The Answer Man

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I am wondering what is the importance of auroras in society. I would also like to know what importance auroras have in the future. I need to know this information for an essay I am writing. I have searched everywhere but I haven't found any information on either of the two topics. Please assist me.

Reply

    I am curious--how did you come to write that essay? Your idea, or an assignment? If the latter, I wonder how other people with the same assignment are faring. By all means, send me your essay when it's done.

    How important are auroras in society? One may just as well ask the same questions about rainbows, or bolts of lightning. All these started as a supernatural mystery--evidence that nature has strange wonders we do not understand, wonders which may be manifestation of some greater and more powerful intelligence, invisible but dominating our lives.

    Gradually, they were explained, and are now viewed as evidence that nature is governed by orderly rules, and is not random or capricious. In fact, they help us learn about those rules. The fact that auroras are not completely understood shows we still have things to learn.

    The geomagnetic storms we have been experiencing cause me to have severe headaches and sometimes visual field aberrations, such as a flattening of my vision and depth perception, as well as some cognitive dysfunction. I have correlated these with the strength of the storms and flares by keeping a diary and checking it against the info put out by spaceweather.com on the daily email lists. My question is do you know of any way to counter act the effect of these ion storms on humans? I am aware of currently proposed research projects for shielding Cardiac ICUs since the storms are correlated with an increase in heart attacks. I have asked this of many doctors, both main stream and alternative practitioners. I always get a no but let me hear from you if you find out.

    Thanks for any info!

Reply

    To a scientist such effects must seem very unlikely. The magnetic field at Earth is about 0.5 Gauss, and magnetic storms change it by 1% at most.

    Have you ever undergone MRI (magnetic resonance imaging) of your head? I have. First you must remove all iron objects from your pockets or body (watches, pens etc.), lest they fly off in the strong magnetic field and stick to the magnet. You then go to a room with a big doughnut-shaped machine, and lie on a pallet which wheels you into the hole of the doughnut, until your head (or other body part being examined) is in its middle. Then it scans you for a few minutes (you may not move, it's a time exposure) with a loud racket, and finally wheels you out again.

    During those minutes your head may be exposed to 1000 gauss--maybe several thousand, I do not know the exact numbers. I never had a headache or sensed the magnetic field. But you may also ask operators of such machines (or search the web) to find more.

    Effects similar to those of magnetic storms occur frequently in Fairbanks, Alaska, during "magnetic substorms" accompanying the polar aurora. You may ask doctors in hospitals there if they find any effects. My guess is that they don't.

(Or: Did our astronauts really land on the Moon?)

    On the Art Bell radio show last night I heard a fellow state that the Van Allen radiation belt's level of radiation was/is so intense... that for the 2 hours each way that our astronauts would have spent in it would have been fatal to them and therefore man being on the moon was impossible to have happened.

    He also specified that whatever shielding was present on their craft would not have spared them.

    Would you be so kind as to illuminate me about the credibility and scientific accuracy of his claims regarding the Van Allen belt's level of radiation ?

Reply

    The argument which you raised keeps coming back in my e-mail; see for instance
        http://www.phy6.org/stargaze/StarFAQ4.htm#q68

    The answer is always--no. The radiation is bad, but not THAT bad. Astronauts went through the belt quickly, and the dosage was minimal. Two hours were certainly not enough to kill anyone--two weeks, maybe, I am not sure (the dosage to the skin would be heavy, but to the heart or brain much less so because most of the inner belt protons do not penetrate far).

Further question: Were those astronauts safe from solar flares?

    Dear Dr. Stern,

    Thank you for your speedy response. Was there a contingency plan for X class solar flares? Would such flares have posed a danger to life for the astronauts?

Reply

    High-energy ions from large solar flares can be very dangerous to human life. They can be quite penetrating and hard to shield against; "can be," because the energies vary from event to event, and the size of a flare is only loosely related to the high-energy ion danger.

    Such flares occur infrequently, a few times each 11-year solar cycle, but if you send people to Mars, they pose a real risk (they also pose a risk on Mars itself, since the thin atmosphere there is not a very good shield).

    We are students working on a science project involving magnetism. We are investigating what types of metals are attracted to magnets. Could you please send us your opinion on this subject along with any other information you may have. Thanks!

Reply

    Iron is attracted to magnets, but why? Because near a magnet, in its "magnetic field" (roughly, its region of influence) ordinary iron turns into a temporary magnet. See
        http://www.phy6.org/earthmag/demagint.htm
and then go to the page "Performing Gilbert's Experiment on Induced Magnetism."

