Cassini/RPWS/HFR-Kronos

Access to Lesia-Meudon data products

Plasma density and temperature with Quasi-Thermal Noise Spectroscopy

Data Set Overview

The Cassini Radio and Plasma Wave Science (RPWS) Quasi Thermal
Noise (QTN) data set contains thermal plasma parameters derived
by QTN spectroscopy analysis applied on data acquired with the
High Frequency Receiver (HFR) during the perikrones of the
entire mission. This data set includes the total electron density
and the core electron temperature, as well as the uncertainties on
the measurements. It also includes ancillary data about the location
of the spacecraft at the time of the measurement: distance to Saturn,
local-time, kronographic latitude and dipolar L-Shell apex distance.
Data are presented in CDF files, which contain a 1D array depending
on time for each parameter. This data set is intended to be the most
comprehensive and complete data set for thermal plasma parameters
measured by the HFR in the Cassini RPWS archive. A browse data set
is included with these data which provides for a graphical search
of the data using a series of thumbnail and full-sized plots which
lead the user to the particular data files of interest.

Parameters

This data set comprises spacecraft event time, radial distance (in
Saturn Radii) from Saturn, latitude (in deg), local time (in hours)
and L-shell (in Saturn Radii) of the spacecraft, total electron number
density (in cm

^{-3}) with the measurement uncertainty, core electron temperature (in eV) with the measurement uncertainty and quality flag that were acquired by QTN analysis on RPWS/HFR Spectra.Processing

The present data set was derived from the level two
data of RPWS/HFR. The analysis was compiled by the LESIA team (Observatoire
de Paris, Meudon, France).

The total electron density is deduced from a strong signal peak near
the upper-hybrid resonance (F

The total electron density Ne is then obtained as:

The error on the density was calculated on the basis of the uncertainty of the HFR receiver spectral relative resolution (df/f = 5%, 10% or 20%).

_{uH}), independently of any calibration. Indeed, the plasma frequency F_{p}can be derived from the F_{uH}resonance and the gyrofrequency F_{g}(derived from magnetic field measurements by the Cassini/MAG instrument [1]):The total electron density Ne is then obtained as:

The error on the density was calculated on the basis of the uncertainty of the HFR receiver spectral relative resolution (df/f = 5%, 10% or 20%).

The core electron temperature is deduced from the thermal plateau
level V

(using S.I. units), V

is the dipole antenna capacitance at low frequencies, with a the wire radius (a ~1.4 cm), and C

_{min}^{2}below F_{uH}, given in [2] as a function of the core temperature T_{c}and Debye length L_{D}(see Eq. 1 of [2]):(using S.I. units), V

_{min}^{2}in V^{2}/Hz. Here F_{v}(kL) is the Cassini V-shaped antenna response, with L the single wire length (L ~ 10m),is the dipole antenna capacitance at low frequencies, with a the wire radius (a ~1.4 cm), and C

_{B}is the base capacitance. We then use an iterative method to deduce T_{c}.The error on the temperature is determined a posteriori by
estimating the averaged 1-sigma dispersion of the temperature level
during the perikrone.

A full description of the methodology and results can be found in [3]

References