Home » Kellerman et al. 2015

Characterization of the energy-dependent response of riometer absorption

Kellerman A. C., Y. Y. Shprits, R. A. Makarevich, E. Spanswick, E. Donovan, G. Reeves, (2015), Characterization of the energy-dependent response of riometer absorption, J. of Geophys. Res. [Space Physics], 120, 615-631, doi:10.1002/2014JA020027

Abstract

AbstractGround-based riometers provide an inexpensive means to continuously remote sense the precipitation of electrons in the dynamic auroral region of Earth's ionosphere. The energy-dependent relationship between riometer absorption and precipitating electrons is thus of great importance for understanding the loss of electrons from the Earth's magnetosphere. In this study, statistical and event-based analyses are applied to determine the energy of electrons to which riometers chiefly respond. Time-lagged correlation analysis of trapped to precipitating fluxes shows that daily averaged absorption best correlates with ∼60 keV trapped electron flux at zero-time lag, although large variability is observed across different phases of the solar cycle. High-time resolution statistical cross-correlation analysis between signatures observed by riometer stations, and assuming electron motion due to gradient and curvature drift, results in inferred energies of 10–100 keV, with a clear maximum in occurrence for 40–60 keV electrons. One event is considered in detail utilizing riometer absorption signatures obtained from several stations. The mean inferred energies for the initial rise time and peak of the absorption after correction for electric field effects were ∼70 keV and ∼60 keV, respectively. The analyses presented provide a means to characterize the energy of electrons to which riometers are responding in both a statistical sense and during the evolution of individual events.

Authors (sorted by name)

Donovan Kellerman Makarevich Reeves Shprits Spanswick

Journal / Conference

Journal Of Geophysical Research (Space Physics)

Acknowledgments

This research was supported by NSF CEDAR grant AGS‐1243183 and UC Lab Fees Research Program grant 116720. The authors would like to thank Reeves et al. [2011] for providing the long‐term daily averaged LANL/GEO data set. The OMNI data are available at ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/omni/omni2.txt, the riometer data are available at ftp://aurora.phys.ucalgary.ca/data/riometer/. This work used computational and storage services associated with the Hoffman2 Shared Cluster provided by UCLA Institute for Digital Research and Education's Research Technology Group.

Grants

116720 AGS‐1243183

Bibtex

@article{doi:10.1002/2014JA020027,
author = {Kellerman, A. C. and Shprits, Y. Y. and Makarevich, R. A. and Spanswick, E. and Donovan, E. and Reeves, G.},
title = {Characterization of the energy-dependent response of riometer absorption},
journal = {Journal of Geophysical Research: Space Physics},
year={2015},
volume = {120},
number = {1},
pages = {615-631},
keywords = {cosmic noise absorption, riometer, electron precipitation, radiation belts, particle modeling, electron energy, nstuff},
doi = {10.1002/2014JA020027},
url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2014JA020027},
eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JA020027},
abstract = {AbstractGround-based riometers provide an inexpensive means to continuously remote sense the precipitation of electrons in the dynamic auroral region of Earth's ionosphere. The energy-dependent relationship between riometer absorption and precipitating electrons is thus of great importance for understanding the loss of electrons from the Earth's magnetosphere. In this study, statistical and event-based analyses are applied to determine the energy of electrons to which riometers chiefly respond. Time-lagged correlation analysis of trapped to precipitating fluxes shows that daily averaged absorption best correlates with ∼60 keV trapped electron flux at zero-time lag, although large variability is observed across different phases of the solar cycle. High-time resolution statistical cross-correlation analysis between signatures observed by riometer stations, and assuming electron motion due to gradient and curvature drift, results in inferred energies of 10–100 keV, with a clear maximum in occurrence for 40–60 keV electrons. One event is considered in detail utilizing riometer absorption signatures obtained from several stations. The mean inferred energies for the initial rise time and peak of the absorption after correction for electric field effects were ∼70 keV and ∼60 keV, respectively. The analyses presented provide a means to characterize the energy of electrons to which riometers are responding in both a statistical sense and during the evolution of individual events.}
}