(38) Skywriting by Aurora
Dear David P. Stern & Mauricio Peredo,
I want to "apply/harness" the northern lights phenomenon and turn the
night sky into a giant TV screen.
I see a satellite like device in geocentric orbit that has an electron
collecting apparatus, perhaps similar to a solar panel, on the side
facing the sun. These collected electrons would then be focused, and
accelerated via a solar powered anode and then aimed/directed by
utilizing and or manipulating the lines of magnetic force generated by
the earth's core along with the magnetosphere.
Once focused, accelerated, and directed, the electron beam could then
be "shot" "Sky Illuminating Electron Gun", or SIEG at the earth's
atmosphere, creating a recognizable/predetermined image by striking
targeted nitrogen and oxygen atoms at various altitudes; thus providing
the necessary primary colors along with a depth of field that would
result in the creation of a three dimensional/holographic image(s)
turning the night sky into a rainbow of choreographed light-ballerinas
dancing across the heavens. Or perhaps a giant illuminated billboard
for advertisement purposes. Do you too find it odd that one must deal
with the devil to get to heaven, or in your case, funding for research?
In your opinion, what would be the theoretical and practical obstacles one might face to pull this off and are these obstacles insurmountable, scientifically speaking..
Thank you Gentlemen,
Reply
Your proposal sounds interesting--at the very least. Still, I am
greatly relieved to be able to say that it will not work, for several
good reasons. Even if it did, I may add, the field line structure of the
Earth's magnetic field is such that the only people able to watch your
display would be inhabitants of Alaska and northern Scandinavia, Russia
and Canada--not the audience to make such a project pay for itself commercially!
In addition, however, there exist technical obstacles, listed here
from the minor to the major:
- If an electron beam from synchronous orbit is to reach the
atmosphere, it must be very narrowly focused along the direction of the
magnetic field. Any electrons moving at an angle to the magnetic field
direction, larger than some very small minimum, will bounce back before
reaching Earth. They may hit the emitting satellite, or anyway form a
belt of trapped electrons which will hit it sooner or later.
It would be hard to prevent the beam from scattering while in
transit. So many negative electrons, repelling each other--things may
get unstable. They probably do in the natural aurora, which is why
auroral beams tend to move across the sky.
- An electron beam from one source will only hit one spot. It is hard
to paint pictures with it.
- The main auroral emissions--responsible for the green and red
aurora--do not lend themselves to rapid changes. They are produced by
atoms of oxygen in a (relatively) long-lived excited state, and are
emitted at delays of the order of one second. The effect is as if you
were drawing a TV picture with a long-persistence phosphor, whose glow
persisted about one second. Auroras viewed through optical filters that
select other emissions can see much faster changes, but for the unaided
human eye the oxygen emissions cannot be removed.
- The energy required to create an artificial aurora can be quite
large: after all, you want to create large-scale illumination, visible
to an eye 100 kilometers below it! Artificial auroras have been created
in the past by accelerators aboard rockets (mainly to trace magnetic
field lines). The patches they produced, if at all seen, were faint.
Nuclear bombs have created bright auroras, but we don't want to do
that--do we?
If is possible to see ion's pass through a cloud chamber, and we know
they are solid particles that contain energy, why can we not develop a
way to capture that energy? Truly using the power of the sun to
generate electricity.
I have an idea! If we were able to channel ions within a magnetic field
with some kind of collector would this not generate electricity?
Possibly developing a type of electrical absorbing gel, that when the
ions pass through, collects this energy and transmits it out.
I apologize if I do not put this idea out clearly, for I am not a
scientist and only see this idea in the abstract.
Reply
Dear Friend
Several reasons why this will not work:
- The sun does not emit enough energetic particles to deliver much
energy, even using an absorber with a fairly large area.
- The Sun emits both positive ions and negative electrons. To extract
the energy of ions (which have most of it) you must screen out the
electrons, an added complication.
- Energetic particles from the sun are stopped a long way from Earth.
Even if one did capture their energy far in space, it is not clear how
it might be transmitted to Earth.
