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Thunderstorm effects on the ionosphere

Discussion of results and the readers' feedback

Volker Grassmann, DF5AI

last update June 18, 2005

Introduction

The articles discussing thunderstorm effects on the ionosphere have resulted in a vivid discussion in the ham community, have stimulated various emails from fellow radio amateurs and have initiated an exchange of thoughts and ideas which I consider worth to be presented here. I am grateful to all fellow hams having contributed to the discussion and for granting the permission of publishing their comments on this webpage.

Note: citations in bold face consider statements which I consider in particular noteworthy.

Email from Geoff, G3NAQ, January 29, 2005 (referring to the manuscript of the article)

Lieber Volker,

Many thanks for the preprint of your paper, which is truly a mammoth effort! ... Of course, I haven't had time to read it all in detail, but I have some comments to make.

The most serious is, I believe, your unjustified assumption made in the first un-numbered point of section 2.1 [Editor's note: Geoff refers to the manuscript, i.e. the numbers may have changed in the final document]. This is that the thunderstorm can only effect the ionosphere through the neutral gas. This is indeed known not to be the case. The Cb clouds generate potential differences of many MV, and these electric fields are known to cause a drift of atmospheric electrons towards the E-layer, charging it up to about 100 - 300 kV above earth potential - as I have pointed out to you before. This is the origin of the constant (but somewhat variable) vertical electric field which appears at the surface of the earth, and which you can easily detect with a modern electrometer. To me, this would seem to be an equally interesting (and perhaps more persuasive) mechanism for coupling between thunder storms and Es, because it provides a source of additional electrons, sweeping them up from the D region. This would be interesting to investigate, since I don't think it has been considered by professionals. How about it? I think however the drift rate is so small, that it would take a long time for individual thunder clouds to have any effect. Some theory required here.

In point 2.2, you seem to fall into the same error as many other people. Surely a wind shear is sufficient to concentrate electrons in a layer; you do not need an actual reversal of wind direction. Any shear will cause electrons moving at higher velocity to catch up with those moving more slowly. Of course, there will also be net movement of the concentrated layer, both horizontally and vertically, but these movements are observed, and may explain the very transient nature of Es.

A strong support for the shear theory which you do not mention is the similarity of the global distribution of Es determined in the International Geophysical Year and the distribution of the magnitude of the vector product of the dip angle of the terrestial magnetic field and a supposed horizontal current (the force being proportional to v^H). Both these distributions can be found in the old ITU "Green Books". My copy: Recommendations of the CCIR,1986 Volume VI: Propagation in Ionized Media. I refer you also to Ionospheric Sporadic-E, ed. E.K.Smith Jr and S. Matsushita, Pergamon 1962; and Worldwide Occurence of Sporadic E, by E.K. Smith Jr, NBS Circular 582 (1957) - some Circular by the way, 278 pages long!

...

Now if the field lines are over the magnetic equator, they are horizontal and hence there can be no net vertical motion, so the electrons cannot be concentrated in horizontal layers. On the other hand, if the field lines are vertical over the magnetic poles, there is no component of the horizontal wind along the field direction, so again no concentrating force. The maximum effect is at mid-magnetic latitudes, as observed. However, the majority of fall-off of Es at higher latitudes is presumably just lower initial ionisation due to the solar angle. This is demonstrated by the occurrence of ArEs when a surfeit of ionisation has been created from an Auroral event, and the magnetic field disturbance has subsided. The lower translation velocity as the dip angle approaches 90 degrees (as you point out, proportional to the cosine of the dip angle) is to some extent compensated by the steeper field lines moving the electrons together more rapidly, the net effect being I believe proportional to cosD.sinD, where D s the dip angle.

In section 2.3 you say that the atmosphere may be considered to be a fluid similar to the ocean. This is a very imperfect analogy, even from the mathematical point of view, because water is an incompressible liquid, and air is a compressible gas. This leads to very different behaviour, and in particular differences in turbulence and energy loss mechanisms.

The global lightening distributions which you show (Figs 2.5 to 2.8) seem to have a very limited relevance, since with their latitudinal cut-off at about +/- 40 degrees, they hardly cover the mid-latitudes, which is the region of Es under investigation. Moreover, the observation that both Es and the occurence of thunderstorms moves north and south of the equator with summer and winter (p.9) is hardly world-shattering; we already know that both are sun-related!

I am sorry to be so critical, but I think that is what I do best, HI !

Best 73,

Geoff, G3NAQ

Editor's note: Geoff, thank you very much indeed for reading the manuscirpt. Most of your contributions have been considered in the final version of the document.