    Iron and some alloys (and I am not sure, but also maybe nickel) turn into fairly strong temporary magnets. These are "ferromagnetic" materials--look up ferromagnetism in an encyclopaedia.

    I want to do an experiment of an aurora and all I can think to do is show the similarity on magnet shavings and a magnet. I feel this is a little lame. Any ideas on how to be more effective.

    I am in the 5th grade, live in Charleston SC and love anything that deals with the sky. Auroras seemed to be a great subject to try to prove but after hours of research I can't find any way to replicate one. any help would be appreciated. Thank you

Reply

    It would be difficult, even a crude experiment would need a vacuum pump and attached glass plumbing.

    The problem is that the aurora occurs high up, in very rarefied air, where the average spacing between molecules and atoms is large, so that an electron (like that of the aurora) has a long free run before it bumps into something. Here at ground level the "mean free path" (that is the technical term) is very short--less than the thickness of a hair.

    The closest you can come in the lab is by phenomena known as gas discharges and cathode rays.

    Air is a poor conductor of electricity, which is why power companies string their lines through the air and never worry about electricity leaking away. To conduct electricity, it needs to contain a small percentage of electrons set free from their atoms. In the dense air we breathe, these bump into molecules so quickly that they almost immediately recombine, so at any time, hardly any are present (except with very high voltages, as in lighting).

    But pump the air down to a few millionths or so of its ordinary pressure (just from memory, numbers need to be checked), and the picture changes. If the rarefied air is inside a glass tube, and you stick two wires into it (through holes with leakproof seals), then put a voltage of say 1000 volts between them, the air begins to glow. Now electrons have few collisions, and the voltage is enough to speed them up so that on colliding, not only do they not get lost, but they knock out some more electrons, so there are always enough of those to conduct a current.

    It looks like the aurora, but it isn't the same--auroral electrons go miles before colliding. Fluorescent tubes are a bit like that, too.

    Pump out more of the air, and the glow gets very dim--it's the collided atoms which emit light, and too few collisions take place (instead the electrons hit the wire at the positive end, which can get hot). This happens in X-ray tubes in the doctor's office, and in TV tubes. The glow can be deflected by a magnet which steers the electrons, but don't try it with your TV tubes because (1) their voltage is really high, (2) a magnet can defocus them permanently (3) their big shape is not good for reaching the electron beam inside and (4) you cannot see that beam anyway. Those beams are more like the aurora, though.

    About 100 years ago a Norwegian physicist named Kristian Birkeland went one step beyond, simulating the aurora by sending a beam of electrons towards a spherical magnet in a vacuum chamber. Read about him in
        http://www.phy6.org/Education/whaur1.html
His experiment however is quite difficult to duplicate.

    I am dong a science project on Cosmic Rays. I found your site, or the site that some of your Research was on, and it was really interesting. I was wondering if it wouldn't be too much trouble for you if you sent me some information about when those air balloons with the photographic plates were sent into the atmosphere. I think that your work is amazing, thank you for all the help I've received from it so far. Thank you

Reply

    High-altitude balloons with photographic plates were first sent up in the 1950s and 1960s, early days of cosmic ray research. Part of the reason was not just to study cosmic rays, but also to investigate the collision of very energetic protons and ions with nuclei, which produced some interesting new short-lived particles and taught physicists about the way elementary particles were made. In those days cosmic rays were the only known source of such fast particles. In later years accelerator machines were built which produced such particles in much, much greater numbers, and those who study this sort of physics shifted to them.

    High-altitude balloons are still used, but they now lift electronic instruments which automatically sort incoming particles--and being bigger than slivers of film scanned by a microscope, they also observe many more of them. Some of them are test-versions of instruments later flown aboard satellites.

    The balloons contain helium, not air. When launched they look like long draggy bags, with a big bubble of helium on top, just enough to lift the payload in the dense atmosphere near the ground. At high altitudes, air is more arefied and much more volume is needed to lift the same weight. However, the bubble expands there and the balloon fills up to a near-spherical shape, supplying that lifting volume.

    My wife is going to buy a mattress with built-in magnets (constant magnets with a diameter of a thumb's nail). Those things are advertised as health products. These built-in magnets should compensate for the decreasing strength of the earth's magnetic field.

