Manager - AB7RG
Manager Notes

Plasma Physics for the Radio Amateur, II

Created by on 2010-04-16

Plasma Physics for the Radio Amateur

Part II

Who Has'ma Plasma?

It was really sad to see them demolish the old plasma lab down at UCLA. Though nearly all of the equipment was rescued and reinstalled in Knudsen Hall, a much more modern facility, the new home really lacks the “vibe” of an old time physics lab. The old lab was built about the time the term “plasma” was coined. It was a scary, creepy, dark place, filled with the fragrance of ozone and vacuum pump oil. Things continually hissed and buzzed in there. I tried my best to capture the flavor of that old lab in my novel, Plasma Dreams, but nothing is quite like BEING there. However, I recognized that the old lab HAD to had been severely damaged in the Northridge earthquake, and had been standing erect more out of habit than out of any structural integrity.

Plasma is sometimes referred to as the fourth state of matter, which, I suppose, is descriptive enough. The real definition of plasma is much more concrete: it's any ionized gas. All plasmas are electrically conductive to some extent. They also exhibit a whole LOT of really weird behaviors besides, which is why plasma physicists will be fully employed for the foreseeable future. As we mentioned in the first part, most of the Universe is made of plasma, so your chances of discovering something relevant and practical to life on Earth by studying plasma is pretty high. I'd recommend any remotely technically minded person to think about plasma physics research as a career field.

Now, the ionosphere is, by any measurable standard, a plasma. There are some profound similarities between “lab plasmas” and “free ranging” plasmas, such as the ionosphere. And there are some differences. “Lab plasmas” encounter anomalous behavior when they encounter a boundary...i.e., the inside of the “can” in which they are contained. This boundary anomaly is one of the great technological hurdles, yet to be overcome, in the creation of contained nuclear fusion. If you didn't need the can, you could probably have controlled nuclear fusion by now.

On the contrary, the ionosphere has no can; it is contained entirely by GRAVITY, which is immensely uniform and consistent. This is why so many fusion power researchers are interested in the can you contain a hot plasma without a container? If you can answer that question, you will be rich and famous.

Be my guest.

The ionosphere is much like many of the other spheres that circle the Earth, such as the Atmosphere, Troposphere, Mesosphere, and such. They're all—well—spherical. Sort of.

Which makes one wonder what people called the atmosphere back before Columbus, when the Earth was flat. The Atmosflat?

In any case, the Earth is surrounded by varying gases of different densities and pressures. The vast, vast, vast majority of these gas molecules are neutrals. They have no electrical charge, and have no effect on radio signals, whatsoever. In the Opus of Amateur Radio Knowledge and Lore, I have a chapter called Electrons: The Tools of the Trade. We said that in all things electronic, it's really the electrons that do all the work. And they really can't do much if they're tied to molecules or atoms, other than keep the molecules or atoms company. Neutral gases are pretty invisible to radio waves; there's really nothing in them to even respond to radio waves.

Starting at an altitude of about 90 kilometers, however, a tiny number of these atoms can get their electrons slapped off their carcasses, which then become free electrons. Or at least, fairly cheap ones. The main electron-slapping ingredient is ultraviolet radiation from the sun, and you don't have to be a rocket scientist to conclude that probably much more electron-slapping happens during the day than at night.

Precisely how many of these electrons get slapped off their host atoms determines how much stuff we have to bounce radio signals off of. Now a whole lot of interesting things happen when electron-slapping happens, all of which falls into the field of plasma physics. Although I worked in the field for many years, I'll avoid the temptation to deliver a course on plasma physics in this chapter. You can get a much more entertaining introduction to that branch of science by reading my novel, Plasma Dreams. (Shameless commercial plug here).

One of the interesting things that happen is that these slap-happy electrons tend to organize in layers of sorts, and begin to exhibit collective behavior, must like your local Teamsters Union. Except they never ask for overtime. That's why they're called free electrons.

Now, the atoms that get their electrons slapped off them are called ions. Ions also exhibit a collective behavior, which is why we call that collection of ions the ionosphere. These ions don't generally affect radio signals directly, but they do give a certain sense of direction to the free electrons. Without the remaining ions, the free electrons would flail off in every direction, because they are, being like-charged, mutually repelled.

Perhaps you're asking why the ions don't go wandering off merrily as well, since they also are now mutually repulsive. Well they do, but very slowly. Even though they have the same magnitude of charge as their off-slapped electrons, they have thousands of times the mass! So, though the ions will gradually drift apart (diffuse), in most regards act mechanically like any other gas. In fact, you actually have weather-like phenomena happening in the ionosphere, just like in the atmosphere. Well not just like, but you do have recognizable patterns of movement and such way up there.

