New results in polarimetry of planetary thermospheric emissions: Earth and Jovian cases. M. Barthelemy (1), J. Lilensten (1), C. Simon (2), H. Lamy(2), G Gronoff (3), H. Menager (1), S. Miller (4), M. Lystrup (5), H. Rothkael (6), J. Moen (7). (1)IPAG, France (2)BIRA-IASB, Belgium (3)NASA, Langley,VA, USA (4)UCL, UK (5)University of Colorado, USA (6)Polish Space Research Center, Poland (7)University in Oslo, Norway 14/03/20111Workshop Meudon

Polarization processes Impact polarization Polarization rate depends of: –Pitch angle distribution –Kind of particles –Energy –Depolarization processes as collisions. Emission in an anisotropic region: for ex Electric field. Ex. Lyman alpha polarization rate by electron impact. Laboratory measurement (from James et al 1998). 14/03/20112Workshop Meudon

Earth case: POLARLIS, or the measurement of the POLarization of the Oxygen thermospheric Red Line In Svalbard. Photo-polarimeter: SPP at KHO in Longyearbyen (Svalbard) and at Hornsund. Steerable Polarization Photometer (SPP) built at the Oslo University (UiO). It includes 2 channels and a pan-tilt unit. Aperture is 2°. Channel 1: Photomultiplier. Red filter centered on 6300 A with a FHWM of 1 nm. Linear polarization analyser. One rotation of the analyser every 4.02 s. Channel 2: Same, without the polarization filter. 14/03/20113Workshop Meudon

17 jan 2007 late afternoon. From Lilensten et al GRL 14/03/20114Workshop Meudon

14/03/2011Workshop Meudon5 Reassessment -Error in calibration angles. Correction around 45° -New measurements at Hornsund (no light pollution) -Confirmation of the detection -But rates around 1% after data processing -Direction close to the vertical (difference was due to the pollution) -Compatible with Bommier et al Raw polarisation before depolarizing collisions: ~18% -Vertical ie //B - Barthelemy et al. submitted 2010.

Jovian case H 3 + emissions in the IR. The emission process is different: No emission due to electronic impact because of the chemical process of formation, but… Possibility to get alignment due the electric fields in the auroral region. 2 half nights observation for August 2008 at the UKIRT with the instrument UIST-IRPOL in the Long L band ( µm). Barthelemy et al. 2010, submitted 14/03/20116Workshop Meudon

14/03/20117Workshop Meudon

Seventh data set: I at 3.95µm q (Normalized Stokes parameter) u (Normalized Stokes parameter) p (%) (Debiaised) Θ (°) (ref is the slit direction) v (Normalized Stokes parameter) The polarization direction are difficult to interpret… 14/03/20118Workshop Meudon

Interpretation: Conclusion and Perspectives 14/03/20119Workshop Meudon

Jovian case. Auroral UV emissions. Lyman , the most promising: Very intense (100 kR) Emission due to electrons and/or protons. Various polarization rate and direction with the energy. Radiative transfer in a presence of magnetic field for an allowed transition. Due to this, possible variation of the polarization rate along the line profile. Need for very high resolution. 14/03/201110Workshop Meudon

14/03/2011Workshop Meudon11 Needed in a dream world Spatial resolution around 100km2 Width of the oval ~200km. Spectral resolution Lyman alpha width is 0.02 nm and it exists H2 lines in coincidence with H-Lyman alpha. Typical lyman alpha filter width (~5nm) Some lines of H2 but faint compared to H-Lyman alpha Polarimetric accuracy under 1% Only in the night side (dayside emission can reach 10% of the auroral emission!)

14/03/2011Workshop Meudon12 Feasability Flux (at Ly alpha) Expected spatial resolution:100 km kR in the oval (i.e. 1e11 ph.cm -2.s -1 averaged in all directions). Orbit : for example EJSM in resonance 2:1 with Europa i.e. around 10 6 km for the centre of the planet i.e ph.cm -2.s -1 Need an effective area of the instrument of 12.5 cm 2 on a basis of 10ph.s -1. pix -1 (with an efficiency of the optics of 0.05, this correspond to an aperture of 250cm 2 ) Pb moving pieces!!! With a “better” orbit (more flux) : example of JUNO. Polar orbit. Closest point 4000km ~12000km above the oval.

14/03/2011Workshop Meudon13 Spectra/Lyman alpha filter Interest of spectra: H 2 lines No mixing between H 2 and Lyman alpha lines if sufficient resolution. –But not enough flux considering EJSM orbits to get H 2 lines. –And possible problem with the grating.

14/03/2011Workshop Meudon14 Optical solution? Exemple: SMESE-Lyot like design (mirrors) From Auchere et al. 1 st SMESE workshop.

14/03/2011Workshop Meudon15 Conclusions Difficult design due to the short wavelength –But Strong interest Best solution? Mission to the planet (EJSM; too late for Juno) VS Space telescope Rq: Saturn has Ly alpha aurora 10 times fainter.

Perspectives and needs. Diversity of processes,diversity of emissions →Specific information for each line and planet. Others examples : –O 8446 Å, O 1304 Å * (Earth, Venus, Mars) –Na I 5890 Å (Mercury)….in progress –Needs for the jovian case –Ab initio calculation of the link between H3+ lines polarization and the fields (E and/or B). –Lab experiment. –In EJSM frame: Difficult to have a Ly alpha polarimeter. H3+ measurement as combined measurements 14/03/201116Workshop Meudon

14/03/2011Workshop Meudon17 Polarisation as a tool to study the Solar System and beyond Hervé Lamy 1 & Mathieu Barthélemy 2 1 Belgian Institute for Space Aeronomy (BISA) 2 Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) COST proposal reference: oc