Objectives: one of the most compelling problems in the giant planet magnetospheres is to understand the confounding dichotomy of net outward transport of plasma mass while conserving magnetic flux.…

This federal contract award is a grant for $421,794.70 to the University of Alaska Fairbanks (UAF) from the National Aeronautics and Space Administration (NASA) Shared Services Center. The grant is part of NASA's Cassini Data Analysis Program (CDAP) and funds research to study plasma transport and magnetic reconnection processes in Saturn's magnetosphere, using data from the Cassini mission.

The research aims to understand how plasma is transported outward from Saturn's moon Enceladus, while conserving magnetic flux. The project will analyze Cassini plasma and magnetic field data to quantify plasma properties, heating rates, and transport mechanisms at both large and small scales. This will involve developing 2D and 3D magnetohydrodynamic models of Saturn's magnetodisc and conducting hybrid simulations of flux tube interchange. The University of Alaska Fairbanks, a land, sea, and space grant institution, has expertise in planetary science and magnetospheric physics that is relevant to this NASA research program.

Objectives: one of the most compelling problems in the giant planet magnetospheres is to understand the confounding dichotomy of net outward transport of plasma mass while conserving magnetic flux. Saturn s strong magnetic field combined with rapid rotation leads to an outward transport of plasma originating at enceladus via a centrifugally-driven flux tube interchange instability, which is determined by the flux tube mass content and flux tube entropy. Outward plasma motion stretches the magnetic field into a magnetodisc configuration in the middle and outer magnetosphere and eventually magnetic reconnection operates to release plasma down the magnetotail. This internally driven reconnection is known as the vasyliunas cycle. In its original form, vasyliunas [1983] illustrated the cycle with a large-scale x-line and o-line in the magnetotail angled toward the dawn flank. But the plasma loss rate from the magnetosphere in observed large-scale reconnection events associated with vasyliunas cycle is insufficient to account for the radial plasma transport rate from enceladus. Recent analyses of cassini MAG data, suggest that much of the vasyliunas cycle of reconnection may occur in the subsolar to dusk sector, releasing plasma in a small (kinetic) scale drizzle . The goal of this proposal is to understand the relative importance of kinetic VS. Large-scale transport of plasma and magnetic flux in saturn s magnetodisc. Focusing on plasma properties and magnetic field geometry, we will address the following questions to identify how, where and on what spatial scale transport occurs: 1. How do plasma properties and turbulent heating rate densities vary as a function magnetic field properties (e.g., fluctuations and geometry). 2. What is the plasma mass outflow rate attributed to kinetic-scale transport? How does this compare with large-scale transport? 3. How does the local and flux tube entropy vary as a function of radial distance and local time? What are the inferred radial transport scales and transport mechanisms using the entropy constraint? Methodology: to address these questions we will: (1) determine average equilibrium configurations for saturn s magnetodisc as a function of local time using empirical constraints and couple to a 2-d axisymmetric magnetodisc equilibrium model [caudal, 1986]; thoroughly investigate and quantify departures from long-term averages in terms of thermal plasma properties (caps instrument) and magnetic field configurations (MAG instrument); catalogue the frequency and properties of transport-related events; scrutinize the plasma data in more detail for select events. (2) conduct high-resolution 3-d MHD simulations of saturn s magnetodisc using initial equilibrium conditions determined from the 2-d axisymmetric magnetodisc model. Conduct local 3-d hybrid simulations of flux tube interchange. Compare ION heating found in hybrid simulations and compare with results from MHD + test particles. (3) estimate the mass transport rates that occur on small scales. Relevance: the proposed study is highly relevant to current and future NASA missions (e.g. cluster, themis, MMS, pioneers 10 and 11, voyagers, galileo, juno, and cassini) and addresses central elements of the 2009 heliophysics roadmap [what are the fundamental physical processes and topologies of magnetic reconnection? How are plasmas and charged particles heated and accelerated?] the objective of the cassini data analysis program (cdap) is to enhance the scientific return of the cassini mission by broadening the scientific participation in the analysis and interpretation of data returned by this mission (APP. C.10, ROSES17). Our proposal combines, 1) data analysis tasks (analysis of caps and MAG data) and 2) non-data analysis tasks that are necessary to analyze or interpret the data (modeling and theory of transport).