28 March 2003 Photophoretic forces for bispherical aerosol particles
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The gravito-photophoretic forces in the free-molecular regime have been calculated for the bispherical aerosol particles by using the Monte-Carlo method to estimate molecular transfer. It is shown that two types of gravito-photophoresis can contribute to levitation of aerosol particles absorbing the Sun and the Earth's radiation. There are the well-known Δα-gravito-photophoresis, its cause is a different in the thermal accommodation coefficient, and ΔT-gravito-photophoresis, when the aerosol aggregate consists of individual particles differing in temperature due to a difference in the physical properties and the radiation absorption power. Both mechanisms can induce large lifting forces able to provide a vertical transport of aerosol particles into the upper atmosphere. A connection between an existence of aerosol layers at altitudes near 20, 50, 70-100 km in the real Earth's atmosphere and a condition of the balance of photophoretic and gravity forces is shown.
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Aleksander A. Cheremisin, Aleksander A. Cheremisin, Yu. V. Vassilyev, Yu. V. Vassilyev, A. V. Kushnarenko, A. V. Kushnarenko, } "Photophoretic forces for bispherical aerosol particles", Proc. SPIE 5027, Ninth Joint International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics. Part II: Laser Sensing and Atmospheric Physics, (28 March 2003); doi: 10.1117/12.497278; https://doi.org/10.1117/12.497278

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