LOFAR Imaging of Jupiter's Radiation Belts: Pipeline & Results

Philippe Zarka

Transcript

1. LOFAR Imaging of Jupiter’s radiation belts:
   pipeline and results
   J. Girard, C. Tasse, P. Zarka, S. Hess
   

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2. I. Planetary imaging pipeline
   II. First results at Jupiter
   LF characterization of the radiation belts
   Flux variability & Beaming
   III. Next ...
   I. Planetary imaging pipeline
   

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3. Jupiter
   ~49’’ (Nov 2011)
   Magnetic dipole : Tilt angle β ≈ 9.6° toward λIII
   = 201.7°
   Magnetic field 4.29 G.RJ
   3 (>>Bearth
   = 0.312 G.RE
   3)
   mag. field line
   mag. equator
   Spin vector : Period = 9h55m29s (System III, 1965)
   spin equator
   

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4. Jovian radio emissions
   e-
   Thermal (λ ~ cm)
   1
   1
   1
   2
   Auroral / Io cyclotron emission (λ ≥ DAM)
   2
   2
   3
   Radiation belts synchrotron emission (λ = dm-m)
   3
   3
   

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5. Jovian radio emissions
   Radiation belts synchrotron emission (λ = dm-m)
   • Belts radiating from ~1 to ~3 RJ
   • Energetic particles (ions, e- of 100s keV → 10s MeV) trapped near the magnetic equator
   • Anisotropic (beamed) and polarized emission (~20-25% linear, <1% circular)
   3
   VLA 5 GHz
   [Santos-Costa et al., 2009]
   

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6. 2.3 GHz / 13 cm
   333 MHz / 90 cm
   14 GHz / 2 cm
   1.4 GHz / 20 cm
   5 GHz / 6 cm
   Previous resolved observations
   LOFAR HBA / ~2 m
   (127-172 MHz)
   -0.011 0.012 0.035 0.059 0.082 0.11 0.13 0.15 0.18
   LF → low e- energies (100s keV) , HF → (10s MeV)
   

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7. Planetary imaging « pipeline »
   LOFAR observation :
   • 49 HBA stations : 20 CS + 9 RS
   • 2 beams : Jupiter (On) & 4C15.05 (Off) , Δθ~4°
   • 2 x 121 SB (23 MHz) covering the band 127-172 MHz
   • δt=0.3ms , δf=3kHz
   elevation (°)
   time (h)
   Jupiter
   4C15.05
   Cas A
   Tau A
   Cyg A
   2011/11/10, 18h24 → 2011/11/11, 4h24 (10 hours)
   1st processing step : Classical Flagging & Calibration (NDPPP, BBS, ...)
   

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8. 4C15.06
   4C15.05
   4C12.10
   4C13.12
   4C16.05
   MRC0210+157
   MRC0156+136
   MRC0156+126
   MRC0206+136
   TXS0201+170
   MRC0157+168
   TXS0209+144
   Calibrator
   • Identification via
   (Nasa Extragalactic
   Database)
   http://ned.ipac.caltech.edu/
   • 4C15.05
   6.5 Jy @ 160 MHz
   • Other sources
   ~1-5 Jy
   • Other sources
   • Image over
   10 SB
   uv=0.2-4 kλ,
   2048 x 2048 pixels
   5°x5°
   

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9. Complex gain solution for antenna CS 026 HBA1, SB 121
   start: 10/11/11 18h24 end:11/11/11 4h24
   XX YY
   Calibration inspection
   

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10. Planetary imaging « pipeline »
    LOFAR observation :
    • 49 HBA stations : 20 CS + 9 RS
    • 2 beams : Jupiter (On) & 4C15.05 (Off) , Δθ~4°
    • 2 x 121 SB (23 MHz) covering the band 127-172 MHz
    • δt=0.3ms , δf=3kHz
    1st processing step : Classical Flagging & Calibration (NDPPP, BBS, ...)
    Planetary Imaging specificity :
    • Proper motion of the planet
    → requires correction of the phase center in the (u,v) plane
    

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11. 166-172 MHz
    150-157 MHz 158-166 MHz
    Δt =18h-20h
    141-149 MHz
    127-133 MHz 133-141 MHz
    uv=0.2~5kλ beam=50’’x30’’ color: 0,1-0,9 Jy/beam
    Jupiter
    NVSS  J020457+114145  
    

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12. 166-172 MHz
    150-157 MHz 158-166 MHz
    141-149 MHz
    127-133 MHz 133-141 MHz
    uv=0.2~5kλ beam=50’’x30’’
    Jupiter
    NVSS  J020457+114145  
    color: 0,1-0,9 Jy/beam
    Δt =20h-22h
    

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13. 166-172 MHz
    150-157 MHz 158-166 MHz
    141-149 MHz
    127-133 MHz 133-141 MHz
    uv=0.2~5kλ beam=50’’x30’’
    Jupiter
    NVSS  J020457+114145  
    color: 0,1-0,9 Jy/beam
    Δt =22h-24h
    

