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Title: The role of chromospheric jet-like events in coupling the chromosphere and corona : a multi-instrument approach
Author: Vanninathan, Kamalam
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2013
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Abstract:
In this thesis we present a study of chromospheric features and their role in coupling the different layers of the solar atmosphere. We investigated the contribution of spicules, the most dominant feature in the chromosphere, to coronal heating as well as their role in active region outflows. We take a multi-instrument approach by using data from instruments on-board space missions such as the Solar Heliospheric Observatory (SoHO). Hinode. the Solar Dynamics Observatory (SDO) and from ground-based facilities such as the Dunn Solar Telescope (DST). We did a case study on large, dynamic spicules and found that they comprise of thin, high velocity jets (50-250 km/s). The large spicules attained a maximum temperature of 300,000K and did not have a coronal counterpart. Thus, we suggested that spicules do not contribute significantly to coronal heating. We further studied the thermal properties of the emission contributing to the Atmospheric Imaging Assembly (AlA) 171 A channel by constructing a Differential Emission Measure (OEM) distribution tram a region dominated by spicules. The results point out that the emission in the Fe IX 171.07 A line which dominates the AlA 171 A channel, comes from plasma at transition region temperatures (400,000K) rather than coronal. Hence, we concluded that observations of spicules in this channel cannot be conclusive evidence to prove that spicule plasma attains 1 MK . To study the spicule contribution to active region outflows we directly imaged the chromosphere and found that spicules are not abundant in this region. The few jets present showed plasma upflows followed by downflows indicating that these jets do not contribute to the coronal outflows. Densities within the outflow region was found to increase at short intervals which suggests repetitive mass influx into the corona. These observations are complemented by magnetic field extrapolations where we found open field lines that could possibly transport plasma into the solar wind. Further work on the source of the active region outflows by means of data driven three dimensional magneto-hydro dynamics simulations is under-way.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.603480  DOI: Not available
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