Title : EUV Spectroscopy of Solar Active Region Jets

Abstract : The million degree temperature of the solar corona has been a continuing puzzle to scientists. A detailed study of energetic events such as solar flares, coronal mass ejection and solar jets may provide important clues about how changes in the magnetic activity lead to explosive eruptions in the corona and contribute to coronal heating.

In this thesis, the author has studied solar jets, ubiquitous energetic transients observed in the solar atmosphere. They have been observed to originate from the edge of active regions and show signatures in different layers of the solar atmosphere. A systematic investigation has been carried out by the author to understand the temperature structure of active region jets (AR jets) by combining imaging and spectroscopic observations using the differential emission measure (DEM) technique. The study gives a new perspective to our understanding of the dynamics involved in AR jets.

Multiwavelength high-resolution imaging observations from space-based telescopes such as the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamic Observatory (SDO), the X-ray Telescope (XRT) on board the Hinode satellite, and spectroscopic observations from the Extreme UV Imaging Spectrometer (EIS) on board the Hinode and the Interface Region Imaging Spectrometer (IRIS) were used to study the physical parameters of jets such as plasma flows, electron number densities, emission measure, peak temperature, velocities (plane-of-sky, Doppler, nonthermal) and filling factors.

In addition, the relationship between AR jets and other phenomena such as photospheric magnetic activity, nonthermal type-III radio bursts and soft/hard X-ray emission has been studied using the Helioseismic and Magnetic Imager (HMI) on board SDO, the WAVES instrument on board the Wind satellite and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) respectively. The observations and results obtained in this study compare well with numerical simulations and theoretical models available in the literature.