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
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
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
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
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]
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)
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, ...)
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°
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
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
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  
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
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
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
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
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
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)
18. Before peeling SB30-39 10°x10°
19. After peeling SB30-39 10°x10°
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] )
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
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’’
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’’
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’’
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
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]
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
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
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
30. NVSS J020530+112338 MRC 0204+110 MRC 0202+114 resolved 1" unresolved after peeling unresolved before peeling resolved 2" Jupiter Clean?
31. (Girard et al., SF2A 2012, adapted from Kloosterman et al., 2008)
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
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
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]
35. I. Planetary imaging pipeline II. First results at Jupiter LF characterization of the radiation belts Flux variability & Beaming III. Next ... III. Next ...
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
37. Spots : secondary maxima in LOFAR image Contours : de Pater, 1991 High latitude emission
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]
39.