    There is a lot published in the internet regarding those "magnetic products" and for me the following questions arose:

    1) If I believe those publications, the earth's magnetic field oscillates constant-periodically with 7.5 Hz. For my understanding, it's a constant field (no oscillation at all); it only decreases by time. What's your opinion?

    2) The magnets on this mattress are attached in rows (magnet distance ~10 cm). The following row is @ 30 cm distance, with all magnets in that row with reversed polarity So I have a couple of alternating N and S - pole rows from the top to the bottom. For my understanding, this doesn't reflect the earth's magnetic field and so the advertising argument, that this product does simulate/increase the earth's magnetic field once you're lying on the mattress. Does it sound logic to you?

    3) These publications above also mention that applying a magnetic field inside a spaceship avoid from any loss of calcium in the astronaut's bones, and astronauts have less depressions, and mice don't loose their coat/skin anymore !? I thought the loss of calcium is due to the gravity and not to the fact that the astronauts are further away from the earth's magnetic field. What's your comment on this and are you aware of any experiments in manned space flight with applying magnetic fields to the ship? Thanks in advance for any helpful answers/comments.

Reply

    (1)     I am not familiar with all the oscillations of the Earth's magnetic field--they exist, in various frequency ranges, but are always very small (and transient). You are right, the field is essentially constant.

    (2)     No significant magnetic effects on human body have ever been found: we do not seem to have magnetic sensors (as homing birds might have), nor do any large currents flow in the body (if they did, they might respond to magnetic forces). Have you ever taken an MRI (magnetic resonance imaging) test? I have--it's a rather noisy experience. You lie on your back on a narrow pallet which slides you in the middle of a ring-shaped magnet, and a field is switched on--I am not sure how strong, but probably a few thousand times the usual Earth's field. Before you go into the imaging room you are asked to remove all objects made of iron--key rings, watches, belts with buckles, etc.--lest they fly off and stick to the magnet. Yet while you lie on that pallet, you cannot tell the moment the magnet is switched on, or any difference when it is.

    So my advice to your wife is, save your money, or spend it instead on a comfortable conventional mattress.

    By the way, a movie is coming out, "The Core", which seems to promote the notion that the Earth's magnetic field is essential to our well-being. Haven't seen it, but from what I have read, it seems to be sci-fi, not solid science.

    (3)     I have heard the stories about astronauts, too. They seem to be flights of fancy.

    Astronauts can lose weight in space (you are right about the cause), especially in long stays on a space station, but the remedy are exercises. I wrote about this in http://www.phy6.org/stargaze/Sskylab.htm

    I am a 12 year old student and was wondering ...I read about your Geiger counter explanation and was wondering if you had any knowledge about a product that would locate missing things based on this technology? many thanks tk

Reply

    Sure, a Geiger counter can be used to locate missing objects--as long as they are radioactive. I read of prospectors using them in searching for uranium ore, at least early in the search (later more sensitive means are used). They are also used in security gates, to make sure no one is smuggling nuclear materials through them.

    Such a counters were used at the gates to the Los Alamos National Laboratory in New Mexico, where nuclear research is being conducted. One day a truck loaded with iron bars for construction work came in and the alarm started ringing. Sure enough, the iron was radioactive, and it turned out to have come from Mexico. Investigators tracked down its source and found that a medical machine containing a large radioactive source was illegally junked (the law requires all radioactive materials to be specially disposed) and ended up in a shipment of scrap iron, which was melted and turned into iron bars for construction. As far as I remember, no one was hurt that time, but inspectors had to track down all shipments of that iron, many of which ended in the US, and some buildings under construction had to be demolished and their iron removed.

    Have we been able to determine if there is an induced voltage or modulation of the earth's magnetosphere at times when the other planets are at various angles to the earth?

Reply

    The short answer to your question is "no." However, you probably deserve a more detailed reply, so here it is.

    First of all, any effects of other planets existed would be more readily observed in interplanetary space outside the magnetosphere, rather than inside the magnetosphere, where they would be muffled by the stronger magnetic fields and hotter plasmas, and obscured by unrelated waves and disturbances created there.

    Second, the propagation of effects to Earth is dominated by the solar wind, flowing outward from the Sun, and to some extent by the interplanetary magnetic field. A planet upstream of Earth in the solar wind, or on the same interplanetary magnetic field line, might possibly affect us, but not otherwise.

