This is one big surprise. Moments of serendipity are some of the best quotes of science: “Hmmm, that’s odd”. As an amateur radio operator myself, I find this study fascinating. If you want to know more about VLF radio, see the NASA online VLF radio receiver link below.
Learn more (and listen to the signals) at NASA’s INSPIRE online VLF radio receiver. – Anthony
From Tel Aviv University: A Lightning Strike in Africa Helps Take the Pulse of the Sun
TAU discovers an accurate tool for tracking solar rotation
Sunspots, which rotate around the sun’s surface, tell us a great deal about our own planet. Scientists rely on them, for instance, to measure the sun’s rotation or to prepare long-range forecasts of the Earth’s health.
But there are some years, like this one, where it’s not possible to see sunspots clearly. When we’re at this “solar minimum,” very few, if any, sunspots are visible from Earth. That poses a problem for scientists in a new scientific field called “Space Weather,” which studies the interaction between the sun and the Earth’s environment.
Thanks to a serendipitous discovery by Tel Aviv University‘s Prof. Colin Price, head of TAU’s Department of Geophysics and Planetary Science, and his graduate student Yuval Reuveni, science now has a more definitive and reliable tool for measuring the sun’s rotation when sunspots aren’t visible — and even when they are. The research, published in the Journal of Geophysical Research – Space Physics, could have important implications for understanding the interactions between the sun and the Earth. Best of all, it’s based on observations of common, garden-variety lightning strikes here on Earth.
Waxing and waning, every 27 days
Using Very Low Frequency (VLF) wire antennas that resemble clotheslines, Prof. Price and his team monitored distant lightning strikes from a field station in Israel’s Negev Desert. Observing lightning signals from Africa, they noticed a strange phenomenon in the lightning strike data — a phenomenon that slowly appeared and disappeared every 27 days, the length of a single full rotation of the sun.
“Even though Africa is thousands of miles from Israel, lightning signals there bounce off the Earth’s ionosphere — the envelope surrounding the Earth — as they move from Africa to Israel,” Prof. Price explains. “We noticed that this bouncing was modulated by the sun, changing throughout its 27-day cycle. The variability of the lightning activity occurring in sync with the sun’s rotation suggested that the sun somehow regulates the lightning pattern.”
He describes it as akin to hearing music or voices from across a lake: depending on the humidity, temperature and wind, sometimes they’re crystal clear and sometimes they’re inaudible. He discovered a similar anomaly in the lightning data due to the changes in the Earth’s ionosphere — signals waxed and waned on a 27-day cycle. Prof. Price was able to show that this variability in the data was not due to changes in the lightning activity itself, but to changes in the Earth’s ionosphere, suspiciously in tandem with the sun’s rotation.
Taking the pulse of the sun
The discovery describes a phenomenon not clearly understood by scientists. Prof. Price, an acclaimed climate change scientist, believes it may help scientists formulate new questions about the sun’s effect on our climate. “This is such a basic parameter and not much is known about it,” says Prof. Price. “We know that Earth rotates once every 24 hours, and the moon once every 27.3 days. But we haven’t been able to precisely measure the rotation rate of the sun, which is a ball of gas rather than a solid object; 27 days is only an approximation. Our findings provide a more accurate way of knowing the real rotation rate, and how it changes over time,” he says.
Prof. Price cannot yet say how this finding will impact life on Earth. “It’s an interesting field to explore,” he says, “because nothing has been done to investigate the links between changing weather patterns and the rotation of the sun.
“Short-term changes in solar activity can also impact satellite performance, navigational accuracy, the health of astronauts, and even electrical power grid failures here on Earth. Many scientists claim that the sun’s variability is linked to changes in climate and weather patterns, so the small changes we observed every 27 days could also be related to small variations in weather patterns.
“Our data may help researchers examine short-term connections between weather, climate, and sun cycles. With this tool, we now have a good system for measuring the pulse of the sun.”
Lightning strikes being short pulsed transient events create a broad spectrum of low frequency radio noise. low meaning audio frequencies; so you can detect it with any sort of long wire antenna connected to the input of a high gain audio amplifier.
These very low audio frequency radio waves actually propagate across the earth along paths that are guided by the earth’s magnetic fields. As a result strong signals at these frequencies can be detected, particularly in areas near either of the earth’s magnetic poles.
VLF radio waves that arrive on the ground after following the field lines, get reflected off thegconductive ground, and return to the other end of the earth again following the earth’s magnetic fields, where they can again be detected at the otehr pole and also re-reflected.
So a lightning stike anywhere on earth can generate a sequence of VLF radio bursts that propagate both ways and irrive near the magnetic poles at different times depending on exactly where the lightning strike occurred.
So simultaneous synchronised receivers at both of those regions, can record the received signals, timed by atomic clocks, and communicate those signals to the sister station at the other end of the earth.
One interesting property of this magnetic field guided mode of radio propagation is that it is dispersive; the velocity of propagation is dependent on the frequency. Depending on the Ionospheric properties, either the lower or the higher frequencies can travel faster.
