title: Far-ultraviolet imaging spectroscopy of Io's atmosphere with HST/STIS.
abstract: Well-resolved far-ultraviolet spectroscopic images of O I, S I, and previously undetected H ILyman-alpha emission from Io were obtained with the Hubble space telescope imaging spectrograph (STIS). Detected O I and S I lines (1250 to 1500 angstroms) have bright equatorial spots (up to 2.5 kilorayleighs) that shift position with jovian magnetic field orientation; limb glow that is brighter on the hemisphere facing the jovian magnetic equator; and faint diffuse emission extending to approximately 20 Io radii. All O I and S I features brightened by approximately 50 percent in the last two images, concurrently with a ground-based observation of increased iogenic [O I] 6300-angstrom emission. The H ILyman-alpha emission, consisting of a small, approximately 2-kilorayleigh patch near each pole, has a different morphology and time variation.
authors.affiliation: Physics Department, University of Wisconsin, 1150 University Avenue, Madison, WI 53706, USA.
authors.forename: F L
authors.initials: FL
authors.lastname: Roesler
authors.forename: H W
authors.initials: HW
authors.lastname: Moos
authors.forename: R J
authors.initials: RJ
authors.lastname: Oliversen
authors.forename: R C
authors.initials: RC
authors.lastname: Woodward
authors.forename: K D
authors.initials: KD
authors.lastname: Retherford
authors.forename: F
authors.initials: F
authors.lastname: Scherb
authors.forename: M A
authors.initials: MA
authors.lastname: McGrath
authors.forename: W H
authors.initials: WH
authors.lastname: Smyth
authors.forename: P D
authors.initials: PD
authors.lastname: Feldman
authors.forename: D F
authors.initials: DF
authors.lastname: Strobel
mesh_terms: D001272:Atmosphere; D005118:Extraterrestrial Environment; D006859:Hydrogen; D018538:Jupiter; D008280:Magnetics; D010100:Oxygen; D013056:Spectrophotometry, Ultraviolet; D013455:Sulfur
chemical_list: D013455:Sulfur; D006859:Hydrogen; D010100:Oxygen