Dear Mr.. Stern,
I was involved with the Virginia Governor's School of Math, Science,
and Technology this past summer, in a class on Space
Physics. I am using my knowledge in this
course to conduct a research project/ experimentation on Geomagnetic
storms and their effect on short radio wave transmissions. I was
planning on using an old radio (one my grandfather used to do his HAM
radio sessions) and monitoring a singular radio station and observing
the relative clarity or disturbances during each observation. I would
then log onto the internet and check the levels of geomagnetic storms at
www.spaceweather.com. I would then compare my observations with the
geomagnetic activity and make a correlation between the two. (higher
activity causes more disturbance)
However, after reading your email, I see that solar disturbances affect
radio wave transmissions more so than Geomagnetic storms. I was just
wondering if you could guide me in refining my procedure so I can obtain
better results. As it is now, I am unsure my project will yield valid
results. Any ideas on your part would be greatly appreciated. Would it
be more effective for me to change my project to measure the affect of
solar disturbances (solar flares, coronal holes, CMEs) on short radio
wave transmission, rather than geomagnetic storms? How can I compare and
correlate the two variables if I do change?
Thank you for bearing with me. I have still have much to learn in the
realm of Solar Physics. Your help is awesome.
Reply
This is YOUR project, so I won't do your homework for you--except
refer you to a few web sites which may answer many of your questions:
http://www.ips.gov.au/papers/richard/hfreport/webrep.htm
http://www.sel.noaa.gov/radio/
http://www.hamradio-online.com/propagation.html
You will also find a lot about space
physics on my other web sites, home page (and index page)
http://www.phy6.org/stargaze/Sintro.htm
Dear Sir:
Would you please explain how the Van Allen Belt affected the first
manned space flights. How were they protected?
Reply
Dear Belinda
All manned flights (except those of Apollo) have stayed below the radiation
belt: the Space Shuttle, for instance, orbits at about 215 miles. The atmosphere is very rarefied there, and radiation belt particles descending to that level may well come back without encountering
anything. However, such particles have thousands of Earthward excursions each day, so the only ones which are likely to survive long are those that are always confined to higher levels.
A more subtle effect is also at work. The equations governing the
motion of trapped particle indicate that each has a characteristic value
of magnetic intensity, below which is cannot penetrate. Suppose a
particle is reflected by the intensity existing at 215 miles. As it
happens, the Earth's magnetic field--its region of magnetic forces--has
some irregularities, so in some regions that intensity is only reached
at 100 miles. Now and then the particle's orbit will happen to descend in that
region, where it penetrates to much deeper (and denser) layers of the
atmosphere, and may be quickly lost, even if elsewhere it stays at safe
heights. One such notorious region exists above the southern Atlantic Ocean.
So the radiation belt does not reach the levels where Mercury, Gemini,
Soyuz and Mir used to orbit and where the Shuttle and Space Station do
so now. The early Russian Sputniks failed to discover the radiation belt
because they too stayed in such low orbits and Explorers 1 and 3 only detected it because they were rather poorly controlled and rose above 1500 miles.
I am writing a science fiction story in which a ship is traveling through space at a percentage of the speed of light (I was thinking about 1/3 c, but that may change depending on how the math works out). In this flight they would need a way of deflecting the particles of dust
in "empty" space because hitting such items at relativistic speed would damage the ship.
My question, then, is: will a magnetic field of sufficient strength repel non-charged particles or would they have to have to be electrons or ions with a charge to be affected? Could a magnetic field deflect say, a hydrogen atom or a helium atom that has the proper amount of electrons to be neutrally charged? And, while we're at it, would the field have to be stronger to deflect bigger particles, say something the size of a grain of sand or a pebble?
thank you very much,
Reply
I am afraid the answer is no--magnetic fields have no effect on uncharged dust or pebbles. Have you ever had an occasion to be examined on an MRI machine? (MRI is Magnetic Resonance Imaging--it used to be called Nuclear Magnetic Resonance, but the word "nuclear" frightened too many people, who did not realize the nuclei in question were stable well-behaved nuclei of hydrogen). You lie still on a pallet which rolls your body until the part being imaged is inside a big doughnut shaped magnet. That magnet is so strong that the attendant will collect from you anything that has iron in it--key chains etc.--lest it is snatched from you and flung towards the machine. Yet when you lie inside it (it makes an infernal racket, by the way) you cannot sense any special magnetic forces on your uncharged body.
