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Planets and Solar System Science at Low
Frequencies Philippe Zarka LESIA,
CNRS-Observatoire de Paris France philippe.zarka_at_o
bspm.fr Towards a European Infrastructure for
Lunar Observatories Bremen, 22-23/3/2005 - EADS /
ASTRON / Radionet
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• Limitations of ground-based LF radioastronomy 
•  RFI (man-made, lightning spherics)
• Ionospheric cutoff (10 MHz)
• propagation effects (30 MHz)
• Sky background (fluctuations)
•  IP, IS scintillations
• (Solar radio emissions)

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• Limitations of LF radioastronomy in Earth
  orbit 
•  RFI (man-made, lightning spherics)
• Auroral Kilometric Radiation
• Sky background (fluctuations)
•  IP, IS scintillations
• (Solar radio emissions)

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• Solar emission/ burst/storm
• Spherics

• LF Earth environment

• AKR day/night (at 60 RE)
• Thermal noise (?flux)
• Galactic background
• Ionospheric LF cutoff
• Solar wind LF cutoff

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• Galactic background for a short dipole antenna,
  i.e. with ?8?/3, A3?2/8?
• Antenna effective area
• A k?2 with k 3/8? 1/8 for a short dipole,
• k N/8 for N dipoles
• A ? ?2 ? ? 1/k 8/N
• LOFAR 104 dipoles

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• Jovian radio emissions (near opposition)

• Solar wind / magnetosphere interaction (auroral
  emissions)
• Io/magnetosphere interaction
• Io torus
• Synchrotron from radiation belts (HF)

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Radiosources in Jupiter's environment
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Io-Jupiter plasma interaction
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• Saturn, Uranus, Neptune auroral emissions

Saturn Uranus Neptune
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• Saturn, Uranus atmospheric lightning

Saturn Uranus
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• Detectability from the ground (Earth)

• In absence of solar bursts spherics
• In absence of RFI / after successful mitigation
•  10-20 MHz
• ? Jovian DAM with C(?dipole/?)?(b?)1/2N(b?)1/2
  100
• (ex  N1, 10 kHz ? 1 sec)
• ? Saturns lightning with C 105 (N200, 10 MHz
  ? 25 msec),
• without access to LF cutoff

C 102 104 106
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• Moon
• Shielding of RFI, spherics, AKR, Solar emissions
• Only limitation to sensitivity sky background
• fluctuations
• Ionospheric LF cutoff ltlt500 kHz

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• Detectability from the Moon

• ? all Jovian emissions Saturn auroral
  emissions with C 100-1000
• (N1-10, 10 kHz ? 1 sec)
• ? Uranus Neptune auroral emissions
• Saturn Uranus lightning (including LF
  cutoff) with C 104 (N10-100, 200 kHz ? 50-500
  msec)

C 102 104 106
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• Long-term magnetospheric radio observations
• ( multi-? correlations)

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• Variabilities/periodicities
• ? magnetospheric dynamics
• (role of SW, planetary rotation, satellite
  interactions, Io volcanism, short-lived bursts,
  substorms ?)
• ? planetary rotation period
• ? B anomalies secular variations
• ? Io torus probing (nKOMFaraday effect)
• ? SW monitoring from 1 to 30 AU

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• Saturn/Titan interaction (other satellites ?)
• SW influence, substorms ?
• Uranus Neptune auroral emissions observed only
  once by Voyager 2 !
• Lightning long-term monitoring, correlation
  with optical observations, planetary comparative
  meteorology

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• Extrasolar Jupiter-like radio emissions at 10 pc
  range

• Flux up to ? 105 Jupiters strength for
  magnetized hot Jupiters with solar-like stellar
  wind input, or unmagnetized hot Jupiters in
  interaction with strongly magnetized star
• possible stronger stellar wind, focussing
  events,

C 103 105 107 109
105 103 10 1
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Magnetic Radio Bode's Law


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• Detectability from the ground (Earth)

• No solar bursts /spherics , RFI mitigation
• 10-20 MHz
• ? requires C107
• (N1000-10000, 1-10 MHz ? 1-10 sec)

C 103 105 107 109
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• Detectability from the Moon

C 103 105 107 109

• 1 order of magnitude better
• (C 105-6  N100, 1-10 MHz ? 1-10 sec)
• access to less energetic sources
• (C 106-7  Ngtgt100)
• access to VLF (weakly magnetized bodies)

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• NB 
• Angular resolution required 1-10
• ? D 6-60 ?
• (18-180 km _at_ 100 kHz  1.8-18 km _at_ 1 MHz)
• if detectability of exo-planetary radio
  emissions ? same for solar-like stellar radio
  emissions
• complementarity to ground-based LOFAR
• difficult from space
• weak scattering/broadening effects at sources
  distances lta few 10s pc

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• possible active sounding of Terrestrial
  magnetosphere (IMAGE)