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FAQ: "Exploration of the Earth's Magnetosphere"

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Questions and answer--listed in the order received

Please note!

    Listed below are questions submitted by users of "The Exploration of the Earth's Magnetosphere" and the answers given to them. This is just a selection--of the many questions that arrive, only a few are listed. The ones included below are either of the sort that keeps coming up again and again--the danger of solar eruptions, the reversal of the Earth's magnetic field, etc.--or else the answers make a special point, going into extra details which might interest other users. Because this is a long list, it is divided into segments

Click here for a listing arranged by topic.

Items covered:

  1. Reversals of the Earth's field (4 queries)
  2. Can the Earth's field be used for spaceflight?
  3. The Sun's magnetic poles
  4. Synchronous satellites
  5. Magnetic field lines
  6. Alternate theory of the Sun and solar wind
  7. The Geiger counter (3 queries)
  8. Measuring the Earth's magnetic field
  9. The strength of the Earth's field
  10. Solar Eclipses
  11. Magnetometer for Observing Magnetic Storms
  12. Cosmic Rays

  13. Magnetic Shielding
  14. Use of solar wind for space propulsion
  15. A working model of the magnetosphere?
  16. The Van Allen Belt
  17. Magnets of different shapes
  18. On building an electromagnet
  19. Capturing the Energy of the Solar Wind
  20. About the Upcoming Solar Maximum
  21. Lining-up of Planets
  22. Radiation Hazards to Air Crews
  23. The Ozone Hole and the Magnetic Field
  24. How are Ions produced?
  25. About the "Starfish" artificial radiation belt
  26. How do Magnetic Reversals affect Animal Migrations?
  27. Which is the "True" North Magnetic Pole?
  28. Electric and Magnetic Energy
  29. Any connection between Solar Wind and Solar Flares?
  30. Ozone and the Magnetic Field
  31. What if the Radiation Belt Reached the Ground... ?

  32. Free Energy from the Earth's Magnetic Field?
  33. Relativity
  34. What is a "REM"?
  35. What exactly does "Radiation" Mean?
  36. Can anything solid be carried by the solar wind?
  37. Dimensions of the Magnetosphere (2 related questions)
  38. Skywriting by Aurora
  39. Capturing the energy of solar wind ions
  40. Radio Propagation
  41. Radiation Belts and Manned Space Flight
  42. Magnetc shielding against neutral matter?
  43. When and where can I see "Northern Lights"?
  44. Universal Time and Magnetic Local Time
  45. Does the magnetosphere affect weather?

  46. "Importance of auroras to society"
  47. Magnetic storms and headaches
  48. Appolo Astronauts and radiation
  49. What materials does a magnet pull?
  50. Experimental simulation of the polar aurora
  51. Cosmic ray research using balloons
  52. Magnetic health products
  53. Geiger counters for locating lost objects
  54. Magnetic effects from other planets
  55. Blocking of the Solar Wind by our Moon?
  56. Fry or Freeze... ?
  57. The Speed of the Solar Wind
  58. What is "Radiation"?
  59. How does one Contain a Plasma?
  60. Soviet Nuclear Explosions in Space
  61. Can Polar Aurora be seen in Atlanta, Georgia?

  62. Why no aurora at the magnetic poles?
  63. When and how were positive ions discovered?
  64. Did astronauts use articifial magnetic shields"?
  65. Harvesting electrons from power lines?
  66. How can the intensely hot Sun be magnetic?
  67. What are "geomagnetic conjugate points"?
  68. What is the smallest magnet possible?
  69. Can plasma physics explain ball lightning?
  70. Harnessing the Energy of the Aurora?
  71. Radiation Belt and Brazil
  72. Risks from stormy "Space Weather"
  73. Man-made triggering of radio emissions
  74. Does our magnetic field stop the atmosphere from getting blown away?
  75. Radius of particle gyration

  76. Are electric storms an "electromagnetic" phenomenon?
  77. How can steady magnetic fields induce electric currents?
  78. There are electromagnetic waves all around us!
  79. Best orbit for a Space Station
  80. Is space debris electrically charged?
  81. Magnetic induction by the Magnetosphere
  82. Questions about the Solar Corona:
                        (1) Why don't its particles separate by weight?
                        (2) What accelerates the solar wind?
  83. Why has the aurora been so frequent lately?
  84. Was the magnetosphere involved in the hole in the ozone layer?

