Results 1 to 12 of 12

Thread: Increased Radiation from Loss of Earth's Magnetic Field?

  1. #1
    Join Date
    Jan 2008
    Posts
    98

    Increased Radiation from Loss of Earth's Magnetic Field?

    How much would radiation levels increase on Earth if Earth's magnetic field were removed? Would any life* at all be affected by the increased radiation?

    I have encountered claims that life would not exist if it were not for Earth's magnetic field because of solar radiation, but I thought that the atmosphere was the primary mechanism for protecting the surface from ionizing radiation from Sol as well as cosmic rays. I know that in low Earth orbit that the magnetosphere has gives some residual protection against ionizing radiation, though my understanding is that there is still danger from the increased radiation levels that solar flares generate.

    If I want to be really generous to the sources that claim life would not exist if Earth did not have a magnetic field, I could take in to account the hypothesis that without a magnetic field the solar wind could over tens of millions of years slowly erode away the atmosphere, and thus life would not exist because of the lack of atmosphere. But it would take an extreme generosity to grant this to some of the television programs and planetarium presentations that I have seen. I know of this hypothesis and I still immediately took their claim to mean that life would die from increased radiation if Earth lost its magnetic field today. Perhaps it would eventually from the slowly decreasing atmosphere over tens of millions of years, but it would not happen within a few thousand years.

    *I am not including effects of the elimination of the magnetic field itself: magnetotactic bacteria would obviously be affected by the loss of the magnetic field directly. Also some insects and birds are thought, though not proven, to be magnetosensitive; and I suppose that this disruption of their behavior could indirectly affect plants; but again these effects follow from the loss of the magnetic field, but not from any increased radiation due to the loss of the magnetic field.
    Last edited by fagricipni; 2015-Oct-17 at 07:44 PM.

  2. #2
    Join Date
    Apr 2007
    Location
    Nowhere (middle)
    Posts
    38,888
    Earth regularly loses and regains its magnetic field during each geomagnetic reversal every half-million or so years. Gaps between the polarities last a few thousand years, during which the magnetic field of Earth is weak enough that it provides little or no protection from solar particles.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  3. #3
    Join Date
    May 2007
    Posts
    1,594
    The claim that life would not exist without the magnetic field and atmosphere would erode away in tens of millions of years is very much false considering Venus has a super-dense atmosphere without a magnetic field and according to newest evidence, Earth actually lacked a magnetic field for most of its existence and had a totally liquid core:

    http://www.iflscience.com/physics/sc...ths-inner-core

    The age of the inner core is 1-1.5 billion years. Oldest life dates back to 3.8 billion years ago. So life did actually live 2.8-2.3 billion years on a planet without a magnetic field. The main reason why Mars has lost most of its atmosphere is the low mass of it - only 0.1x of Earth.

    It should be said through that the birth of Earth's magnetic field coincides with the rise of complex multicellular life - but then, that time also registered the rise of free oxygen https://en.wikipedia.org/wiki/Great_...tion-atm-2.svg , so multicellular life might have sprung up even on a non-magnetic Earth. It might have originated nevertheless, but existence on land would be harsh. If Earth lost a magnetic field overnight, it would not be as bad as the Precambrian conditions, given Earth at that time lacked an ozone layer as well, but cancer rates would probably go up. It would be unwise to go outside during coronal activity. It wouldn't be like the Core (the awful movie where solar microwaves melt the Golden Gate bridge and they nuke the inner core), you would not feel anything, but you would feel the tumors from taking a walk in the middle of a solar storm.

    It should be said that magnetic field only really plays a role in deflecting charged particle radiation. It does nothing to stop X-rays, gamma, or UV. Gamma and X-rays are stopped simply by impacting our dense atmosphere (meaning even in the Precambrian there was a certain protection) while UV is stopped by the ozone layer. Ozone layer forms naturally when UV strikes free oxygen, which means it started to exist when free oxygen started to be present in our atmosphere in major quantities.

    A planet with a similiar history and size to Earth, but one that never developed a magnetic field would probably have a different evolutionary development of organisms. On such a planet, photosynthesis would eventually produce major quantities of free oxygen and an ozone layer. So it would be protected against most radiation, but not charged particles. Local life might evolve interesting shelter or hiding behaviors against solar storms, similiar to what you might find on habitable planets of young red dwarfs with flare activity.

    The weirdest thing is, history of Mars in this regard is pretty much the opposite of Earth. It had a strong magnetic field during the first 500 million years of its existence while Earth had none until 1-1.5 billion years ago, but Martian magnetism quickly died while Earth's sprung up relatively geologically recently.
    Last edited by m1omg; 2015-Oct-18 at 12:11 AM.

  4. #4
    Join Date
    Jan 2008
    Posts
    98
    I haven't thought of The Core in years, I read the review of The Core at Bad Astronomy; I think I saw some advertising for the movie as well.

    I was not thinking of The Core; I was thinking of what were supposed to be scientific fact programs on television and in one case at the planetarium. Now I know the quality of scientific programs on television has gone into the crapper -- I mean The Weather Channel called jets from super-massive black holes "space tornadoes" --, but I still had to wonder if there were any truth to these claims.

    I know that eliminating the magnetic field would not cause changes in the purely electromagnetic forms of radiation. Also as far as feeling anything, humans can get a fatal dose of ionizing radiation without perceiving a thing and only later have symptoms of radiation exposure.

