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Proposal ID Klimchuk_86

Date of Proposal
97/03/14

firstname
James

lastname
Klimchuk

institute
Naval Research Lab

address
Code 7675JAK
Naval Research Lab
Washington, DC 20375-5352
USA

email
klimchuk@bandit.nrl.navy.mil

phone
(202)404-8136

fax
(202)404-7997

proposal
Soft X-ray images from Yohkoh reveal that hot (T greater than 2 MK) coronal loops
have surprisingly uniform thicknesses (Klimchuk et al. 1992). That is, the
loops diverge with height to a much lesser extent than is expected from
the presumed divergence of the magnetic field. Klimchuk et al. (1992)
suggested that the observed plasma loops may correspond to flux tubes that
are relatively highly twisted and thus carry strong electric currents.
Subsequently, McClymont and Mikic (1994) showed that many current-carrying
magnetic fields in force-free extrapolation models do, indeed, diverge
less rapidly with height than the corresponding potential fields; however, the
currents in these models are rather broadly distributed and not concentrated
in individually-twisted loops, as envisioned by Klimchuk et al.
There is a hint in the Yohkoh data that cool (T ~ 1 MK) loops may be
heated very differently from the hotter loops to which Yohkoh is most
sensitive (Cargill and Klimchuk 1997). Since the heating of a loop may be
physically related to its structure (e.g., twisted loops carry more electric
current, which might produce greater heating), it is important that the
thickness/divergence properties of cooler loops be studied. The EIT images
from SOHO are ideally suited for such a study, and we therefore propose to
repeat our analysis of loop thickness variations using this data. The
software tools for this analysis have already been developed, and a
description of the analysis procedure can be found in Klimchuk et al.
(1992).

Cargill, P. J., and Klimchuk, J. A. 1997, ApJ, April 1 issue.
Klimchuk, J. A., Lemen, J. R., Feldman, U., Tsuneta, S., and Uchida, Y.
1992, PASJ, 44, L181.
McClymont, A. N., and Mikic, Z. 1994, ApJ, 422, 899

inside_collab
Dan Moses
Fabrice Portier-Fozzani

consortium
no

topic
Coronal Loops

topic

title
Thickness Variations Along Coronal Loops


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