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Acceleration of voyager spacecraft

  1. Jun 11, 2008 #1
    Could the anomalous acceleration of the voyager spacecraft towards the sun be explained by its surface becoming electrically charged by friction with dust particles and the interaction of the electric charges with the sun's magnetic field?
  2. jcsd
  3. Jun 11, 2008 #2
  4. Jun 12, 2008 #3
    I mean pioneer.And how do we know that the acceleration isn't due
    to the sun having an uneven mass distribution or a large mass moving close to pioneer? And is the signal pioneer sends faulty after all this time?
    Last edited: Jun 12, 2008
  5. Jun 13, 2008 #4


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    We can be pretty sure that it isn't due to something moving close to Pioneer because the effect was evidenced in both Pioneer 10 and 11 (which are nowhere near one another), as well as Galileo and Cassini.
  6. Jun 13, 2008 #5
    Thanks for the clarification, battery - so we are actually all thinking about the same spacecraft.

    Now I have already been in error with my statements so often, so don't take what I say now too seriously. But anyway: I don't think that interaction of a (possible) electrical charge of the spacecraft with the solar magnetic field might be the cause. A charged body moving through a magnetic field would be accelerated perpendicular to its velocity vector. But this spacecraft is moving away from the sun, and the strange extra acceleration is pointing towards the sun (right ?), so its in fact antiparalel to the velocity vector .
    Last edited: Jun 13, 2008
  7. Jun 13, 2008 #6


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    Perpendicular wrt its velocity vector is confusing. Clarify your point. The pioneer anomaly has nothing to do with solar effects, so far as I know.
  8. Jun 14, 2008 #7
    The pioneer craft would have to be moving at exactly 90 degrees to the sun's surface to have a zero acceleration towards or away from it.This angle is unlikely and if there is some charge on pioneer then there will be a small force acting on pioneer.Also there are electric charges in the space around the sun that could attach themselves to pioneer.The question is: would there be a large excess of positive charges over negative charges or vice versa.
    If Pioneer has large solar panels then these may be accumulating charge from space or perhaps solar radiation is kicking electrons out of the panels leaving them with a net positive charge.
    And how do we know the acceleration is real - is this acceleration due to a faulty signal coming from pioneer or from some faulty analysis by Nasa?
    Last edited: Jun 14, 2008
  9. Jun 14, 2008 #8

    If you have a body with the charge q, that is moving with velocity v through a magnetic field B ,then it will experience a Lorentz force

    F = q(v x B)

    This force is perpendicular to the velocity v and perpendicular to the magnetic field B. Or to put it another way, it is perpendicular to the plane that is defined by v and B. And I was no talking about solar effects in general (this would be interesting too), I was just trying to argue that an interaction between a possibly charged pioneer spacecraft and the magnetic field of the sun should not be cause of the anomaly.


    You are right, surely it is not exactly 90 degrees, so there would be a (small) component of the acceleration pointing towards the sun. But there would also be a (larger) lateral component. Now if people are sure that the anomaly exclusively consists of the (extra) acceleration towards the sun, i.e. there is no lateral component, then I would insist that interaction with the suns magnetic field cannot be the cause.

    If, however, there might be an unknown, lateral component, then you are right. And this might just be the case. Maybe they can measure the acceleration towards the sun with a high accuracy (Doppler perhaps ?), but have no idea whether there is any lateral acceleration of the same order of magnitude.
    Last edited: Jun 14, 2008
  10. Jun 15, 2008 #9


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    No magnetic force has been suggested.
  11. Jun 15, 2008 #10
    I think that possibility has been considered.

    However, the anomalous Pioneer acceleration has been shown to be a constant 8.7 X 10^-8 cm/sec^2 toward the sun....constant in both time and in solar distance between 20 AU and 70 AU.

    Since the Lorentz force is dependent upon the strength of the solar B field, which must vary as approx. the inverse cube of solar distance , then it is not likely to be the causal candidate for a constant acceleration, (unless of course the velocity is increasing by the same factor which it isn't).

