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Titolo:
A NEW INTERPRETATION OF SCATTERED-LIGHT MEASUREMENTS AT TITANS LIMB
Autore:
RANNOU P; CABANE M; BOTET R; CHASSEFIERE E;
Indirizzi:
NASA,AMES RES CTR,MAIL STOP 245-3 MOFFETT FIELD CA 94035 UNIV PARIS 11,PHYS SOLIDES LAB F-91405 ORSAY FRANCE UNIV PARIS 06,SERV AERON F-75252 PARIS FRANCE
Titolo Testata:
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
fascicolo: E5, volume: 102, anno: 1997,
pagine: 10997 - 11013
SICI:
2169-9097(1997)102:E5<10997:ANIOSM>2.0.ZU;2-3
Fonte:
ISI
Lingua:
ENG
Soggetto:
OPTICAL-PROPERTIES; VERTICAL-DISTRIBUTION; AGGREGATE PARTICLES; ATMOSPHERE; AEROSOLS; TEMPERATURE; HAZES; MODEL;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
36
Recensione:
Indirizzi per estratti:
Citazione:
P. Rannou et al., "A NEW INTERPRETATION OF SCATTERED-LIGHT MEASUREMENTS AT TITANS LIMB", J GEO R-PLA, 102(E5), 1997, pp. 10997-11013

Abstract

Images of Titan, taken by Voyager 2 at phase angles Phi=140 degrees and Phi=155 degrees have provided radial intensity profiles at the bright and dark limbs, which provide information on the vertical and latitudinal distribution of organic hazes. In previous work, the deduced extinction coefficient, using ad hoc particle sizes, was obtained without help of microphysics, and it appeared difficult to compare it with coefficients computed from theoretical models. We use here our fractal approach of microphysical modeling and optics of aggregates to computeintensity profiles of the main haze at the bright limb, and compare to the Voyager observations. Fractal aerosol distributions are obtainedusing different production altitudes and rates. Scattering and absorption of light are described by an improved model, based on the use of fractal aggregates made of spherical (Mie) particles. We show that thefractal dimension of aggregates has to be D-f approximate to 2, as predicted by microphysical arguments. Only a production altitude z(0) approximate to 385 +/- 60 km, corresponding to a monomer radius r(m) approximate to 0.066 mu m, is fully consistent with both phase angle data. We also point out that the production rate of the aerosols decreasesby a factor approximate to 2 between 30 degrees S and the midnorthernlatitude and further, increases up to 80 degrees N. The average valueof the production rate is Q approximate to 1.4 x 10(-13) kg/m(2)/s; we give arguments in favor of dynamical processes rather than of a purely microphysical mechanisms to explain such latitudinal variations.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 23/09/20 alle ore 07:26:02