, the showers coming from specific directions do interest me, but they are not crucial to what I do ... yet.

Also, some of the maths is a bit heavy going. I have done a lot of maths in my time. I just think that I do not wish to get involved again at this stage in my life. By this I mean advanced maths. I am happy with ohms law and so forth, but complex formulae are not what I need to think about right now.

Having said all this, I really enjoyed reading it. McKinley allowed me to pass a lot of the maths by, as he has written excellent summaries. Each chapter begins with a general explanation, and these would be worth reading on their own. After that I could decide how carefully I would read the rest of the chapter.

I was particularly interested in the coverage of the development of radio astronomy in this area. I knew that meteor reflections (like sporadic E and aurora) were researched around the time of the Second World War. Also, the Jodrell Bank observatory was largely filled with war surplus material to begin with. But I did not realise that entire wartime radar systems were released for meteor research at the end of the war. What had been seen as strange effects getting in the way of military projects became legitimate areas of research.

Some of the figures really intrigued me. The idea of 1000 tonnes of material being swept up by the Earth each day as it orbits the Sun is a bit of a shock. I have heard figures like this before, but I had some idea that not much material reached the surface. I read that not only does it reach the Earth, but it can be found on the ocean floor. Most of this material is microscopic and forms dust.

Two graphs which interested me were on the subject of the distribution of meteors over time. The annual distribution looks pretty much like a sine wave with the (fairly flat) trough in February and March, and the similar peak in July and August. The value of the peak is about 2.5 times the trough, measured in hourly meteor rates. Roughly speaking, if the trough is about 100 in relative units, it remains below 120 between December and April - which is interesting as there are notable showers in both December and April.

The graph for daily distribution is similar in shape, with the trough at about 18:30 and the peak at about 04:00. However, this has shallower slopes so the top and bottom are more fleeting events. Once again the variation is about 2.5:1 in terms of hourly meteor rates.

I know that these are combinations of various findings, often combining random and shower meteors, but I can work both. So, during the winter trough the daily peak roughly equals the summer peak at the daily trough. Peak time of year and peak time of day will see five times as many meteors as the double troughs.

Now this I find fascinating. There are amateurs who stay off the bands in February on the basis that there is nothing to work. But yet, pick the peak time of day and there are as many meteors then as at 18:30 in July. Even at midnight or 08:00, winter rates are quite good.

I need to process all this information. Canny amateur meteor operators already know all this. On Sunday I worked OZ1JXY on 4 metres. OK, it took us just over 2 hours to exchange six pieces of information at just about the worst time of year and certainly the worst time of day (we finished at 17:30). But it is not true that it cannot be done. Henning pointed out that if we all sit and read a book we will not work anyone, whereas if we call CQ we might - he worked four stations last weekend and four again this weekend. Not bad for the worst time of year. I think he might have worked a few more if they had been on the band.

On Saturday I tried for three hours to work Tomas EA2BCJ on 4m. I got good copy from him, but he did not hear me.

Well, you win some and you lose some. But Tomas is 1500km from me, Henning only 732km. Maybe it is a different proposition for longer distances. Here is where I think I may need the geometry.

Probability also comes into the equation. Unlike astronomers who are averaging signals over a long period, we are expecting a reply to our CQ, report, or whatever. The fact that there might be five bursts in the ten minutes after I stop, does not please me when I have had none over the previous 2 hours. With probabilities like this, a pattern of that nature would not be unlikely.

When McKinley describes forward scatter experiments in his book, he is talking about high power transmissions with high gain antennas. The idea of modulating the signals is more a theory than a reality, and all the experiments seem to be "one way" (i.e. a tx station and an rx station, widely spaced). For me, my 100 watts is a lot, and my antennas quite bold, but on his scale they are minuscule. Many amateur meteor watchers look for signals from massively powerful broadcast transmitters: I am looking for tiddlers by comparison. I also expect two-way communication which affects the probability of success quite a lot.

What has changed over the years since the book was written is really the excellent equipment we amateurs can now use. Joe Taylor has given us the wonderful WSJT software suite. What a amateur can achieve with simple commercial equipment in today's world is remarkable. Examples might be high performance GaAsFET pre-amps and the excellent sensitivity and low noise performance now offered by commercial VHF receivers.

