Download A Brief History of Solar Terrestrial Physics: 2000 BCE to 1800

ESS 154/200C
Lecture 1
A Brief History of Solar Terrestrial Physics
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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)
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Topic
Instructor
A Brief History of Solar Terrestrial Physics
CTR
Upper Atmosphere / Ionosphere
CTR
The Sun: Core to Chromosphere
CTR
The Corona, Solar Cycle, Solar Activity
Coronal Mass Ejections, and Flares
CTR
The Solar Wind and Heliosphere, Part 1
CTR
The Solar Wind and Heliosphere, Part 2
CTR
Physics of Plasmas
RJS
MHD including Waves
RJS
Solar Wind Interactions: Magnetized Planets YM
Solar Wind Interactions: Unmagnetized Planets YM
Collisionless Shocks
CTR
Mid-Term
Solar Wind Magnetosphere Coupling I
CTR
Solar Wind Magnetosphere Coupling II;
The Inner Magnetosphere I
CTR
The Inner Magnetosphere II
CTR
Planetary Magnetospheres
CTR
The Auroral Ionosphere
RJS
Waves in Plasmas 1
RJS
Waves in Plasmas 2
RJS
Review
CTR/RJS
Final
Due
PS1
PS2
PS3
PS4
PS5
PS6
PS7
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, AddisonWesley, 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.
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Magnetospheres
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Magnetospheres module allows you to measure the dipole magnetic field at different
planets.
It allows the study of different magnetospheres
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Dipole
Image dipole
Spherical dipole
Elliptical magnetopause
Empirical magnetosphere
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Particle Motion
• You can examine how charged particles move in magnetic and electric
fields of different geometry
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Uniform B
Cross electric and magnetic field
Curved magnetic fields
Mirror geometry magnetic fields
Harris current sheet
Dipole magnetic field
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Plasma Waves
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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
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MHD/Shocks
• MHD/Shock exercise allows you to calculate behavior of shocks and
MHD waves in a magnetized plasma
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Rankine-Hugoniot graphs
Rankine-Hugoniot case studies
MHD Wave velocities
MHD Wave case studies
Shock foot
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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
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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.
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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.
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A Brief History of Solar Terrestrial Physics:
2000 BCE to 1800
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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.
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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.
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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
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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).
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The Ionosphere and Magnetosphere
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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 us15
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.
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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
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properties of the solar wind, including its continuous flow.
The Age of Space Exploration
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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 18
that the spacecraft is sweeping through it.
Deflecting the Supersonic Solar Wind
Around the Magnetosphere
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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.
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Inner Magnetosphere:
Magnetic Configuration
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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.
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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.
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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.
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Planetary Exploration:
Induced and Intrinsic Magnetospheres
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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
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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
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The Importance of Space Physics to
Earth’s Inhabitants
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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
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Communication paths
Electric power transmission
Satellite operations
Safety of transpolar flights
Many other aspects of daily life
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