So, the end result is, we have this big sluggish ionosphere keeping free electrons on a very long leash. The result of all this couldn't work better for radio propagation if it was intentionally planned. (Actually, I'm one of those folks who sincerely believe the ionosphere was specifically created for bouncing radio signals off of. Just like believing that trees were created as antenna supports. But that's just me).

Now, there's an interesting little item called the electron density profile. It's sort of a perverted bell curve sort of thing lying on its side. You can see this as a black line on many ionograms available online. (I use the HAARP ionosonde, which shows conditions valid for most of Alaska. ( You can find a nearby ionosonde by looking at the Lowell Digisonde site map. )

What the electron density profile shows you is the relative number of free electrons at any altitude from about fifty kilometers to about six hundred kilometers. This is the best indication of how good the sky is going to be at reflecting radio signals at any particular time. Now, why the funny curve, and not just a straight line? Good question. We actually have two conflicting things happening.

Since air pressure is highest at ground level, and decreases as we go up, there are more atoms available to get their electrons slapped off of. So the lower we go, the greater potential for the creation of free electrons. But—and it's a big but—the ultraviolet light has to travel farther though absorptive air to get to those high density atoms. So while there are more atoms to ionize at lower altitudes, it is easier to ionize them at higher altitudes. The breakeven point is usually at around 250 km altitude or so, the normal peak of the “bell curve”. It is generally around here where you will find the most number of free electrons milling about. There's also usually a smaller peak at around 100 km or so.

Now, we haven't really explained how an electron reflects a radio signal, though we've described how these electrons congregate. Actually, you CAN reflect a radio signal off a single electron, and there are scientific devices called incoherent scatter radars which do just that, but this is pretty science-geeky stuff. As radio amateurs, we're much more interested in reflecting radio signals off mobs of electrons.

If we have a decent, well-behaved ionosphere, we have more or less a sheet of electrons, which in some ways, acts a bit like a sheet of copper. We have a region of sky that is highly electrically conductive. Unlike a wire, it's conductive in all directions, north-east-west, and south, not just along a line. We also have some conductivity up and down, because our electron sheet can be many kilometers thick. Oh, I must also clarify one point here. Please do not get the impression that we have any significant volume of sky that consists of nothing but electrons, any more than we have any volume containing nothing but ions. Any region of the ionosphere we look at will have all three items: electrons, neutrals, and ions occupying the region in varying concentrations. High free-electron content just means there are a lot more free electrons at that height than at other heights.

Well, back to our conductive sheet analogy. The electrons are free to accelerate in any direction in response to a radio wave impinging on them. They will line up and slosh back and forth in accordance with the electrical part of the wave passing through their midst. But what do sloshing electrons do? Why, they create radio waves! This is why we were emphatic about the reciprocity theorem in the antenna chapter. It doesn't matter whether you're a slosher or a sloshee. One creates the other, and the other creates the one. (Important reminder: Remember, it's acceleration of electrons that creates electromagnetic fields, not their mere movement. This is a crucial distinction. The acceleration can be linear or angular, though for free electrons, it's usually linear acceleration we're most concerned about).

This is also why I was reluctant to describe the ionosphere as reflecting radio waves. It actually absorbs and re-radiates them. Looking at what happens from the vantage point of your station on the ground, this may seem to be a minor point of semantics, but it makes a big difference when we look at the more peculiar aspects of ionospheric or “skywave” radio.

Now, if all those nice slap-happy free electrons happened to coagulate in a nice spherical shell at about 250 kilometers, all around the round Earth, life would be wonderful all the time. Worldwide skywave communications would be possible anywhere at any time.

But alas, there are several flies in the ointment.

We'll discuss some of these flies in Part III

WA2JJH 2010-04-29
RE: Plasma Physics for the Radio Amateur, II
Yes CP antenna's are used in broadcasting for two reasons.

For VHF/UHF CP ants have great rejection to multipath

For 7 GIG terrestrial use CP antennas also allow 2 transmitter/receiver links to operate on opposite 1/2 split freqs away from center channel. One TX/rx pair will use the left polarisation, the other tx/rx pair will use the right polarisation.

