Energetic particle signatures at Ganymede: Implications for Ganymede's magnetic field

Williams, D. J.; Mauk, B. H.; McEntire, R. W.; Roelof, E. C.; Armstrong, T. P.; Wilken, B.; Roederer, Juan G.; Krimigis, S. M.; Fritz, T. A.; Lanzerotti, L. J.; Murphy, N.

doi:10.1029/97gl01931

Cited by 71 publications

(55 citation statements)

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“…In particular, energetic particle measurementswith the LEMMS sensor during close flybys provide vital and often unique results that identify the character of the moon-magnetosphere interaction. For example, as has been shown at Jupiter, energetic particle observations provide a measure of the moon's surface magnetic field (Williams et al, 1997b); directly measure the effect of the moon and its environment on the convecting magnetospheric plasma ; provide a direct measure of the amount of scattering occurring on planetary field lines intersecting the moon ; provide a measure of the conductivity of the moon and its environment (Paranicas et al, 1998); provide a direct measure of the effectiveness of sputtering in the formation of the moon's atmosphere, ionosphere, and associated gas torus as well as for surface mass redistribution effects (Ip et al, , 1998Lagg et al, 1998); and for moons with magnetic fields can identify the existence of trapped particles within that field .…”

Section: Satellite Interactions and Auroramentioning

confidence: 95%

Magnetosphere Imaging Instrument (MIMI) on the Cassini Mission to Saturn/Titan

et al. 2004

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The magnetospheric imaging instrument (MIMI) is a neutral and charged particle detection system on the Cassini orbiter spacecraft designed to perform both global imaging and in-situ measurements to study the overall configuration and dynamics of Saturn's magnetosphere and its interactions with the solar wind, Saturn's atmosphere, Titan, and the icy satellites. The processes responsible for Saturn's aurora will be investigated; a search will be performed for substorms at Saturn; and the origins of magnetospheric hot plasmas will be determined. Further, the Jovian magnetosphere and Io torus will be imaged during Jupiter flyby. The investigative approach is twofold. (1) Perform remote sensing of the magnetospheric energetic (E > 7 keV) ion plasmas by detecting and imaging charge-exchange neutrals, created when magnetospheric ions capture electrons from ambient neutral gas. Such escaping neutrals were detected by the Voyager l spacecraft outside Saturn's magnetosphere and can be used like photons to form images of the emitting regions, as has been demonstrated at Earth. (2) Determine through in-situ measurements the 3-D particle distribution functions including ion composition and charge states (E > 3 keV/e). The combination of in-situ measurements with global images, together with analysis and interpretation techniques that include direct "forward modeling" and deconvolution by tomography, is expected to yield a global assessment of magnetospheric structure and dynamics, including (a) magnetospheric ring currents and hot plasma populations, (b) magnetic field distortions, (c) electric field configuration, (d) particle injection boundaries associated with magnetic storms and substorms, and (e) the connection of the magnetosphere to ionospheric altitudes. Titan and its torus will stand out in energetic neutral images throughout the Cassini orbit, and thus serve as a continuous remote probe of ion flux variations near 20R S (e.g., magnetopause crossings and substorm plasma injections). The Titan exosphere and its cometary interaction with magnetospheric plasmas will be imaged in detail on each flyby. The three principal sensors of MIMI consists of an ion and neutral camera (INCA), a charge-energy-mass-spectrometer (CHEMS) essentially identical to our instrument flown on the ISTP/Geotail spacecraft, and the low energy magnetospheric measurements system (LEMMS), an advanced design of one of our sensors flown on the Galileo spacecraft. The INCA head is a large geometry factor (G ∼ 2.4 cm 2 sr) foil time-of-flight (TOF) 234 S. M. KRIMIGIS ET AL. camera that separately registers the incident direction of either energetic neutral atoms (ENA) or ion species (≥5 • full width half maximum) over the range 7 keV/nuc < E < 3 MeV/nuc. CHEMS uses electrostatic deflection, TOF, and energy measurement to determine ion energy, charge state, mass, and 3-D anisotropy in the range 3 ≤ E ≤ 220 keV/e with good (∼0.05 cm 2 sr) sensitivity. LEMMS is a two-ended telescope that measures ions in the range 0.03 ≤ E ≤ 18 MeV and electrons 0.015 ≤ ...

