CRII

Cosmic Ray Induced Ionization: Do-it-yourself kit

Pre-calculated tables of cosmic ray induced ionization (CRII) in units of [ion pairs /g /sec] - see full description in Usoskin and Kovaltsov (JGR, 111, D21206, 2006) and Usoskin, Kovaltsov and Mironova, (JGR, 115, D10302, 2010).

Tables are compressed into a zip-file file. The tables are given in ASCII files with names S_XXXXXX.RES, where XXXXXX stands for the residual atmospheric depth in [0.01 g/cm2] (e.g., S_000010.RES corresponds to 0.1 g/cm2 and S_011000.RES to 110 g/cm2). Each file is organized as follows:

  • First line: values of the modulation potential Phi (see comment below) in MV from 0 to 1500 MV.
  • Following lines give: the geomagnetic cutoff rigidity Pc in GV (first number) followed by CRII for the corresponding values of Pc (raw) and Phi (column).

    • CRII is given as the ionization rate (number of ion pairs per gram of air per second, in order to obtain the ionization rate per cm3 per second, this value should be multiplied by the air density) caused by galactic cosmic rays at given atmospheric height (atmospheric depth corresponding to the file's name as described above), location (via the geomagnetic cutoff rigidity) and time (via the heliospheric modulation of cosmic rays).

    Numerical recipe

    In order to calculate CRII for given values of the atmospheric depth h, geomagnetic cutoff rigidity Pc and the modulation potential Phi, one needs to proceed as follows.
  • (1) open the appropriate file with the name S_XXXXXX.RES;
  • (2) read the value of CRII from the crossing of the appropriate raw (the value of Pc) and column (the value of Phi).
  • (3) If the given values of h, Pc and Phi do not coincide with the grid of the tabulated CRII, an interpolation can be used, since the CRII is quite a smooth function of the parameters. We recommend power-law interpolation but a linear one also can be applied.

    • The user is expected to independently provide the values of Pc and Phi. Updated values of Phi can be found here.

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    Last modified 02.11.2011 by Ilya Usoskin (ilya.usoskin @ oulu.fi)