Although not as pronounced as that on MF and HF, this event is still common on VHF regardless of the current stage in the solar cycle. Most notable daily events seem to occur between 1700 and 1900utc, or roughly that of solar noon. It is within this time that there also seems to be steady diurnal magnetic fluxuations (usually in excess of -50nt) in the X-component of the local magnetometers. (oddly, stations south of 65 degrees Pace seem to have more obvious deviations) Capturing accurate results of this phenomenon are somewhat crude without “high-tech” equipment. Nonetheless, levels of attenuation are still measurable using accurate values of time, frequency and perhaps (to some extent) qtf. Interesting observations of attenuation progression from roughly 5mcs up thru 28mcs versus that of time is somewhat predictable.
Attenuation of larger proportions:
Events of much larger energy also contribute to attenuation. Slow-moving, high-energy protons seem to pool in the Polar Cleft and Northern Arctic areas. During stages of high density, a Polar cap Absorption Event can take place. (PCA) It is during these events that massive attenuation takes place. Located north of my EO36 radio locale, these bodies produce large amounts of radio absorbing energies. Not only does the strata seem to be Field aligned, but there also seems to be near-vertical streams of positive current, (perhaps protonic matter is a better term) located directly to the north of me. It is during these events that I can usually see a decrease in signal strength of sometimes up to 18db on 50mcs, and perhaps as much as 10db on 144mcs.
What an interesting and a common event in the auroral environment. I would say (in general) that the current doppler shift equation seems somewhat accurate. The problem arises with the ever changing velocity of the auroral reflector. The constants are fine. (i.e.:speed of the radio wave, and frequency of the transmitted wave). The equation gets disrupted in results by the unknown value of that which is the apparent velocity of the auroral reflector. (of which can rapidly fluctuate between say 500 and 5,000 meters per second in a short time period.)
I would say on normal evenings from the auroral zone, that the direction and magnitude of the Doppler shift are somewhat predictable. On semi-quiet evenings (Kp<2) or (<-50nt locally) the aurora shifted signal will usually appear about 150-200 cycles to the positive of the center frequency. This event occurs from late afternoon thru the early evenings and is somewhat constant in nature. If the level of aurora stays at this magnitude, constant results are in yield. It is not unil near (or after) midnight that the doppler appears in the opposite or negative direction. It is usually after the Haraang Discontinuity that the Doppler shift from positive to negative will take place. I have never witnessed the actual event of migration from positive to negative, other than those that were short-term events, and could not be positively related to the actual reverse in current flow. The dopplered values on 144mcs are similar in nature to those on 50mcs, but with increased levels of shift. They seem to follow the same progression, although one must add an additional (say) 500 to 1,000 cycles. Keeping in mind the previous was at relatively quiet conditions, the other end of the spectrum is also interesting. On evenings of large disturbances, great (and often wild) values of Doppler are experienced. Not only are we talking six meter signals dopplered in excess of 1kc, but to that value, with rapid fluctuations of both the positive and negative. (please note: the term positive and negative in regards to shift will be relative to the criteria of transmitting station location, receiving station location, and physical location of said scattering matter and it’s overall function in the scheme of MHD and time) (perhaps the easiest way to explain the above, is that conditions are not constant for different locales)
QTF for aurora:
We should begin this section by clarifying direction at this radio locale. Located at nearly 68 degrees north (PACE), and it’s relative longitudinal position to magnetic north, my deviation is very small. (at least compared to others in Northern Europe or KL7) So, for basic terms, the term “North” can be implied as 000 degrees for this discussion. One common question asked to me is, “what direction were you pointed during our auroral qso?” As there are two disctinctive forms of aurora, (au-e and pure au) we shall begin with the most simple. I would say that 95% of all auroral-e contacts (non link related) would come from the “direct” heading. These signals are usually quite strong, T-9, and can sometimes last for long durations. Another interesting (yet sad) comment is that all au-e contacts seem to originate between 65-110 kilometers in the ionosphere, indicating an E-layer hop, perhaps even multiple hop. Even though some of my long distance au-e qso’s would tend to lean that way, I must rule out auroral collisional ionization (the process involved to produce auroral signals) above 110 kilometers. Now back to the QTF of pure aurora signals. I think most folks will find it interesting that I have never made (ever) an aurora contact in which the beam was towards the South. The only quadrants emitting aurora comes from roughly 20 degrees of North. Longer distance contacts can take place with the beam at nearly 90 degrees form North, but these are not that common at EO36. Working back into WInnipeg on a nightly basis has my beam at 000. The city is roughly 500 miles South of my location. Often the visual aurora is on the southern horizon, yet all the scattering seems to come from the north.