  85. Who Discovered Sunspots?
  86. "Soda-Bottle Magnetometer"
  87. Magnetism and Weather
  88. Is the Polar Cusp visible to the Eye?
  89. Effects of Radiation beyond the Van Allen Belts
  90. Deflection of a beam of Electrons in the Earth's Field

  91. Space Tether
  92. Does the Earth's magnetic field rotate?
  93. Dynamo currents at Jupiter's moons
  94. A Russian space tether experiment?
  95. How come a magnetic field can block particle radiation but not light?
  96. What is a "magnetic moment"?
  97. Is fire a plasma?
  98. Do interplanetary field lines guide the solar wind back?
  99. Magnetic connections between planets and the Sun
  100. The solar wind and solar escape velocity

If you have a relevant question of your own, you can send it to
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  1.    Space Tether

    The space tether seems to extract kinetic energy from the orbital motion of the shuttle.

        But as the shuttle loses energy, it descends to a lower orbit and must speed up. How can the shuttle lose energy AND speed up?

    Reply

    You are right, the kinetic energy of the shuttle increases. But it loses potential energy, like any object which descends from a high location to a lower one. In the final balance, the sum of potential+kinetic energy gets smaller.

  2.    Does the Earth's magnetic field rotate?

        Hello David,

        My 8 year old son and I are conducting simple experiments involving electricity and, particularly, magnetism.

        We noticed that iron filings sprinkled upon a horizontal plane suspended above a pole of a dipole magnet do not appear to move when the magnet is rotated about the line extending between its two poles.

        Yet, we understand that the accepted scientific view is that the Earth's magnetic field rotates (nearly) synchronously with the Earth.

        So, our question is: Does the Earth's magnetic field rotate? If so, how do we know this?

    Reply

        Your question is not a simple one, and has in the past confused quite a few people. A rough outline of the answer follows below; it is not exactly simple, and I can only hope that you and your son will have the patience to follow it to the end.

        I take it you refer to the axially symmetric parts of the field. The observed field also has many irregularities, and these certainly rotate with the Earth. For instance, the north magnetic pole (and the south one, too) is separated by something like 1000 kilometers from the geographic pole, the pole around which the Earth rotates. And indeed, the magnetic pole rotates every day a full 360° around the geographic one. What you have in mind--what your experiment involves--is something else: a symmetric field rotating around it s axis of symmetry.

        If you have a source of magnetic field in empty space--iron magnet, coil--and you rotate it around an axis of symmetry, there is no extra effect, and therefore, nearby objects will not feel any force to make them share the rotation.

        For instance, if you have a bar magnet and twirl it around its length, around the line connecting the poles, you get no observable change. At any point in the surrounding space, the magnetic force sensed (say, by a compass needle) is not changed by the rotation.

        All that is true in empty space. And to a very good approximation, it also holds if the space contains substances which do not conduct electric currents--air, wood, paper, glass etc. In all these cases, just having the source of magnetism rotate has no measurable effect.

        But if space is filled with a substance which can conduct electricity, and the rotating magnet also conducts electricity, the situation is different. Under certain conditions, electric currents may then be produced, and in that case, two effects are added:

    • First electric currents are SOURCES of magnetic fields, and therefore the magnetic field may be modified.
    • Secondly--more important here--magnetic fields exert a FORCE on the carrier of electric current, and in this case, in general, that force tends to make it share the rotation.

        Space around Earth--except for the lower atmosphere--does conduct electricity. In the ionosphere--say 120 kilometers up (70 miles) and higher, sunlight rips off