When you see big events like the NYC marathon, to any
broadcast using many live hot switched camera's
Circular polarization allows the broadaster to use many more wireless cameras.
WA2JJH 2010-04-29
RE: Plasma Physics for the Radio Amateur, II
yikes!!! jUST back from Thailand. I had to sPlit early because of a plasma like civil war in Bangkok.

How dare I, add anything to this broth of plasma physics, psuedo-intellectual parallels to the female mystic. Yes, I had plenty of that in Pattaya beach Thailand.

A I was taught at a young age that plasma is a quasi-4th state of matter. Anything that cannot be expressed as a liquid, solid or gas can be refered to as plasma.
Ionised gas in some types of lasers are refered to as plasma. The gas in some types of gas lasers have tw states.o
Gas state and plasma state. At below lasing threshld, the laser medium is gas. Then at lasing, the excited gas is plamsa. Photon energy is emitted. The photon is emitted from the plasma state of the gas medium.

Plasma is a term often used and abused to describe anything that the math or physics do not check.

For ham radio, Many posters have given decent explainations of the ionised states of layers in the ionsphere can perdict multi path, DX, NVIS or even pedestrian L.O.S communication.

Yes, the term plasma is used in hemotology. In regular human blood , plasma refers to what is left of blood after it is "spun off" centerfuged.
It has been found that blood is best stored by its componants.
Plasma is what if left of the blood after the red and white blood cells are removed.

Plasmatic states of female behavior. I think the line in the movie....."IS THIS AS GOOD AS IT GETS?"

THE LINE: The Jack Nickolson character is asked......HOW DO UNDERSTAND WOMAN SO WELL?
Jack snaps back.........I take a mans psyche. I then remove 90% emotional common sense and add in the fact that woman are allowed to get away with acts that would
embarass or have a mans sanity to be questioned.

I add in that woman are victims of their own nuerotransmitters. The two that come to mind are estrogene and oxytocin.

I was reminded by this by how if I allowed a woman I was involved with in Pattaya beach,to delay my cab by 2 hours..........I would have missed one of the last flights out of BangKOK.
If you watch the News in Asia. Look at the Plasma-like activity of the RED and Yellow shirts. The woman I thought loved me, was trying to make me trapped in her country.
The word PLASMA is very much like my spelling and gammar.......ENTROPIC INDEED.

KL7AJ 2010-04-27
RE: Plasma Physics for the Radio Amateur, II
Here's the "unofficial" Part IV

Plasma Physics for the Radio Amateur

Part IV

Are you Ordinary or Extraordinary?

We now come to my favorite part of radio physics, and a phenomenon that explains more of the “odd” behaviors of ionospheric propagation than any other factor. And you’ll find scant mention of it anywhere in Amateur Radio literature.
A picture is worth a thousand words, so let’s look at a picture first and go from there. Here is a very typical ionogram, taken from the HAARP Digisonde ionospheric sounder.

You can get more local ionograms in most parts of the country, and around the world.

Notice the very well defined RED and GREEN traces in this ionogram. The red trace is the ORDINARY wave, which is clockwise circularly polarized in the Northern hemisphere. The GREEN trace is the EXTRAORDINARY wave (or X wave), which is counterclockwise circular polarized in the northern hemisphere. ALL ionospherically reflected signals will result in these two separate waves. You don’t have to TRANSMIT circular polarized signals to get these two rays…the ionosphere does it all by itself, with any linearly polarized “upward” signal.
This is because a MAGNETIZED plasma (which is what the ionosphere is) is what we call “birefringent.” It has two different refractive indexes. There are two different velocities of propagation, two different critical frequencies, and two different heights of reflection. And of course, two different polarizations…that’s the only way the ionosonde can really separate the two returning waves!
One thing you DON’T see in the ionogram is the huge divergent in AZIMUTH between the O and the X wave signals. At LOW ANGLES of radiation, these two waves can diverge well over 90 degrees in azimuth, and counter-intuitively enough, NEITHER ONE of them follows a Great Circle route, at least in magnetic polar regions. If you’re near the magnetic equator, the divergence of these two rays will be a bit less.
Now, even though you ALWAYS get both rays when you transmit a signal into the ionosphere, most hams have no way of knowing which ray they are actually receiving from a distant station because there isn’t one ham in 100,000 that uses circular polarization on H.F.! This is a huge mistake, as we shall clearly see.
Now, before we go too much into the practical implications of this, we need to talk a little bit about what’s called the Appleton-Hartree dispersion formula.