Even for shielding yourself from fast ions and electrons in space, it would be hard to create a magnetic field strong enough and extensive enough. For a spaceship moving at c/3, though, shielding is not that hard--all the stuff coming at it moves essentially in one direction, so one only has to provide some armor on the front side. A very, very thick armor, maybe, but only right in front, no need to cover space all around.
When and where am I most likely to see Northern Lights?
Reply
What matters most is "where," or as they say in the real estate
business--location, location, location. Your best bet is Fairbanks,
Alaska; you may also see northern lights in Winnipeg, Canada, or even
International Falls, Minnesota, but they could only be near the northern
horizon.
Scientists call the phenomenon the "polar aurora." Earlier it was
named "aurora borealis" meaning "northern dawn" in Latin, since in
Europe it was mostly seen as a glow near the northern horizon. However,
it also occurs near the south pole, so "polar aurora" is now preferred.
Aurora is caused by electrons energized in the Earth's magnetic
environment, the magnetosphere, and guided earthward along magnetic
field lines (lines of force) along which they slide, a bit like beads
sliding along a wire. They move at about 1/5 the speed of light and in
many ways they resemble electrons beamed at the screen inside the
picture tube of a TV receiver. Where picture-tube electrons produce
light when they hit the screen, auroral electrons do so when they hit
the fringes of the atmosphere, about 100 kilometers (60 miles) up.
The field lines on which this happens are the ones coming down along
a circle centered near the magnetic pole ("auroral circle" or "auroral
oval"), and that is where the accelerated electrons end up. The circle
can expand and contract, but it usually passes near Fairbanks.
When? Don't expect to see aurora in the Alaskan tourist season, during
the summer, it just does not get dark enough. Just as near-polar winter
nights are long and dark, summer days are long and bright, and even
after the Sun sets, twilight persists. September has some darkness,
October much more--March and April are also OK, and so is winter, if you
do not mind the cold. When? The brightest auroras come from the night
side of the magnetosphere, so you should see them around midnight, or
later because of Alaska's time zone. If you stay in a hotel, ask the
desk clerk to wake you when a good display occurs.
What about the 11-year sunspot cycle? Occasionally, but especially in
years of peak sunspot activity, the Sun sends out blobs of hot gas,
which hit the magnetosphere and agitate it, causing "magnetic storms."
At such times the "auroral circle" expands and reaches the lower 48
states of the US and mid-latitude Europe. The agitation also produces
fine auroras, as happened on 5 November 2001, when the US was favorably
located. However, since Fairbanks is located near the normal auroral
circle, auroras are observed there throughout the 11-year cycle. The
main factor is the slanting of interplanetary magnetic field lines
(which come from the Sun)--southward slant, auroras likely, northward
slant, not so much. That slant varies randomly, though satellites
monitor it, and you can read their latest reports on the web.
I am a computer science major in New Mexico. The summer before last I did research on the ionosphere and, yet, I have not found a good explanation/definition of magnetic local time (MLT) and/or universal time (UT). I used a computer language called Interactive Data Language to graph sets of data from magnetometers in the North Polar Region..
Would you explain these items and how they relate to the study of science research of the earth's magnetic fields and magnetic storms, etc.?
Thank you very much!!!
Reply
Kind of hard to work on a house when the foundation is shaky, no? Your teachers and your texts should really answer those questions, but let me try, anyway.
How do you measure time? A good "clock" is the rotation of the Earth, and in early times this was checked by the position of the Sun. When the Sun was highest above the horizon--and exactly to the south--the time was noon, and the interval from one noon to the next was a DAY, or more precisely a solar day.
