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Title: The structure and dynamic nature of the solar atmosphere
Author: Marsh, Michael Stewart
Awarding Body: University of Central Lancashire
Current Institution: University of Central Lancashire
Date of Award: 2005
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This thesis presents an examination of a range of dynamic phenomena present throughout the solar atmosphere, from the photosphere to the corona. Above the photosphere, where the plasma fi is small, the emitting plasma structure and dynamics are tied intimately to the solar magnetic field. Firstly, a wavelet analysis is applied to multi-temperature spectroscopic data observing network-internetwork regions across a coronal hole boundary region. The nature of quasiperiodic variability is investigated through the different temperature lines across the observed structures. Statistically significant periods are found within the range 100-900 seconds, along with short period wavepackets with periods 50-100 seconds. These oscillations are discussed in terms of possible wave mechanisms. An example of a time-dependent period is observed above the network region on the coronal hole boundary and possible theoretical origins are discussed. Secondly, a detailed analysis is applied to an active region observed on the solar limb. A dynamic transition region loop, and closely associated ejection event are observed within the active region. These structures are characterised by their emission line profiles; the transition region loop is found to have a flow geometry of -20---*40 km c 1 , and the ejection event is found to have a velocity gradient up to -20—*50 km across its width, suggesting a rotating transition region structure consistent with a macrospicule. Thirdly, an upwardly propagating disturbance is observed along a coronal loop associated with a plage region with a velocity 50-195 km s perpendicular to the line of sight, and period of 5 minutes. A wavelet analysis reveals that the five minute period is present in co-spatial, co-temporal chromospheric and transition region observations. This is interpreted as the first observation of a 5-mm p-mode propagating through the chromosphere, transition region and into a coronal loop. Fourthly, an observing campaign is designed and executed to probe the connectivity between the chromosphere, transition region and corona within active regions. Oscillations within the 3-min band are observed above the umbra of a sunspot active region. These oscillations show two closely separated frequencies of 6.1 & 7.1 mHz in the chromosphere, 5.9 & 7.3 mHz in the transition region and 5.9 & 7.3 mHz in the corona. These observations are interpreted as acoustic/maneto-acoustic wave modes propagating upwards through the chromosphere, transition region and into the corona. The frequencies are observed as oscillations in the chromosphere and transition region, and propagations in the emerging coronal loops, due to the combined effect of the temperature scale height in the different spectral lines and the diverging magnetic flux geometry above the sunspot. The energy flux of acoustic waves is estimated in the different temperature lines as 28.3 erg cm 2 in the chromosphere, 201.0 erg cm2 sin the transition region and 225.6 erg cm 2 in the corona. Finally, future work is discussed in terms of progressing the work completed, and exploiting upcoming spaced based missions.
Supervisor: Not available Sponsor: Particle Physics and Astronomy Research Council (PPARC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QB Astronomy