NRL Scientists Develop 3D Model of the Ionosphere F-region

From the Naval Research Lab, not our normal fare, but interesting for its uniqueness.

The first global simulation study of equatorial spread F (ESF) bubble evolution using a comprehensive 3D ionosphere model, SAMI3, has been demonstrated. The model self-consistently solves for the neutral wind driven dynamo electric field and the gravity driven electric field associated with plasma bubbles.


Contour plot of the electron density as a function of magnetic local time (MLT) and altitude. A fully 3D spatial model of ESF describing the motion of ions along and transverse to the geomagnetic field in a narrow longitudinal wedge of the post-sunset ionosphere.
U.S. Naval Research Laboratory (2010)

Developed by Dr. Joseph Huba and Dr. Glenn Joyce at the NRL Plasma Physics Division, SAMI3 is a fully three-dimensional model of the low- to mid-latitude ionosphere. SAMI3 has been modified recently to use a sun-fixed coordinate system to eliminate rotation of the dawn-dusk line and a high-resolution longitudinal grid to capture the evolution of equatorial plasma bubbles in the pre- to post-sunset sector.

The new modeling capability with SAMI3 has found that ESF can be triggered by pre-sunset ionospheric density perturbations and that an existing ESF plasma bubble can trigger a new bubble.

“Understanding and modeling ESF is important because of its impact on space weather,” said Dr. Joseph Huba, head of the Space Plasma Physics Section of the Beam Physics Branch. “ESF anomalies can cause radio wave scintillation that degrades communication and navigation systems and serves as the primary focus of the Air Force Communications/ Navigation Outage Forecast System.

Post-sunset ionospheric irregularities in the equatorial F-region were first observed in 1938 by terrestrial magnetism researchers, H.G. Booker and H.W. Wells at the Carnegie Institution of Washington. During that time, analysis of the scattering of radio waves by the F-region of the ionosphere at an equatorial location (Huancayo, Peru) revealed ESF is fundamentally a nighttime event, with greatest frequency of occurrence in the period from four hours before midnight to four hours after midnight.

“The ionosphere builds up after sunrise and reaches a maximum electron density in mid-afternoon, said Huba. “Subsequently, the ionosphere can be lifted to higher altitudes just after sunset because of the pre-reversal enhancement of the eastward electric field. During this time the ionosphere can become unstable.”

The F-region of the ionosphere is home to the F-layer, or Appleton layer, and is the densest part of the ionosphere as it extends from about 200 km to more than 500 km above the surface of Earth. Beyond this layer is the topside ionosphere. Here extreme ultraviolet solar radiation ionizes atomic oxygen. The F-layer consists of one layer at night, but during the day, a deformation often forms creating layers labeled F1 and F2 . The F-region is the region of the ionosphere that is very important for high-frequency (HF) radio wave propagation facilitating HF radio communications over long distances.

The upgraded version of SAMI3 represents a unique resource to investigate the physics of equatorial spread F, particularly the processes that control the day-to-day variability of ESFs. Future improvements to the current model include: modification to the geomagnetic field to have a tilt allowing the inclusion of longitudinal effects; coupling SAMI3 with a physics-based model of the thermosphere; and replacement of the full donor cell algorithm, currently being used for crossfield transport, with a high-order flux transport algorithm allowing for the capture of complex bubble evolution involving bifurcation.

Advertisements

35 thoughts on “NRL Scientists Develop 3D Model of the Ionosphere F-region

  1. ah, is this the phenomenon Vukcevik illustrated a while back, interesting pic found also here? These plasma blobs track the geomagnetic equator more or less, but in parallel, on each side. They seem to have a resonance factor. Quite fascinating.

    If this is right, you might like to add this picture to the article.