    Upstream we have only two planets, with relatively small wakes. The one of Venus is scarcely wider than the planet, since Venus has no magnetic field. Mercury has a field, but it is weak and the planet is small, so its wake is narrow, too. I am not aware of either wake being detected near Earth, but it is possible someone has observed one. The effect on Earth, in any case, is small. About the effect of the Moon's wake, see next question below!

    Jupiter has a giant magnetosphere and a huge wake, and I vaguely recall that wake being credited for a strange observation by a space probe near the orbit of Saturn, but of course Earth is upstream of the planet and the wake will never hit it. Jupiter's magnetosphere was also at one time given credit for energetic electrons (1 MeV or so) in the Earth's magnetosphere. It was claimed that those electrons were more plentiful at times when Earth and Jupiter were linked by the same bunch of magnetic field lines. However, I have not heard that explanation recently and believe most researchers now feel they are generated in our own magnetosphere--though the process responsible remains unclear.

    So, here is your answer. It still boils down to "no."

    Dear Dr. Stern

    What effect does our moon have on the solar winds? Could our moon act as a shield for the earth, from the full impact of the solar storm, when it is upstream? Thank you.

Reply

    Yes, when the moon is upstream of Earth it will intercept some of the solar wind which would otherwise impinge on the front of the magnetosphere. But the effect is small, because the moon is small, too. I have never read of anyone detecting it.

    The radius of the Moon is about 1/3 that of Earth, whereas the radius of the magnetosphere abreast of Earth is about 15 Earth radii. If you take 10 Earth radii as the radius of the "front," you find the moon covers only 1/900 of the front area. A weakening of that extent in the flow of solar wind would be lost in the disorderly "noise."

    Neither do I think that the moon casts a sharp (even if small) "solar wind shadow" on the magnetosphere. At a distance of 60 Earth radii, it is about 180 moon radii away. Near the moon, on the side facing away from the Sun, the observed "shadow" is sharp, but at a distance of 90 times the width of the obstacle I expect it to be washed out, especially since the bow shock of the Earth intervenes, with its disorderly "foreshock" ahead and "magnetosheath" behind.

    David,

    Found your data on the earth's magnetosphere. Wanted to know how far out in space it extends. It doesn't make it to the moon, or does it?

    This new data on Mars suggests men would fry there due to cosmic radiation...so I was wondering why the Apollo crews didn't...

Reply

    You wrote " found your data on the earth's magnetosphere"; but what files you were reading? The dimensions of the magnetosphere (and its shape) are discussed in

    Dr. Stern;

    I just read your Solar Wind web article (Oct 2002). I was trying to find the speed of the solar wind when I found you article, and am emailing you with that question.

    What is the speed of the solar wind with respect to the sun?

Reply

    The average solar wind moves at about 400 kilometers/second, a little more than 1/1000 of the speed of light--about 4 Earth radii per minute, about 4 days to cover the distance from the Sun to us. The magnetic field near the Sun may impede this motion; at times when the field lines linking the solar wind to its region of origin stick straight out (rather than bend around or arch back to the Sun), it gets a clear path and its velocity may rise to 700 km/s. At some other times its velocity may be only 300 km/s.

    As eclipse photos have suggested, field lines above the poles of the Sun do stick straight out, and it was predicted that this sort of fast flow, which only occurs sporadically at the orbit of the Earth (mainly around years of sunspot minimum) should be the norm above the Sun's poles. When the Ulysses spacecraft passed above the polar caps of the Sun, that prediction was confirmed.

    What is "radiation"? And--if you "nuke" food in a microwave oven, can it become radioactive?

Reply

    The word "radiation" in common use has (unfortunately) more than one meaning. And to answer the 2nd question--no, microwave radiation and nuclear radiation (involving radioactivity) are very, very different.

    "Radiation" essentially means some effect which spreads radially in all directions, along straight lines (along the radius). Examples are light and its close relatives, infra-red (IR) radiation (emitted by hot objects) and ultra-violet (UV) radiation.

    In the middle 1800s James Clerk Maxwell concluded that light was an electromagnetic wave. That suggested such waves could be created by purely electrical means and in 1886 Heinrich Hertz did so, producing radio waves. The microwave radiation in your oven is also produced electrically, it is just a short-wave radio wave, developed in World War II for use in radar. When physicists talk of "radiation" they usually mean "electromagnetic radiation," the large family covering light, IR, UV, radio and microwaves.

