Hercules A

Hercules A
Radio-Optical View of the Galaxy Hercules A - Many thanks to: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Thursday, September 1, 2016

" Modeling Jovian hectometric attenuation lanes during the Cassini flyby of Jupiter "

I take note of :

Masafumi Imai , Alain Lecacheux , Michel Moncuquet , Fran Bagenal , Charles A. Higgins , Kazumasa Imai , James R. Thieman,  2015 :

"Modeling Jovian hectometric attenuation lanes during the Cassini flyby of Jupiter"



"The Jupiter encounter by the Cassini spacecraft in late 2000 and early 2001 unveiled persistent properties of Jupiter's hectometric (HOM) radiation originating along auroral magnetic field lines in the polar regions. One of the unique properties of the HOM dynamic spectrum, known as attenuation lanes, appears as rotationally modulated, well-defined regions of lowered intensity, flanked by regions of enhancement. These lanes seem to be the result of refraction of radio waves in a high-density medium–either caused by Case (i) enhanced density in the magnetic L-shell connected to Io's orbit or Case (ii) in the Io plasma torus itself or both. In this paper, we investigate the HOM ray paths of 0.5–3.0 MHz emissions with various cone half-angles in the continuous radio longitudes generating at the magnetic L-value equal to 30. We use bi-kappa particle distributions to derive diffusive equilibrium distributions of density in the Io plasma torus. The enhanced density irregularities along the Io flux shell “ribbon” region can be described with a Gaussian density distribution of a maximum density n0 and breadth (half-width of the distribution across the flux shell) sigma. As a result, we found that the interpretation of Case (i) can be accounted for by the attenuation lanes which appear for all cone half-angles, and the reasonable flux shell density n0 is, on top of specific latitude-dependent density from the diffusive equilibrium model, estimated as 100 per cubic cm with the half-width sigma = 5.0 Io radii."