  2. Speaking as a radio amateur who has been playing with the ionosphere for a fair few years now, this looks most interesting. If anyone from the Naval Research Lab reads this … any chance of a screensaver version? ;)

  3. Lucy, don’t see anything thing directly tied to climate off the top but I do see two curious things in that graph. One, look how the max is not at noon but at 2:30 to 3:00 just as maximum normal temperatures are hit on the ground. Must mean the disassociation of the oxygen must be accumulative and not instantaneous as I had always thought. I would have guessed noon.

    And those cool ringing waves just after sunset, I have a long wire antenna hooked to an am radio in the garage that I can pick up New York, Atlanta from ok bounced from the ionosphere but I had always had wondered why you would get this thirty minute period of no signal, then thirty minutes of signal, back and forth until later in the night. Could that be exactly what this plot is showing in those waves? But that’s am frequency, not hf.

  4. Now that’s some real cool science Anthony, thanks. As I tell kids, you can learn your whole life and you will never run out of interesting things in this physical world!

  5. @WUWT
    > The F-region of the ionosphere is home to the F-layer, or Appleton layer, and is
    > the densest part of the ionosphere as it extends from about 200 km to
    > more than 500 km above the surface of Earth.

    Atmospheric density decreases with altitude, so the D- and E-layers, which are lower in altitude, are certainly more dense than the F-layer. Were you perhaps referring to electron density, which does peak around 300km I believe?

    Slightly O/T but interesting is this 1933 article on the “Luxembourg Effect”. Radio Luxembourg had started broadcasting in that year on longwave (230kz) with a very powerful (for its time) transmitter, 150kw or so (eventually increased to 1.2 megawatts!).

    This signal actually heated up (in the thermodynamic sense) the ionosphere, such that it modulated other radio signals broadcasting on entirely different frequencies. For example, Radio Lux’s programming could be heard on a relatively weak Swiss station monitored in England. The Swiss signal passed over Luxembourg in the F-layer, where it was thermally modulated by the Radio Lux signal:
    http://durenberger.com/resources/documents/LUXEMBOURGEFFECT0235.pdf

    This illustrates how sensitive the ionosphere is to external stimuli.

    Someone will joke that environmentalists will protest this when they hear about “radio stations destroying the environment”. Too late, they’re already up in arms about HAARP, the DOD’s experimential research station in Alaska for studying the Luxembourg Effect, i.e. the effect of ground-based transmitters on ionospheric and auroral phenomena:
    http://en.wikipedia.org/wiki/High_Frequency_Active_Auroral_Research_Program

  6. wayne says:
    January 19, 2011 at 2:41 am

    Living in Zurich in the 70s, I’d turn on AFN on my radio to listen to US sports and music. I couldn’t get Stuttgart, but I could get Frankfurt, with the signal strength oscillating for about two hours after sundown. Nice to see the image confirm what I’d suspected was the cause. No cross modulation though, that would have been interesting.

  7. Love your semi-quote from Santayana, one of my favorite quotes. If only alarmists would take it to heart.

  8. We have been able to do relatively accurate predictions of F layer behavior for a long time. Back (not that long ago) when short wave was important for international communications, the behavior of the ionosphere was a ‘big deal’.

    There is a lot of historical data about the behavior of the F layer. Ionospheric sounding involves launching an RF signal (at various frequencies) toward the ionosphere and watching how much of the signal bounced back. As far as I can tell, this was done by many governments all over the world. http://en.wikipedia.org/wiki/Ionospheric_sounding

    The ionosphere during the day is influenced directly by the sun. At night, it is influenced by cosmic rays.

    I don’t know if anyone is using the results of ionospheric sounding to cross check against other measures of incoming galactic radiation but the data is there. Given that some people (Piers Corbyn for instance) are using gamma rays to predict the weather, it might be interesting to see if there is any correlation between the ionospheric sounding data and climate.

  9. @commiebob
    > I don’t know if anyone is using the results of ionospheric sounding to
    > cross check against other measures of incoming galactic radiation
    > but the data is there.

