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Title: Multi-fluid model of a sun-grazing comet in the rapidly ionizing, magnetized low corona

Two Sun-grazing comets were recently imaged in the low solar corona by space telescopes in unprecedented detail, revealing a wide range of new phenomena. This sparked growing interest in the interaction of comets with the coronal plasma and magnetic field and their diagnostic potential as solar probes. However, interpretation of such rich observational data requires profound understanding of relevant physical processes in an unexplored regime. Here advanced numerical modeling can provide critical clues. To this end, we present a prototype, multi-fluid, magnetohydrodynamic model of a steady-state comet in the low solar corona. These simulation results are compared with previously modeled comets in the solar wind environment. By inspecting their projection and column densities, we find a dominance of O{sup 6+} ions in the cometary tail, which can explain the observed extreme ultraviolet emission. The tail is found to be comparable to recent EUV images of these comets. In addition, the comet tail appears wider when the observer's line of sight is perpendicular rather than parallel to the local magnetic field. This is opposite to the trend in the interplanetary space permeated in the solar wind, because the ratio between dynamic pressure and magnetic pressure is an order of magnitude smallermore » than at 1 AU. On the other hand, we find that iron ions in the comet head build up to a density comparable to that of oxygen ions, but are unlikely to form a visible tail because of the shorter mean free paths of the neutrals.« less
Authors:
;  [1] ;  [2] ;  [3]
  1. IGPP and EPSS, University of California, Los Angeles, CA 90095 (United States)
  2. Stanford-Lockheed Institute for Space Research, Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Palo Alto, CA 94304 (United States)
  3. AOSS, University of Michigan, Ann Arbor, MI 48109 (United States)
Publication Date:
OSTI Identifier:
22369968
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 796; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COMETS; COMPARATIVE EVALUATIONS; DENSITY; EMISSION; EXTREME ULTRAVIOLET RADIATION; INTERPLANETARY SPACE; IRON IONS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MEAN FREE PATH; OXYGEN IONS; PLANETS; PLASMA; SATELLITES; SIMULATION; SOLAR CORONA; SOLAR WIND; STEADY-STATE CONDITIONS; SUN; TELESCOPES