|dc.contributor.author||Ozeke, Louis G.
Mann, Ian R.
Murphy, Kyle R.
Rae, I. Jonathan
Milling, David K.
Elkington, Scot R.
Chan, Anthony A.
Singer, Howard J.
Ozeke, Louis G., Mann, Ian R., Murphy, Kyle R., et al.. "ULF wave derived radiation belt radial diffusion coefficients." Journal of Geophysical Research, 117, (2012) A04222. http://dx.doi.org/10.1029/2011JA017463.
Waves in the ultra-low-frequency (ULF) band have frequencies which can be drift
resonant with electrons in the outer radiation belt, suggesting the potential for strong
interactions and enhanced radial diffusion. Previous radial diffusion coefficient models
such as those presented by Brautigam and Albert (2000) have typically used semiempirical
representations for both the ULF wave’s electric and magnetic field power spectral
densities (PSD) in space in the magnetic equatorial plane. In contrast, here we use
ground- and space-based observations of ULF wave power to characterize the electric and
magnetic diffusion coefficients. Expressions for the electric field power spectral
densities are derived from ground-based magnetometer measurements of the magnetic field
PSD, and in situ AMPTE and GOES spacecraft measurements are used to derive
expressions for the compressional magnetic field PSD as functions of Kp, solar wind
speed, and L-shell. Magnetic PSD results measured on the ground are mapped along the
field line to give the electric field PSD in the equatorial plane assuming a guided
Alfvén wave solution and a thin sheet ionosphere. The ULF wave PSDs are then used to
derive a set of new ULF-wave driven diffusion coefficients. These new diffusion
coefficients are compared to estimates of the electric and magnetic field diffusion
coefficients made by Brautigam and Albert (2000) and Brautigam et al. (2005).
Significantly, our results, derived explicitly from ULF wave observations, indicate that
electric field diffusion is much more important than magnetic field diffusion in the
transport and energization of the radiation belt electrons.
ULF wave derived radiation belt radial diffusion coefficients
National Aeronautics and Space Administration
Journal of Geophysical Research
American Geophysical Union
NNX08AM36G (National Aeronautics and Space Administration)
NNX10AL02G (National Aeronautics and Space Administration)