Event Title

Simulation of the Magnetosphere- Ionosphere Connection at Saturn

Location

Yosemite National Park

Start Date

2-14-2014 9:05 AM

End Date

2-14-2014 9:35 AM

Description

The giant planets in our solar system such as Saturn and Jupiter represent fascinating worlds which exhibit a range of electro-magnetic, collisional and chemical processes coupling the upper atmospheres with the magnetospheres and some of their moons. Observationally, they are explored either in-situ through magnetic and electric field as well as plasma observations, or remotely by observing auroral emissions or atmospheric occultations. Magnetosphere-ionosphere coupling has over the past decades been studied in depth on Earth and matured as a field, but for the giant planets our understanding is still in its early stages. A key aid for our understanding of the underlying physics are numerical models which simulate the relevant neutral-ion and ion-magnetosphere coupling processes. Some of the key currently unresolved science questions for Saturn include the origin of its high thermosphere temperatures ("energy crisis"), of its highly variable and structured ionosphere as well as the observed variations of Saturn's apparent rotation rate. Work over the past years has shown that these all in one way or another rely on understanding magnetosphere-atmosphere coupling. Comparisons of Saturn and Earth are particularly interesting as well, as similar physical processes - well studied for Earth - act on both, but under different boundary conditions. Using our Saturn Thermosphere-Ionosphere model (STIM) with inputs from the University of Michigan Block Adaptive Tree Solar wind Roe-type Upwind Scheme (BATSRUS) MHD model, we calculate the coupling of Saturn's magnetosphere with the planet's upper atmosphere. At high latitudes STIM relies on electric fields and incident energetic particle fluxes which in turn ionise the upper atmosphere and generate ionospheric currents. These, in turn, lead to westward (anti-corotational) acceleration of ions and thereby neutral winds, whereby angular momentum is transferred from atmosphere to magnetospheric plasma. Within the atmosphere, strong auroral heating occurs which drives a complex system of global circulation and energy redistribution. For the first time we present calculations made at high spatial resolution and illustrate the relevance of that. By examining the time-dependent response of Saturn's atmosphere to variations in solar wind pressure (via its magnetosphere), we infer the relevant physical processes and intrinsic atmospheric time scales. Our Saturn calculations are constrained by and compared with key observations, and parallels are drawn to any terrestrial equivalents in behaviour. We address the energy crisis and discuss possible solutions. Our simulations and tools, in tandem with Cassini and ground based observations form an important step towards understanding ''space weather'' on Saturn.

Streaming Media

This document is currently not available here.

Share

COinS
 
Feb 14th, 9:05 AM Feb 14th, 9:35 AM

Simulation of the Magnetosphere- Ionosphere Connection at Saturn

Yosemite National Park

The giant planets in our solar system such as Saturn and Jupiter represent fascinating worlds which exhibit a range of electro-magnetic, collisional and chemical processes coupling the upper atmospheres with the magnetospheres and some of their moons. Observationally, they are explored either in-situ through magnetic and electric field as well as plasma observations, or remotely by observing auroral emissions or atmospheric occultations. Magnetosphere-ionosphere coupling has over the past decades been studied in depth on Earth and matured as a field, but for the giant planets our understanding is still in its early stages. A key aid for our understanding of the underlying physics are numerical models which simulate the relevant neutral-ion and ion-magnetosphere coupling processes. Some of the key currently unresolved science questions for Saturn include the origin of its high thermosphere temperatures ("energy crisis"), of its highly variable and structured ionosphere as well as the observed variations of Saturn's apparent rotation rate. Work over the past years has shown that these all in one way or another rely on understanding magnetosphere-atmosphere coupling. Comparisons of Saturn and Earth are particularly interesting as well, as similar physical processes - well studied for Earth - act on both, but under different boundary conditions. Using our Saturn Thermosphere-Ionosphere model (STIM) with inputs from the University of Michigan Block Adaptive Tree Solar wind Roe-type Upwind Scheme (BATSRUS) MHD model, we calculate the coupling of Saturn's magnetosphere with the planet's upper atmosphere. At high latitudes STIM relies on electric fields and incident energetic particle fluxes which in turn ionise the upper atmosphere and generate ionospheric currents. These, in turn, lead to westward (anti-corotational) acceleration of ions and thereby neutral winds, whereby angular momentum is transferred from atmosphere to magnetospheric plasma. Within the atmosphere, strong auroral heating occurs which drives a complex system of global circulation and energy redistribution. For the first time we present calculations made at high spatial resolution and illustrate the relevance of that. By examining the time-dependent response of Saturn's atmosphere to variations in solar wind pressure (via its magnetosphere), we infer the relevant physical processes and intrinsic atmospheric time scales. Our Saturn calculations are constrained by and compared with key observations, and parallels are drawn to any terrestrial equivalents in behaviour. We address the energy crisis and discuss possible solutions. Our simulations and tools, in tandem with Cassini and ground based observations form an important step towards understanding ''space weather'' on Saturn.