1 Paris, May 5th 2008 Exospheric Sodium Observation of Mercury at TNG V. Mangano, C. Barbieri, F. Leblanc, G. Cremonese, C. Grava (1) INAF-Interplanetary Space Physics Institute, Roma (2) University of Padova, Astronomy Department (3) Service d'Aéronomie du CNRS, Verrières-Le-Buisson, France (4) INAF- Astronomical Observatory of Padova (5) CISAS- University of Padova

2 TNG site and description The TNG (Telescopio Nazionale Galileo) is the 3.58 m Italian Alt-Az telescope located in the island of La Palma, Canaries. It is equipped with an active optics system and its 2 Nasmyth foci host 5 instruments permanently mounted. Among these instruments, there is SARG, an high efficiency spectrograph with an echelle grating designed for the spectral range from 370 up to 900 nm, for a resolution from R=29000 to R= Altitude 2387 m a.s.l. Lat. 28º 45’ 28” N Long. 17º 53’ 38” W Paris, May 5th 2008

3 Mercury Observations at TNG 2002 (August 23rd-24th)  published on PSS 52 (2004) Barbieri C., Verani S., Cremonese G., Sprague A., Mendillo M., Cosentino R., Hunten D., First observations of the Na exosphere of Mercury with the high-resolution spectrograph of the 3.5 M Telescopio Nazionale Galileo 2003 (August 8,9 and 10th)  published on ICARUS 185 (2006) Leblanc F., Barbieri C., Cremonese G., Verani S., Cosentino R., Mendillo M., Sprague A., Hunten, D., Observation of Mercury’s exosphere: spatial distributions and variations of its Na component during August 8,9 and 10, (June 29,30th, July 1th)  paper in preparation (Mangano V. et al.) 2006 (June 16th to 18th)  first of the IMW coordinated campaign work still in progress first results showed by Barbieri in Boston, 2006 Paris, May 5th 2008

4 Results for the June 16, 2006 evening - 2 Log 10 scale D2 For better visual clarity, I show only the D2 intensities in ADUs. Each slit is 27 arcsec long. 46,55 44,48

5 TNG 2005 data set June 29th June 30th July 1st During the 2005 campaign 3 nights of observation were performed (at sunset at about 19:00 UT, for 1 hour). Main Mercury Parameters: Angular diameter: arcsec Elongation: º E Heliocentric distance: AU Sun-Mercury-Earth angle: º True Anomaly Angle º Paris, May 5th 2008

6 Long slit (26.7” x 0.4”) Resolution: Na filter (no order overlapping) 60 Å wide Scan in the north-south direction: equator ± 4” Exposure time: 120”

77 Paris, May 5th 2008 SARG CCD is a mosaic of two thinned back illuminated detectors dimensions: 2048x4096 pixels pixel size: 13.5 µm Phase 1: pre-analysis D2 D1 D 2 D 1

8 Paris, May 5th Correcting spectra for sky and diffuse light 2.Matching theorical dopplershifted D1 and D2 lines (red dotted line) with observed ones Phase 2: Analysis

9 Paris, May 5th Reproducing the Fraunhofer absorption bands throught three different profiles : a)Voigt, b) Solar spectrum, and c) straight line; comparison and extraction of the emission line

10 NB: In some cases the differences are negligible, but not in other slits. Hence, we choose the straight line profile as the best for all cases.

11 Paris, May 5th Creation of a reflectance model of the illuminated disk by following the Hapke theory

12 Paris, May 5th Comparison of this model with the continuum as a method to derive the calibration factor for the conversion ADU  Rayleigh 6. The output provides the D2 and D1 sodium profiles along the slit

13 Paris, May 5th st night: June 29th 2005 Slit Number Obs.Time (UT) Theoretical Position Final Position Seeing Sigma Calibration Factor HYLN004520: HYLN004620: HYLN004720: D composition /1:

14 Paris, May 5th nd night: June 30th D composition /2: Slit Number Obs.Time (UT) Theoretical Position Final Position Seeing Sigma Calibration Factor HYNB005320: HYNB005420: HYNB005520: HYNB005620: HYNB005720: HYNB005820: HYNB005920: HYNB006020:

15 Paris, May 5th rd night: July 1st D composition /3: Slit Number Obs.Time (UT) Theoretical Position Final Position Seeing Sigma Calibration Factor HYQB004420: HYQB004520: HYQB004620: HYQB004720: HYQB004820:

16 Paris, May 5th 2008 Two features are clearly visible: 1.An emission peak in the southern hemisphere at mid latitude: Related surface feature? Opening of the magnetic field southern cusp? 2.A global enhancement of sodium emission during the second night (50%) Related solar events? Phase 3: Interpretation

17 Paris, May 5th The peak appear to be at about: º E, 10-40º S Radar bright spots: (A. Sprague) A (15° E, 25° S), B(15° E, 55° N),C(120° E,15°N) (J. Harmon) A (12° E, 34° S), B(17° E, 58° N),C(114° E, 11°N), (18° E, 27° S), Bartok crater Location of the peak

18 Paris, May 5th No match with the radar bright spots. Maybe with the faint feature associated to the Bartok crater?

19 Paris, May 5th Opening of the magnetic cusps The mid-latitude position of the peak suggests a relation with the opening of the magnetic cusps: IMF Bx > 0  injection in southern hemisphere IMF Bx < 0  injection in the northern hemisphere (-) → IMF Bx > 0 (+) → IMF Bx < 0 IMF Bx (flipped) time Coronal Field ‘Wrong’ direction of the IMF Bx component!

20 Paris, May 5th Solar conditions – impulsive events Paris, May 5th 2008 Wilcox Solar Obs. photospheric field CR#2031SoHO/EIT (Fe XV 284 Å) image 29-June :00 UT Coronal Hole Fast Stream Active Region AR0781 (CMEs) 20

21 Paris, May 5th June 29th CME :30 UT, v 0 = 350 km/s Estimated arrival time: July 1st, 17:00 UT June 28th CME :05 UT, v 0 = 600/400 km/s Estimated arrival time: June 30th, 03:00 UT June 30th, 15:00 UT CME #2 CME #3 CME #1 June 28th HALO CME :30 UT, v 0 = 1750 km/s Estimated arrival time: June 30th, 05:00 UT

22 Paris, May 5th 2008 To summarise: 29-Jun (180) 30-Jun (181) 01-Jul (182) 20:00 UT20:00 UT 20:00 UT IMF Bx < 0 CME#1 CME#2 CME#3 time is Na intensification correlated to CME? N-S asymmetry? related to IMF Bx? Coronal hole