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Contamination in electron observations of the silicon detector on board Cluster/RAPID/IES instrument in Earth's radiation belts and ring current

Kronberg E. A., M. V. Rashev, P. W. Daly, Y. Y. Shprits, D. L. Turner, A. Y. Drozdov, M. Dobynde, A. C. Kellerman, T. A. Fritz, V. Pierrard, K. Borremans, B. Klecker, R. Friedel, (2016), Contamination in electron observations of the silicon detector on board Cluster/RAPID/IES instrument in Earth’s radiation belts and ring current, J. Space Weather Space Clim., 14, 449-462, doi:10.1002/2016SW001369

Abstract

Abstract Since more than 15 years, the Cluster mission passes through Earth's radiation belts at least once every 2 days for several hours, measuring the electron intensity at energies from 30 to 400 keV. These data have previously been considered not usable due to contamination caused by penetrating energetic particles (protons at >100 keV and electrons at >400 keV). In this study, we assess the level of distortion of energetic electron spectra from the Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector, determining the efficiency of its shielding. We base our assessment on the analysis of experimental data and a radiation transport code (Geant4). In simulations, we use the incident particle energy distribution of the AE9/AP9 radiation belt models. We identify the Roederer L values, L⋆, and energy channels that should be used with caution: at 3≤L⋆≤4, all energy channels (40–400 keV) are contaminated by protons (≃230 to 630 keV and >600 MeV); at L⋆≃1 and 4–6, the energy channels at 95–400 keV are contaminated by high-energy electrons (>400 keV). Comparison of the data with electron and proton observations from RBSP/MagEIS indicates that the subtraction of proton fluxes at energies ≃ 230–630 keV from the IES electron data adequately removes the proton contamination. We demonstrate the usefulness of the corrected data for scientific applications.

Authors (sorted by name)

Borremans Daly Dobynde Drozdov Friedel Fritz Kellerman Klecker Kronberg Pierrard Rashev Shprits Turner

Journal / Conference

J. Space Weather Space Clim.

Acknowledgments

We would like to thank Chris Perry and Patrick Cruce for useful discussions. We acknowledge the Deutsches Zentrum für Luft und Raumfahrt (DLR) for supporting the RAPID instrument at MPS under grant 50 OC 1401. The Cluster data can be found at CSA Archive: http://www.cosmos.esa.int/web/csa/. We acknowledge RBSP ECT team for the MagEIS data. They can be found at http://www.rbsp-ect.lanl.gov/. The NIST tables are available at http://physics.nist.gov/PhysRefData/Star/Text/ESTAR.html. The SRIM software was taken from http://www.srim.org/#SRIM. The AE9/AP9/SPM software is provided under the link https://www.vdl.afrl.af.mil/programs/ae9ap9. For calculations we used SciPy software package version 0.16.1 available at http://www.scipy.org/.

Grants

50 OC 1401

Bibtex

@article{doi:10.1002/2016SW001369,
author = {Kronberg, E.A. and Rashev, M.V. and Daly, P.W. and Shprits, Y.Y. and Turner, D.L. and Drozdov, A.Y. and Dobynde, M. and Kellerman, A.C. and Fritz, T.A. and Pierrard, V. and Borremans, K. and Klecker, B. and Friedel, R.},
title = {Contamination in electron observations of the silicon detector on board Cluster/RAPID/IES instrument in Earth's radiation belts and ring current},
year={2016},
journal = {Space Weather},
volume = {14},
number = {6},
pages = {449-462},
keywords = {silicon detector, radiation belts, contamination},
doi = {10.1002/2016SW001369},
url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2016SW001369},
eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016SW001369},
abstract = {Abstract Since more than 15 years, the Cluster mission passes through Earth's radiation belts at least once every 2 days for several hours, measuring the electron intensity at energies from 30 to 400 keV. These data have previously been considered not usable due to contamination caused by penetrating energetic particles (protons at >100 keV and electrons at >400 keV). In this study, we assess the level of distortion of energetic electron spectra from the Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector, determining the efficiency of its shielding. We base our assessment on the analysis of experimental data and a radiation transport code (Geant4). In simulations, we use the incident particle energy distribution of the AE9/AP9 radiation belt models. We identify the Roederer L values, L⋆, and energy channels that should be used with caution: at 3≤L⋆≤4, all energy channels (40–400 keV) are contaminated by protons (≃230 to 630 keV and >600 MeV); at L⋆≃1 and 4–6, the energy channels at 95–400 keV are contaminated by high-energy electrons (>400 keV). Comparison of the data with electron and proton observations from RBSP/MagEIS indicates that the subtraction of proton fluxes at energies ≃ 230–630 keV from the IES electron data adequately removes the proton contamination. We demonstrate the usefulness of the corrected data for scientific applications.}
}