    HAARP makes a lot of its historical and current data, including radiosondes, publicly available. For example, here are some daily plots (from 2010) which could be correlated with other data.

    http://maestro.haarp.alaska.edu/cgi-bin/digisonde/scaled.cgi?endTime=20100127&pwidth=1W&var=foF2

    [The HAARP radiosonde sounder is down for repairs until Feb 2011, so no current data is online now]

    REPLY: Normally all discussions of HARRP are deleted, due to the nutcases that think it is about weather control. In this case I’ll allow it due to it having a datasource mentioned. – Anthony

  10. orkneygal says: January 19, 2011 at 3:36 am
    Do we now have a Green Flash predictor?

    No, green flash takes enough air to refract the light, and the ionosphere is waaaay too thin. For twenty years I’ve watched for green flashes over ocean sunsets while flying and never seen one. I’ve seen just about every other photometeor, though.

  11. @Anthony
    > The F-region of the ionosphere is home to the F-layer, or Appleton layer, and is
    > the densest part of the ionosphere as it extends from about 200 km to
    > more than 500 km above the surface of Earth.

    Anthony, atmospheric density decreases with altitude, so the D- and E-layers, which are lower in altitude, are certainly more dense than the F-layer. Were you perhaps referring to electron density?

  12. Ask the world’s HAM operators to digitize their logs and send them to a central location. Their contacts will mirror this picture.

  13. DonS says:
    January 19, 2011 at 9:24 am
    Ask the world’s HAM operators to digitize their logs and send them to a central location. Their contacts will mirror this picture.

    No need to do that. Automated NCDXF ham-radio beacons are deployed world-wide to allow automatic monitoring of band conditions at selected amateur radio frequencies.

    http://www.ncdxf.org/beacon/beaconschedule.html

    Of course, someone has to listen to and analyze what the beacons send. Here’s what the 14Mhz and 18Mhz NCDXF and other HF analyses looks like in Alaska.
    http://maestro.haarp.alaska.edu/data/spectrum2/www/beacon14.html
    http://maestro.haarp.alaska.edu/data/spectrum2/www/beacon18.html
    http://maestro.haarp.alaska.edu/data/spectrum2/www/hf.html

  14. Looks like more heuristic rumination.
    “The model self-consistently solves for the neutral wind driven dynamo electric field and the gravity driven electric field associated with plasma bubbles.” Uh, Oh there goes my bs detector. On top of that we have bubbles spawning bubbles which sounds a lot like science fiction. I also am not aware that science has the understanding of gravity in its back pocket. Have bubbles actually been observed (especially spawning) or are these just a bunch of heuristic claims.
    NASA has long known about the diurnal bulge or the expansion of the atmosphere due to the earth’s direct exposure to the sun on the day side and it does indeed peak at about 2:30pm. The bulge involves the entire atmosphere including the F layer. So why does the article not mention anything about it?

    John Day (january 19, 2011 at 3:58am)
    ” This signal actually heated up (in the thermodynamic sense) the ionosphere, such that it modulated other radio signals broadcasting on entirely different frequencies.”
    This interpretation must be yours as nowhere in the article on the Luxembourg Effect
    does it state this. It does however state that “When we attempt to explain the matter in somewhat greater detail our difficulties begin and at present there is NO generally accepted theory of this ionospheric cross-modulation, as we may, perhaps, term it.”
    The word “perhaps” shows that they are not even sure this is the correct handle for it. Also, highly specific geographical conditions are required for this “effect”to happen.
    Your conclusion that “This illustrates how sensitive the ionosphere is to external stimuli.” is, BASELESS.
    Don S – Their contacts will mirror this picture — NOT!
    I am a ham radio op. The first in Canada at age 13. I have been in and out of this hobby for the last 37 yrs and this article is junk science looking for funding. Lots of bafflegab for people to read.
    All we ham ops care about in regards to shortwave communications is a peak in the solar cycle.

  15. As mentioned above, this doesn’t seem to be new or surprising… but I wonder if the Navy’s desire to understand skip in finer detail indicates a desire to return to HF for communication.