    Dear Doctor Stern,

    Can you help me with this question? How do make a container that can hold plasma? I am 9 years old. I go to Scared Heart of Jesus. I have 4 sisters. My dad works at N.T.I.A. and is also helping me. Thank you.

Reply

    So how can you contain a plasma? Two ways have been tried.

    With a rarefied plasma, one can continually supply fresh energy and keep heating it up. This is what happens with a fluorescent lightbulb, which contains plasma. The wires leading to the lightbulb continually supply fresh electric energy, so the plasma is continually renovated, which allows it to continue carrying an electric current.

    The gas inside the lightbulb also absorbs energy from the plasma, and emits it as light, which turns out to be a very efficient way of producing light--more efficient than that of lightbulbs whose light comes from a hot wire.

    The other way is to use a strong magnetic force to keep the plasma confined: this is made possible by the electrical properties of a plasma, which determine the way it interacts with magnetism. This is the way favored by researchers trying to confine a dense plasma. The plasma is inside some container, but the magnetic "field" (region of magnetic forces) keeps it from touching the walls. The trouble is that this sort of situation can be very unstable--the plasma also creates its own magnetic field, which modifies the one keeping it trapped, and so far, just when things get interesting, it is likely to shake itself loose, slip away to the walls, cool down and be gone.

    Dr. David Stern

    I noticed your web page on the GSFC site, with the reference to the early bomb tests, http://www-istp.gsfc.nasa.gov/Education/whradbel.html . You mention the Soviet tests - but not the year in which they were conducted. Can you fill in the missing info?

Reply

    The Soviets conducted three high-altitude tests above the Russian arctic region, on October 22, 28 and November 1, 1962. The first two were sub megaton, the 3rd in the megaton range. Unlike the US "Starfish" explosion the preceding July, they were on field lines extending further into space, with less stable trapping, and they decayed within weeks. Interestingly, the US launched "Explorer 15" on October 27, just in time to observe the resulting radiation belts. That satellite was built in response to the unexpected damage and longevity of the "Starfish" belts. NASA engineers, under pressure, went into the "museum" display in bldg. 1 of Goddard Space Flight Center, retrieved the engineering test model of Explorer 12 and converted it into a usable satellite, all in the record time of 91 days. I wish NASA still had that agility and in-house capability!

    I live in Woodstock, GA, a suburban area of Atlanta. We, in this area, have had some strange occurrences this year including an earthquake. It was a small one, but since I am a native Georgian, and it was the first I've experienced--the quake got my attention. As a writer for a small publishing company, I like to record events like this as possible material for later use.

    To the point, I was told by a fellow worker (a former teacher and fellow student in a Master's writing program at Kennesaw State University) that there would be an aurora borealis visible in the Georgia night skies on May 30 and 31. I looked for other sources to predict this unusual event, but there was no mention of it anywhere else. I looked, not too hard though since I suspected an urban legend in the making. Please tell me, is it possible, ever, that an aurora borealis would appear this far south?

Reply

    It wasn't a hoax, just perhaps wishful thinking. Eruptions on the Sun occur now and then, some are quite big, and conditions may be ripe for a widespread aurora, yet often nothing happens. How often have you heard a tornado warning on the radio, but none materialized? A large flare on the Sun, a Coronal Mass Ejection (CME) heading our way--all these are necessary, but until the disturbance actually arrives, who can tell if the interplanetary magnetic field is right (it should tilt southward, not northward), how big that CME actually is, and other imponderables? The best a prediction can do is state a likelihood, never a certainty (just as with a tornado).

    Predictions were made that day: see

http://www.sel.noaa.gov/ftpdir/forecasts/RSGA/0530RSGA.txt
http://www.sel.noaa.gov/advisories/bulletins.html
http://www.sel.noaa.gov/forecast.html

    Aurora may be visible from Atlanta, but only rarely--perhaps once in a decade. On 5 November 2001 aurora was widely seen across the lower 48 states; my son in Purcellville, Virginia, saw it (I looked but saw nothing--city lights may have blotted it out). I was alerted by a message from a family in Chicago and the story is on this web collection at wnovstrm.htm . It may or may not have reached Atlanta, but a larger storm in March 1989 probably did get that far. For a picture of that storm from space (not at its greatest extent) see weather.html on this collection of web sites Reportedly, the aurora following the great flare of 1 Sept. 1859--the first ever observed--reached Havana, Cuba. About this solar event, see whcarr.html. Finally, for an overview about the polar aurora, see (also here) at aurora.htm .