Electron capture collisions relevant to X-ray emission from comets

S. OTRANTO, R. E. OLSON AND P. BEIERSDORFER

Creta, Grecia

Simposio; XX International Symposium on Ion-Atom collisions (ISIAC); 2007

As the result of the detection of X-ray emission from comet Hyakutake in 1996 [1], spectroscopic observations of comets has gained the attention of both the astrophysical and the atomic physics communities. Since then, charge exchange between solar wind ions and the cometary gases in the comet coma has been recognized as the mechanism responsible for the observed spectral emissions. One of the key issues concerning the charge exchange process between highly charged solar ions and cometary targets is the capability of a theoretical model to predict the critical n,l-levels populations, which are the input for the photon cascades. Even though several models are capable of providing the most probable n-level for capture, the l-level distributions were unknown and high energy or ad-hoc approximations originally were incorrectly applied [2-3]. In our work which is detailed in Refs. [4-5], we use CTMC calculations that inherently provide the n,lstates populations after charge exchange. The spectra of the Linear C/1999 S4 and McNaught-Hartley C/1999 T1 comets have been studied using this model and are well-reproduced when ion abundances measured by the Advanced Composition Explorer (ACE) satellite are utilized. Work in UMR supported by the OFES-DOE. Work in UNS supported by PGI 24 F/038. References [1] T. E. Cravens, Science 296 (2002) 1042. [2] R. M. Häberli et al., Science 276 (1997) 939. [3] R. Wegmann et al., Planet. Space. Sci. 46 (1998) 603 [4] S. Otranto, R. E. Olson and P. Beiersdorfer, Phys. Rev. A 73 (2006) 022723. [5] S. Otranto, R. E. Olson and P. Beiersdorfer, J. Phys. B 40 (2007) 1755.296 (2002) 1042. [2] R. M. Häberli et al., Science 276 (1997) 939. [3] R. Wegmann et al., Planet. Space. Sci. 46 (1998) 603 [4] S. Otranto, R. E. Olson and P. Beiersdorfer, Phys. Rev. A 73 (2006) 022723. [5] S. Otranto, R. E. Olson and P. Beiersdorfer, J. Phys. B 40 (2007) 1755.46 (1998) 603 [4] S. Otranto, R. E. Olson and P. Beiersdorfer, Phys. Rev. A 73 (2006) 022723. [5] S. Otranto, R. E. Olson and P. Beiersdorfer, J. Phys. B 40 (2007) 1755.73 (2006) 022723. [5] S. Otranto, R. E. Olson and P. Beiersdorfer, J. Phys. B 40 (2007) 1755.40 (2007) 1755.