Astrophysics and Space Science

, Volume 31, Issue 1, pp 37–42 | Cite as

Particle lifetimes in strong diffusion

  • Michael Schulz


The mean lifetime τ of a particle distribution, driven to isotropy by intense pitch-angle diffusion, is calculated by analytical means for conditions applicable to the Earth's magnetosphere. The resulting algebraic expressions reduce to τ≈[64La/35 c 2 (1−η)] in the limit of a small equatorial loss cone (half-angle α c ), wherev is the particle speed,L is the magnetic shell parameter,a is the radius of the Earth, and η is the particle albedo from the atmosphere at either foot of the field line. Distinction is made in the full expressions for τ between complete isotropy (caused by strong pitch-angle diffusion all along the field line) and incomplete isotropy (caused by strong diffusion that is localized at the magnetic equator) over the upward hemisphere in velocity space.


Isotropy Field Line Particle Distribution Velocity Space Algebraic Expression 
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Copyright information

© D. Reidel Publishing Company 1974

Authors and Affiliations

  • Michael Schulz
    • 1
  1. 1.Space Physics LaboratoryThe Aerospace CorporationEl SegundoUSA

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