TY - JOUR

T1 - Stellar occultations by turbulent planetary atmospheres

T2 - A heuristic scattering model

AU - Hubbard, W. B.

AU - Jokipii, J. R.

N1 - Funding Information:
This work wa~ supported in part by NASA under Grants NSG-7045 (W.B.H.) and NSG-7101 (J.R.J.).

PY - 1977/3

Y1 - 1977/3

N2 - A model of ray refraction by an isothermal atmosphere with a scattering screen at the center of bending is used to generate analytic results which simulate the effects of real atmospheric turbulence on occultations. Calculations are carried through for scattering which is constant with height and for exponential height dependence. The effect of the scattering is to bias the the mean intensity of the occulted source, and hence systematically to distort bending angles and height differences obtained from inversion of the intensity data. However, the effect is of order 〈δε{lunate}2〉/ε{lunate}2 for either model, where 〈δε{lunate}2〉 is the mean square scattering angle and ε{lunate} is the average bending angle. The effect turns out to be small for plausible turbulence, since 〈δε{lunate}2〉/gfe2 is of approximately the same order as the relative mean square density fluctuation. Thus the random effects of turbulence are unlikely to be a source of large systematic error in occultations, provided that the data can be meaningfully averaged either temporally or over a number of occultation events.

AB - A model of ray refraction by an isothermal atmosphere with a scattering screen at the center of bending is used to generate analytic results which simulate the effects of real atmospheric turbulence on occultations. Calculations are carried through for scattering which is constant with height and for exponential height dependence. The effect of the scattering is to bias the the mean intensity of the occulted source, and hence systematically to distort bending angles and height differences obtained from inversion of the intensity data. However, the effect is of order 〈δε{lunate}2〉/ε{lunate}2 for either model, where 〈δε{lunate}2〉 is the mean square scattering angle and ε{lunate} is the average bending angle. The effect turns out to be small for plausible turbulence, since 〈δε{lunate}2〉/gfe2 is of approximately the same order as the relative mean square density fluctuation. Thus the random effects of turbulence are unlikely to be a source of large systematic error in occultations, provided that the data can be meaningfully averaged either temporally or over a number of occultation events.

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U2 - 10.1016/0019-1035(77)90106-3

DO - 10.1016/0019-1035(77)90106-3

M3 - Article

AN - SCOPUS:0141435335

SN - 0019-1035

VL - 30

SP - 531

EP - 536

JO - Icarus

JF - Icarus

IS - 3

ER -