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Homework Help: Calculate the neutrino flux from the sun

  1. Apr 3, 2010 #1
    1. The problem statement, all variables and given/known data

    Every reaction in the sun has the energy equivalent to 0.03 mp, and generates 2 neutrinos per reaction. Calculate the number of neutrinos per second, and calculate the neutrino flux at Earth.

    Astronomy generally uses the CGS (centimeter gram second) system, so just be aware of that when I do my calculations.

    2. Relevant equations



    3. The attempt at a solution

    nreactions * Ereaction = Luminositysun

    nreactions * mc2 = Luminositysun

    nreactions * (.03 * mp)(3*1010)2 = Luminositysun

    nreactions * (.03 * 1.67*10-24)(3*1010)2 = Luminositysun

    nreactions * (.03 * 1.67*10-24)(3*1010)2 = 3.9*1033

    nreactions * 4.51*10-5 erg = 3.9*1033 erg s-1

    nreactions = 3.9*1033 erg s-1 / 4.51*10-5 erg

    nreactions = 8.67*1037 reactions/s

    nreactions / s * 2 neutrinos / reaction = 1.73*1038 neutrinos

    Nneutrinos / Area = Fneutrino

    Area = 4*pi*R2 [R = 1 AU = 1.5*1013cm]

    Area = 2.83*1027cm2

    So divide Nneutrinos and Area, and I get 6.1*1010 neutrinos/cm2

    I looked online, and found answers which were also approx 6, but were a different order of magnitude. Did I do anything wrong?
     
  2. jcsd
  3. Apr 4, 2010 #2

    ideasrule

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    Your answer's right. Where did you find the values online?
     
  4. Apr 4, 2010 #3
  5. Apr 4, 2010 #4

    ideasrule

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    That link gives 6.296541*10^14 /(m^2*s). Your answer is in /(cm^2*s).
     
  6. Apr 4, 2010 #5

    right right, right you are, thanks
     
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