This is another area in which the textbooks need updating. I think everyone knows by now the rules governing signal strength versus that of angle of incidence and angle of reflection in regards to the field line. (and on top of that, assume at least 6db of attenuation for each degree of deviation) At my magnetic latitude, it doesn’t take a genius to figure out I am looking at steep magnetic field lines. Perhaps as much as 90% of my signals are being scattered into space. Due to the lack of hams in these regions, experimentation has been difficult. In theory, the elevation does seem to yield “close-in” patterns. What comes to mind here are the qrp beacon experiments carried out in 1996 from near Split Lake, Mb. I was utilizing a half-wave dipole located close to the ground. (trying to develop an ineffective radiator of high-angle waves)(much like those used on the Canopus’ Riometer antenna) This was one of the few times I was able to receive auroral returns at a distance of only about seven miles. (it’s hard to say if this was a by-product of the beacon running qrp) (and my ability to copy it auroral, and not being overrun by the usual blasting 100 watt tropo signal) Monitoring the VE4VHF/b on a horizontal yagi from horizontal to about 45 degrees, yielded little difference in signal strength. Once past about 45 degreees, and then on to 90 degrees (straight up) the signal actually decreased in strength. It’s hard to be precise without a detailed reference of the receiving antenna’s plane, in both the horizontal and vertical. (also the cone radiation above the horizontal plane) After all this time, I still believe the signals are originating from a scattering point well to the Northern horizon. Similar correlation goes back to studies done at Alaska’s Geophysical Institute in the 1960′s, that ended up with similar conclusions.
Localized band noise from the auroral zone:
Anyone who has operated the six-meter band from a large city knows how frustrating all the man-made noise can be. It is not uncommon to hear of fellows suffering from a S-6 noise level on a continuous basis. Having been there myself, it is a great pleasure to enjoy the wilds of the un-developed North. Imagine having the closest power lines greater than several hundred miles away! Imagine knowing any computer noise or cordless phone noise is dx, and actually welcome events like that to know your system is working. However, the North is not completely immune from natural- occuring emissions. I have seen on several occasions, noise coming from the Northern quadrants, on seemingly quiet nights. It is somewhat strange to swing the beam South to a quiet sky, and then back to North for S-4, 5, or 6 noise. The noise seems similar to that of solar noise, yet is very much in a discernable part of the sky.
Since 1995 there has been a growing number of Polar Path routes used by International flights. Not only do these Jumbo Jets make for wonderful (time-lapsed) images in our photographs, it is very interesting to listen to them (or their reflection) on VHF. Since both the 50 and 144mcs beacons point north, have good gain, run good power, and are roughly 60 miles abeam my location, they provide almost a “radar” of sorts for these objects! The usual multipath flutter sounds of that much like an auroral return. (sometimes on quiet nights I have been fooled into thinking there was aurora, only to hear engines and have the flutter go away) On North to South flights I can usually hear them coming about 15 minutes away. It’s fun to watch them appear, only to have the signal diminish. Stronger flutter occurs when the plane passes from East to West (or vice-versa) and the beam hits the target broadside. There was one plane in particular that was fun to watch. It was a Lufthansa 747 (400 series) enroute to Los Angeles. I would follow it every afternoon on HF (8.891 usb out of Churchill) (which at times was also highly auroral) from Coral Harbor to 70 North, then on to 90 West. (frequency change to Churchill VHF at 90 West) (to which about this time I could begin to hear his flutter on 50.063 while out over Hudson Bay) I watched this for several days, and it would show up just like clockwork, directly overhead.