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14. 166-172 MHz
    150-157 MHz 158-166 MHz
    141-149 MHz
    127-133 MHz 133-141 MHz
    uv=0.2~5kλ beam=50’’x30’’
    Jupiter
    NVSS  J020457+114145  
    color: 0,1-0,9 Jy/beam
    Δt =00h-02h
    

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15. 166-172 MHz
    150-157 MHz 158-166 MHz
    141-149 MHz
    127-133 MHz 133-141 MHz
    uv=0.2~5kλ beam=50’’x30’’
    Jupiter
    NVSS  J020457+114145  
    color: 0,1-0,9 Jy/beam
    Δt =02h-04h
    

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16. Planetary imaging « pipeline »
    1st processing step : Classical Flagging & Calibration (NDPPP, BBS, ...)
    LOFAR observation :
    • 49 HBA stations : 20 CS + 9 RS
    • 2 beams : Jupiter (On) & 4C15.05 (Off) , Δθ~4°
    • 2 x 121 SB (23 MHz) covering the band 127-172 MHz
    • δt=0.3ms , δf=3kHz
    Planetary Imaging specificity :
    • Proper motion of the planet
    → requires correction of the phase center in the (u,v) plane
    • Moving sources around planet center = wobbling of the magnetic equator
    → requires correction via rotations in the (u,v) plane
    magnetic equator
    projection
    [Levin et al., 2001] http://juno.wisc.edu/science_magnetosphere.html
    VLA 1.4 GHz
    

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17. Planetary imaging « pipeline »
    1st processing step : Classical Flagging & Calibration (NDPPP, BBS, ...)
    LOFAR observation :
    • 49 HBA stations : 20 CS + 9 RS
    • 2 beams : Jupiter (On) & 4C15.05 (Off) , Δθ~4°
    • 2 x 121 SB (23 MHz) covering the band 127-172 MHz
    • δt=0.3ms , δf=3kHz
    Planetary Imaging specificity :
    • Proper motion of the planet
    → requires correction of the phase center in the (u,v) plane
    • Moving sources around planet center = wobbling of the magnetic equator
    → requires correction via rotations in the (u,v) plane
    VLA 1.4 GHz
    ” but will cause smearing of other sources in the field → substract these sources first
    2nd processing step : Widefield Imaging (AWImager) [Tasse, 2012]
    • Automatic identification of sources above threshold
    • Peeling of the sources ≠ planet (Sagecal-like algorithm - C. Tasse)
    

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18. Before peeling SB30-39
    10°x10°
    

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19. After peeling SB30-39
    10°x10°
    

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20. Planetary imaging « pipeline »
    1st processing step : Classical Flagging & Calibration (NDPPP, BBS, ...)
    LOFAR observation :
    • 49 HBA stations : 20 CS + 9 RS
    • 2 beams : Jupiter (On) & 4C15.05 (Off) , Δθ~4°
    • 2 x 121 SB (23 MHz) covering the band 127-172 MHz
    • δt=0.3ms , δf=3kHz
    Planetary Imaging specificity :
    • Proper motion of the planet
    → requires correction of the phase center in the (u,v) plane
    • Moving sources around planet center = wobbling of the magnetic equator
    → requires correction via rotations in the (u,v) plane
    VLA 1.4 GHz
    ” but will cause smearing of other sources in the field → substract these sources first
    2nd processing step : Widefield Imaging (AWImager) [Tasse, 2012]
    • Automatic identification of sources above threshold
    • Peeling of the sources ≠ planet (Sagecal-like algorithm - C. Tasse)
    3rd processing step : Apply uv corrections (motion, rotation of Jupiter source)
    → 2 data cubes :
    • 12 Rotation-averaged images ( 12 subbands x 7h [=19h-2h] )
    • 12 x 5 2-hour images ( 12 subbands x 2h [5 time intervals of 2h] )
    

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21. I. Planetary imaging pipeline
    II. First results at Jupiter
    LF characterization of the radiation belts
    Flux variability & Beaming
    III. Next ...
    II. First results at Jupiter
    LF characterization of the radiation belts
    

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22. 18h-20h 20h-22h 22h-00h
    00h-02h 02h-04h
    distorsion (low elevation)
    2-hour & Frequency averaged images
    Δf = 127-172 MHz), Δt = 2h, uv= 0-15 kλ corrected from motion & wobble,
    Beam = 17.8’’x15.5’’, Pixel = 2", Jupiter disk = 49’’
    

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23. Rotation & Frequency averaged image
    Δf = 127-172 MHz), Δt = 7h, uv= 0-15 kλ, Beam = 17.8’’x15.5’’, Pixel = 1", Jupiter disk = 49’’
    

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24. Contours @ 15 GHz [de Pater & Dunn, 2003]
    -0.058 -0.035 -0.011 0.012 0.035 0.059 0.082 0.11 0.13 0.15 0.18
    55.0 50.0 45.0 2:06:40.0 35.0 30.0
    30.0
    18:00.0
    30.0
    11:17:00.0
    30.0
    16:00.0
    30.0
    Jy/beam
    RA
    Dec(°)
    Rotation & Frequency averaged image
    Δf = 127-172 MHz), Δt = 7h, uv= 0-15 kλ, Beam = 17.8’’x15.5’’, Pixel = 1", Jupiter disk = 49’’
    

