Total Ionospheric Conductance: Summation of Sources

Conductivity of the ionosphere allows the complex system of
magnetospheric currents to flow through. Conductivity is governed by
several factors including electron density and temperature, whose
influence is highly dynamic during geomagnetic storm events. Thus, it is
a crucial parameter that must be determined for space weather modeling
to specify the coupling between the magnetosphere, ionosphere and
thermosphere systems. Major sources of ionospheric conductivity are
solar EUV and particle precipitation which includes Diffuse (Diff.),
Monoenergetic (ME) and Broadband (BB) precipitations. Conductance Σ is
the height integrated version of conductivity. Empirically, total
ionospheric conductance (Hall and Pedersen) is known to be the root sum
square of individual conductance terms [Wallis and Budzinski, 1981],
considering that conductivity resulting from different processes are not
linearly additive and corresponding ionization rates shall be added at
each altitude and then integrated over the desired altitude range. With
the inclusion of the less energetic broadband precipitation that was
found to cause ionization in the bottom-side F region, the expression
for the total ionospheric conductance was modified by the linear
addition of the contribution of the broadband precipitation to the total
Hall and Pedersen conductance[Zhang et al., 2015].In this study,
using a 3-dimensional global physics based model GITM (Global Ionosphere
Thermosphere Model), the validity of this combination of vector and
linear addition of individual source terms to the total ionospheric
conductance is examined and the more accurate expression for the
summation of sources contributing to the total conductance is
quantified. GITM is employed to calculate the Hall and Pedersen
conductance using the average energy, potential and energy flux for each
of the sources of conductance. Several scenarios are simulated where the
different sources of precipitation are paired with solar EUV radiation,
and the total conductance is obtained. Linear and vector summation of
conductance resulting from combinations of sources and individual
sources indicate that the contribution of broadband precipitation to the
total conductance also follows vector addition. To quantify the result
that the total conductance is the vector sum of individual sources,
error histograms are plotted and a set of metrics including RMSE, mean
error, standard deviation, correlation coefficient and fractional error
are enumerated for both linear and vector summation of individual
sources to produce the total conductance.