As a result, the original lightning strike, that sound like an instantaneous clap if it lands in your backyard; byt the time, it has lathced on the the magnetic train, it will arrive at the magnetic polar stations, time sorted by frequency, and the resulting audio signal received, is either a rising or falling chirped audio frequency signal.
These radio atmospheric noises go by a number of names depending on the nature of the frequency sorting and its cause. “Whistlers”, “Howlers”, and “Dawn Chorus” are just some of the lightning caused audio frequency radio signals that propagate via the earth’s magnetic field (and the Ionosphere of course).
The DSIR in Wellngton New Zealand (actually Lower Hutt) used to be one of the stations that was paired up with a sister station somewhere in Scandinavia; I believe it was Norway; but I could be wrong on that.
The interesting thing working with those other end scientists, is that each received signal, once reflected back to the other station, undergoaes a further time separation of the frequencies, so the chirp gets longer in time, and the Scandinavian station signals neatly interleaved with out signlas, and of course were intermediate in time stretching with out signals.
As a result of this co-operative effort, it was possible to deduce quite a lot of information about both the earth’s magnetic fields, and also the ionospheric conditions over very long radia path lengths; half the circumference of the earth.
I doubt that this work is still ongoing (talking late 1950s), and I believe the DSIR now has a longer fancier official title.
At one time you could buy an LP record called “Out of This World”, which had on one side of it, recordings of all sorts of these audio frequency atmospheric radio signals. The other side was equally fascinating since it had earthquake recordings on it. Seismograph signals were recorded on tape running at 0.02 inches per second, and thent he recorded signals were played back and redubbed at a tape speed of 7.5 inches per second.
As a result the sub audio waves of an earthquake, were up shifted into the audible range, and came out sounding like thunder. Well of course these earthquake thunderclaps, are sound waves propagating through the earth, and depending on the location of the quake relative to the seismic station, you could here different types of echoes as the signals bounced around inside the planet. A variety of totally weird extraneous sounds were also audible on this recording (was recorded in the Western United States); bearing in mind that the frequency range was scaled up by a factor of 375.
The DSIR was also doing a lot of analog computer simulation of building responses to earthquakes, to help design better earthquake immunity into buildings. Since Wellington is a fairly active earthquake region, it was a good location to do this sort of research. There were a number of apartment complexes, that had periodic visits from “the meter readers” who were not related to the power company in any way, but needed new tapes loaded in the basement “equipment”.
Never imagined that a short stint at that institution would come back to haunt me all these years later.
Jeff L (16:13:29)
“An initial thought though – the orbit of the moon has a periodicity of 27.3 days,… very close to the 27 day periodicity described in the article, so why do the researchers think this is a solar related phenomena & not a lunar phenomena??”
Dang good point.
Agreed. Radio waves bouncing off the moon… hmm
Oliver Heaviside would be delighted but old-timers will just smile.
Any new information is interesting. The ionosphere has been recorded and studied for years, if less so these days. It was and is critical to long distance radio. See the panel on the right giving radio conditions?
Solar rotation data has been available in radio data for many years. For example it is in the radio 10.7 data which has been measured since just after WW2.
Twiddle, twiddle, here we are, extracted from a dataset I have on hand. Be a mismash of rotation signal from 1947 onwards.
http://www.gpsl.net/data/solar-rotation-10_7.png
chillybean (15:46:14) :
I found it interesting up to this point.
‘Prof. Price, an acclaimed climate change scientist,’
Yes, now that we know what we’re dealing with, we can accurately calibrate the interpretation of the discovery.
First off, the sun does not rotate every 27 days, it’s not a solid body and there is a different rotation rate for each latitude. This is what stretches and winds the magnetic fields, leading to sunspots.
Secondly, as anyone who listens to shortwave radio or is a ham radio operator knows, the ionosphere changes dramatically from day to night, and from season to season. Higher frequencies are used during the day time and summer; lower frequencies bounce better at night and during the winter. Shortwave stations regularly adjust the frequencies they use to accommodate these changes in order to reach their target audience. Anyone who listens to commercial AM radio (which is medium wave) at night has noticed that you can pick up AM stations from quite a distance at night; this too is due to ionosphere reflection.
That said, ionosphere reflection primarily affects shortwave signals, the longer the wave length, the less the effect. Short wave length means high frequency. These guys are using VLF radio. Low frequency means long wave length.
If the phenomenon they have noticed is real, my guess is that it is bouncing off the moon rather than the ionosphere. This would produce a waxing and waning with approximately the periodicity they have observed.
Tim Channon (17:56:10) :
Oliver Heaviside would be delighted but old-timers will just smile.
Any new information is interesting. The ionosphere has been recorded and studied for years, if less so these days. It was and is critical to long distance radio. See the panel on the right giving radio conditions?
Actually Tim, I had not noticed the panel on the right giving radio conditions – until you pointed it out.
Thanks much.
Perhaps it’s time once again:
http://www.writing-kit.com/apostrophes/index.html
Talking of VLF.
