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Energetic Particle Impacts in Saturns Magnetic Field:

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Images of Tethys by Cassini and Voyager revealed many puzzling surface features ... Appears, at this stage, that singly-ionized oxygen is the cause of Tethys' albedo ... – PowerPoint PPT presentation

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Title: Energetic Particle Impacts in Saturns Magnetic Field:


1
Energetic Particle Impacts in Saturns Magnetic
Field
  • Simulating Charged Particle Motion to Explain
    Satellite Surface Features
  • Rob Zellem and Geraint Jones (University College
    London)

2
Tethys Images
  • Images of Tethys by Cassini and Voyager revealed
    many puzzling surface features
  • Equatorial areas of differing surface brightness

Stooke 2002
3
Tethys Images
http//www.planetary.org/blog/article/00001813/
4
Other Studies
  • Similar features have been detected on Jupiters
    Galilean moons
  • Studies have been conducted to determine if these
    surface features are due to energetic charged
    particle impacts
  • Cooper et al. 2001, Pospieszalska Johnson 1989
  • Simulated particle collisions with the moons
  • Determined that their results satisfactorily
    explained such brightness features
  • Interestingly, such a study has yet to be
    conducted in the Saturnian system

5
The Goal
  • To build our own simulation software to determine
    if the brightness features on Tethys are caused
    by the impact by highly energetic charged
    particles
  • Aided by data from Cassinis Magnetosphere
    Imaging Instrument (MIMI), which observes the
    energetic charged particle population trapped in
    Saturns magnetosphere
  • Allow a realistic representation of the moons
    environments and increase the simulations
    efficiency
  • Simulator outputs collision position, allowing
    the construction of a surface collision map
  • Compared to the Voyager and Cassini images to
    determine which particle population has caused
    the moons brightness variations

6
Motions of Charged Particles in a Planetary
Magnetic Field
  • Helical Motion

?
Bz
v

7
Motions of Charged Particles in a Planetary
Magnetic Field
  • Sine and cosine equations
  • Gyroradius
  • Gyroperiod

Parks 2004
8
Motions of Charged Particles in a Planetary
Magnetic Field
http//www-ssg.sr.unh.edu/tof/Smart/Students/lees/
periods.html
9
Change previous image to include Saturn, flipping
B-field, and add a moon
  • Might also want to include a slide of physical
    properties and make sure to say that Tethys
    orbit is synchronous

10
Bounce and Drift Motion
Parks 2004
11
Parmot Particle Motion Simulator

North celestial pole
10rmoon
B
Saturn
(0, 0, 0)
Direction of moon orbital motion

























10rmoon

10rmoon
12
Parmot input from MIMI
13
Parmot Particle Motion Simulator
14
Output
  • Electrons - overall, there were 16,316 collisions
  • Simulation time
  • Electrons 7 hours
  • Protons 4 hours
  • Singly-ionized oxygen 4 hours

15
(No Transcript)
16
Proton Plot
17
Electron Plot
18
Singly-ionized Oxygen Plot
19
Initial Conclusions
  • Appears Tethys surface features are due to
  • Lack of collisions by electrons
  • Collisions by singly-ionized oxygen
  • Particle efficiency
  • Oxygen impacts likely more efficient than
    electron impacts due to larger mass
  • Appears, at this stage, that singly-ionized
    oxygen is the cause of Tethys albedo

20
Future Tasks
  • Magnetic field
  • Existence of magnetic field gradient
  • Assumed that the B-field inside the simulation
    box is constant as simulation box size is much
    smaller than the overall magnetic field line
    length
  • Needed as it causes particle drift
  • Magnetic field x-y plane is slightly above
    Tethys equator
  • Both limited by available simulation time
  • Preliminary runs of Parmot with a more realistic
    magnetic field have indicated that they will take
    longer than a few days
  • Run Parmot on multiple computers
  • Trying to port Parmot to run on three computers
    (one for each particle type) in the lab for a few
    days

21
Thank you
  • Any questions?
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