TITLE:
Transport in Astrophysics: II. Diffusion with Advection in Expanding Nebulae
AUTHORS:
Lorenzo Zaninetti
KEYWORDS:
Particle Diffusion, Random Walks
JOURNAL NAME:
International Journal of Astronomy and Astrophysics,
Vol.12 No.3,
July
28,
2022
ABSTRACT: The structure across an expanding shell in which drift and diffusion redistribute material requires careful consideration in order to correlate the surface brightness with the physical parameters. A new solution in terms of Fourier series is suggested for 1D diffusion in the presence of a drift velocity. The astrophysical parameters are chosen in agreement with the astronomical data for the planetary nebula A39. The new solution is then inserted into the existing theory for the astrophysical image which allows dealing with the intensity of radiation emitted in a spherical layer.