This is another fascinating event that shows much different results with the increase of frequency. Many people ask me what causes the “buzz” or “whispering” effects on aurora signals. I suppose the simplest way to describe this event is like this: (I shall jump to the fact that we all understand the signal scattering that takes place in and along magnetic field lines by large amounts of incoming energies) Now, imagine your VHF signal to be sent into this realm, and become subject to numerous amounts of rapid fading. (this is in time from when the signal leaves the transmitter, to the intersection of the scattering medium, and then back to the receiver) during this time, a rapid amount of (seperate) fades can begin. Mild, often weak aurora can be the product of only “tens” of fades per second. This usually resembles a light flutter, and can often be mistaken for some other prop mode. When a signal is subject to “hundreds” of fades per second, then we get into a more disturbed pattern of voice, perhaps that resembling a “hiss”. The aurora does not stop there. When fades to the magnitude of several thousands per second arrive, speech is very difficult to decipher. (I personally believe this could reach the power of “tens of thousands” of fades per second, producing emissions that are unintelligible) As far as why these conditions exist is somewhat unclear. We must assume that the scattering columns are numerous, and are working (perhaps) in and out of phase simultaneously. (this would also concur with previous studies on the theory of constructive and destructive properties of ionization) (much like that of the products of ordinary and extraordinary radio waves found in certain Plasma Instabilities)
Misconceptions of the Teslas:
It does appear that since the invention (or at least the data availability) of the magnetometers, some baselines have come forward. (albeit right or wrong, these ideals seem to be emerging) Can we assume that magnetic force is the cornerstone for auroral development? Is it now possible to say that all electric fields run perpendicular to magnetic fields while suspended within a magneto plasma? There seem to be several internet auroral plotting sites that utilize algorithms that bias the X-component in the magnetic vector quantity. Surely the physics of the Ionospheric aurora, it’s relationship to photo luminescence, and numerous sorts of energy dispersal, is not lead by the Gauss? I know this is not true, but I often hear others speak in this area, using simplistic overtones.
AU-E Distances from the Auroral Zone:
Common nocturnal 50mcs auroral-e contacts usually range in the area of 600 to 2,000 miles. Reception of the VE8BY/b (985 miles) and VE8WD/b (821 miles) can be expected on (in my estimate) nearly every night of the week for the entire year. On slow, quiet evenings, these may only appear for several minutes, but are usually quite strong in magnitude. Other nights can see these beacons at S-9+60 for hours on-end. There have been numerous occasions where the FP53 beacon was stronger then my EO26/b. (located close by) There have even been times where I could “un-hook” the coax to the transmitter and still receive the signal! Also found on a nightly basis are the farther-distant beacons. The OX3SIX/b (1,918 miles) is also a nightly visitor. Even with a Kp of zero, there is usually some point in the evening when it’s coming thru. Northern KL7′s are also very common. KL7NO BP54 (1,859 miles) and KL7NN BQ50 (1,815 miles) can be expected with nightly signals as well. Now that more Northern stations are becoming qrv, there are increasing chances for the nightly “rag chew” at S-9+60! (just think of the electron density profiles for that region) One promising outlook for the idea of an F layer auroral hop, would be the number of Scandinavian ten meter signals that are highly auroral. The OH9TEN/b (3,406 miles) is often found to be one the more common beacons that run auroral after around 2000 utc. In fact, I have often found the OH9/b to be the only signal on the band, well into the night. (runing 4-1-8au) The SK7 and LA4 ten-meter beacons are also similar. Does this spell any conclusions? (either good or bad) Auroral-e on 144 mcs is still nil on my end. The lack of available hams at the “right place at the right time” seem to have cursed this band. There is no doubt that this mode exists, but as it will occur less frequently than that at 50mcs, great time and effort will be needed. The FM broadcast band is another good indicator of localized MUF’s. It is nice (for once) to be in a place of no local FM broadcasts. How pleasant it is, when any (I repeat any) signal on this band will be dx! (as long as one is smart enough to decipher short meteor bursts)
Why there is not massive aurora at Solar Maximum:
Hasn’t anyone ever wondered why we don’t see more aurora at this time in the cycle? People are always calling me saying, “that X-3 flare was geo-effective, and has an accompanying CME”. (“It’s shock speed was over 1,000Kms, and it’ll be here in three days, so get ready!”) One would logically think Solar Max would yield tons of aurora. (as the amount of flares, CME’s, filament eruptions, and coronal holes are up ten-fold) This may be a true statement, but what we don’t see is the complex nature of our sun. Even though the Chromoshpere has since changed phase, (by-the-way, was that a Chromosphere or Photosphere event?) (has anyone figured that out yet?) the sub-surface is still chalked-full of bipolar (and numerous unipolar) spots. So yes, we are seeing massive amounts of ejecta, but these particle streams are full of “canceling” energies. This process can be objectively viewed on a detailed Bz chart. For the formation of a high-energy auroral electro jet, we must get back to unipolar wind streams, and preferable long durations of “magnetic clouds” that dictate our IMF. Have you ever looked at magnetic isobars near Beta-Gamma spots at solar maximum? The deltas that form here contain steep magnetic gradients of both negative and positive polarity. I can not begin to express how complex this process is. As the relationship between the Sun and the Earth’s magnetic field are all closely related, it is clear to see just how complicated this is.