    Last edited: Jun 15, 2008
  12. Jun 15, 2008 #11

    Could a constant magnetic force caused by solar radiation accelerating charges in the interplanetary medium close to pioneer be pulling pioneer towards the sun on the side of pioneer facing the sun, while a smaller magnetic force (also caused by interaction of solar radiation and interplanetary charges) in pioneer's shadow is
    pulling in the opposite direction.The net force on pioneer might stay constant with distance from the sun because the solar radiation becomes less intense with increasing distance but
    the charges in the interplanetary medium might also be more dense
    and therfore more likely to interact with the solar radiation.
    Last edited: Jun 15, 2008
  13. Jun 15, 2008 #12
    On second thoughts I think this scenario is unlikely because less and less energy is involved
    as the sun becomes more distant.
  14. Jun 15, 2008 #13
    I think the only realistic possibility is that pioneer becomes electrically charged more and more the further it moves from the sun by either friction with dust particles/charges in space or by its solar panels becoming positively charged by x rays,gamma rays and other energetic particles kicking out electrons - more electrons as time passes.
    If by some chance pioneer is getting struck on one side by some freak radiation source then that source could be detectable from Earth when the Earth is in line with the radiation source and the sun as pioneer must be.
  15. Jun 15, 2008 #14
    The fact that the planets do not seem to have this anomalous acceleration suggests that the solution lies with things that are metallic - like pioneer 11 and hence can conduct electricity and interact with magnetic fields.Electrons escaping from the sun and moving close to the speed of light and close to pioneer 11 could generate a large enough magnetic field to pull it towards the sun, in concert with any electric charges from the sun that stick to pioneer's surface, and interact with the sun's magnetic field to produce a force in the sun's direction.Over time more charges would stick to pioneer's surface as, with increasing distance from the sun, fewer solar photons strike pioneer with the energy needed to eject charges off the surface and more charges emitted from the sun have slowed down because of the sun's gravity and so don't bounce straight off the surface.
    Last edited: Jun 15, 2008
  16. Jun 16, 2008 #15


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    No. Any such effect would follow the inverse square law thing, not linear acceleration.
    Last edited: Jun 16, 2008
  17. Jun 16, 2008 #16

    I disagree with this. FORCE = qvB for charge moving through a magnetic field.

    For a steady force with time then if velocity is constant charge must increase as magnetic field B decreases.B gets smaller with the cube of distance from the Sun.
    So we need charge on pioneer to be inversely proportional to magnetic field cubed ( q~1/ B^3).If charge on pioneer is proportional to time of travel ( more charges could stick to pioneer as time goes by) for length ,width and depth of pioneer spacecraft then it is not impossible that a relationship such as q~1/ B^3 exists.
    Last edited: Jun 16, 2008
  18. Jun 16, 2008 #17
    Sorry,the writing above doesn't make sense and should read:

    For a steady force with time then if velocity is constant, charge must increase as magnetic field B decreases.B gets smaller with the cube of distance from the Sun.
    So we need the charge on pioneer to be proportional to the cube of the radius from the sun, to give a force that stays constant with time.
    Last edited: Jun 16, 2008
  19. Jun 16, 2008 #18

    battery; That may be possible in principle,.... but apparently my seemingly naive comments about the solar B field ..... have mislead you.

    I used the VERY general idea that a dipole field decreases as 1/r^3 simply to merely show in one specific way the quite GENERAL incompatability of a Lorentz type force with the measured constancy of the anomalous acceleration, not to give license for an exact derivation.

    In reality the solar magnetic field is far more complex and far more dynamic than I implied, its magnitude varying both with the solar sunspot cycle and with position throughout the interplanetary region.

    The solar B field at the solar surface varies with time and is max. during solar sunspot max. and the field lines are carried outward in a complex way by the solar 'wind' into the interplanetary regions. The solar winds goes out radially but due to the sun's rotation, the B field actually goes out in a spiral pattern.

    Furthermore, every 1/2 solar cycle (11 years) the magnetic field REVERSES.

    These and other complications should certainly put to rest any idea that an electromagnetic Lorentz force could be responsible for a long term constancy in the Pioneer acceleration....(even with charge accumulation). :wink:

    See here for some details and to catch up on some info that should reveal the veracity of my above statement.

    http://science.nasa.gov/headlines/y2001/ast15feb_1.htm [Broken]

    http://www.oulu.fi/~spaceweb/textbook/solarwind.html [Broken]


    Creator :biggrin:
    Last edited by a moderator: May 3, 2017
  20. Jun 17, 2008 #19
    I read that the Mars Polar Lander and the Mars Beagle mission both ended disastrously and in the same region of space relative to the sun ( decemebers 4 years apart 1999 and 2003).Did rocks in space hit these craft? Are rocks in space causing the anomalous accelerations of pioneer and galileo?
  21. Jun 17, 2008 #20
    I suspected this could be the case and my suggestion is unlikely because we would expect to see a little of the charging on satellites near to Earth and perhaps charging of the Earth and effect on the Earth's magnetic field and position in space!

    I read that the Mars Polar Lander and the Mars Beagle mission both ended disastrously and in the same region of space relative to the sun ( decembers 4 years apart 1999 and 2003).Did rocks in space hit these craft? Are rocks in space causing the anomalous accelerations of pioneer and galileo? Was the crater seen close to Beagle caused by Beagle or by a rock that hit beagle?
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