Universal Time is essentially the time in Greenwich, England, and serves as reference time for astronomical events (e.g. the observed onset of the 1987 supernova). It's sort of a "world time" not tied to any local clock. There exists a small correction, but if the above is good enough for you, you may skip the next 2 paragraphs.
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[ As it happens, the Sun's position among the stars also varies, and that motion contributes to the length of the day (about 4 minutes--see web site). Unfortunately, that contribution varies slightly throughout the year, because the Earth's uneven motion around the Sun, etc., so the "noon-to-noon" day varies slightly in length. Astronomers use instead a MEAN SOLAR DAY averaged over the year, which is a good gauge of the Earth's rotation.
But measuring time in mean solar days is not all. One must also decide when each day begins! Astronomers have agreed that each mean day begins with (mean) midnight at the Royal Astronomical Observatory in Greenwich, England, and time defined that way is known as UNIVERSAL TIME (UT). "Greenwich Mean Time" (GMT) is similar, but is counted from noon.]
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So, UNIVERSAL TIME essentially measures time, using the rotation of the Earth around its axis. LOCAL TIME (LT), on the other hand, measures not time but position relative to the Sun.
Suppose you cover the Earth with a network of lines of latitude and longitude
(see on the web http://www.phy6.org/stargaze/Slatlong.htm )
The at UT=0 it is midnight in Greenwich, 11 am in Russia, 6 pm in the Eastern US, and so forth; these are the LOCAL TIMES at these locations. Three hours later you add 3 hours to all these local times--and so forth, for other locations and other times. The local time at each location depends on the difference between its longitude ("meridian") and the longitude where it happens to be midnight. (You need not use time zones, but take the exact difference in longitude, for exact local time.) Your local time is 12 noon if your location faces the Sun, LT=24 (midnight) if it faces away from the Sun, and other values of LT for other relative positions of the Sun.
One can similarly cover the Earth with lines of MAGNETIC LATITUDE and LONGITUDE, the latter converging not at the geographic poles but at the magnetic poles. As the globe rotates, we can say as before that all points on the same magnetic longitude have a certain MAGNETIC LOCAL TIME (MLT). We have MLT=12 (noon) on the magnetic meridian (magnetic line of longitude) facing the Sun, and MLT=0 (or 24) on the meridian facing the opposite direction, and so on,. It is completely similar to ordinary LT.
Why is MLT important? Because the shape of the magnetic environment of the Earth--the magnetosphere--is determined by the solar wind, which "blows" almost exactly from the sun. So at MLT=12 a point faces in the"upwind" direction, and at MLT=24 in the "downwind" direction. Phenomena related to the action of the solar wind on the Earth's magnetic field, such as the polar aurora or daily magnetic variations, depend very much on MLT.
Hope this makes it clear.
I was wondering if the magnetosphere affected the Earth's weather in any way?
And if so please explain in detail.
Reply
I don't think so, we have no evidence for it. For at least two reasons, we do not expect any, either.
First, our atmosphere is electrically neutral and does not conduct electricity (below 50 km, anyway--and weather stays below 10-20 km). Substances of this kind (except maybe permanent magnet, a very special case) do not react to magnetic fields. When a doctor puts your body inside the strong magnet of an MRI machine, you feel no difference, except maybe for the loud noise that machine makes.
Second, weather gets its energy from heat deposited by sunlight on the surface of Earth. The energy of the magnetosphere, on the other hand, comes from the solar wind. A beam of the solar wind as wide as the magnetosphere carries only about 1/3500 as much energy as sunlight hitting Earth, and only about 1% of that is given to the magnetosphere. Of that, only a fraction reaches the upper atmosphere. It seems too little to make a difference, and it is not clear how it might move further down.
Practically all that energy, by the way, is channeled to the auroral zone, near the poles. As was said--no clear correlation has been observed, there or elsewhere. You may not get a scientist to say "absolutely no," but "very unlikely" may be just as good.