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Still confused about solar flares. . .

  1. Jan 26, 2017 #1
    I seek from an SF writing point of view some much-needed clarification about solar flares, in particular their shortwave radiation components. So, given that x-rays, gammas and the like, propagate through space at light-speed - along with the rest of the electromagnetic spectrum - I take it then that this 'pure' radiation precedes, usually by a hefty margin, the charged particles aspect of a given solar flare (clumsily put, but I hope it makes sense). This in turn implies that there can be absolutely NO advance notice given about these incoming radiation emissions. . . yes? no? If the latter, then depending on the strength of these flare-based x-ray emissions (yet another conundrum for me!*) could they alone prove to be fatal for an unsuspecting astronaut, say, doing an EVA in interplanetary space?

    NB. Conscious as I am of having already raised this issue, I'm now presented with a plot scene in which an X-class solar flare engulfs Mars. This strike results in a high number of casulties among the (human) explorers, the primary cause here being radiation sickness. The crucial point for me, though, is this: the resulting death toll does not come from the flare's plasma cloud striking the surface of Mars; rather it's due to an earlier bombardment of intense x-ray emissions (the flare's advance stormtroopers, so to speak) for which there can be no prior warning given. Is this a halfway realistic proposition?

    * Yes, I'm aware that solar flares are measured by their x-ray strength; but the strong impression I get from the literature is that this high-end radiation and the flare's plasma cloud are all one thing, leastways in terms of their overall impact. Yet to me this simply isn't true. . . the various elements that comprise a solar flare are separated in time and space, often hugely so in view of the distances involved. At least that's how it seems to me. I'm just trying to get the science right, that's all.
  2. jcsd
  3. Jan 26, 2017 #2


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    Most energy is released as high-energetic particles, not as electromagnetic radiation. Even an X20 flare without any shielding just leads to something like 1 mSv per minute (averaged over the body). Add shielding (at least a space suit) and consider the short duration of the flares (=short duration of electromagnetic radiation) and the effect gets negligible.

    Divide the number by 2 to 2.8 for Mars due to its larger distance.
  4. Jan 26, 2017 #3
    It might be possible to get advanced warning of a flare by observing activity on the sun itself. But this would be like predicting tornados and storms on Earth - doable but inexact.
  5. Jan 28, 2017 #4
    mfb - many thanks for pointing out the facts about solar flares. I take it then that shielding from cosmic rays and the charged particles coming from the Sun is the real challenge for astronautics, not 'pure' shortwave radiation, like x-rays.

    Algor - yes, I recently came upon a website (Wikipedia?) indicating that advance warning of a flare might be possible, as you suggest. If I remember right the hard electromagnetic radiation associated with solar flares comes in (or may come in) in three distinct phases. It was all pretty theoretical, though, as I recall.
  6. Jan 28, 2017 #5


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    Just a note on advance warnings - there's another way to get them. Since the Sun rotates, it is possible to detect backscatter from increased activity on the far side before the rotation brings it to the near side. In fact, that's exactly what SOHO's SWAN instrument does:
  7. Jan 29, 2017 #6
    An interesting link, I must say. An instance of science fact stealing a march on science fiction?
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