    Most communication and broadcasting is now in VHF, UHF and even SHF bands, which has left HF relatively vacant. Sort of like an older Streetcar Suburb that was, um, skipped over in the dash toward far-out areas with big lots and McMansions. I’ve been thinking it’s about time to reclaim and re-gentrify HF, which has significant advantages. Maybe the Navy is thinking along the same lines?

  16. polistra
    You can trace the decline in use of the sw band (160m – 10m) to the rise of the internet as a global communications network. It is not subject to QSB(fading) nor is vhf, uhf and above. QSB(fading) can make conditions quite tortuous when trying to communicate. Still, there is no experience quite like ferreting out a weak station on the low end (morse code is my fav) of say the 20 meter band, finding out that he is halfway around the world and that he answers your call! Now that’s wireless communication!

  17. John Day (january 19, 2011 at 3:58am)
    ” This signal actually heated up (in the thermodynamic sense) the ionosphere, such that it modulated other radio signals broadcasting on entirely different frequencies.”
    This interpretation must be yours as nowhere in the article on the Luxembourg Effect

    The article was written before they figured out how these RF heaters work:
    http://en.wikipedia.org/wiki/Ionospheric_heater

    Your conclusion that “This illustrates how sensitive the ionosphere is to external stimuli.” is, BASELESS.

    Hmm, would you agree me if I base my conclusion on the Luxembourg Effect?

    Imagine! A tiny transmitter sitting in a tiny room located in an extremely tiny country actually created observable effects in the Ionosphere. Eat your heart out, Sol! /sarc off

    In other words, you don’t need a gigawatt to heat the ionosphere, 150kw is enough to be noticed.
    http://en.wikipedia.org/wiki/EISCAT

  18. Fascinating stuff!
    Doubts about it because its a computer model, or its gobbledegook in pursuit of funding are unwarrented I think. I would suspect that this research is the public tip of an iceberg of military research. As the veteren sw hams have mentioned bouncing signals of the ionisphere layers can get you global communication without satellites – if your lucky and know what the ionosphere is doing…
    The signal may be weak and distorted/intermittent, but with modern digital packaging of data and redundent coding I bet it would be possible to send text messages. I seem too remeber radio hams sending slow scan video over shortwave over hemisphere distances a few years ago. Knowing what layers are doing so you can maximize the chances of bouncing a signal could be very useful.

    As to any possible influence on the weather or climate…
    Well there isn’t much ‘stuff’ around at that altitude, the possible energy density at ~200km is very low, without calculating it I would guess a couple of orders of magnitude below the ~1.2W/m2 from the CO2 rise in the troposphere. So any process that enabled changes in the ionosphere F layer is going to need MASSIVE positive feedback mechanisms to amplify it enough to have a measurable effect at lower levels. Any corelation is most likely to be due to a third factor that affects both the ionosphere and the surface climate. Best candidate for that would be something that modifies albedo via clouds. Svenmark has that covered, but the best evidence at present is that cloud formation is dominated by sulphide areosols from oceanic algae.

  19. John Day
    No I most certainly DON’T agree with you.
    “Imagine! A tiny transmitter sitting in a tiny room located in an extremely tiny country actually created observable effects in the Ionosphere.”
    A. I would imagine no such thing.
    B. If you think 150kw is “tiny” then try communicating with 3w(QRP) or less.
    C. If you think the Luxembourg Effect is due to heating of the atmosphere by rf then you know very little about the basics of radio.
    Throwing wikis at me won’t help you but it will help me. Haarp uses up to 4 Billion watts of erp. Is that tiny? How about Hipas at 70 million watts or Sura in Russia at 190 million watts. Why do you think such high power is used?
    All I can say is “Believe what you want to Believe fella and good luck to you.”

  20. This model appears to be based on the assumption that the ionization observed in the F layer of the ionosphere is the result of Extreme Ultra Violet radiation from the sun.