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Section: Satellite Interactions and Auroramentioning

confidence: 95%

Magnetosphere Imaging Instrument (MIMI) on the Cassini Mission to Saturn/Titan

et al. 2004

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“…Energetic particles can also at times remotely sense magnetic topology in a fashion that cannot be ascertained by measuring local fields alone. For example, the energeticelectron angular measurements made by Galileo at the icy satellite Ganymede were highly instrumental in confirming the existence of, and determining the configuration of, Ganymede's internal magnetic field (Williams et al 1997). …”

Section: Determine the Structure Of Mercury's Internal Magnetic Fieldmentioning

confidence: 97%

The Energetic Particle and Plasma Spectrometer Instrument on the MESSENGER Spacecraft

et al. 2007

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The Energetic Particle and Plasma Spectrometer (EPPS) package on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury is composed of two sensors, the Energetic Particle Spectrometer (EPS) and the Fast Imaging Plasma Spectrometer (FIPS). EPS measures the energy, angular, and compositional distributions of the high-energy components of the in situ electrons (>20 keV) and ions (>5 keV/nucleon), while FIPS measures the energy, angular, and compositional distributions of the low-energy components of the ion distributions (<50 eV/charge to 20 keV/charge). Both EPS and FIPS have very small footprints, and their combined mass (∼3 kg) is significantly lower than that of comparable instruments.

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“…There is clear evidence that on those passes Galileo encountered field lines linked to Ganymede at most at one end, with the other end linked to Jupiter's ionosphere [Williams et al, 1997a;1998]. The final pass (designated G8, as it occurred on Galileo's eighth orbit around Jupiter) cut through the upstream magnetosphere with closest approach at 28.3 ø Ganymede latitude at an altitude of 1606 km or 0.61 RG, with Ganymede's radius RG = 2634 km.…”

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Probing Ganymede's magnetosphere with field line resonances

Volwerk¹,

Kivelson²,

Khurana³

et al. 1999

J. Geophys. Res.

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Abstract. We report on the spectrum of field line resonances identified in data acquired by the Galileo spacecraft within Ganymede' s magnetosphere on a relatively low latitude pass. We infer properties of the plasma distribution and its transport from the observed spectrum. The harmonic structure in the spectrum of the magnetometer data agrees very well with the freq_3uencies predicted for resonances of a dipole field. The spectrum implies a density of 2 amu cm near the equator on closed field lines of Ganymede's magnetic field inside of 2 RG (Ganymede radii). This density is significantly r3educed relative to the local density of the Jovian plasma sheet near Ganymede (_< 8 electrons cm-, or -100 amu cm -3 for an average ion mass per charge of 20 amu and average charge of 1.5 electron charges). A shadowing effect of Ganymede for the flow of particles injected at a reconnection layer on the side of the moon downstream relative to the direction of torus plasma flow accounts for the marked density depletion.Implications for conducting paths near Ganymede's surface are considered.

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Energetic particle signatures at Ganymede: Implications for Ganymede's magnetic field

Abstract: Abstract.The second encounter of the Galileo satellite with the Galilean moon

Cited by 71 publications

References 6 publications

Magnetosphere Imaging Instrument (MIMI) on the Cassini Mission to Saturn/Titan

Magnetosphere Imaging Instrument (MIMI) on the Cassini Mission to Saturn/Titan

The Energetic Particle and Plasma Spectrometer Instrument on the MESSENGER Spacecraft

Probing Ganymede's magnetosphere with field line resonances

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