Actually, that’s about ALL we need to say about it. What this formula does is tell you the refractive index of a magnetized plasma. There are TWO solutions to this equation, one which gives you the O mode refractive index and one that gives you the X mode refractive index. If you feel like working it out, be my guest.
There’s actually a pretty good Wikipedia article on it here:

Now, I’m not a mathematical sadist, so instead I’ll really tell you what it means in real life. What it means is that you will see a HUGE difference by using circular polarization on H.F.! The only case you might not care is if you’re using NVIS, in which case, you will receive both the X and the O modes in the same location…but with a slight time delay. But if you’re more than a few hundred miles or so from the transmitting station, the X and O waves will have diverged by a large margin. You will be receiving ONLY and X mode or O mode signal at your particular location. This is easy to see with a very simple CPOL antenna, such as a turnstile (two dipoles at right angles fed with a 90 degree phase shift.) You will typically see at least a 3 S-unit difference between being the correct polarization and the “wrong” sense polarization. It’s theoretically possible to get INFINITE rejection of the opposite sense wave, but only if the signal is arriving precisely normal to the antenna, and this isn’t going to happen often.
In any case, the only way to really know if you’re receiving the X wave or the O wave is to USE circular polarization.

Now, for a news flash. Don’t let ANYONE tell you that the polarization of H.F. signals is “random.” It is NOT. It is absolutely predictable. Appleton-Hartree will tell you. It is Right Hand circular, or it is Left Hand circular. One or the other. Always. The only thing that may be random is your knowledge of which of the two rays is arriving at your particular QTH! Is it any wonder that so many hams think that H.F. is randomly polarized when they haven’t even been told that it’s CIRCULAR in the first place?!

Of all the phenomena observable in plasma physics, this whole X and O mode business is one of the EASIEST to demonstrate in your own shack. The results are clear and predictable. Build a CPOL antenna for yourself and see!

Now here’s another neat little trick that CPOL will allow you to do. Remember how we said how difficult it can sometimes be to determine the direction of arrival of distant signals? Well, one way you can determine if a turnstile antenna is looking “down the barrel” of an incoming CPOL wave, is to check for the circularity! (This can be done with a two channel oscilloscope in the X-Y mode, each channel looking at one dipole of the turnstile) A wave arriving “dead on” will have the ROUNDEST display possible. In fact, this is the method the Digisonde uses to determine direction of arrival, when it’s used in the oblique sounding mode (something not all Digisondes are set up to do). It uses some fancy footwork to “steer” the antenna array electrically, rather than physically scanning the sky. But the principle is the same.

Stay tuned!

K4JSR 2010-04-26
RE: April, May-an' June, September 23
Come mas Zarigueya!
That is my story and I'm sticking to it.
73, Cal K4JSR
AE6RO 2010-04-24
RE: April, May-an' June, September 23
K4SJR: Of course, amigo, I can play along. I was just thinking today how some, if not most people don't deserve any warning about December 21, 2012 anyway.

So. I gazed into my Crystal Skull transceiver and realized it will really be a Great Time of Peace, Love, and Understanding. It's not that anything is happening to the Sun because our learned scientist/priests say so.

Oh, yes. I'll just sit around waiting for Cycle 24 to begin because it Always Has Before. 73, John

P.S. I've found several unique ways to cope with Night Mares.
K4JSR 2010-04-24
April, Mayan June....
EA6RO said, "The Mayans didn't practice ham radio as far as I know."

Sir; Times have changed!!! The Mayans not only have ham radio, they have formed their version of ARES to
deal with 2012. Since all good Mayans work during daylight their nets meet in the evenings. They call themselves "The Night MARES".
So, I am not worried. I know that there are Mayans
with shirt pocket ham shacks out there to save us all.
So don't worry. Be happy!

I must go now. The nurse is here with my chemical cocktail.

73, Cal K4JSR
KL7AJ 2010-04-24

Having a switchable sense cpol antenna will give you a kind of diversity capability, but not in the sense that you normally think. The X wave and the O wave actually travel in different routes, and being able to select X or O mode will allow you to determine which ray you're working,

AE6RO 2010-04-22
To be fair, 1984 was not an end-of-the-world date. It came and went and nobody noticed.

Y2K was entirely a man-made problem which was prepared for and dealt with. So nothing really bad happened. But December 21, 2012 was ordained, if you will, by God.

The problems you mentioned, such as climate changes, overpopulation and fossil fuel shortage will indeed become more troublesome as 2012 gets closer. 73, John
KT8K 2010-04-21
I wonder if I should start working on having two sets of circularly-polarized HF antennas, one right-handed and one left-handed. I thought I was getting around this with diversity reception using antennas of different polarities ... does that accomplish the same end?