A layperson’s definition of the Aurora:
Have you ever had anyone ask you what causes the aurora? Imagine spending nearly 10,000 hours in the auroral zone, usually in highly remote surroundings, and performing odd, nocturnal studies with large antennae. One can imagine all the questions put to myself. When they ask me, “what causes the aurora”? My answer is always the same: “It’s the large-scale interaction between the Earth’s magneteosphere, and the solar wind”. (To which one man in Rankin once answered: “you mean it’s not that whole bit about the sun reflecting off the Ice Cap?”)
Decreased Plasma Injection with Positive Bz:
Physical (anatomical) dangers of the Aurora:
As this may not be a pleasant section to all, I suggest the “weak of stomach” to move on to the next sections. We all know how much power the aurora is capable of. Unfortunately, some of this power is transformed into “unwanted” radiation. It’s not hard to imagine the values of note here. (i.e.: hemispheric power in the ten’s of gigawatts, massive gamma, Ultra Violet, and cosmic particles located directly above our heads) Could seven years of direct research have been harmful to myself? I realize there have been some instances where the effects on my body were of that unlike those found to the South. I recall all those times of the “sudden Impulses”, the local readings of over 3,000nt directly over our heads. I recall my ELF detector going wild, no matter which direction I pointed the probe. There is no doubt, at times, I was o nly 65 kilometers (above my head) away from energy not found on this Earth. (that is, energy in the fifth state of matter) (or better known as Plasma!) I used to joke to Kim about wearing our “helmets” whenever we were outdoors at these times. (but it was so dog-gone inconvenient) I assured her that, for the most part, the aurora was non radioactive, and besides, there were many people who watched the blast at Bikini or Alamogordo, and they were just fine! I even told her of my friend Anatoly who was very near the event at Novaya Zemlya, and look how he turned out. I read once where the radiation from an auroral storm (at high latitudes) could produce the equivalent of sixteen chest X-rays to the torso. I sometimes wonder what is “in store” for my body in the next few years?
Atmospheric Temperature (non ionospheric):
The reported values of Ionospheric temperature (or IMF stream temperature) play an important role in the development of aurora. However, more interesting (although playing no vital role whatsoever) are those numbers found as local atmospheric temperatures. (local wx) After seven years of study, (and most of that in winter) I have been very fortunate to observe the beauty of Nature’s wrath. Some of the more interesting weather-related events are those of: Ice Fog, Snow grains, Ice Crystals, Freezing Fog, Polar Vortexes, Whiteouts and Blizzards. I have also had the pleasure of conducting antenna tuning, assembly, dissasembly, maintenance, and various other events while outdoors. I can honestly and proudly say I have experienced these duties with temperatures below the -40′s C for extended periods of time. One of the latest trials was that in January of 2002. That day brought a temperature of -48C, and a nice bit of wind out of the North. (even the 9913 was a bit stiff) As the ice also wreaks havoc on the aerials, I’ve learned to pre-tune the antennas to at least 500kcs higher than my preferred resonant frequency. (one night of Ice, and “voila” I am 1:1 on 50.125) (I wish I had a dollar for every element, director, and reflector I’ve broken as a result of the cold)
Initial sources of the aurora:
As the process of Magnetohydrodynamics is somewhat complex, and perhaps beyond the scope of this outline, we shall accept the current terms of (MHD) generation. As we are concerned with VHF Radio Aurora, I will concentrate on the Earth-bound events, rather than the origin of said matter.
