Survey analysis of chorus intensity at Saturn

Abstract

In order to conduct theoretical studies or modeling of pitch angle scattering of electrons by whistler mode chorus emission at Saturn, a knowledge of chorus occurrence and magnetic intensity levels, P B , as well as the distribution of P B relative to frequency and spatial parameters is essential. In this paper an extensive survey of whistler mode magnetic intensity levels at Saturn is carried out, and Gaussian fits of P B are performed. We fit the spectrum of wave magnetic intensity between the lower hybrid frequency and f ceq /2 and for frequencies in the interval f ceq /2 < f < 0.9 f ceq , where f ceq is the cyclotron frequency mapped to the equator. Saturn chorus is observed over most local times, but is dominant on the nightside in the range of 4.5 < L <7.5, with minimum power at the equator and peak power in the range of 5°< λ < 10°. Saturn wave magnetic intensity averaged in frequency bins peaks in the range of 10 À5 < P B < 10 À4 nT 2 for 0.4 < β < 0.5 (β = f/f ceq ). Gaussian fits of P B with frequency and latitude are obtained for lower band chorus. Plasma injection regions are occasionally encountered with significant chorus power levels. Upper band chorus is seen almost exclusively within plasma injection regions, and the number of events is very limited, but when present, the average levels of P B can be higher than the lower band chorus. The overall magnetic intensity contribution of the upper band, however, is insignificant relative to the lower band.

Survey of Saturn electrostatic cyclotron harmonic wave intensity

“…This is also the region where Saturn chorus intensity emission peaks. Menietti et al [2014] report that this occurs near L = 5.5. In addition, the peak Z-mode intensity at Saturn is found inside the inner edge of the Enceladus Figure 10.…”

Rapid Electron Acceleration in Low‐Density Regions of Saturn's Radiation Belt by Whistler Mode Chorus Waves

“…The chorus wave power survey in Menietti et al (2014) covered radial distances from 4.5 R S to 7.5 R S ; in this paper we have extended the lower range of the survey to 2.5 R S using similar methodology to Menietti et al (2014;see supporting information). We use the wave power in the magnetic field given by equation (1)…”

Combined Effects of Equatorial Chorus Waves and High‐Latitude Z‐Mode Waves on Saturn's Radiation Belt Electrons

“…According to previous studies (Menietti et al, 2014(Menietti et al, , 2015Shprits et al, 2012;Woodfield et al, 2018), the adopted wave model parameters are shown in the Table 1.…”

“…Based on the models described above, we obtain the bounce-averaged diffusion coefficients driven by plasma waves through the quasi-linear theory at L = 6 (Glauert & Horne, 2005). In this region, chorus waves are mainly near the equator, Z-mode waves are confined at high latitudes, and both emissions are intense, according to the statistical studies (Menietti et al, 2014(Menietti et al, , 2015. Figures 2a-2f show the chorus and Z-mode wave-driven bounce-averaged pitch angle (<D αα >/p 2 ), cross (|<D αp >|/p 2 ), and momentum (<D pp >/p 2 ) diffusion coefficients, respectively.…”