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5 – 6 May 2008 IMW Meeting PARIS

THEMISObservations (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)

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5 – 6 May 2008 IMW Meeting PARIS

THEMIS, Tenerife, Canarias0.90-m Solar telescope

Spectral range 400 to 1000 nm at R ~ 220000 Slit: 0.5" & 2’ long

Resolution of 450,000 with Slit: 0.25" & 74 " long

May and October 2007 campaigns

Spectral resolution 0.027 Å Spectral dispersion 10.2 mÅ Four individual cameras

D1 Na at 5896 Å OKD2 Na at 5889 Å OKD1 K at 7699 Å No ident.Li at 6707 Å No ident.

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5 – 6 May 2008 IMW Meeting PARIS

Two years of observations

Date ResultsPhase Angle

TAA

05/28/2007 – 01/06/2007 5 days, Seeing ~2″ 92° / 103° 102°/117°

10/14/2007 - 10/16/2007 3 days, Seeing ~2″ 120° / 130° 264° / 272°

04/19/2008 - 04/29/2008 10 days, Seeing ~2″ 12° / 53° 325° / 25°

07/11/2008 - 07/18/2008 TBD -75° / -48° 297° / 337°

09/01/2008 - 09/05/2008 TBD 111° / 123° 173° / 184°

10/30/2008 - 11/09/2008 TBD -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

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5 – 6 May 2008 IMW Meeting PARIS

May Campaign01/06/2007

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 intoaccount absorption

effects)

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5 – 6 May 2008 IMW Meeting PARIS

D2 NaObserved D2 and D1emission intensities

Total:D2: 1.34±0.10 105 kR

D1: 1.04±0.06 105 kR

Uncertainty taking into account:

- Noise level- Uncertainty on seeing

value- Uncertainty on

position of Mercury

D1 Na

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5 – 6 May 2008 IMW Meeting PARIS

D2 NaObserved D2 and D1emission intensities

Simultaneous peaksof emission

Following Potter et al. (2006) due to solar

pressure effect inducing a strong recycling

Solar pressure acceleration

= 35% of gravityacceleration

D1 Na

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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

andoptical thin

D2 = 0.3 D1 = 0.15

D1 Na

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5 – 6 May 2008 IMW Meeting PARIS

D2 Na Observed Doppler width

10-6 probability to find these values at these

places

Equivalent temperature:- 810 - 960 K for “cold”

regions -890-990 K for “hot”

regions

Good agreement with Killen et al. (1999)

D1 Na

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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?

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5 – 6 May 2008 IMW Meeting PARIS

October’s campaign: 10/14/2007, D2 Na

14:34 UT - SeeingFWHM = 0.55 RM

Tot. Emiss. = 1.62±0.22 105 kR

16:48 UT - SeeingFWHM = 0.58 RM

Tot. Emiss. = 1.66±0.58 105 kR

13:46 UT - SeeingFWHM = 0.48 RM

Tot. Emiss. = 1.86±0.79 105 kR15:38 UT - SeeingFWHM = 0.54 RM

Tot. Emiss. = 1.95±0.76 105 kR

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5 – 6 May 2008 IMW Meeting PARIS

10/16/2007 D2 Na14:35 UT - SeeingFWHM = 0.45 RM

Tot. Emiss. = 1.74±0.23 105 kR

16:16 UT - SeeingFWHM = 0.40 RM

Tot. Emiss. = 2.00±0.31 105 kR

17:19 UT - SeeingFWHM = 0.52 RM

Tot. Emiss. = 2.46±0.47 105 kR

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5 – 6 May 2008 IMW Meeting PARIS

D2 Continuum D1 Continuum

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5 – 6 May 2008 IMW Meeting PARIS

FWHM D2 Doppler D2

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5 – 6 May 2008 IMW Meeting PARIS

Comparison with Potter et al. data set (2006)

A rather good agreement A steady exosphere to model…

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5 – 6 May 2008 IMW Meeting PARIS

Expected coverage at the end of 2008 campaign

Red dawn sideOrange dusk side A 2009 campaign?