Spatially Resolved Spectroscopy of Io's Pele Plume and SO2 Atmosphere

McGrath, M. A.

doi:10.1006/icar.1999.6412

Cited by 88 publications

(78 citation statements)

References 60 publications

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“…As there are no electron impact excitation cross sections or collision strengths available for the S i] 1479 forbidden multiplet, the S i] 1900 intercombination dou- blet is used for the analysis. We use the electron excitation rate presented in Figure 9a of McGrath et al (2000).…”

Section: Constraints On T E and N Ementioning

confidence: 99%

“…Despite the recent advances in quantifying Io's atmosphere, including investigating the inhomogeneity and impact of volcanic activity (Feldman et al 2000;McGrath et al 2000;Spencer et al 2000), analyzing the air glow (Geissler et al 1999), and resolving the morphology (Roesler et al 1999;Retherford et al 2000), and the fact that several sets of sulfur and oxygen emission-line data have been acquired and analyzed (Ballester 1989;McGrath et al 2000;Oliversen et al 2001;Wolven et al 2001), the abundances are still not well constrained. Various observational measurements and theoretical models have placed loose bounds on the sulfur column density (N S ).…”

Section: Introductionmentioning

confidence: 99%

“…Various observational measurements and theoretical models have placed loose bounds on the sulfur column density (N S ). Previously, electron densities and temperatures were assumed in order to estimate N S , resulting in limits of 2:2 Â 10 12 cm À2 < N S < 7 Â 10 15 cm À2 (Ballester et al 1987;McGrath et al 2000). Recent observations make both optically thick and optically thin regimes available in a single exposure, allowing us to constrain N S without assuming a specific T e or n e .…”

Section: Introductionmentioning

confidence: 99%

“…Significant progress has been made in characterizing both the spatial distribution and temporal variability of the SO 2 atmosphere (Ballester et al 1994;Trafton et al 1996;McGrath et al 2000;Feldman et al 2000;Spencer et al 2000;. The current picture includes a higher column density equatorial, subsolar region, N SO 2 $ 1 5 ð ÞÂ10 16 cm À2 , with a strong poleward gradient, where N SO 2 decreases to less than 10 15 cm À2 (Feldman et al 2000; and column densities greater than 10 16 cm À2 above active volcanic regions Spencer et al 2000).…”

Section: Introductionmentioning

confidence: 99%

“…In order to minimize scattered-light contamination, only the first seven groups of the data, corresponding to Io in eclipse, were used. The data were reduced in the same manner as presented in McGrath et al (2000) and were rebinned by 2 pixels and smoothed by 3.…”

Section: Introductionmentioning

confidence: 99%

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The Abundance of Atomic Sulfur in the Atmosphere of Io

Feaga

McGrath

Feldman

2002

ApJ

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Observations with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope have been used to constrain the atomic sulfur column density in Io's atmosphere. The S i 1479 dipole allowed and forbidden transition multiplets have been resolved for the first time at Io, enabling the study of both optically thick and thin transitions from a single atomic species. The allowed transitions contribute 62% AE 8% and the forbidden transitions 38% AE 8%, on average, to the total signal of the S i 1479 multiplets. Using the optically thick and thin transitions of S i 1479 observed near the limbs of Io, we derive a tangential atmospheric sulfur column abundance of 3:6 Â 10 12 cm À2 < N S < 1:7 Â 10 13 cm À2 , which is independent of electron temperature and density. A low-density SO 2 atmosphere, N SO 2 $ 5 10 ð ÞÂ10 15 cm À2 , consistent with that inferred from other recent observations, is most consistent with these bounds.

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Section: Constraints On T E and N Ementioning

confidence: 99%