+52° 22′ 48.35″, -1° 10′ 16.34″ is about centre of the Rugby UK VLF communications aerial array.
DaveE.
Aerial is antenna for our American cousins.
DaveE.
jorgekafkazar (18:37:22) :
I have a pet hate…
The possessive apostrophe…
Mark Webbers car, no apostrophe!
Alan Jones’ car, apostrophe!
DaveE.
Do you think it is possible that the earth could be tipped a little different right now, which could hide the sun spots that have usually been visable? If the earth is tipped a few degrees out of the normal, this would actually speed up the earths rotation. As well as the moons rotation which balance’s the earth. This increase in rotation speed, would generate thermal heat, creating a greenhouse gas affect and melting ice. And maybe shorten days overall.
I think the earth and the moon are rotating faster than they were, this is the cause of the thermal heat.
I think time has sped up from only a couple of years ago.
Yaakoba,
Pass some of that down over here.
Sorry, Yaak, we keep close track of the “tipping” (obliquity). Yeah, it appears to be a dominant factor in what triggers an ice age, but it’s a 41,000-year cycle.
“Axe” Moerner discovered that there is a very, very slight variation in earth’s rotation depending on sea level. But the differences are truly minuscule.
jeez (19:30:19) :
I want some too!
There is some small evidence pointing to LOD as an influence on warming though.
DaveE.
Yes, but don’t you think that if the sea levels are rising, wouldn’t this increase the speed of the earths rotation, which of course the moon would have to also increase it’s rotating speed? Causing heat and shorter days.
‘fraid not … (now, how those magnetic fields may affect the ionophere which affect radio waves is another issue)
Were above assertion true, only N-S propagation would be possible, and I think OMEGA (10 kHz to 13 kHz area) had no such limitations. You will find that ‘ground currents (and they run deep at these frequencies), due to the continuous ‘knife edge RF diffraction’ (usually described at shorter wavelengths and described as a wave ‘breaking’ over the earth) is more the effect in play.
http://jproc.ca/hyperbolic/omega.html
http://tycho.usno.navy.mil/ptti/1988/Vol%2020_12.pdf
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DaveE (19:01:27) :
Say, what?!
I think you need to reexamine.
So if lightning in Africa stops, the Sun stops. A connection to Brazil hydro would have made it go super nova.
evanmjones (19:39:17) :
Only going by what I was taught 50+ years ago.
The possessive is the same as the plural
The plural of Jones is Jones’ NOT Joneses.
You also have the plural possessive, so a car belonging to the Webbers would be the Webbers’ car and a car belonging to the Jones’ would be the Jones’ car, (no need for multiple apostrophes).
DaveE.
Yes, but don’t you think that if the sea levels are rising, wouldn’t this increase the speed of the earths rotation, which of course the moon would have to also increase it’s rotating speed? Causing heat and shorter days.
No, it would decrease. The extra water humps up ever so slightly in a band around the equator. Earth spins slower for the same reason a twirling figure skater extending her arms spins slower. (The differences, however, are almost immeasurably small.)
I don’t see why moon’s orbit would measurably increase. It’s just falling around the centered mass of earth. Regardless of whether that mass is rotating, it’s still the same amount of mass.
Dunno where the edit came from.
DaveE.
After a little research, I’m not certain about the moon bounce theory. I know that radio signals routinely are bounced off the moon, and that sometimes very low power signals can be picked up after a lunar bounce, in the milliwatt range.
However radio signals that are bounced tend to be at higher frequencies that what is being discussed in this article. Microwave, UHF and VHF readily bounce off the moon and are used for EME (earth-moon-earth) communication. However the practical lower end for the method is about 30 MHz.
The lowest frequency that has been intentionly bounced for communciation purposes is 6.7925 Mhz. According to the display above, they are looking at 640 – 2560 Hz, much lower. A moon bounce will have a 2.4 sec delay (770,000 km round trip).
On the other hand, a lightening strike isn’t exactly a modulated signal, and doubtless has some power behind it.
Given the daily changes in the Ionosphere as it’s pushed and pulled by solar wind, and the d layer coming and going with the light,it’s rather difficult to believe that there is a 27 day solar signal that is modulating the signal from lightening strikes. I mean what exactly is a “calibrated” lightening strike so that you could measure the effect?
Not entirely (I say entirely, because there is still quite distinct measured and definite effects on these lower frequency/longer wavelength signals although effects at HF are/can be seen most dramatically) true; recommend the first link in my post above re: Omega and the paragraph within titlled: “VLF WAVE GUIDED MODE”.
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What’s this about my car – and why the hell don’t I get an apostrophe’s
DaveE’s rule?
Yaakoba (19:37:52) :
Think of an ice skater in a spin, as the arms are extended, the rotational speed decreases, the Earth equivalent would be an increase in LOD.
DaveE.
It would increase in speed, because there is more gravity from the weight of the salt.
Mark Webbers (19:58:16) :
Hey, you’d get one, it would be Mark Webbers’ car 😉
DaveE.