I am left with the following thoughts (and quite a few unformed thoughts):-

1) I need to rethink what I can do at the troughs of the meteor cycles
2) I should try harder to understand random meteors (as there seem to be a lot of them)
3) The book does not really deal with my low power, relatively short distance contacts - nothing seems to.

Thanks to Richard for the loan of the book. It certainly made me think.

73

Jim
GM4FVM

A pleasant little aurora.

I have been reading up on meteors and meteor scatter propagation. But more of that another time.

On 20 January there was an interesting aurora. I said in the title "little" but it was of long duration, only little in the sense that I only worked 6 stations in 4 DXCC. But nice all the same.

Solar ham gave a warning of a pulse arriving from the Sun in the early hours on 19 January. Although that might suggest that an aurora was on its way, they did say that the pulse was "weak". Whether the activity the next day was part of the same event I am not sure, but the Bz component of the magnetic field of the solar wind began to turn from strongly positive to strongly negative around 11:00 on 20 January.

The solar wind speed was under 400, which usually means either a weak or non-existent aurora. I find that a wind speed over 400 is needed for a good opening. The three factors, negative Bz, raised wind speed and increased proton density are good but not always necessary. Raised X-ray intensity is another good guide. It is not simple to predict what might happen when you have four indicators of how intense the aurora might be. They will rarely be simultaneously perfect, which is what makes radio aurora watching so interesting.

Anyway, the auroral oval shown by the Ovation website and repeated on Solarham is also a key factor. Under normal conditions there is a gap in the oval, and the gap circulates round the Earth over the North Pole (or South Pole for Aurora Australis). If the gap is over Western Europe then it does not matter much how good the other factors are, there will be no effects at GM4FVM.

The gap in the oval covers the period from early Morning to around 15:00 local time. If the solar activity is especially strong the hole in the oval will tend to fill in and it becomes more or less continuous but less strong where the hold would otherwise be. On the other hand, when geomagnetic activity is weak then the gap tends to widen and any aurora will start later.

You can watch the hole in the oval track round the earth if there are auroral contacts going on. I might have to wait until 15:00, but OH stations are a couple of hours ahead of me, so I can see them on dxMpas working Russian stations at 13:00 my time (but 15:00 OH time). Rather like F layer propagation, the arc of auroral contacts move with the rotation of the Earth (so they appear to come towards us from the East).

And so it proved. I could see lots of activity spreading East from Russia (on 2m) and then around the Baltic Sea (on 4m). Bang on schedule the Northern Ireland beacons, both 2m (NGI) and 4m (CFG) appeared around 15:00. In the event I could hear CFG for the next 5 hours. Sadly there were no GI stations to be heard.

Due to the rotation of the hole in the auroral oval I find I need to use magnetometers roughly along my longitude to get a reasonable indication of what is happening. Slightly East gives warning so I often use the stackplot of Norwegian readings shown in the sidebar of this blog. Also useful is Sundsvall, which is featured under "more magnetometers" on the Solarham site. Here is Sundsvall on 20th:-

Latitude is another factor. The Norwegian stackplot is better for assessing that. Each geomagnetic disturbance seems to affect different lattitudes differently, but I do not understand how that process works. Maybe it depends on the energy levels of the particles in the solar wind.

I could hear LA stations on CW on 2m but they were sending FAR too fast for me. I turned to 4m for some sanity and worked Clive GM4VVX at 16:40. I also heard the 4m Faeroes beacon around then.

Try as I might, I could not work anyone on either 2m or 6m. I know that the Doppler distortion on SSB signals on 2m tends to drive people towards CW. But I was struggling to be heard on 6m as well. I called one SM station several times and he could hear me but could not make out my callsign.

I do not want to go for big linears, but I suspect that several 6m stations are running 400w and more. Big 6m linears are easily available at a hefty price. Whilst I am running more or less the same power as the others on 2m and 4m, I am not in that class on 6m.

Anyway, on the aurora I worked OZ5AGJ, ON7EQ, G4EHD, GM4PMK  on Mull and MM5DWW on Orkney. No new squares and I have worked almost all of them before. I finally packed it in just after 19:00.

It was interesting that the openings to each station were quite short. The solar wind speed stayed low, which probably ruled out any real DX.

Now, on 22 January it seems that gemagnetic conditions are hotting up again. As I write this it is 13:44, so the hole in the oval is still over my path northwards (see Ovation map below). However, I can see no reported contacts to my East. So maybe this one is not to be.

