ASTR-7500: Topics in Solar Physics



General Information

 This course is targeted at students enrolled in graduate degrees in physics, astronomy/astrophysics, planetary sciences, or space science, although interested students pursuing graduate degrees in other areas are encouraged to contact the instructors to see if the class is suitable for them. There is no formal course prerequisites, but students having had no undergraduate exposure to astrophysics or basic fluid dynamics may have to do a bit of extra reading in the first few weeks of class.

Our general philosophy is to put the emphasis on simple, quantitative physical models of the phenomena under study. Rather than survey the whole of solar physics, we will study in depth four specific topics. The idea is that proper understanding of the four topic areas will equip you with the necessary physical, mathematical and numerical tools required to deal with other related subjects.

Instructors:

Course schedule:

Tue/Thu, 3:30-4:45, F931 Duane Physics (Gamov Tower).

Office Hours:

Fri, 9:30-11:00, F223 Duane Physics (Gamov Tower); ON DEMAND ONLY: send e-mail if you want us to be there.

Textbook:

None. Extensive class notes will be provided.

Evaluation:

One take-home exam in december.

Course Outline (as of 3 September 1997)

Introduction (P. Charbonneau; 1 lecture)

  1. A brief History of Solar Physics

Part I: The Large-Scale Dynamics of the Solar Wind (P. Charbonneau; 4 lectures)

  1. Static corona models

    1. Governing equations
    2. Regimes and limitations
    3. Thermodynamic divertion: polytropic and isothermal flows
    4. Application: Static corona models

  2. Thermally-driven Winds: I. Isothermal Models.

    1. A flow example: the DeLaval nozzle
    2. The isothermal wind solution of Parker
    3. Force balance in the Parker isothermal solution
    4. Comparison with the observed solar wind

  3. Thermally-driven Winds: II. Polytropic Models.

    1. A basic polytropic wind solution
    2. Force balance and asymptotic behavior
    3. Energetics
    4. Another comparison with the observed solar wind

  4. Rotating, magnetized, thermally-driven winds

    1. Flux freezing and the high electrical conductivity limit
    2. Magnetic fields in the solar wind: observational aspects
    3. The Weber-Davis solution
    4. Yet another comparison with the observed solar wind
    5. Asymptotic behavior
    6. Effect of mass loss on solar structure

Part II: Solar Rotation (Paul Charbonneau; 5 lectures)

  1. Angular momentum loss and rotational evolution

    1. The rotation of solar-type stars
    2. Structural evolution and rotation
    3. The Skumanich t1/2 relationship
    4. The spin-down of ZAMS late-type stars

  2. Helioseismology (Guest lecturer S. Tomczyk, HAO/NCAR)

  3. The solar radiative core

    1. Order-of-magnitude estimates
    2. Viscous transport of angular momentum
    3. Advective transport of angular momentum
    4. Turbulent transport of angular momentum
    5. Magnetic transport of angular momentum

  4. The solar convective envelope

    1. Angular momentum in the solar convective envelope
    2. Reynolds stresses in turbulent fluids
    3. Models of the solar envelope rotation

  5. The solar tachocline

    1. Viscous boundary layers
    2. The hydrodynamical tachocline
    3. The stability of horizontal shear flows
    4. The magnetized tachocline

Part III: Sunspots (T.J. Bogdan; 10 lectures)

  1. Introduction

    1. Historical Perspective
    2. Sunspot Structure & Evolution

  2. Oscillations of Stratified Atmospheres

    1. Plane-parallel Atmospheres
    2. Transition to Spherical Geometry

  3. Oscillations of Stratified Magnetoatmospheres

    1. Plane-parallel Atmospheres
    2. Transition to Spherical Geometry

  4. Sunspot Seismology

    1. Modal-Decomposition Methods
    2. Time-Distance Helioseismology
    3. Data Reduction and Analysis
    4. The Inverse Problem

  5. Conclusion: Open Questions

Part IV: The Solar Dynamo (Charbonneau, Bogdan, Galloway; 10 lectures)

  1. The Solar Magnetic Field

    1. Origin of magnetic fields
    2. The solar magnetic field: observational aspects
    3. Generators and mechanical dynamos

  2. The Kinematic Evolution of Magnetic Fields

    1. The diffusive decay of magnetic fields
    2. The advective evolution of magnetic fields
    3. The advective/diffusive evolution of magnetic fields
    4. Cowling's anti-dynamo theorem

  3. Fast dynamos

    1. Fast dynamos and chaos
    2. Numerical calculations
    3. Some analytic results
    4. Including the Lorentz Force

  4. Mean-field electrodynamics

    1. Turbulent flows
    2. Scale separation and statistical averages
    3. The alpha-effect and turbulent diffusivity
    4. Cartesian solutions: dynamo waves

  5. Mean-field Solar Dynamo Models

    1. Problem formulation
    2. Kinematic, linear alpha-Omega solutions
    3. Mean-field dynamos with solar-like differential rotation
    4. Nonlinearities

  6. Conclusion: Is the Sun a dynamo ?

    1. Interface dynamos
    2. Babcock-Leighton dynamos
    3. Flux tube dynamos

Image Gallery

The following links let you access various image material complementing the class notes.

Animation Gallery

The following links let you access various animations complementing the class notes. A separate subpage has been set up for each chapter in the notes were reference to an animation is made. Typically, the headers below correspond to the title of the section where the animations are referenced, with the leading roman numerals indicating the corresponding part of the course. The format of each animation is described, but little background material is provided with the animations, so you should have the class notes at hand if you really want to understand what is going on. All animations are in .mpeg format, and should be viewable with either Mosaic or Netscape browsers.

Part II: Solar Rotation

Part IV: The Solar Dynamo

Problems: Software and data

The following links give you access to various pieces of software and data useful or necessary to do some of the problems in the class notes. A separate subpage has been set up for each problem in the notes were software or some additional material is being made available for some of the problems. For example II.5.2 refers to problem (5.2) in part II of the class notes.

Class Notes: Errata

Part I: The large-scale dynamics of the solar wind

Part II: Solar rotation

Part III: The seismology of sunspots

Part IV: The solar dynamo

Return to HAO homepage. -Written by paulchar@hao.ucar.edu.

-Last Revised 17 November 1997 by paulchar@hao.ucar.edu.