Transcript Plasma measurements at and on Ganymede

International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
Ganymede is composed of rock and ice. It has intrinsic
magnetic field, that makes it an exciting object for investigation.
Its plasma composition is c consists of Jupiter
magnetospheric particles and ions originated from the surface of
Ganymede. Interaction of Ganymede’s and Jovian magnetospheres
leads to acceleration of ions and complicated transport.
Analysis of ion flux, composition and velocity distribution
provides important tool for Ganymede’s soil composition and
characteristics, not only on local scale but also on planetary scale,
due to transport within Ganymede’s environment.
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
FOOTPRINT OF GANYMEDE
Auroral footprint of Ganymede is produced by electric currents generated by motion of the satellite relative Jovian
magnetic field. This current flows along Jupiter's magnetic field lines and exites the glow of the upper atmosphere.
This ultraviolet image of Jupiter was taken with the Hubble Space Telescope Imaging Spectrograph (STIS) on
November 26, 1998.
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
Tenuous oxygen atmosphere of 1.2 × 108–7 × 108 cm−3 and hydrogen atoms
of ~ 1.5 × 104 cm−3
Intrinsic magnetic moment is about 1.3 × 1013 T·m3 directed against the
Jovian magnetic moment. 720 nT at equator (Jovian magnetic field 120 nT).
Moves relative to Jovian magnetic field with subsonic velocity. Its
magnetosphere has diameter is 4–5 RG (RG = 2,631.2 km)
Ganymede has airglow near ± 50° latitude, which is exactly the boundary
between the open and closed field lines of the Ganymedian
magnetosphere
Relative motion induces magnetic field that suggests highly conducting
ocean.
Energetic electrons and ions (tens and hundreds of kiloelectronvolts) hit
Ganymede’s surface that leads to sputtering
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
Measurements requirements
Combination of internal and induced magnetic fields -> open magnetosphere
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
Ganymede’s surface and atmosphere
Atmospheric/ion composition and its losses to the
magnetosphere
Fluxes of accelerated ions and electrons near Ganymede and/or at its
surface.
Surface sputtering and implantation of energetic ions
Mapping of surface composition
Jovian magnetosphere and its interaction with Ganymede
Ion composition of plasma and accelerated particles
Ganymede’s role in magnetospheric plasma population
Magnetospheric plasma dynamics
Electromagnetic interaction with Jupiter
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
Measurements of flux and velocity distribution of suprathermal and
energetic ions, and mass/charge ion composition for investigation:
- influence on Ganymede’s surface
- surface composition
- Ganymede’s atmospheric losses
- composition of Ganymede and its atmosphere
- Jovian magnetospheric plasma dynamics and the role of
Ganymede in Jovian magnetosphere
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
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1 – collimator, 2 – electrostatic analyzer, 3 – light trap,
4 – diaphragm, 5 – wedge magnet, 6 – drift tube,
7 – grids, 8 – secondary electron multiplier (SEM),
9 – DC amplifier, 10 – pulse counter
Velocity distributions of proton- and α-s
measurements in May 1972.
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
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Structure of the instrument:
1 – angular scanner,
2 – electrostatic analyzer,
3 – drift tube,
4 – magnet,
5 – focusing electrode,
6 – MCP detector
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Simulation results for solar wind ions
Fe+7- Fe+12 and O+5 and O+6 with E/Q =
1 keV (1…20 keV/Q capability)
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International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
Energy range, keV/Q
Mass range, M/Q
1…20
2…9
Mass resolution, M/Δm
Full angle of view
Angular resolution
10-40 for E/Q = 1 keV
300х300 for E/Q = 1 keV
~20
Analyzer dimensions, mm
Estimated mass, kg
230х170х120
3.5
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"
— Measurements of ions, electrons and secondary neutral
particles provide important tools for investigation of
Ganymede’s surface characteristics and composition
— Ion spectrometer under development can be considered as
candidate for plasma suite developed by MSSL and IKI for
exploration of planetary surfaces and planetary
magnetospheres
International Colloquium and Workshop "Ganymede Lander: scientific goals and experiments"