Menietti J. D., G. B. Hospodarsky, Y. Y. Shprits, D. A. Gurnett, (2014), Saturn chorus latitudinal variations, J. Geophys. Res. [Space Physics], 119, 4656-4667, doi:10.1002/2014JA019914

Abstract

Abstract The variation of propagation properties of whistler mode chorus as a function of latitude is not well known at Saturn but is important for the calculation of pitch angle diffusion and nonlinear growth of chorus. The Cassini spacecraft has spent a portion of its orbital time in high-inclination orbits, allowing traversal of the magnetic equator at nearly constant L shell for several passes. This is important since chorus is believed to propagate dominantly close to the magnetic field direction. We have investigated the change of wave normal angle, whistler mode magnetic intensity, and ambient magnetic field inhomogeneity as a function of latitude observed by the Radio and Plasma Wave investigation onboard the Cassini instrument. We find that wave normal angles along a nearly constant L shell remain close to field-aligned, except nearest the equator, and whistler mode wave intensity increases from the magnetic equator, according to a power law. The ambient magnetic field shows an inhomogeneity that is lower than Earth's, but there is a lack of drifting-frequency signatures nearest the equator. The bandwidth of the chorus emission can be described by a simple exponential. The bandwidth increases from the equator, peaking a few degrees away in a region of strong nonlinear growth and then decreases at higher latitudes.

Authors (sorted by name)

Gurnett Hospodarsky Menietti Shprits

Journal / Conference

Journal Of Geophysical Research (Space Physics)

Acknowledgments

We wish to thank J. Barnholdt for administrative assistance, J. Chrisinger for help with several figures, and T. Averkamp for assistance with the WNA code. J.D.M. acknowledges support from JPL contract 1415150 and NASA grant NNX11AM36G. Cassini RPWS data are archived in calibrated, full resolution at the NASA Planetary Data System website: http://pds.nasa.gov/ds‐view/pds/viewDataset.jsp?dsid=CO‐V/E/J/S/SS‐RPWS‐3‐RDR‐LRFULL‐V1.0. The calibrated, full resolution WFR data are located at the same site: dsid = CO‐V/E/J/S/SS‐RPWS‐2‐REFDR‐WFRFULL‐V1.0.

Grants

1415150 NNX11AM36G

Bibtex

@article{doi:10.1002/2014JA019914,
author = {Menietti, J. D. and Hospodarsky, G. B. and Shprits, Y. Y. and Gurnett, D. A.},
title = {Saturn chorus latitudinal variations},
journal = {Journal of Geophysical Research: Space Physics},
year = {2014},
volume = {119},
number = {6},
pages = {4656-4667},
keywords = {Parameterization of chorus emission with latitude},
doi = {10.1002/2014JA019914},
url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2014JA019914},
eprint = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JA019914},
abstract = {Abstract The variation of propagation properties of whistler mode chorus as a function of latitude is not well known at Saturn but is important for the calculation of pitch angle diffusion and nonlinear growth of chorus. The Cassini spacecraft has spent a portion of its orbital time in high-inclination orbits, allowing traversal of the magnetic equator at nearly constant L shell for several passes. This is important since chorus is believed to propagate dominantly close to the magnetic field direction. We have investigated the change of wave normal angle, whistler mode magnetic intensity, and ambient magnetic field inhomogeneity as a function of latitude observed by the Radio and Plasma Wave investigation onboard the Cassini instrument. We find that wave normal angles along a nearly constant L shell remain close to field-aligned, except nearest the equator, and whistler mode wave intensity increases from the magnetic equator, according to a power law. The ambient magnetic field shows an inhomogeneity that is lower than Earth's, but there is a lack of drifting-frequency signatures nearest the equator. The bandwidth of the chorus emission can be described by a simple exponential. The bandwidth increases from the equator, peaking a few degrees away in a region of strong nonlinear growth and then decreases at higher latitudes.}
}