Lecture

Astrophysics: Solar Magnetic Fields and Dynamo Theory

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In course

PHYS-424: Plasma II

This course completes the knowledge in plasma physics that students have acquired in the previous two courses, with a discussion of different applications, in the fields of magnetic confinement and controlled fusion, astrophysical and space plasmas, and so ...

Description

This lecture delves into the structure and dynamics of solar magnetic fields, exploring topics such as the origin of cosmic magnetic fields, dynamo theory, and the role of turbulence in magnetic field amplification. The instructor discusses the solar cycle, sunspots, and the generation of magnetic fields through dynamo processes. Various theorems related to kinematic dynamo theory are presented, along with insights into solar rotation and helioseismology. The lecture also covers the magnetic Reynolds number in the Sun, meridional circulation, and the expulsion and concentration of magnetic fields in turbulent environments.

Instructor

Holger Reimerdes

Teaching & PhD PhD Students Martim Zurita, Marta Pedrini, Benjamin Yong Kwak Brown, Pierre Louis Sintre, Massimo Carpita, Richard Alexander David Ducker, Giuseppe Iunior Drago Past EPFL PhD Students Mirko Wensing, Claudia Colandrea, Guang-Yu Sun Past EPFL PhD Students as codirector Gustavo Paganini Canal, Joyeeta Sinha, Roberto Maurizio Courses Control and Operation of Tokamaks PHYS-748 This course treats the main issues in operation and control of a tokamak. Control-oriented models are de

Official source

Ontological neighbourhood

Physics

Plasma physics: Space-plasma physics

Related concepts (32)

Solar cycle

The solar cycle, also known as the solar magnetic activity cycle, sunspot cycle, or Schwabe cycle, is a nearly periodic 11-year change in the Sun's activity measured in terms of variations in the number of observed sunspots on the Sun's surface. Over the period of a solar cycle, levels of solar radiation and ejection of solar material, the number and size of sunspots, solar flares, and coronal loops all exhibit a synchronized fluctuation from a period of minimum activity to a period of a maximum activity back to a period of minimum activity.

Solar wind

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5keV. The composition of the solar wind plasma also includes a mixture of materials found in the solar plasma: trace amounts of heavy ions and atomic nuclei of elements such as C, N, O, Ne, Mg, Si, S, and Fe. There are also rarer traces of some other nuclei and isotopes such as P, Ti, Cr, 54Fe and 56Fe, and 58Ni, 60Ni, and 62Ni.

Magnetic reconnection

Magnetic reconnection is a physical process occurring in electrically conducting plasmas, in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle acceleration. Magnetic reconnection involves plasma flows at a substantial fraction of the Alfvén wave speed, which is the fundamental speed for mechanical information flow in a magnetized plasma. The concept of magnetic reconnection was developed in parallel by researchers working in solar physics and in the interaction between the solar wind and magnetized planets.

Solar phenomena

Solar phenomena are natural phenomena which occur within the atmosphere of the Sun. These phenomena take many forms, including solar wind, radio wave flux, solar flares, coronal mass ejections, coronal heating and sunspots. These phenomena are believed to be generated by a helical dynamo, located near the center of the Sun's mass, which generates strong magnetic fields, as well as a chaotic dynamo, located near the surface, which generates smaller magnetic field fluctuations.

Earth's magnetic field

Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo.

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