Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsm23a0303s&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #SM23A-0303
Physics
2774 Radiation Belts
Scientific paper
We present results of our recent investigation of the Jovian synchrotron emission based on a particle transport code. The features of the two-dimensional brightness distributions, radio spectra and beaming curves are correlated to the different phenomena driven the dynamics of the electron radiation belts. The adiabatic invariant theory was used for performing this analysis work. The theoretical approach first enabled us to describe the electron radiation belts by modeling the interactions between high-energy trapped particles and plasmas, neutrals, moons, dust and magnetic field. Then radio observations were used to discuss the computed particle distributions in the inner magnetosphere of Jupiter. The simulated brightness mappings were compared with VLA observations made at two wavelengths (20 and 6 cm). The beaming curve comparisons at 13-cm wavelength were performed for different epochs in order to evaluate the dependence of the model to the geometric factor De. The computed radio spectra were discussed with measurements made in the [0.5-20] GHz radio band. The simulation results match the different remote observations very well and thus allowed us to study the phenomenology of the Jovian synchrotron radio emission. The analysis of the Jovian synchrotron emission demonstrates that during the inward particle transport, local losses associated with the Jovian moons set the extension and intensity of the synchrotron radiation along the magnetic equator. Close to the planet, trapped electrons suffer from the interactions with dust and magnetic field, resulting in the transport of particles toward the high latitudes. The quantity of particles transported away from the equator is sufficient to produce the measurable secondary radio emissions. The simulations show that the moon sweeping effect controls both the transport toward the planet and at high latitudes by reducing the abundance of particles constrained to populate the regions out of the equator. Among the phenomena taken into consideration in our model, the moons (Amalthea and Thebe) are the moderator for the intensity of the radiation emitted at high latitudes. Moon losses also affect the amplitude of the double- peaked beaming curve. The sweeping effect amplifies its intrinsic amplitude while the energy resonances occurring near Amalthea and Thebe belong to the phenomena setting it to the right level. The results from our modeling conclude that the interactions with dust do not cause significant changes on the characteristics of the radio spectrum. The effect of the interactions of the trapped particles with the magnetic field are only noticeable at high frequencies. The general features of the radio spectrum are driven by the moon sweeping effect. The absorption by Amalthea affects its shape for frequencies beyond 0.7 GHz more than Thebe does. But the resonances occurring near Thebe's orbit prominently modulate the shape of the radio spectrum. Nevertheless, the resonances taking place near Amalthea and Thebe are both responsible of the slope of the radio spectrum. The effect of the radial transport on the characteristics of the two-dimensional brightness distributions, radio spectra and beaming curves will be discussed based on our ongoing work.
Bolton James S.
Levin Mark Sh.
Mansergh Thorne Richard
Santos-Costa Daniel
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