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25. Radiation belts extent at LF ~ 6-7 RJ , L-shell ~ 1-3.5 RJ
    Slightly more extended than at HF [Dessler, 1983]
    6-7 RJ
    Rotation & Frequency averaged image
    

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26. E & W peaks location on 10-hr time integrated images
    1.43 – 1.67 Rj
    1.5 Rj
    1.30 – 1.78 Rj
    1.35 Rj
    VLA 5 GHz
    [Santos-Costa et al., 2009]
    

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27. Consistent with radial excursions measured at HF (e.g. ~ 0.25 Rj
    from 1.45 to 1.7 Rj
    )
    [Dulk et al., 1997]
    E & W peaks location on 2-hr time integrated images
    1.13 – 1.70 Rj
    1.22 – 1.54 Rj
    

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28. I. Planetary imaging pipeline
    II. First results at Jupiter
    LF characterization of the radiation belts
    Flux variability & Beaming
    III. Next ...
    II. First results at Jupiter
    Flux variability & Beaming
    

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29. Bright sources around Jupiter
    1) MRC 0204+110
    S=2.24±0.23 Jy @ 73.8 MHz
    α=-1.0
    2) NVSS J020530+112338
    S=1.00±0.12 Jy @ 73.8 MHz
    α=-0.9
    3) MRC 0202+114
    S=1.94±0.17 Jy @ 73.8 MHz
    α=-0.9
    [NED http://ned.ipac.caltech.edu/ ]
    1
    2
    3
    Jupiter
    Wide-field unresolved image before peeling
    

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30. NVSS J020530+112338
    MRC 0204+110
    MRC 0202+114
    resolved 1"
    unresolved after peeling
    unresolved before peeling
    resolved 2"
    Jupiter
    Clean?
    

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31. (Girard et al., SF2A 2012, adapted from Kloosterman et al., 2008)
    

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32. [Berge, 1966]
    Beaming
    Emission is maximum when observer is in the magnetic equator
    Magnetic Latitude = DE
    + 9.6° cos(CML-λ
    III
    )
    DE
    = jovicentric latitude of Earth = 3.29° in Nov. 2011
    

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33. Emission is maximum when observer is in the magnetic equator
    Magnetic Latitude = DE
    + 9.6° cos(CML-λ
    III
    )
    DE
    = jovicentric latitude of Earth = 3.29° in Nov. 2011
    Beaming
    λ
    III M
    =318°
    λ
    III M
    =104°
    West
    East
    

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34. Beaming
    λIII M
    =318°
    λIII M
    =104°
    λIII E = CML-90°
    toward
    observer
    W
    λIII W = CML-90°
    λIII M = CML
    E
    Hot spot @ λ
    III
    = 204° - 255° ?
    [Conway & Stannard, 1972 ;
    de Pater 1983;
    Leblanc, 1997]
    

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35. I. Planetary imaging pipeline
    II. First results at Jupiter
    LF characterization of the radiation belts
    Flux variability & Beaming
    III. Next ...
    III. Next ...
    

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36. (adapted from Santos-Costa, 2009)
    DE
    ~ 0° (1997 & 2002)
    DE
    ~ 3.29° (2011)
    East-West Peak Brightness Emission Ratio
    Central Meridian Longitude (deg.)
    06 May 1997
    07 May 1997
    11 May 1997
    12 May 1997
    28 Oct 2002
    01 Nov 2002
    05 Nov 2002
    08 Nov 2002
    10 Nov 2002
    11 Nov 2002
    21 Nov 2002
    04 Dec 2002
    11 Dec 2002
    +
    +
    *
    *
    11 Nov 2011
    11 Nov 2011
    E/W intensity ratio
    

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37. Spots : secondary maxima in LOFAR image Contours : de Pater, 1991
    High latitude emission
    

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38. • Specific routines developed for processing planetary observations
    • First resolved images at 127-172 MHz, 20-25 mJy/beam
    • Girard et al. proceedings published [SF2A, 2012] ; A&A paper in preparation
    Summary & Perspectives
    • LC0_005 proposal « Saturn’s deep atmosphere » (Courtin et al.) : HBA
    • LC0_007 proposal «Exoplanet radio search » (Zarka et al.) : LBA
    • LC0_006 proposal « Jupiter's Synchrotron Radiation » (de Pater et al.) : LBA & HBA + possible joint
    - polarization, extent to LF ? (LBA range), spectral variations ?
    - 3D reconstruction of B field by tomography
    - topology of multipolar BJup at low latitudes close to the planet
    - electron acceleration & transport : pitch angle scattering, inward diffusion, effect of satellites, inter
    - comparison with models (Salammbô 3D)
    - time variability, magnetospheric dynamics
    [de Pater & Sault, 1998]
    [Connerney et al., 1993 ; Santos-Costa, 2009]
    

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39. 
    
    

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