In the meantime, ... 2012? I survived all the previous "ends of the world", including 1984 and Y2K, so I'm not too worried about 2012. We've got big problems ahead with overpopulation and its side effects such as dwindling fossil fuel supplies, climate change (any), economic fluctuations, infrastructure disruptions (natural or manmade), mass population movements, etc., but it's unlikely 2012 will be much different from any other year in the period.

A Big Thanks to Eric for another great article series. Best rx & 73 to all de kt8k - Tim
AE6RO 2010-04-20
Whatsamatter, chicos? Don't feel like fighting any more? Cheer up, the Solar Flux is up to 76 so Cycle 24 is starting up Real Soon now! John
AE6RO 2010-04-20
Looks like everyone here is having a nice time. Enjoy it, because after December 21, 2012 the ionosphere will be sleeping for a long, long time.

The Mayans didn't practice ham radio as far as I know. Unless those crystal skulls were really transceivers of a sort. And don't forget September 23, 2010. Things will become more clear then. In the meantime good DX! 73, John
K4JSR 2010-04-19
Okay, Eric. You're up next. Let the music begin,
or shall we say, "DUET TO IT!"

Feee-Lipp has his Terror-Min ready. Time to start scaring wild life and neighbors.
Maybe you two could get a Bagpiper to join in the
merriment!!! Time to start some Alaskan Wailing!!

GET 'ER DONE!!! Make that Aurora really dance!!!

73, Cal K4JSR
N5TGL 2010-04-19
RE: Plasma Physics for the Radio Amateur, II
"Part iV is going to deal specifically with the Ordianary and Extraordinary (X and O) modes."

Awesome. In all the searching of the intertubes, I never found an explanation of the difference, or why I should care. I look forward with great interest to part IV. Thanks!

KA4KOE 2010-04-18

here is my theremin, or as the ever-supportive family calls it, "Daddy's Screaming Machine".


KL7AJ 2010-04-18
RE: In fact HAARP uses nothing but a bunch of cros
"You sound like the kinda guy who has plasma in his blood."

That would make me a rarity indeed! :)

N4UM 2010-04-18
RE: In fact HAARP uses nothing but a bunch of crossed

You sound like the kinda guy who has plasma in his blood.
K4JSR 2010-04-17
In fact HAARP uses nothing but a bunch of crossed
You and KA4KOE should get together and play a duet.
You on your HAARPsichord and Feeee-lip on his world
infamous Theremin (Home made, no less!)
Feee-lip already has a penguin suit for the performance. I think you two could make some really, ummm, unusual MOOSE SICK together. SEAL the deal!
Then you two could collaborate on a hybrid article drawing from both of your fields of endeavor,
"DEAD PLASMA DUDES". Yes, that title does indeed have
a certain "AURORA" around it.
My work here is done for the moment. I think I will
just kick back, pop some popcorn, open a cold 807 and
watch what comes next.
73 and just remember that if you can't stand the heat,
get out the Vapor Phase Reflow machine. You might just
KL7AJ 2010-04-17
RE: Plasma Physics for the Radio Amateur, II

It's very easy to create a circular polarized H.F. antenna. In ionospheric research, you seldom use anything more exotic than a turnstile antenna, which is just two dipoles at right angles, fed with a 90 degree phase shift between the elements. The real trick is keeping the phasing at 90 degrees over a wide frequency range.

In fact HAARP uses nothing but a bunch of crossed dipoles:

The way they do the phasing at HAARP for R.H. or L.H. circular polarization is to feed EACH element (North-South or East-West dipole) with a separate transmitter. The phase twiddling is done at very low power levels AHEAD of the transmitters. That way they can do very fast switching between right hand corkscrew and left-hand corkscrew transmission. (As well as a lot of other very clever pattern manipulations)
KE7FD 2010-04-17
RE: Plasma Physics for the Radio Amateur, II
Eric, great prose. My brain doesn't hurt as much as I thought it might after reading your article. I know to that at least I benefit from your dumbing things down to ground level. I think material like this written in a way that doesn't make the reader feel denser that a rock is how many of us quasi techno-science geeks feel we can actually understand the fundamentals behind the hobby.

Now, if could just impose a permanent clockwise corkscrew pattern onto the wire of my cloud-burner that wouldn't cancel itself out....