    I would have thought that at worst (as far as things within the biosphere*), that there might be a detectable increase in natural background radiation, but that such an increase would not be something worth worrying about.

    *This excludes anything above about 12 km.

  5. #5
    Join Date
    May 2007
    Posts
    1,594
    To be fair, the increase of cancer rates is mostly my guess. And thinking about Mars and Earth, their magnetic history actually makes perfect sense - Earth lacked a magnetic field for the first ~3 billion years of its history, because the core was too hot to solidify at the center. Mars was "born" with a colder core to start with, so it was already solid at the center, but liquid on the outside, so it had a magnetic field earlier, but it quickly stopped as it all solidified while Earth's core was hot and energetic and only "recently" (a billion years ago) reached the "sweet spot" for a magnetic field. I might be wrong when it comes to the Martian core through. It should be said, due to the gravity, Mars would have lost much of its atmosphere even with a magnetic field anyways, even if maybe a bit less and the pressure maybe could have been slighly above the triple point of water as opposed to slightly below it.

    Honestly, pop-sci programmes make me angry. There is just so much simplification and misconceptions. Also, many of these programs make the impression that Earth is a "fine-tuned" planet, disregarding the fact it was quite different in the past (for example, I think Sagan once said our atmosphere could have contained slight amounts of ammonia, a noxious, toxic gas for humans as late as Early Cambrian, which means trilobites might have lived on a planet that had a toxic atmosphere for us).
    Last edited by m1omg; 2015-Oct-18 at 11:23 AM.

  6. #6
    Join Date
    Jun 2007
    Posts
    6,073
    I recall reading about searches for any signals in the biological fossil record that match up with those in the magnetic fossil record, specifically to determine if the loss of the magnetic field had any effect. Those searches came up empty. Granted, there's room for effects too subtle to show up in the fossil record, but it clearly isn't a major catastrophe for life on Earth. And it isn't something that just happens every once in a while, either: https://upload.wikimedia.org/wikiped...e_cenozoic.png

  7. #7
    Join Date
    Jan 2008
    Posts
    98
    Quote Originally Posted by m1omg View Post
    To be fair, the increase of cancer rates is mostly my guess.
    I wouldn't be surprised to find that it an increase could be detected with statistical methods on large populations, but on an individual level I would not expect it to be a increase that would be a cause for legitimate particular concern. Of course, it would be nice if we could get some numbers.

    Quote Originally Posted by m1omg View Post
    Honestly, pop-sci programmes make me angry. There is just so much simplification and misconceptions.
    It seems to me things were better when I was growing up in the 1980's and science documentaries were practically limited to government-funded television stations (PBS [note that I am from the US]), but what really surprises me is seeing these problems in a program being shown in a university-run planetarium even if the program is just meant for the general public. Though, I've seen other problems besides this one: one show at the same planetarium showed the ISS traveling though the aurora. I have come to expect problems with television programs in recent years, though; it surprises me to see even planetarium shows succumbing to the same fate.

  8. #8
    Join Date
    Jan 2008
    Posts
    98
    Some are comparing conditions during a magnetic field reversal to normal conditions, but fail to note that a magnetic field reversal event is not the same as having no magnetic field to speak of. Though, it does make a point of absence of evidence, if there were effects during a magnetic field reversal, one would expect at least as severe effects if the magnetic field just went away.

  9. #9
    Join Date
    Jun 2007
    Posts
    6,073
    Even Venus, Mars, and the Moon don't have "no magnetic field to speak of", they just lack a strong overall field. During a magnetic reversal, Earth's magnetic field does become much weaker, and the strength even as a dipole varies widely. Also, a magnetic field does not hinder particle motion parallel to the field, and a disorganized field would not be nearly as effective at shielding, and would actually frequently focus charged particles at a particular region. The presence of the atmosphere means this would mainly result in an interesting auroral display at night.

  10. #10
    Join Date
    Feb 2009
    Posts
    2,291
    Magnetic field already does not protect magnetic poles from radiation.

  11. #11
    Join Date
    Jul 2006
    Posts
    12,235
    Fagricipni, welcome to the boards.

    m1omg,

    interestingly Mars lost the majority of it's atmosphere due to having an erratic magnetic field. According to paper I was linked to here it seems an erratic magnetic field is worse than not having one.

    This works out because instead of a steady loss to the solar wind, a partial, continent sized field, corrals large bites of atmospheric gases in bubbles of charged particles and these get blown off in large wads.
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

  12. #12
    Join Date
    Feb 2021
    Posts
    2
    If, at some earlier time, the earthís core iron was above the curie temperature, the rotation through the sunís field lines would induce currents in the core iron. Near side (to the sun) would cause North-South currents in one direction and the revers for the far side. As some of the outer iron cooled and solidified, the induced magnetic field orientation would get fixed. Since the core sphere is not uniform, the liquid core flow patterns would be slowly migrating due to the eventual development of external contours, somewhat like an inside-out river bed. If a particular localized region developed an east-west flow, or an eddy, where the net induce field was zero, as it cooled and froze, the measured field strength at the planetís surface might be weakened. If the cooling persisted until the whole core was solid, would the very innermost iron shunt the magnetic field enough to make measurement at the surface nearly zero?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •