Lecture 1 A Brief History of Solar Terrestrial Physics ESS 154/200C Lecture 1 A Brief History of Solar Terrestrial Physics

Date Day Topic Instructor Due ESS 200C Space Plasma Physics ESS 154 Solar Terrestrial Physics M/W/F 10:00 – 11:15 AM Geology 4677 Instructors: C.T. Russell (Tel. x-53188; Office: Slichter 6869) R.J. Strangeway (Tel. x-66247; Office: Slichter 6869) Date Day Topic Instructor Due 1/4 M A Brief History of Solar Terrestrial Physics CTR 1/6 W Upper Atmosphere / Ionosphere CTR 1/8 F The Sun: Core to Chromosphere CTR 1/11 M The Corona, Solar Cycle, Solar Activity Coronal Mass Ejections, and Flares CTR PS1 1/13 W The Solar Wind and Heliosphere, Part 1 CTR 1/15 F The Solar Wind and Heliosphere, Part 2 CTR 1/20 W Physics of Plasmas RJS PS2 1/22 F MHD including Waves RJS 1/25 M Solar Wind Interactions: Magnetized Planets YM PS3 1/27 W Solar Wind Interactions: Unmagnetized Planets YM 1/29 F Collisionless Shocks CTR 2/1 M Mid-Term PS4 2/3 W Solar Wind Magnetosphere Coupling I CTR 2/5 F Solar Wind Magnetosphere Coupling II; The Inner Magnetosphere I CTR 2/8 M The Inner Magnetosphere II CTR PS5 2/10 W Planetary Magnetospheres CTR 2/12 F The Auroral Ionosphere RJS 2/17 W Waves in Plasmas 1 RJS PS6 2/19 F Waves in Plasmas 2 RJS 2/26 F Review CTR/RJS PS7 2/29 M Final

ESS 200C – Space Physics ESS 154 Solar Terrestrial Physics Textbook: Space Physics: An Introduction (Draft on web; Publication date early 2016) - There will be two examinations and 7 homework assignments. - These are different for ESS 154 and ESS 200C. - The grade will be based on - 30% Midterm (1/29/14) - 35% Final (3/3/14) - 35% Homework - References - Kivelson, M.G. and C.T. Russell, Introduction to Space Physics, Cambridge University Press, 1995. - Gombosi, T.I., Physics of the Space Environment, Cambridge University Press, 1998. - Kallenrode, M.B., Space Physics, An Introduction to Plasmas and Particles in the Heliosphere and Magnetospheres, Springer, 2000. - Clemmow, P.C. and J.P. Dougherty, Electrodynamics of Particles and Plasmas, Addison-Wesley, reissued, 1990. - Computer Exercises – spacephysics.ucla.edu - Computer exercises will be used to illustrate and solve problems - Seven modules currently working: Magnetospheres, Particle Motion, Plasma Waves, MHD/Shock, Solar Wind, Ionosphere (One module in development: Solar magnetic fields) - Prerequisites for 200C: Assume upper division electricity and magnetism and calculus

Space Physics Exercises Space Physics Exercises covers magnetospheric magnetic fields, particle motion, plasma waves, MHD/Shocks, solar wind, auroral currents, ionospheres, and eventually solar magnetic fields. Allows you to experiment and train your physical intuition.

Magnetospheres Magnetospheres module allows you to measure the dipole magnetic field at different planets. It allows the study of different magnetospheres Dipole Image dipole Spherical dipole Elliptical magnetopause Empirical magnetosphere

Particle Motion You can examine how charged particles move in magnetic and electric fields of different geometry Uniform B Cross electric and magnetic field Curved magnetic fields Mirror geometry magnetic fields Harris current sheet Dipole magnetic field

Plasma Waves Calculates properties of electromagnetic waves in a cold magnetized plasma Index of refraction Phase velocity Group velocity (parallel and perpendicular) Ellipticity Wave length Plasma can have multiple ions

MHD/Shocks MHD/Shock exercise allows you to calculate behavior of shocks and MHD waves in a magnetized plasma Rankine-Hugoniot graphs Rankine-Hugoniot case studies MHD Wave velocities MHD Wave case studies Shock foot

Solar Wind You can study the Parker spiral magnetic field for different solar wind speeds in the equatorial plane and in 3D. You can examine the configuration of the heliospheric current sheet.

Currents Auroral electrojet model allows you to calculate the field seen on the surface of the Earth from currents flowing overhead. Also allows the Dst index to be “predicted” from solar wind input given varying responses of the magnetosphere.

Ionosphere Allows one to calculate the altitude profile of a “Chapman” ionosphere in photochemical equilibrium. Also allows one to calculate a solar zenith angle plot.

A Brief History of Solar Terrestrial Physics: 2000 BCE to 1800 Space is filled with charged particles and magnetic fields that link events on the Sun to the Earth in ways early inhabitants of Earth could not understand Gradually the inhabitants of Earth sensed that space was not empty. Since well before the common epoch, aurora have been sensed. For over 1000 years, the magnetic field of the Earth has been used for navigation. Eventually it was discovered that the magnetic field varied on long and short time scales. This required electric currents both below the surface of the Earth and above. The currents above the Earth are carried by plasma – ions and electrons equally balanced in charge but otherwise free to move.

Solar Activity Dec. 31, 2012 Around 1600, sunspots were discovered and sketches of the Sun’s surface were made. Eventually a system for “counting” sunspots was invented and the sunspot cycle discovered. We are now in a deep solar minimum as has not been observed for 200 years. The sunspot number on this solar photograph is 38. Back in the early 1800’s, the maximum average sunspot number was about 40. Will this be true for the next solar maximum?

Aurora Auroras came under intense scientific scrutiny in the 1800’s and 1900’s. Attempts were made to reproduce them in the lab. Scientists triangulated their positions to determine their heights. They mapped out when they occur in latitude (an auroral zone).

The Ionosphere and Magnetosphere Eventually solar activity was linked to auroral activity and geomagnetic activity, thus establishing the field of “Solar-Terrestrial Physics”. Still, the way in which solar activity affected the terrestrial environment was not known. The geomagnetic fluctuations implied that plasma existed in the upper atmosphere that could carry current. Radio waves enabled the electron density profile to be probed. Numerical calculations showed that the Earth’s magnetic field could both shield us and trap some of the charged particles.

Formation of a Geomagnetic Cavity Outflows of plasma from the Sun were postulated to intersect the Earth and compress the magnetic field. Originally streams were believed to be intermittent. The magnetic field does not penetrate into the very highly conducting plasma. This model can explain the properties of geomagnetic storms.

Using Plasma Physics and MHD to Probe the Magnetosphere and Solar Wind Knowledge of how the velocity of waves in a magnetized plasma enabled scientists to understand the dispersion of whistlers and deduce the density structure of cold plasma in the magnetosphere. Understanding how a flowing magnetized plasma would interact with a comet, a ball of gas, helped scientists to deduce the properties of the solar wind, including its continuous flow.

The Age of Space Exploration In the late 1950’s, mankind finally was able to get above the atmosphere and probe deep space. Much has been learned about the Earth’s environment by highly eccentric orbiters, such as Explorer 12, OGO-1, 3 and 5, the ISEE mission, the Polar mission, and currently, THEMIS. As the Earth circles the Sun, the spacecraft orbit stays fixed in inertial space and the magnetosphere sweeps over it. In the frame of the magnetosphere, it appears that the spacecraft is sweeping through it.

Deflecting the Supersonic Solar Wind Around the Magnetosphere The charged particles in the solar wind cannot easily penetrate the magnetosphere because they are deflected by the magnetic field. Thus, a cavity is formed. In a subsonic flow where the flow speed is less than the thermal speed, a pressure gradient builds up and the plasma is smoothly deflected around the obstacle. The solar wind is almost never subsonic, necessitating a strong shock front to bound the pressure jump. This causes many interesting phenomena, including the reflection of some particles upstream. The shock also causes heating. Often there is enough heating to send particles back into the solar wind where they interact with the flow.

Inner Magnetosphere: Magnetic Configuration The magnetic field is stretched in the anti-solar direction, exposing a polar cusp that allows penetration of solar wind plasma deep into the magnetosphere. The magnetospheric plasma sits on magnetic field lines that are attached to the ionosphere. Thus, the two plasmas move together. Momentum coupling is accomplished via a set of currents, long field lines that connect pressure-driven currents in the magnetosphere to ionospheric currents.

The Radiation Belts Energetic particles can be trapped in the dipole mirror geometry of the Earth’s magnetic field. These intensities build up and can be dangerous to spacecraft.

Energy Coupling to the Magnetosphere: The Role of the Magnetic Field The magnetosphere is an imperfect shield against the solar wind. This imperfection becomes greater when the solar wind magnetic field is opposite the direction of the terrestrial magnetic field at the subsolar point. The solar wind field and the terrestrial field become linked, the magnetosphere is stirred, and the particles energized.

Planetary Exploration: Induced and Intrinsic Magnetospheres Early planetary exploration began in the 1960’s, but expanded rapidly in the 1970’s with missions to Mercury, Venus, Mars, Jupiter, Saturn, and eventually going all the way to Uranus and Neptune. Mercury, Jupiter, Saturn, Uranus and Neptune all have magnetospheres supported by electric currents flowing deep in their interiors. These are intrinsic magnetospheres. Venus and Mars deflect the solar wind because their ionospheres are sufficiently electrically conducting that the magnetic field cannot diffuse through it before the field changes again. These are induced magnetospheres.

Types of Missions of Interest to Space Physicists Textbook includes lists of the key missions of interest: Aeronomy – Terrestrial, low-altitude missions studying ionosphere, upper atmosphere, polar caps Space Physics – Terrestrial, mid- to high-altitude missions studying radiation belts and solar wind interactions Inner solar system – Planetary, Cometary, and Solar, flyby, orbiters, balloons, atmospheric probes, landers Outer planets – Planetary, flyby, orbiter, atmospheric probe

The Importance of Space Physics to Earth’s Inhabitants Space Weather is a term developed to describe the science associated with determining the conditions at Earth due to varying solar activity. The Solar wind and energetic particles from the Sun can affect Communication paths Electric power transmission Satellite operations Safety of transpolar flights Many other aspects of daily life