Glen - KE7FD
KL7AJ 2010-04-16
RE: Plasma Physics for the Radio Amateur, II

You're making the very common mistake of confusing temperature and heat. Indeed the upper atmosphere is extremely cold, because the HEAT CAPACITY is so low. Heat is a function of SPECIFIC HEAT of a material and total mass. As we've explained above, the MASS of the ionosphere is nearly nothing. It's ability to retain heat is also next to nothing. But the small numbers of particle there can have very high TEMPERATURES as measured in electron volts.

For example, the filament of a flashlight bulb runs at about 2000 degrees F. It has a very high temperature. But the total thermal mass of the filament is almost'd take a lifetime trying to boil a gallon of water with the thing.

So, likewise, the ionosphere has a very small number of very high energy particles. High temperature, low heat.

Hope this helps some.

KL7AJ 2010-04-16
RE: Plasma Physics for the Radio Amateur, II

Glad you asked about the Extraordinary mode. In fact, Part iV is going to deal specifically with the Ordianary and Extraordinary (X and O) modes. (Nobody said physicists could spell!)

Here's a little intro, though. When you launch a signal into the ionosphere, it splits into two rays, one clockwise circular polarized and one counterclockwise. In the Northern Hemisphere, the O mode is clockwise, and the X mode is counterclockwise.

These two rays are clearly defined in the ionograms from Digisonde. The red traces are the O waves, and the X mode is the green trace. These signals take two very different paths through the ionosphere, and unless you have a circularly polarized antenna, you really don't have any idea which ray you're using.

However, you can always gain about 3db of signal strength over a dipole just by using circular polarization. If your "sense" of rotation is backwards, the signal will just about disappear.


K5END 2010-04-16
RE: Plasma Physics for the Radio Amateur, II
KOE, you were right in the first place. It is a gas, by definition.

The criterion is that it is a low density, ionized gas.

There is a chapter or section in one of my college E&M textbooks (Lorrain & Corson) entitled, "plane wave propagation in low density ionized gases," or something similar to that.

After becoming interested in the topic recently, I dug out that old book and learned far more than I did the first time around. If I had realized at the time how interesting this is, I would have made better grades! hihi.

Eric, when are you going to get into the real physics of this topic; I mean, you know--the good stuff? How many more chapters do you plan to post on the subject?
AE6RO 2010-04-16
RE: Plasma Physics for the Radio Amateur, II
I was under the impression that the upper reaches of the atmosphere were stone cold, not hot. I mean, table salt is full of ions and it isn't even in plasma form. Maybe we can fire potato cannons at the sky loaded with salt and get the ionosphere to work again.

Better to just crawl under the sheets with your favorite Feminine Mind. After December 21 2012, she'll probably want to just to stay warm.

'Cause it will be even colder by then. 73, John
K5END 2010-04-16
RE: Plasma Physics for the Radio Amateur, II
"...Men have been studying the Human Female mind for centuries, still no luck...:

The first step to maintaining sanity is to abandon any expectation that what is observed will make sense to the male mind.

However, there in an interesting body to the subject matter.
KA4KOE 2010-04-16
RE: Plasma Physics for the Radio Amateur, II
It's a gas!!!

...well, almost.

VO1FZ 2010-04-16
RE: Plasma Physics for the Radio Amateur, II
Amen, and long live the difference!
AF6AU 2010-04-16
RE: Plasma Physics for the Radio Amateur, II
What Humamkind knows about plasmas begins with the first discharge of electricity in a partial vacuum, late 1800's or so. We know volumes ablot plasma.

Men have been studying the Human Female mind for centuries, still no luck.
VO1FZ 2010-04-16
Plasma Physics for the Radio Amateur, II

Please, please, please write some articles on wife behaviour. Please don't call it Wives for Dummies though ;)

Seriously - excellent explanation on the whole topic - only wish calculus was so well explained in my earlier years.
N5TGL 2010-04-16
Plasma Physics for the Radio Amateur, II
"One of the interesting things that happen is that these slap-happy electrons tend to organize in layers of sorts, and begin to exhibit collective behavior, must like your local Teamsters Union. Except they never ask for overtime. That's why they're called free electrons."

This just about made me spit coffee this morning. :)

Great writing style, and I'm also happy to see that you are pulling ionograms into the discussion. I've been looking at them, and you can certainly find out some very interesting stuff from (attempting) to scale them.

One question for you: I've never really seen it explained what the "extraordinary" part of the ionogram is/means. If you could shed some light on that, I'd be very grateful.

Thanks for your articles!