Email from Thomas, KN4LF, April 23, 2005 (PSC email reflector)

Volker et all,

The tie in between Es and a thunderstorm is the sprite and elve. http://www.kn4lf.com/thunderstormpheno.jpg

73 & GUD DX,Thomas F. Giella, KN4LF
Retired Space & Atmospheric Weather Forecaster
Plant City, FL, USA
Grid Square EL87WX
Lat & Long 27 58 33.6397 N 82 09 52.4052 W.

Volker's reply, DF5AI, April 25, 2005 (PSC email reflector)

Thomas,

Thanks for this reference and your comment. I wouldn't be surprised if someone would document a relationship between sprites and elves on one hand and ionospheric irregularities on the other hand - however, nobody did so far (as far as I know). Because reliable information appears not yet available at this stage of investigation, I haven't considered a detailed discussion of sprites in the "thunderstorm article".

I wish meteorologists and ionosheric scientists would develop some sort of cooperation in this area - we all can smell the presence of unexpected results still awaiting their discovery, can't we?

By the way: I wonder if radio amateurs can develop an experimental method to detect sprites in the middle atmosphere - very likely, we can't but, on the other hand, we haven't discussed the potentials yet. Is this an issue PSC may address?

Email from Ken, WB2AMU, April 25, 2005

Hi Volker:

I think that the thunderstorm correlation with Sporadic-E is an indirect relationship that will be hard to prove with current technology. More current information shows a global transport of ions as discussed by Forbes and Carter at the following link (Please note the detailed schematic):

http://www.copernicus.org/EGU/annales/17/ag17/190.pdf

This paper explains a lot, along with previous papers by Sheila Kirkwood.

Email from Thomas, KN4LF, April 26, 2005 (PSC email reflector)

Volker et all,

On my website KN4LF LF/MF/HF Radio Propagation Theory Notes at http://www.kn4lf.com/kn4lf8.htm I have published the following:

18.) Sporadic-E (Es) Absorption, Blocking & Refraction

Just as the E-layer is the main refraction medium for medium frequency (300-3000 kc) signal propagation within approximately 5000 km/3100 mi, so is Sporadic-E (Es). Sporadic-E clouds occur at approximately 100 km/60 miles in altitude and generally move from west to east but at times east to west. Like stratospheric level warming and troposphere level temperature and moisture discontinuities, Sporadic-E can depending on the circumstances absorb, block and refract medium, high and very high frequency RF signals in an unpredictable manner.

  • The main source for high latitude Sporadic E is radio aurora activity.
  • The main sources for mid latitude Sporadic-E include wind shear, internal buoyancy/gravity waves (IBGW's), and traveling ionosphere disturbances (TID's), most of which are produced by severe thunderstorm cell complexes. The tie in between Sporadic-E and a severe thunderstorm is the sprite and elve.
  • The main sources for low latitude Sporadic-E include wind shear, internal buoyancy/gravity waves (IBGW's), and traveling ionosphere disturbances, most of which are produced by severe thunderstorm cell complexes tied to tropical cyclones.

The forecasting of Sporadic-E has long been considered to be impossible. However it is possible to identify certain troposphere level meteorological conditions that can lead to the formation of Sporadic-E. One is as mentioned above the severe thunderstorm cell complex.

Sporadic-E have been observed to occur within approximately 150 km/90 mi to the left of a severe thunderstorm cell complex in the northern hemisphere, with the opposite being observed in the southern hemisphere. To complicate matters is the fact that Sporadic-E clouds not only have been observed to move from west to east but at times also east to west. So one has to look for Sporadic-E on either side of a severe thunderstorm cell complex.

Not all thunderstorm cell complexes reach severe levels and not all severe thunderstorm cell complexes produce Sporadic-E. This is where knowledge in tropospheric physics and weather forecasting is necessary. Coincidentally I have a B.S. in Meteorology and an M.S. in Space Plasma Physics and am qualified to identify which severe thunderstorm complexes are most likely to produce Sporadic-E.

Some but not all key elements in identifying which severe thunderstorm cell complexes have the potential to produce Sporadic-E via wind shear, internal buoyancy/gravity waves, traveling ionosphere disturbances, sprites and elves include:

1.) Negative tilted mid level long wave troughs.
 
2.) Approximate 150 knot/170 mph jet stream jet maxes that produce divergence and therefore create a sucking vacuum effect above thunderstorm cells, that assist thunderstorm cells in reaching and penetrating the tropopause into the stratosphere.
 
3.) 500 mb temperatures of -20 deg. C or colder, which produce numerous positive and negative lightning bolts and inter-related sprites and elves.
 
4.) Approximate 150-175 knot/172-200 mph updrafts within thunderstorm cells that create overshooting tops that penetrate the tropopause into the stratosphere (See definition #20 on Stratospheric Warming), launching upwardly propagating internal buoyancy/gravity waves, traveling ionosphere disturbances and wind shear.

