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How are solar particle events predicted? And related to flares/CMEs?

  1. Aug 24, 2014 #1
    Hello everyone,

    I'm new here. I'm a space engineering student and every time I learn something 1000 new questions come to my mind (as usual with science!). Most of my education was from an industrial (practical) point of view, so I feel very, very curious about the science behind the technique. (And I want to be the kind of engineer who understands science rather than applying it blindly). Ok, enough intro, let's go to the question.

    What I know: SPEs are mostly protons at several hundred MeV, can cause a dose-equivalent of a few Sv in a matter of hours, but relatively easy to shield. Usually a small storm shelter is designed in a manned spacecraft. The space agency can predict such events, but "how" is not the industry's business :-/ Anyway a radiation detector shall be included in case the prediction fails or communications are impossible.

    What I've searched: Read several articles around the internet during my education, now searched the forum before posting and there were several threads. The most useful links I found there are this and this.

    What remains unanswered/I'd like to know:

    1) How do scientists predict SPEs? Is it magnetic reconnection in the Sun's magnetic field?

    2) How do SPEs relate to flares and coronal mass ejections (CME), do they always cause SPEs? Sometimes?

    3) How much proton radiation (in Gy or Sv) can a CME cause? Is it small? If not, why was I only taught about SPEs if CMEs are also dangerous? (Also, not sure I fully understand the difference between an SPE and a CME).

    Of course, as I'm willing to learn, I will greatly appreciate links to articles for further reading.

  2. jcsd
  3. Aug 24, 2014 #2


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    hi there
    welcome top PF :smile:

    the sun is monitored 24/7 by various ground and space based observatories
    SOHO used to be one spacecraft in solar orbit between the orbits of Earth and Venus. It had 24/7 visibility of the sun. it was replaced just a few yrs ago by SDO ( Solar dynamics Observatory). They gave great early warning of approaching SPE's and CME's

    Solar astronomers keep an eye on sunspots and filaments to determine their changing complexity which can lead to flares, CME's and proton events. The occurrence of these events can be observed on the sun and by estimating their strength, their velocities/travel times can be calculated

    Solar flares quite dangerous to astronauts because of the emission of intense X-rays
    SPE's also because of the intense emission of charged particles ( protons and Ions - cosmic rays)
    CME's are more likened to a plasma state and are of much lower energies

    They are all related

    CME sources are commonly from or close to flare sites. Many CME's are also produced by "disappearing filaments" ( a filament that breaks up and gets blasted out into space)
    SPE's are produced by strong CME's.

    I'm not sure of the radiation levels ... something I haven't read about

    That first paper answers most of your queries :)
    There is one weird thing in there tho ... Table 3 where it was talking about Proton velocities

    The last line has to be a typo error surely ??

    for 1GeV protons a velocity of 0.875c but gets here in 1.2 minutes ????
    so its only going 87% the speed of light but can get here faster than light ?
    remember it takes light ~ 4.25 minutes to get from sun to earth

    I haven't checked the figures for the other velocities :wink:

    I have been an amateur solar astronomer since the early 1970's. It can be quite exciting at times

    Last edited: Aug 24, 2014
  4. Aug 26, 2014 #3


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    ohhh I typo'ed

    should have been
    ..... remember it takes light ~ 8.25 minutes to get from sun to earth.....

  5. Aug 26, 2014 #4
    I was assuming your photons are travelling in an Alcubierre drive :p

    Thanks for the awesome explanation.
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