Energy analysis of post mass ejection solar coronal x-ray loops.

By: Contributor(s): Series: NCAR Cooperative Thesis ; 166Boulder, CO : National Center for Atmospheric Research (NCAR), 1999Description: xxii, 344 leaves : ill. ; 28 cmContent type:
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Subject(s): Dissertation note: Thesis (Ph. D.)--University of Colorado, 1999. Summary: Solar coronal mass ejections have been shown in the past to be associated with the enhancement of solar x-ray emission of several hours duration. Analysis of solar x-ray images has shown that these long-duration x-ray events are due to an arcade of post mass ejection loops that form over the magnetic polarity inversion line that lies underneath the mass ejections. While this has been successfully described qualitatively in past work, we seek to apply a quantitative analysis to understand the detailed evolution of energy balance in the system, including the evolution of heating and cooling mechanisms We measured a set of intensity-time profiles as a function of height for particularly well observed arcade events on the solar limb with relatively simple morphology. We developed a semi-theoretical model, with the basic premise that at each point in space, the intensity is the response to an interplay between a source term and a cooling term. This principle is developed for models with increasingly sophisticated geometries in order to test the effect of line-of-sight integration of x-ray emission in the image data. The models for the data are expressed in terms of a set of free parameters, which are then optimized to provide the best fit of the model to the data. Our best-fit parameters enable us to make several inferences about the physical nature of the system. The region of heating develops early in the event and spans a surprisingly large vertical dimension. The heating continues throughout much of the duration of the event. The enhancement of x-ray emission is primarily due to an enhancement of density of plasma in the loops, although there is a small increase in temperature. During the early phase of the event, radiative and conductive cooling are of similar magnitude, but increase more slowly than heating. Once the cooling mechanisms surpass heating the event enters the cooling phase. During this phase, the radiative cooling decreases relatively quickly and conductive cooling becomes the dominant cooling mechanism. We compare the energy of the heating with the energies of an approximate model for the coronal magnetic field to make an estimate of the energy released by magnetic reconnection.
Holdings
Item type Current library Call number Copy number Status Date due Barcode Item holds
BOOK BOOK NCAR Library Mesa Lab QB523 .B174 1999 1 Available 50583020038414
BOOK BOOK NCAR Library Foothills Lab QB523 .B174 1999 1 Available 50583010361602
Total holds: 0

Thesis (Ph. D.)--University of Colorado, 1999.

Includes bibliographical references (leaves 301-311).

Solar coronal mass ejections have been shown in the past to be associated with the enhancement of solar x-ray emission of several hours duration. Analysis of solar x-ray images has shown that these long-duration x-ray events are due to an arcade of post mass ejection loops that form over the magnetic polarity inversion line that lies underneath the mass ejections. While this has been successfully described qualitatively in past work, we seek to apply a quantitative analysis to understand the detailed evolution of energy balance in the system, including the evolution of heating and cooling mechanisms We measured a set of intensity-time profiles as a function of height for particularly well observed arcade events on the solar limb with relatively simple morphology. We developed a semi-theoretical model, with the basic premise that at each point in space, the intensity is the response to an interplay between a source term and a cooling term. This principle is developed for models with increasingly sophisticated geometries in order to test the effect of line-of-sight integration of x-ray emission in the image data. The models for the data are expressed in terms of a set of free parameters, which are then optimized to provide the best fit of the model to the data. Our best-fit parameters enable us to make several inferences about the physical nature of the system. The region of heating develops early in the event and spans a surprisingly large vertical dimension. The heating continues throughout much of the duration of the event. The enhancement of x-ray emission is primarily due to an enhancement of density of plasma in the loops, although there is a small increase in temperature. During the early phase of the event, radiative and conductive cooling are of similar magnitude, but increase more slowly than heating. Once the cooling mechanisms surpass heating the event enters the cooling phase. During this phase, the radiative cooling decreases relatively quickly and conductive cooling becomes the dominant cooling mechanism. We compare the energy of the heating with the energies of an approximate model for the coronal magnetic field to make an estimate of the energy released by magnetic reconnection.

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