Student-Faculty Programs Office
Summer 2017 Announcements of Opportunity

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Project:  The Interior Dynamics of Jupiter and Europa
Disciplines:  Planetary Science, Geophysics
Mentor:  David Stevenson, Marvin L. Goldberger Professor of Planetary Scienc, (GPS), djs@gps.caltech.edu, Phone: (626) 395-6534
AO Contact:  Hao Cao, haocao@caltech.edu
Background:  Gravity and magnetic fields are windows into the interior structure and dynamics of a planetary body. Jupiter has a global magnetic field more than 10 times stronger than that of the Earth’s. Earth-based radio telescope and past space missions to Jupiter (Pioneer 10 & 11, Voyager 1 & 2, Galileo) have established the bulk features of Jupiter’s magnetic field, including an upper limit on the time variability of the dipole moments. The Juno mission, arrived at Jupiter on July 4th 2016, is currently mapping Jupiter’s magnetic field to unprecedented resolution.

Flows in the highly conducting region of a planet (e.g. the liquid outer core of the Earth and the metallic hydrogen region of Jupiter) will advect the existing planetary magnetic field. This leads to the observed time variation in the planetary magnetic field. In principle, the bulk flow characteristics in the highly conducting region of a planet can be inferred from the measured time variation in the magnetic field. This is how we learn about the flows in the Earth’s outer core, and this is how we will learn about the flows in the metallic hydrogen region of Jupiter. However, the connection between the externally measurable time variation of Jupiter's intrinsic magnetic field and the interior flows of Jupiter has not been well established due to the radially varying nature of the background electrical conductivity.

The existence of subsurface oceans in Jupiter’s icy satellites Europa and Callisto have been revealed through their interaction with Jupiter’s magnetic field. No observational constraints have been established about the dynamics in these subsurface oceans. The relatively low electrical conductivity of the subsurface oceans and the relatively low strength of the background magnetic field at Europa indicate negligible magnetic signal associated with ocean dynamics. Thus, gravity signal associated with ocean dynamics likely is the best candidate to be measurable at Europa. However, no quantitative analysis of the gravity signal of subsurface ocean dynamics has been carried out.
Description:  Here I present description of two possible projects.

1. The interior flows of Jupiter from measured time variation of its magnetic field.

The lack of a well-established connection between the externally measurable time variation of Jupiter's intrinsic magnetic field and the interior flows of Jupiter arises from the complexity introduced by a radially varying electrical conductivity. The forward problem of advecting magnetic fields by a given interior flow with a radially varying electrical conductivity has not been solved.

In this SURF project, we will first solve this forward problem using a simple pseudo-spectral numerical model developed here. The kinematic nature of our approach allows us to survey various kinds of interior flows. This project will enable us to establish a framework to derive the interior flows of Jupiter from present and future time variation measurement of its magnetic field.

2. Gravity Signal of Ocean Current in the Sub-Surface Ocean of Europa.

In this SURF project, we will carry out a quantitative analysis of the gravity signal of subsurface ocean dynamics of Europa and assess its detectability with the planned Europa Clipper mission.

A highly precise method to forward calculate the gravity moments of a rotating planetary body, the Concentric Maclaurin Spheroid (CMS) method, has recently been developed and is suitable for this project.

With the CMS method, we will first forward calculate the gravity moments and internal layer shape associated with the solid body rotation of Europa. We will then forward calculate the gravity moments and internal layer shape associated with various assumed flows in the subsurface oceans of Europa. The effects of ocean salinity variation as a function of depth can also be investigated. This project will allow us to assess of the detectability of the gravity signal of subsurface ocean dynamics of Europa.
References:  https://www.missionjuno.swri.edu
http://www.jpl.nasa.gov/missions/europa-mission/
Student Requirements:  Introductory Courses on Electrodynamics & Partial Differential Equations (Preferred but not required).
Programs:  This AO can be done under the following programs:

  Program    Available To
       SURF    Caltech students only 

Click on a program name for program info and application requirements.


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Problems with or questions about submitting an AO?  Call Jen Manglos of the Student-Faculty Programs Office at (626) 395-2885.
 
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