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Planets and Solar System Science at Low Frequencies Philippe Zarka LESIA, CNRS-Observatoire de Paris France Towards a European.

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Presentation on theme: "Planets and Solar System Science at Low Frequencies Philippe Zarka LESIA, CNRS-Observatoire de Paris France Towards a European."— Presentation transcript:

1 Planets and Solar System Science at Low Frequencies Philippe Zarka LESIA, CNRS-Observatoire de Paris France Towards a European Infrastructure for Lunar Observatories Bremen, 22-23/3/ EADS / ASTRON / Radionet

2 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)

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

4 LF Earth environment :  AKR day/night (at 60 R E )  Thermal noise (≠flux)  Galactic background  Ionospheric LF cutoff  Solar wind LF cutoff  Solar emission/ burst/storm  Spherics

5 Galactic background for a short dipole antenna, i.e. with  =8  /3, A=3 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 ~ 10 4 dipoles

6 Jovian radio emissions (near opposition) :  Solar wind / magnetosphere interaction (auroral emissions)  Io/magnetosphere interaction  Io torus  + Synchrotron from radiation belts (HF)

7 Radiosources in Jupiter's environment

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9 Io-Jupiter plasma interaction

10 + Saturn, Uranus, Neptune auroral emissions : Saturn Uranus Neptune

11 + Saturn, Uranus atmospheric lightning : Saturn Uranus  LF cutoff  dayside peak ionospheric density

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13 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  ) 1/2 ~N( b  ) 1/2 ≥100 (ex : N=1, 10 kHz  1 sec)   Saturn’s lightning with C ≥10 5 (N=200, 10 MHz  25 msec), without access to LF cutoff C

14 Moon :  Shielding of RFI, spherics, AKR, Solar emissions  Only limitation to sensitivity = sky background fluctuations  Ionospheric LF cutoff <<500 kHz

15 Detectability from the Moon :   all Jovian emissions + Saturn auroral emissions with C ≥ (N=1-10, 10 kHz  1 sec)  + Uranus & Neptune auroral emissions + Saturn & Uranus lightning (including LF cutoff) with C ≥ 10 4 (N= , 200 kHz  msec) C

16  Long-term magnetospheric radio observations (+ multi- correlations)

17  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 (nKOM+Faraday effect)   SW monitoring from 1 to 30 AU

18  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

19 Extrasolar Jupiter-like radio emissions at 10 pc range :  Flux up to  10 5 Jupiter’s 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

20 Magnetic Radio Bode's Law Hot Jupiters ?

21 Detectability from the ground (Earth) : C  No solar bursts /spherics, RFI mitigation  ≥10-20 MHz   requires C≥10 7 (N= , 1-10 MHz  1-10 sec)

22 Detectability from the Moon : C  ≥1 order of magnitude better (C ≥ : N=100, 1-10 MHz  1-10 sec)  + access to less energetic sources (C ≥ : N>>100)  + access to VLF (weakly magnetized bodies)

23 NB :  Angular resolution required ~1°-10°  D = 6-60 ( kHz ; 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

24  possible active sounding of Terrestrial magnetosphere (~IMAGE)


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