1 5 – 6 May 2008 IMW Meeting PARIS THEMIS Observations (2007) F. Leblanc (Service d'Aéronomie), A. Doressoundiram (Observatoire de Paris),V. Mangano (IFSI), A. López Ariste (THEMIS), C. Lemen(THEMIS), B. Gelly (THEMIS), C. Barbieri (Padova University), G. Cremonese (INAF, Padova) and N. Schneider (LASP)

2 5 – 6 May 2008 IMW Meeting PARIS THEMIS, Tenerife, Canarias 0.90-m Solar telescope Spectral range 400 to 1000 nm at R ~ Slit: 0.5" & 2’ long Resolution of 450,000 with Slit: 0.25" & 74 " long May and October 2007 campaigns Spectral resolution Å Spectral dispersion 10.2 mÅ Four individual cameras D1 Na at 5896 Å OK D2 Na at 5889 Å OK D1 K at 7699 Å No ident. Li at 6707 ÅNo ident.

3 5 – 6 May 2008 IMW Meeting PARIS Two years of observations DateResults Phase Angle TAA 05/28/2007 – 01/06/20075 days, Seeing ~2″92° / 103°102°/117° 10/14/ /16/20073 days, Seeing ~2″120° / 130°264° / 272° 04/19/ /29/ days, Seeing ~2″12° / 53°325° / 25° 07/11/ /18/2008TBD-75° / -48°297° / 337° 09/01/ /05/2008TBD111° / 123°173° / 184° 10/30/ /09/2008TBD-53° / -26°72° / 114° Scanning of Mercury’s exosphere: typically 17 exposures of ~8 mm separated by the width of the slit (0.5 ″ ) + tip tilt + tracking

4 5 – 6 May 2008 IMW Meeting PARIS May Campaign 01/06/2007 Hapke Model Measured D2 continuum Use of Mercury’s surface (Hapke 1986; Mallama et al. 2002) to : - Measure Seeing value and variation (here 2.05 ″ ±0.36″) - Calibrate (taking into account absorption effects)

5 5 – 6 May 2008 IMW Meeting PARIS D2 Na Observed D2 and D1 emission intensities Total: D2: 1.34± kR D1: 1.04± kR Uncertainty taking into account: - Noise level - Uncertainty on seeing value - Uncertainty on position of Mercury D1 Na

6 5 – 6 May 2008 IMW Meeting PARIS D2 Na Observed D2 and D1 emission intensities Simultaneous peaks of emission Following Potter et al. (2006) due to solar pressure effect inducing a strong recycling  Solar pressure acceleration = 35% of gravity acceleration D1 Na

7 5 – 6 May 2008 IMW Meeting PARIS D2 Na Observed Doppler width Fit of the spectral line by Gaussian distribution 1.37 km/s resolution of THEMIS But 2.5 – 2.8 km/s doppler width of exospheric line and optical thin  D2 = 0.3  D1 = 0.15 D1 Na

8 5 – 6 May 2008 IMW Meeting PARIS D2 Na Observed Doppler width probability to find these values at these places Equivalent temperature: K for “cold” regions K for “hot” regions Good agreement with Killen et al. (1999) D1 Na

9 5 – 6 May 2008 IMW Meeting PARIS Conclusions of 06/01/2007 observations The high latitude peaks are produced by an energetic process with respect to the bulk exosphere - Cannot be thermal desorption - Meteoroid vaporization, difficult to produce symmetric peaks - Could be photon stimulated desorption if local peaks of surface density are formed (following Potter et al. (2006) suggestions) - Most probably solar wind sputtering but how to have symmetric magnetospheric impact?

10 5 – 6 May 2008 IMW Meeting PARIS October’s campaign: 10/14/2007, D2 Na 14:34 UT - Seeing FWHM = 0.55 R M Tot. Emiss. = 1.62± kR 16:48 UT - Seeing FWHM = 0.58 R M Tot. Emiss. = 1.66± kR 13:46 UT - Seeing FWHM = 0.48 R M Tot. Emiss. = 1.86± kR 15:38 UT - Seeing FWHM = 0.54 R M Tot. Emiss. = 1.95± kR

11 5 – 6 May 2008 IMW Meeting PARIS 10/16/2007 D2 Na 14:35 UT - Seeing FWHM = 0.45 R M Tot. Emiss. = 1.74± kR 16:16 UT - Seeing FWHM = 0.40 R M Tot. Emiss. = 2.00± kR 17:19 UT - Seeing FWHM = 0.52 R M Tot. Emiss. = 2.46± kR

12 5 – 6 May 2008 IMW Meeting PARIS D2 Continuum D1 Continuum

13 5 – 6 May 2008 IMW Meeting PARIS FWHM D2 Doppler D2

14 5 – 6 May 2008 IMW Meeting PARIS Comparison with Potter et al. data set (2006) A rather good agreement  A steady exosphere to model…

15 5 – 6 May 2008 IMW Meeting PARIS Expected coverage at the end of 2008 campaign Red dawn side Orange dusk side  A 2009 campaign?