Detailed responses in the Juno JADE-E sensor and electron dynamics in Saturn's magnetosphere

Date
2014
Authors
Clark, George Barnes
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Abstract

Onboard NASA's Juno mission is the Jovian Auroral Distribution Experiment (JADE) instrument suite that will measure the in-situ plasma environment over the Jovian polar magnetosphere. These measurements are needed to further our understanding of the mechanisms present over Jupiter's aurora. JADE is made up of an ion (JADE-I) sensor and three identical electron (JADE-E) sensors. This thesis focuses on JADE-E. JADE-E provides the full pitch angle distribution (PAD) of electrons over an energy range of ~0.1 - 100 keV with a 1 second cadence. JADE-E is a top-hat Electrostatic Analyzer (ESA) with a pair of deflector plates and a position sensitive detector made up of individual anodes. In preparation for scientific analysis of JADE-E data we investigate the detailed instrument response through a combination of laboratory data and instrument models. Here, we identify three instrument responses to be modeled and tested: 1) The energy, pitch angle, and geometric factor response of an ESA to a strong external magnetic field; 2) The response of backscattered electrons (BSEs) generated within an ESA; and 3) The energy dependence of the analyzer constant. We present laboratory measurements with JADE-E, particle simulation models, and analytical approaches (where appropriate) to address these detailed instrument responses. Juno will not arrive at Jupiter until mid-2016 and during the cruise phase, JADE-E has been off except for planned high voltage check out tests. In preparation of Juno's arrival, a large statistical analysis of PADs was performed using the Low Energy Magnetospheric Measurement System (LEMMS) onboard the Cassini spacecraft at Saturn. The analysis focuses on ~20 keV to 800 keV electrons. We present results from our study that show three distinct regions of PAD shapes in Saturn's magnetosphere with a strong energy dependent transition region near 13 Saturn radii. Results from LEMMS are compared with a theoretical diffusion model that includes adiabatic transport and Coulomb interactions with the neutral cloud. These results are compared to work done at Jupiter, which open new science questions that can be addressed with JADE-E.

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Keywords
Electron dynamics, Electrostatic analyzer, Jupiter, Saturn, Space-based instrumentation, Space physics
Citation
Department
Physics and Astronomy