@misc{oai:ir.soken.ac.jp:00000416,
 author = {宮腰, 剛広 and ミヤゴシ, タケヒロ and MIYAGOSHI, Takehiro},
 month = {2016-02-17},
 note = {It is well established that sunspots and active regions are formed by the emergence of magnetic fluxes from the interior of the Sun into the atmosphere.  The newly emerged bipolar active regions are called emerging flux regions (EFRs).  There are several observational evidences which indicate the emergence and rising motion of magnetic flux tubes in EFRs.
  The emerging flux causes active phenomena and energy release in the solar corona.  The Yohkoh satellite discovered many dynamic phenomena in the solar corona.  One of the most interesting findings among such dynamic phenomena is solar coronal X-ray jets, which are observed as transitory X-ray enhancements with an apparent collimated motion.  Based on the frequent observations of X-ray jets from emerging flux regions, Shibata et al.(1994) proposed a phenomenological model which explains the occurrence mechanism of these X-ray jets:  magnetic energy of X-ray jets are released by magnetic reconnection between the emerging flux and the pre existing coronal magnetic field.
  The aim of this thesis is to understand the emerging flux and associated active phenomena of the Sun.  This thesis is organized as follows:
  Chapter 1.  Introductory Review:  In this chapter, we briefly review the observations and theories of the emerging flux and associated active phenomena in the corona.
  Chapter 2.  MID Numerical Simulations of Solar Coronal Jets based on Magnetic Reconnection Model including Anisotropic Heat Conduction Effect:  In this chapter, we studied about properties of solar coronal X-ray jets by MHD numerical simulations based on the magnetic reconnection model including anisotropic heat conduction effect.  Yokoyama & Shibata (1995, 1996) performed a two dimensional MHD simulation and succeeded to reproduce the plasma collimated flow along magnetic fields.  We extended their works to study evaporated dense jets as X-ray brightening feature caused by magnetic reconnection between the emerging flux and pre-existing coronal fields.  Key physical processes are included, such as emergence of magnetic fluxes from the convection zone, magnetic reconnection with the coronal magnetic fields, heat conduction to the chromosphere, and the chromospheric evaporation.   High density evaporation jets were successfully reproduced in the simulations.  Mass of the evaporation jets M is described as M=6.8x10 12g(B/10G)15/7(Tcor/10 6K)5/14(sflare/5000km)(t/400s), where B is the strength of magnetic fields, Tcor is the coronal temrerature, sflare is the height of the reconnection region, and t is the duration of ejection, respectively.
  Chapter 3.  Three-dimensional MHD Numerical Simulations of a Twisted Emerging Flux Tube from below the Photosphere:  According to several studies of the emerging flux process from convection zone to the corona, the magnetic field rising through the convection zone have the shape of an isolated tube with twisted magnetic fields.  In this chapter, we performed three-dimensional MHD numerical simulations of the isolated magnetic flux tube's emergence.  The purpose of this study is to investigate coronal magnetic structure formed by the emerging flux tube.  We found that the strength of twists of the magnetic flux tube greatly affects the final magnetic structure in the corona.  The S shaped (like a sigmoid) structure is formed when the magnetic flux tube is strongly twisted initially, while helical magnetic structure is formed at the bottom of the tube when the tube is weakly twisted.  This is because of the magnetic reconnection caused by convective plasma motion with the flux emergence.
  Chapter 4.  Three-dimensional MHD Numerical Simulations of Coronal Loop Oscillations Associated with Flares:  Recently, coronal loop oscillations associated with flares have observed by TRACE(e.g., Nakariakov et al.1999, Aschwanden et al.1999).  To investigate these oscillating loops, we performed three dimensional numerical MHD simulations.  We found that (1) loop oscillation period is determined by its Alfven time, and (2) the amplitude of oscillation decreases exponentially in time.  This is explained as energy transport by fast-mode MHD waves.  The damping rate ω damp is described as ω damp～Va/R where Va is the Alfven speed and R is the radius of the loop, respectively.
  Chapter 5.  Summary and Future Directions:  Finally summary of the thesis and the future directions are shown in this chapter.  We also discuss application of the magnetic flux emergence and magnetic reconnection model to other astronomical objects such as accretion disks, galaxies, and so on., application/pdf, 総研大甲第671号},
 title = {Theoretical and Numerical Studies of an Emerging Flux and associated Active Phenomena of the Sun},
 year = {}
}