Reconstructing Equatorial Electron Flux Measurements from
low-Earth-orbit: A Conjunction Based Framework
Abstract
We present an artificial neural network (ANN) model that reconstructs
> 30 keV electron flux measurements near the geomagnetic
equator from low-Earth-orbit (LEO) observations, exploiting the global
coherent nature of the high-energy trapped electrons that constitute the
radiation belts. To provide training data, we analyze magnetic
conjunctions between one of National Oceanic and Atmospheric
Administration’s (NOAA’s) Polar Orbiting Environmental Satellites (POES)
and National Aeronautics and Space Administration’s (NASA’s) Van Allen
Probes. These conjunctions occur when the satellites are connected along
the same magnetic field line and allow for a direct comparison of
satellites’ electron flux measurements for one integral energy channel,
> 30 keV and over 64,000 such conjunctions have been
identified. For each conjunction, we fit the equatorial pitch angle
distribution (PAD) parameterized by the function JD = C·sinNα. The
resulting conjunction dataset contains the POES electron flux
measurements, L and MLT coordinates, geomagnetic activity AE index, and
C and N coefficients from the PAD fit for each conjunction. We test
combinations of input variables from the conjunction dataset and achieve
the best model performance when we use all the input variables during
training. We present our model’s prediction for the out-of-sample data
that agrees well with observations, R2 > 0.80. We
demonstrate the ability to nowcast and reconstruct equatorial electron
flux measurements from LEO without the need for an in-situ equatorial
satellite. The model can be expanded to include existing LEO data and
has the potential to be used as a basis of future radiation-belt
monitoring LEO constellations.