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Fe XXIV Emission in Solar Flares Observed with the NRL/ATM XUV Slitless Spectrograph

Published online by Cambridge University Press:  14 August 2015

Kenneth G. Widing
Kenneth G. Widing*
Affiliation:
E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, D.C. U.S.A.

Abstract

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During the Skylab Mission, the NRL slitless spectrograph photographed a number of flares in the 170–600 Å region with a spatial resolution approaching 2″. At flare maximum the 2s2S1/2 — — 2p2P1/2, 3/2 transitions of Fe XXIV are present, and show the location of the (approx.) 20 × 106 deg plasma with respect to the surface magnetic field and chromospheric (He iiemissions. Three examples are discussed (two only briefly).

In the small, intense disk flare of 1973, August 9 the high temperature region appears at the foot of a low altitude arch. The estimated electron density is 5 × 1011 cm–3.

In the limb flare of 1974, January 15 the hot X-ray emitting component is at a very low altitude compared to the flare loops.

In the impulsive double ribbon flare of 1973, June 15 the Fe XXIV emission is centered over the neutral line, forming a bridge-like structure between magnetic regions of opposite polarity. The estimated electron density is 5 × 1010 cm–3.

The Fe XXIV emission was visible 8 to 10 min as compared with a calculated cooling time by conduction of only 5 min. The lengthened life of the emission may be associated with the observed ‘turbulence’, which inhibits the heat conduction, or alternatively, with a slower energy release prolonged beyond the end of the burst phase.

Type
Part 3: Solar Flares
Information
Symposium - International Astronomical Union , Volume 68: Solar X, Gamma, and EUV Radiation , 1975 , pp. 153 - 163
Copyright
Copyright © Reidel 1975 

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