    To explain the high free electron content of the night side, a plasma bubble and daytime disturbances in the ionosphere are visualized. The bubble’s morphology is then animated by the computer to match the observed electron density (only in 3D this time). Then the model is used to self-consistently explain variables that might cause the bubble to “evolve,” or “trigger a new bubble.”

    So my question, if I understand this beautiful bubble model gift which the Greeks are bringing us, is why not consider instead that the increase in electron density (by orders of magnitude) in the F layer are coupled instead with the solar wind circuit through the magnetosphere, or with the ring current that exists in the magnetosphere?

    I seriously doubt the Navy will risk the loss of HF communications and the disruption of satelite links because of scintillations, by leaving the question to a bubble model. My suggestion is that they give this as a gift to NASA.

  21. Brian W says:
    January 19, 2011 at 2:05 pm
    John Day
    No I most certainly DON’T agree with you.
    “Imagine! A tiny transmitter sitting in a tiny room located in an extremely tiny country actually created observable effects in the Ionosphere.”
    A. I would imagine no such thing.
    B. If you think 150kw is “tiny” then try communicating with 3w(QRP) or less.
    C. If you think the Luxembourg Effect is due to heating of the atmosphere by rf then you know very little about the basics of radio.
    Throwing wikis at me won’t help you but it will help me. Haarp uses up to 4 Billion watts of erp. Is that tiny? How about Hipas at 70 million watts or Sura in Russia at 190 million watts. Why do you think such high power is used?
    All I can say is “Believe what you want to Believe fella and good luck to you.”

    Ok, you don’t like Wikipedia, so I invite you to look at the HAARP Fact Sheet: http://www.haarp.alaska.edu/haarp/factSheet.html

    “Lightning is known to cause substantial heating and ionization density enhancement in the lower ionosphere, and there are indications that ground-based HF transmitters, including radars and strong radio stations , also modify the ionosphere and influence the performance of systems whose radio paths traverse the modified region. Perhaps the most famous example of the latter is the “Luxembourg” effect, first observed in 1933.

    Straight from the horse’s mouth.
    :-|

  22. Reading the comments here, I am struck by how many of us are Radio Hams
    or Short wave Listeners. Are all Hams sceptics? Or is it that our training in
    radio gives us insight into the Laws of Physics (Ohm’s Law etc).
    I think Anthony is a Radio Ham, but how many sceptical scientist are too?
    Percentage wise against the population I mean.
    Still waiting for a cycle lift…
    Ken

    REPLY: yes, KA9NWM

  23. FYI,
    I was Googling for more information on SAMI3 model (mentioned in the article) and stumbled upon NRL’s Plasma Physics Division web page:
    http://wwwppd.nrl.navy.mil

    Didn’t find out much about SAMI3, but I did discover that the previous model, SAMI2, developed by the same authors, is an open source project, written in Fortran, which can be compiled by most Fortran 77 compilers:
    http://wwwppd.nrl.navy.mil/sami2-OSP/index.html

    Even if you’re not interested in downloading the code, you’ll find a tutorial on how to run the model and other information about the modeling techniques developed by Drs. Huba and Joyce.

  24. John Day

    ““Lightning is known to cause substantial heating and ionization density enhancement in the lower ionosphere, and there are indications that ground-based HF transmitters, including radars and strong radio stations , also modify the ionosphere and influence the performance of systems whose radio paths traverse the modified region. Perhaps the most famous example of the latter is the “Luxembourg” effect, first observed in 1933.”

    Lightning also produces big static crashes in the sw band. Lightning also produces red sprites, elves, blue jets and halos. Lightning is not Haarp!(radio transmitter).

