European Space Agency

European Space Agency

Royal Belgian Institute for Aeronomy

Royal Belgian Institute for Aeronomy

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make_lstar1 - Compute magnetic coordinates

subroutine  make_lstar1(ntime, kext, options, sysaxes, year, doy, ut, xin1, xin2, xin3, maginput, lm, lstar, blocal, bmin, xj, mlt)
Parameters:

  • ntime [integer4,in] :: number of locations

  • kext [integer4,in] :: external magnetic field model number

  • options (5) [integer4,in] :: control options for calculation

  • sysaxes [integer4,in] :: coordinate system index see sysaxes

  • year (ntime) [integer4,in] :: years for locations

  • doy (ntime) [integer4,in] :: day of year for locations

  • ut (ntime) [real8,in] :: universal time [s] for locations

  • xin1 (ntime) [real8,in] :: 1st coordinate according to sysaxes

  • xin2 (ntime) [real8,in] :: 2nd coordinate according to sysaxes

  • xin3 (ntime) [real8,in] :: 3rd coordinate according to sysaxes

  • maginput (25,ntime) [real8,in] :: magnetic field inputs

  • lm (ntime) [real8,out] :: McIlwain L shell [Earth radii]

  • lstar (ntime) [real8,out] :: Roederer Lstar [Earth radii]

  • blocal (ntime) [real8,out] :: magnetic field magnitude [nT]

  • bmin (ntime) [real8,out] :: mirror point magnetic field magnitude [nT]

  • xj (ntime) [real8,out] :: I, related to 2nd adiabatic invariant [Earth radii]

  • mlt (ntime) [real8,out] :: magnetic local time [hours]

Description

For each coordinate specified by (year, doy, ut, xin1, xin2, xin3) the magnetic field parameters are returned:

  • McIlwain L [Earth Radii]

  • Roederer L* [Earth Radii]

  • local magnetic field magnitude [nT]

  • mirror point magnetic field magnitude [nT]

  • I [Earth radii]

  • Magnetic Local Time [hours]

IRBEM subroutine documentation

IRBEM Common argument definitions

Control Options

  1. L* / \(\phi\) calculation:

    • 0 - don’t compute L* or \(\phi\);

    • 1 - compute L*;

    • 2 - compute \(\phi\)

  2. IGRF field (re)initialisation.

    • 0 - initialise IGRF field once per year;

    • n is the frequency (in days) starting on January 1st of each year (i.e. if options(2nd element)=15 then IGRF will be updated on the following days of the year: 1, 15, 30, 45 …)

  3. L* field line resolution [0 to 9], where 0 is the recomended value to ensure a good ratio precision/computation time (i.e. an error of ~2% at L=6). The higher the value the better will be the precision, the longer will be the computing time. Generally there is not much improvement for values larger than 4. Note that this parameter defines the integration step (θ) along the field line such as dθ=(π)/(720*[options(3rd element)+1])

  4. L* drift shell resolution [0 to 9]. The higher the value the better will be the precision, the longer will be the computing time. It is recommended to use 0 (usually sufficient) unless L* is not computed on a LEO orbit. For LEO orbit higher values are recommended. Note that this parameter defines the integration step (φ) along the drift shell such as dφ=(2π)/(25*[options(4th element)+1])

  5. internal magnetic field model selection (default is set to IGRF)

    • 0 = IGRF

    • 1 = Eccentric tilted dipole

    • 2 = Jensen&Cain 1960

    • 3 = GSFC 12/66 updated to 1970

    • 4 = User own magnetic field. The library then called a routine which has to be written by the user myOwnMagField(xGEO,Bxint) where inputs are xGEO a double array of 3 elements (x,y,z) containing geographic cartesian coordinates in Re and outputs are Bxint a double array of 3 elements (Bx,By,Bz) containing magnetic field components in geographic cartesian coordinates in nT

    • 5 = Centered dipole

UNILIB/tags/v3.02