Robust Statistical Techniques for Operational Maintenance of the 10.7 cm
Solar Radio Flux
Abstract
The F10.7 solar radio flux is a critical quantity for operational space
weather nowcasting and forecasting, where it is routinely used as a
driver for coupled atmospheric models to estimate a variety of
important quantities such as the neutral atmospheric density. Although
there have been several successful developments in the way of
parametric modeling to ensure F10.7 coverage during outages (often
using the sunspot number or radio flux observations at neighboring
wavelengths), these developments refrained from employing
comprehensive cross-validation schemes to ensure model generalizability,
and can stand to benefit from recently-developed techniques for
modeling nonlinear phenomena. We present an approach that uses Feature
Ordering by Conditional Independence (FOCI) to identify favorable
surrogates for the F10.7 index through a series of distance
computations, and combines this with modeling of F10.7 with linear
models and Generalized Additive Models (GAM). We find that this
approach offers notable improvements in reconstructing F10.7 over gaps
of various lengths, with GAMs yielding mean error of ∼2.7%,
compared to polynomial methods that yield mean errors of
∼3.1%. We additionally demonstrate the effect of
reconstruction error on neutral densities modeled by the NRLMSISE2.0
thermosphere model.