Laboratory Measurements of Solar-Wind/Comet X-Ray Emission and Charge-Exchange Cross Sections

Details Laboratory Measurements of Solar-Wind/Comet X-Ray Emission and Charge-Exchange Cross Sections Laboratory Measurements of Solar-Wind/Comet X-Ray Emission and Charge-Exchange Cross Sections

Nov 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002nla..work..117c&link_type=abstract

NASA Laboratory Astrophysics Workshop, held May 1-3 2002 at NASA Ames Research Center, Moffett Field, CA 94035-1000. Publisher:

Astronomy and Astrophysics

Astrophysics

Scientific paper

The detection of X-rays from comets such as Hyakutake, Hale-Bopp, d'Arrest, and Linear as they approach the Sun has been both unexpected and exciting. This phenomenon, moreover, should be quite general, occurring wherever a fast solar or stellar wind interacts with neutrals in a comet, a planetary atmosphere, or a circumstellar cloud. Comet-modeling calculations to date have (a) used an approximate, over-barrier expression for the charge-exchange (CE) cross section, (b) assumed a flat energy dependence of cross section, and (c) neglected multiple charge exchanges. In support of the understanding of the X-ray emissions (their intensity and spatial extent) laboratory measurements have been carred out at the JPL Highly-Charged Ion Facility [1]. The projectiles have been partially- and fully-stripped H, He, C, N, O, and Ne ions interacting with the comet molecules He, H2, CO, CO2, and H2O. Absolute CE cross sections have been measured, and normalized X-ray emission cross sections reported for these major HCI components of the solar wind [2-5]. The minor, heavier HCI components will produce high-energy X-rays. A large body of data has been acquired on Fe(5-13)+[6]. The experimental approach will be discussed and results given. Future work will be extended to Mgq+ charge states, and include as well NH3 as the target. R. Mawhorter thanks the National Research Council for a fellowship though the NASA-NRC program. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, and was supported under contract with the National Aeronautics and Space Administration.

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