Physics
Scientific paper
Aug 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000icar..146..568m&link_type=abstract
Icarus, Volume 146, Issue 2, pp. 568-582 (2000).
Physics
24
Scientific paper
General structure and composition of the near-solar dust cloud are investigated. Based on estimates for sources and transport of dust to the near-solar region, we derive a representative set of trajectories of dust grains by numerical integrations and obtain the spatial distribution of different dust populations within 10 solar radii (Rsolar) from the Sun. For the radial structure, we find the dust number density to be enhanced by a factor of 1 to 4 in a typical heliocentric distance zone with a width of 0.2Rsolar in the sublimation region-the formation of a dust ring-depending on the materials and porosities considered. The excess density in the ring increases with increasing initial size for porous grains and decreases for compact ones. Non-zero eccentricities of the dust orbits decrease the enhancement. Moderate enhancements that we predict are consistent with eclipse observations, most of which have not shown any peak features in the F-corona brightness at several solar radii. We describe typical features of β-meteoroids formed by the sublimation of particles near the Sun and estimate the total mass loss due to this mechanism to range between 1 and 10 kg s-1. For the vertical structure of the dust cloud we show that grains larger than ~10 μm in size keep in a disk with a typical thickness of tens degrees; grains with radii of several μm fill in a broader disk-like volume which is tilted off the ecliptic plane by a variable angle depending on the solar activity cycle; submicrometer-sized grains form a nearly spherical halo around the Sun with a radius of more than 10Rsolar. From our present knowledge we cannot exclude the existence of an additional spheroidal component of larger grains near the Sun, which depends on how effective long-period comets are as sources of dust. Estimates of absolute number densities and local fluxes of dust show that simple extrapolation of the interplanetary dust cloud into the solar vicinity does not describe the dust cloud near the Sun properly. A complex latitudinal dependence of the fluxes of micrometer-sized grains, as well as variability of these fluxes with the solar activity phase, are predicted. The fluxes and their time variations depend on the physical and chemical properties of dust.
Kimura Hiroshi
Krivov Alexander
Mann Ingrid
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