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NASA Technical Reports Server (NTRS) 19990027916: Models of Plumes:... |
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by NASA Technical Reports Server (NTRS) |
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There are two types of plume flow models: (1) 1D models |
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using ad hoc spreading functions, f(r); (2) |
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MagnetoHydroDynamics (MHD) models. 1D models can be |
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multifluid, time dependent, and incorporate very general |
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descriptions of the energetics. They confirm empirical |
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results that plume flow is slow relative to requirements |
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for high speed wind. But, no published 1 D model |
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incorporates the rapid local spreading at the base |
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(fl(r)) which has an important effect on mass flux. The |
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one published MHD model is isothermal, but confirms that |
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if b=8*pi*p/absolute value(B)2<<l then the field is |
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nearly potential below -70,000 km. Building on the MHD |
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result, we apply a two scale approximation to calculate |
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fl(r). We also compute the global spreading (fg(r)) out |
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to 5.0 RSUN imposed by coronal hole geometry. Global MHD |
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models provide a potent method of calculating fg(r). |
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Unambiguous plume signatures have not yet been found in |
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the solar wind. This is probably due to strong mixing of |
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plume and interplume flows near the Sun. We describe a |
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physical source for strong mixing due to the observed |
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flows being unstable to shear instabilities that lead to |
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rapid disruption. |
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Date Published: 2016-10-15 11:33:22 |
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Identifier: NASA_NTRS_Archive_19990027916 |
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Item Size: 15664948 |
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Language: english |
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Media Type: texts |
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