POMME is a scientific main field model representing the geomagnetic field in the
region from the Earth's surface to an altitude of a couple of thousand
kilometers. The time variations of the internal field are given by a piece-wise
of the spherical harmonic (Gauss) coefficients of the magnetic potential.
Pomme-8 was produced from
vector magnetic measurements from July 2000 up to September 2010 and
total field measurements from January 2010
to January 2013. It has the same parametrization of the magnetospheric field as POMME-6 and POMME-7.
The model is more accurate if the present state of the magnetosphere
is provided as an input in the form of magnetic indices.
The magnetospheric ring current is tracked by
(the default values for Est and Ist are both 0.0).
The Interplanetary magnetic field and F10.7 index are available from
OMNIWEB (default IMF-BY = 0.0).
The merging electric field Em is a parameter derived from the solar wind
Em (in mV/m) = V * BT * sin(beta/2.0) * sin(beta/2.0) / 1000,
where V is the solar wind flow speed in km/s, BT is the strength of the
interplanetary magnetic field perpendicular to the Sun-Earth axis and
beta is the clock angle acos(Bz/BT). A default value of 0.5 mV/m
is to be used if the value of Em is not known.
The model uses the 81-day average value of the F10.7 solar flux,
20 months prior to the given date, to track changes in the ring current base line
with solar cycle progression (F10.7 default value is 120.0).