SPCE0011 – Solar Physics (Term 2) Prerequisites This is a course, which can accommodate a wide range of backgrounds. Although no specific courses are required, a basic knowledge of electromagnetic theory and astrophysical concepts (e.g. spectroscopy) is required. Aims of the Course This course will enable students to learn about: • the place of the Sun in the evolutionary progress of stars • the internal structure of the Sun • its energy source • its magnetic fields and activity cycle • its activity, including flares and coronal mass ejections • its extended atmosphere • the solar wind • the nature of the heliosphere The course should be helpful for students wishing to proceed to a PhD in Astronomy or Astrophysics. It also provides a useful background for people seeking careers in geophysics-related industries and meteorology. Objectives On completion of this course, students should be able to: • explain the past and likely future evolution of the Sun as a star • enumerate the nuclear reactions that generate the Sun’s energy • explain the modes of energy transport within the Sun • describe the Standard Model of the solar interior • explain the solar neutrino problem and give an account of its likely resolution • describe the techniques of helio-seismology and results obtained • discuss the nature of the solar plasma in relation to magnetic fields • explain solar activity - its manifestations and evolution and the dynamo theory of the solar magnetic cycle • describe the solar atmosphere, chromosphere, transition region and corona • explain current ideas of how the atmosphere is heated to very high temperatures • explain the relationship between coronal holes and the solar wind • explain a model of the solar wind • describe solar flares and the related models based on magnetic reconnection • explain coronal mass ejections and indicate possible models for their origin • indicate the nature of the heliosphere and how it is defined by the solar wind Methodology and Assessment This is a 30-lecture course and Problems with a discussion of solutions (four problem sheets). Video displays of solar phenomena will be presented. Assessment is based on the results obtained in the final written examination (90%) and three problem sheets (10%). Textbooks • 15 Million Degrees, L. Green, Viking, Penguin Random House, 2016, ISBN 978-0-670-92219-2 • The Sun, Leon Golub and Jay M. Pasachoff, Cambridge UP, 2017. ISBN 978 1 78023 757 2 • Solar Astrophysics, P. Foukal, Wiley-Interscience,1990. ISBN 0 471 839353 • Astrophysics of the Sun, H. Zirin, Cambridge UP, 1988. ISBN 0 521 316073 • Neutrino Astrophysics, J. Bahcall, Cambridge UP, 1989. ISBN 0 521 37975X • The Stars; their structure and evolution by R.J. Taylor, Wykeham Science Series - Taylor and Francis, 1972. ISBN 0 85109 110 5 • Guide to the Sun, K.J. H. Phillips, Cambridge UP, 1992. ISBN 0 521 39483 X • Astronomical Spectroscopy, J. Tennyson, Imperial College Press, 2005. ISBN 1860945139 Syllabus (The approximate allocation of lectures to topics is shown in brackets below) Introduction [1] Introduction to solar physics: basics and properties of the Sun. The Solar Interior and Photosphere [8] The solar interior. Structure of the interior and the Standard Solar Model - assumptions, processes, relevant equations, energy generation, and transport. Sun's evolution from birth to white dwarf. Nuclear reactions and the solar neutrino problem. The onset of convective instability. Convective rolls. Reflection of acoustic waves in the interior, oscillations, helioseismology. The structure of the solar interior as deduced from helioseismology. Improving the Standard Solar Model with input from helioseismology. The Solar Atmosphere – Chromosphere and Corona [9] The solar atmosphere. Total solar irradiance (solar "constant"). The photosphere - processes and basic structure. Sunspots and solar rotation. Local thermodynamic equilibrium. The chromosphere - heating, network, spicules. The corona - its high temperature and ionization properties. Coronal structure: streamers, active regions, coronal holes, X-ray bright points. Plasma properties, ionization and excitation conditions. Using spectroscopy to find temperatures and densities in the corona. The coronal heating problem: waves versus nanoflares. Coronal elemental composition. Solar Magnetic Fields/Solar Activity [6] Solar magnetic fields. Magneto-hydrodynamics - basic effects and equations, frozen-in fields. Equilibrium in sunspots, filaments, and prominences. Force-free fields, current sheets. Generation of magnetic fields, dynamo theories, the emergence of new magnetic flux. Solar activity and solar magnetic cycle. Sunspots and active regions. Solar Flares and Coronal Mass Ejections [4] Observations of the high and low-temperature aspects of flares - thermal and non-thermal phenomena, particle emission, mass motions, magnetic field changes. Pre-flare energy storage, the role of the magnetic field. Energy release mechanisms, the role of current sheets and magnetic field dissipation. Hard X-rays from flares, energetic particles and their acceleration. Chromospheric evaporation. Coronal mass ejections - observations and models. Association with flares. Energetics. Travel into the heliosphere and interaction with the Earth. Space weather. The Solar Wind and the Heliosphere[2] The formation and characteristics of the solar wind. Parker's solar wind equations. Fast wind and slow wind. Heliosphere.