Email from Thomas, KN4LF, April 26, 2005 (PSC email reflector)

Volker et all,

Are you familiar with the Propnet 10 & 6 meter propagation beacon network created by W2EV here in the U.S.? The website is at http://w2ev.rochesterny.org/PropNET/ and the Yahoo eGroup is at http://groups.yahoo.com/group/PropNET-Online/ .

We transmit around the clock mainly on 10 and 6 meters using PSK31 and specially designed DSP software written by N7YG found at http://home.earthlink.net/~propnetpsk/propnetpsk/index.html . At 2359 UTC the software automatically emails the propagation path connection "catch results" to http://groups.yahoo.com/group/CATCHes/ . Past hour and 24 hour path connections can be monitored live via LiveX and APRS/findu.com. Those websites are at http://propnet.findu.com/catch.cgi?last=1&band=hy and http://propnet.findu.com/catch.cgi?hours=24 . They show text data and path connections made via a map. Callsigns in black are path connections and if the two stations are spaced far enough apart you will see a black line.

At this time of season and place in the sunspot cycle most of the propagation path connections are via Sporadic-E. I've been able to take this data and verify personal Sporadic-E (Es) forecasts that correlate with severe thunderstorm cell group occurrences. So at least one form of mid latitude Sporadic-E is forecastable.

Email from Väinö, OH2LX, April 26, 2005

Dear Volker,

You refer to meteorologists etc. Present IARU Region 1 Es Studies Coordinator is meteorologist and in his earlier articles he has continuously mentioned thunderstorms, jet streams etc. ... he probably can not write everything again and again.

I wonder if anyone has ever seen the document books of 'real' "Scientific Es Conferences" held in change of 1960-70's. Unfortunate my copies are abt 100 km from here and no chance whatsoever to visit that place.

Has anyone seen all those hundreds of documents produced by Serge Canivenc F8SH, the earlier Es Studies Coordinator? His documents also were carried to that same place long ago.

As I see it, Thomas Giella is wrong in that main source of TID's more probably is auroral type of heating of some kind.

Should it be recommended everyone to see at least some of the material produced by F8SH, and his successor, and Es Conferences.

Email from Väinö, OH2LX, April 26, 2005

Volker,

I succeeded in making a short lousy translation of Es Literature List of 1981. All this is considered part of History... The main point is that it includes some of the works of Serge Canivenc F8SH and also the Es Conferences:

Radio Science, collections of papers on:

  • 1st Seminar on the Cause and structure of Temperate Latitude Sporadic-E, 9-11. June 1965, Estes Park, Colorado.
  • 2nd Seminar on the Cause and structure of Temperate Latitude Sporadic-E, 19-22. June 1968, Vail, Colorado.
  • 3rd Seminar on the Cause and structure of Temperate Latitude Sporadic-E, 13-15. September 1971, Logan, Utah.

MY QUESTION is: How many has even seen these...? It would be a big mistake to overlook the earlier work of eg Serge F8SH. Sprites or Elves have been observed for some time but they dont any way change the main principles of exotic propagation modes like Es. The only give some more perspective to observers.

Editor's note: Väinö provides two documents, i.e.

  • a list of references in scientific literture (RTF format, 36 KB) SpecialTopics1d.
  • ... and an article on this issue (Word document, 2 MB, written in Finnish language) SpecialTopics1d1.

Email from Bob, ZL3NE, May 31, 2005

Hello Volker,

... Your publication in Dubus was quite appropriate as I was talking at our VHF Society on May the 16th so your article and that of Gene W3ZZ gave me a fantastic opening to the subject of 2 meter propagation. All propagation at 144 MHz is governed purely by the weather conditions and nothing else! If it wasn't I could not predict the opening as easy as I can. Others here as following my advice and having excellent success at predicting openings as well ... It is well known out here that I have predicted openings time after time of big openings on most bands from 6m,  2 meters and 70cm. One of my best being predicting the 6 meter opening from Christchurch to CT3 three days before it took place. It had never happened before and may never happen again. When speaking at any conference on VHF subjects I have always given predictions for the next day and yes they have always been correct ...

My best of regards to you Volker and hope you enjoy your studies.

 Bob Gyde ZL3NE

Email from Prof. Antich, CO2KK, June 18, 2005

... I was not a bit surprised by your results about 144 MHz E's and thunderstorms... Way back in 1965 and 1966 I did some very interesting and indeed rewarding research on that topic, using the Havana, Cuba Ionospheric Vertical Incidence Sounder and an instrument that I designed and built to provide an indication of thunderstorm activity. My results, presented at the First National Forum on Telecommunications, Havana, 1966 have a lot of coincidence with your recent findings...

Yours truly

Prof. Arnaldo Coro Antich, Senior Consultant to the Director General Radio Havana Cuba

From: http://www.df5ai.net

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