Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Reading my first Astrophys paper

  1. May 28, 2008 #1
    I'm getting a little stuck on terminology, but most of it can be looked up in wikipedia. However, there's one term I'm having trouble with.

    The paper is for a model of micrometeorites entering the atmosphere. It says:

    "Entry velocities ranged between 11.2 and 72 km/sec following a v^-5,394 velocity distribution,"

    What is a "a v^-5,394 velocity distribution" ?
  2. jcsd
  3. May 28, 2008 #2
    That just means that the distribution of micrometeorite velocities between 11.2 and 72 km/s looks like the plot of v^{-5394}.

    i.e. - it falls off really steeply as velocity increases.
  4. May 28, 2008 #3
    Okay, that makes sense. Any idea how I could convince MatLab to make such a matrix for me :)
  5. May 29, 2008 #4
    Ah, what they're describing in the paper isn't a matrix, it's best viewed as a probability density function.

    If you wanted to display it as a probability distribution, you would just plot v^{-5394}, but would need to multiply it by a normalization constant. That constant (using latex formating) will be 1 / (\int_11.2^72 v^{-5394}). That is to say, 1 over the integral of v^{-5394} from 11.2 km/s to 72 km/s.

    Do you need a matrix for some other reason?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook