Linear prediction filter analysis of relativistic electron properties at 6.6 R_E

Abstract

Electrons with energies >500 keV in the Earth's outer magnetosphere exhibit very hard energy spectra and highly variable absolute intensities. The fluxes often show a strong 27‐day periodicity which is related to recurrent solar wind stream variations at 1 AU. We have used available solar wind speed data as well as continuous geomagnetic indices such as Kp and AE in order to characterize the relationship of relativistic electrons to these geophysical parameters. The present analysis emphasizes data taken in 1982–1985 and employs electron measurements from 3 to 40 MeV at geostationary orbit along with geomagnetic data from the National Geophysical Data Center CD ROM. The method of linear prediction filter (LPF) analysis is used to characterize and predict the general relationship between solar wind or geomagnetic indices as input time series and electron properties as the output time series. Filters are found that generally decrease strongly at zero lag time and then peak strongly at lags of 2–3 days. Cross‐covariance analyses show strong correlative peaks between electron fluxes and geomagnetic parameters at multiples of 13 and 27 days. The present analysis allows enhanced understanding of the relativistic electron behavior on both short and long time scales and permits improved prediction of both high‐altitude spacecraft operational environments and magnetosphere‐atmosphere coupling relationships.

Online NARMAX model for electron fluxes at GEO

“…The CC and the PE show that the models are accurate; however, since a high accuracy is relative, the > 2 MeV electron flux model was compared to another online electron flux model. This model was the NOAA-SWPC model based on the work by Baker et al (1990). This was the final hurdle that the model needed to pass before it was deemed suitable for real-time online implementation.…”

“…The forecast is calculated from the LPF model by Baker et al (1990), which, as described in Sect. 1, employs the solar wind velocity, Kp index and AE index.…”

“…An alternative approach to developing a model based on first principles is to deduce a forecasting model for the radiation belt electron fluxes directly from data (Baker et al, 1990;Freeman et al, 1998;Wei et al, 2011). Baker et al (1990) employed linear prediction filters (LPFs) to characterize and to predict the 3-40 MeV electron measurements using solar wind velocity and geomagnetic indices such as Kp and AE as inputs.…”

“…Baker et al (1990) employed linear prediction filters (LPFs) to characterize and to predict the 3-40 MeV electron measurements using solar wind velocity and geomagnetic indices such as Kp and AE as inputs. The use of LPFs allowed the authors to analyse how the inputs influence the output, reporting a 27-day periodicity and a peak lag at 2-3 days.…”

Space Weather Forecasting: A Grand Challenge

“…Using this empirical relationship, models (e.g., Baker et al, 1990) have been developed to forecast the enhancement of the electrons at geosynchronous orbit.…”