    After much digging into this phenomenon I didn’t realize that this effect has been unexplained since 1933 and everyone has just run with the cross-mod hypothesis.
    Well I’m here to tell you that it’s not the horses mouth but the horses ass instead.
    The idea that heating the ionosphere causes a change in it that can also cause a change in the wavelength of a radio wave passing through it is patently wrong. I’ll also be the first to tell you that the long standing belief of cross modulation is also completely wrong. It’s physically impossible!
    If there are “indications” trot ’em out for me to examine.
    The “performance” of a radio system is not at issue. The issue is one of frequency and wavelength. Haarp is wrong and so is the current belief. If you believe in it then EXPLAIN how the Luxembourg Effect is achieved using cross mod.
    If you do this, hell, even if you make an attempt to explain it I’ll show you why you’re wrong. I’ll then go on to give you the real reason for this phenomenon. I can even explain why the second station will ALWAYS be in the background. In otherwords it will never be observed to compete in any way with the main received station. So go ahead give it a shot I dare you.

  25. “”””” Here extreme ultraviolet solar radiation ionizes atomic oxygen. “””””

    “” Atomic Oxygen; Who dat ? “”

    In the past, Phil has pointed out that atomic species such as O exist in the ionosphere, because of the long mean free paths at those low pressures. Presumably Atomic Oxygen itself is also created by the slightly less than extreme UV from the sun; and that of course is the first process in the creation of ozone, O3

    So O2 itself is an important attenuator of solar UV. I don’t know what the binding energy of O2 is, so I don’t know what the operating range of UV wavelengths is. It has often been pointed out that it is O2 that protects humans from solar UV, and that Ozone is simply the evidence that the O2 is doing its job. And in the Ionosphere, there are incoming solar photons energetic enough to ionize the O atoms.

    Solar color temperature studies in the first half of the 20th century showed both seasonal and other changes in the sun’s apparent color Temperature; and this was ascribed to variations in the incoming solar UV and near UV spectrum. And since O3 also has absorption in the 500-650 nm region, that is prima facie evidence for the existence of Ozone holes long before any inquisitive scientist at the British Antarctic Survey Station in Antarctica, said; Let’s look for Ozone holes, and let’s call them Ozone holes , and make a big stink about something that has always been there.

  26. @Brian W
    > Haarp is wrong and so is the current belief. If you believe in it then EXPLAIN
    > how the Luxembourg Effect is achieved using cross mod.
    > If you do this, hell, even if you make an attempt to explain it I’ll show
    > you why you’re wrong.

    I’m curious to hear your explanation why the folks at HAARP and EISCAT are all wrong. No hand-waving please.

    Here is the explanation offered by the EISCAT staff:
    (from “Introduction to ionospheric heating at Tromsø—I. Experimental overview”,
    http://www.eiscat.no/heating/data/antenna_details/Rietveld_JATP_1993.pdf, pg 584)

    “Figure 6 shows schematically the timescales as a function of height for the various nonlinearities experienced by a powerful HF wave in the ionosphere. A distinction can be made between different characteristic types of nonlinearity in a plasma. The first is collisional heating of electrons in the electric field of the wave, resulting in Ohmic, or non-deviative (because the refractive index, n g 1, and there is little bending of the ray path) absorption of the wave, and was first noticed by TELLEGEN (1933) in what is now called the Luxembourg effect. This thermal effect, which is largest in the D-region where the product of electron density (NJ and electron-neutral collision frequency (ve) is largest, causes v, and therefore the electron temperature (T,) to increase, so that the absorption increases with power at heights where fi >> vi (70-80 km), but decreases with power where fi >> vi. The time constant for this process is short, of the order of tens of microseconds in the lower Dregion, increasing to about a millisecond at 90 km. This means that high power waves modulated in the audio frequency range experience distortion, as well as modulating other radio waves passing through the same region.

  27. Herzberg points out that the earth atmosphere is strongly absorbent at and below 190o Angstoms (190 nm) , which is why that region is considered the vaccuum UV region. The Lyman Alpha line of the Hydrogen spectrum is at about 121.57 nm (Herzberg), which explains why the Lyman series was not discovered early on in the solar spectrum; since virtually nothing below 190 survives to sea level.

Comments are closed.