I will try after 15:00 to see if it has decided to play ball again today.

73

Jim
GM4FVM

Happy New Year etc ...

Welcome to our newest reader, our neighbour Amanda. Google has worked out that she and I share the same post code, and have started "serving" her a link to my blog. So although she does not seem to be interested in Earth Science, she has to both look at my antennas and be pursued by my blog.

I do dislike that word "served", meaning that the internet providers throw advertisements at us.

You can tell it is the holiday season from my conversation with Mrs FVM.

Her "Please get the cob nuts out of the garage"
Me "There are no cob nuts in the garage"
Her "Yes there are, they are in the cupboard marked 'apples'".

Of course. Why didn't I think of that? I had never thought to look for the nuts in the cupboard marked apples. I did not pursue it, because I know that the real reason why the nuts are filed under apples is that the rest of the garage is full of antennas, bits of antennas, and aluminium poles. No doubt if there was room, there would be a cupboard marked "nuts".

The cob nuts in question are otherwise known as hazel nuts. We have two hazel trees, and the nuts from both are stored in one string bag in a cupboard marked "apples". One of the trees produces wonderful nuts, the other one produces wonderful shells with no nut inside. You have to crack them open and find out which type you have in your hand. You could sort them out as you picked them, but that would take the surprise out of cracking them on New Year's Day.

So nuts are a seasonal treat in the FVM household. Another thing we harvest ourselves is soft fruit, such as apples for crumbles. We also grow raspberries and strawberries. Some of the strawberry crop is frozen to make Cranachan. Cranachan is a local winter pudding made of raspberries (fresh is best, but frozen is OK), oat meal, whipped cream and whisky. The raspberries are home grown, and the other ingredients come from within 20 miles or so. It is a bit like boozy "Eton Mess". A real treat at Christmas and New Year.

New Year is a big thing round here. Know as "The Bells", many people wait in the frozen air for midnight to toast the New Year in with copious quantities of whisky. In my childhood, it was the tradition that people would call at your house bringing gifts of lumps of coal and small bottles of whisky. In exchange for this, my father would treat them to large tumblers full of his whisky. As a child, this spectacle was a bit scary, as drunken strangers would pound round the house at 2am, falling over the dog and breaking the crockery. They used to sing out of tune and dance about, giving me a life-long dislike of seeing in the New Year.

But never mind about that. Happy New Year to all our interested readers (and Amanda). It was good fun on VHF over the New Year period, but accounts of that will have to wait.

It would be wrong of me to name anyone as having been particularly helpful, as I am bound to miss someone. But I still will. I hope that does not leave anyone feeling missed out, as you can blame my memory or lack of it. So I will deal with groups of you.

Thanks to those of you who just read the posts (tens of thousands of hits!). Best wishes for the new year to the silent majority.

Thanks to those of you who sit on hill tops and freeze in the cause of VHF, or operate long hours in contests to give me elusive grid squares (and this group includes Gordon G8PNN, Eddie G0EHV, Andy GM4JR and many others).

To some fellow VHF experimenters around me who I have never met but who still offer advice and are willing to do endless tests (such as Chris GM4ZJI and Rob 2E1IIP), many good wishes of the season.

Warm felicitations to that fine bunch of people who listen for my data signals for hours on end, (particularly Henning, OZ1JXY, Jerzy SP9HWY, P.O. SM5EPO, and all the world-wide WSPR mob).

Thanks to those of you who emailed me and to some who pulled me up on things or made me think a bit more (including Richard GI4DOH, Gianfranco IU1DZZ and Roger MI6USC).

Special thanks to those of you who came round to see me, sat in coffee shops at garden centres and blethered, bartered accessories, climbed poles and drilled holes (particularly Doug GM6ZFI and Derrick GM4CXP).

Appreciation also goes to Bri, G0MJI, who encouraged me to write in the first place.

And thanks too for my "mentor" Bob G3KML who discussed the finer points of wave theory, mag loop antennas and so forth, at great length, many times this year.

Plus special thanks to everybody else too.

As you sit and enjoy your New Year festivities, maybe not Cranachan and nuts, or maybe not at home but in Gran Canaria or some other wonderful winter holiday location, please accept my thanks for all your support.

Have a great New Year, everybody.

CUAGN in 2016.

73

Jim
GM4FVM