As these topics are delving into areas that are becoming more complex, the abilitiy for error (on a long chain of mathematical principles) is ever-increasing. Therefore, certain theories must be accepted for us to move on. To begin with, we must define how a VHF radio wave will react within a uniform magneto plasma. The formula for refractive indices (for ionized medium within magnetic fields) has long-since been published. (I am not sure if this formula contains a certain “cutoff” frequency?) Nonetheless, some of the unknowns are, (since I cannot produce mathematical characters on my computer, word form will be used) the electron gyro frequency, electron collision frequency, angular wave frequency, and angular plasma frequency.
Cross Field (Gradient Drift) Instability:
This event is caused (generically speaking) by charge separation. (or perhaps the act of) This may also be better known as the E cross, B drift theory. The charge separation is caused by electrons having different drift velocities and perhaps directions. I guess the simplest way to say this is, that the electrons will move perpendicular to the electric field with drift, while the ions move in the same direction as the electric field. (I am also uncertain how these values might change from the F layer, down to the E layer?) Charlie Newton (G2FKZ) has a better concept of this approach in his book on Radio Auroras. How these instabilities grow and decay is somewhat confusing to myself. More confusing are the long lines of Instabilities themselves. When they develop, how the develop, and where they develop is all dependent on the individual instabiltity itself. However, it seems evident that all these processes play a vital role in the progression of aurora. If we could get a handle on the order and reason for these episodes to occur, the questions to aurora might be at hand. Might one think that the Plasma Instabilities are the basic origin of VHF auroral signals? How far back must we begin? (might a good place for this topic be on a 75-meter (phone) round-table?)
The Dreaded “One-Way Trap”
One radio event that became evident early on, was that of one-way qso’s. To state more clearly, these were (mostly hf, non auroral) contacts, or attempted contacts, between high-latitude stations, and their counterparts to the South. How frustrating to be ready for a 40 meter cw contact, (to convey vital Solar Terrestrial Indices) hear the station at S-9, and not be able to manage a qso. There would often be times when I could hear the other station so well, I thought they were playing jokes on me. To hear a station call you over and over again on cw at S-9 without them even knowing you are there is very irritating. In the early years, I would often dismiss this event as having a poor transmitting station on my end. Later, after re-vamping the hf antenna system, and having it work just superb in the lower latitudes, I realized something else was wrong. These situations would also occur when I was in the middle of a conversation (with everything working normally) with no problems whatsoever, and have the station to the South lose me altogether. The strange part was the ability for me to hear those Southern stations with no loss of signal! They (the Southern stations) would then call me over and over again, only to figure I must have had something else better to do, or had left the scene. Not that I am 100% convinced of the reasons for this situation, but I must admit the criteria involved raise some interesting facts. I think few hams realize that behaviors of radio waves within a magneto plasma can exhibit odd characteristics. Could the aurora actually separate radio waves into two circular waves whose electric vectors are in phase at the horizontal, but are hence rotating in opposite directions? All you EME’ers had to deal with this for some time. I realize that Faraday would not fully explain the above, but added with spatial polarization, these mechanisms could be satisfied. As I assume Faraday is nearly non-existent above 1296, can anyone tell me the rate for signals much lower in frequency? (Is it logarithmic?) Imagine my surprise when G4DMA (now residing in KL7) asked me if I had ever heard of such a phenomenon! At times like that, it’s very re-assuring to know you’re not actually crazy! (thanks Flo)
Keeping pace with Saskatoon and the Soviets
What a small world in which we live! As I have discovered in the past ten years, the people of aurora research tend to congregate in the same areas. Unfortunately, I may have arrived ten to twenty years too late. It does seem the “Golden Age” for VHF radio research has since “come and gone”. It is hard to believe that the present day EO26 beacon sits near the site of the once great “Long Spruce” radio array used by the University of Saskatchewan. Today all that remains are photographs. On occasion, I will still have people come up to me, while I am there, and ask if I had anything to do with that outfit.
As this is, and always will be, a “work in progress” project, here are my conclusions leading up to October of 2002.
“Overall the aurora is a large-scale event, made up of numerous, small, localized events that add power and scope to the over-all whole picture.” Jeffrey Leer
What is possible?
It is difficult to explain in one paragraph, what has taken me ten years to discover. Perhaps the best way to finish is some insight on what I may think is possible.
Q. Will transpolar auroral VHF paths ever take place?
Q. Has the advent of the internet been a 100% positive attribute towards your studies?
Q. Does the aurora ever become boring, dull or mundane?