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Home , Aurora, Magnetosphere

The and

Aurora Videos: http://vimeo.com/21419634 http://www.youtube.com/watch?v=Ezobpz55EEY&list=PL8BFE181ECA3A14D3 and Aurora Once ions are formed in the it becomes part of a large circuit (like a resistor) that connects via the to the magnetosphere.

Ions and in the magnetosphere flow into the atmosphere where they collide with thermospheric gasses and give off . This is called AURORA starts, then expands

Dayside UV and EUV

Aurora borealis during substorm Great Magnetosphere education resource at class website: http://www.ess.washington.edu/Space/ESS205/Education/Intro.html

• The of the 's Magnetosphere • Ever since the launch of the first Sputnik in 1957, has advanced on two fronts, manned and unmanned. The manned missions are well known--from , Gemini and Apollo, to the Space Shuttle and the proposed Space Station Freedom. Millions have watched "Apollo 13" or "The Right Stuff." • In contrast, the exploration of space by unmanned spacecraft has remained almost invisible. The world applauded in 1958, when Explorers 1 and 3 Since the is a good conductor, generators in space drive currents along magnetic fields lines and through the ionosphere Neutral and charged particles in the ionosphere

neutral

charged Populations:

• The D region is located in the from 60-90 km. • Its ion population is + + dominated by NO and O2

• The E region is located in the from 90-150 km. • Its ion population is also + + dominated by NO and O2

• The F region is located in the Thermosphere from 150-800 km. • Its ion population is dominated by O+ So, what is a ?

• A plasma is an ionized gas (‘ionized’ means that electrons have been removed from some or all of the atoms, leaving positive ions, and free electrons) • A plasma is often referred to as the “4th state of matter” • A plasma is a good conductor and can reflect, or slow down radio waves • 99.9% of the universe is said to be a plasma Image Credit link Charged and Neutral Structure Extreme Variability!

F

E http://www.youtube.com/watch?v=PaSFAbATPvk&feature=related Great Red Aurora pipeline History

Aurora was historically known by high natives back to ancient times For those who saw it daily it was like the and the . For those at lower , elaborate myths surrounded the observations of the aurora

See http://earthweb.ess.washington.edu/bobholz/Holzworth_folklore_EO056i010p00686_rga.pdf aurora Electrical currents aligned with Jupiter’s strong magnetic field couple the , , and with Jupiter’s high- latitude ionosphere. Bright auroral emissions observed at the footpoints of the magnetic flux tubes linking the moons to the ionosphere (inset) are the signature of this coupling, the physics of which is only partially understood. (The letters superposed on the auroral in the inset identify the emission features associated with the footpoints of Io, Ganymede, and Europa.) The boundary of the magnetosphere is a pressure balance surface between the kinetic pressure of the solar and the magnetic field energy density The Magnetosphere is a plasma cavity carved out of the by the earth’s magnetic field Substorm starts, then expands

Dayside UV and EUV

Aurora borealis during substorm

Auroral Light ?

• The most common wavelength in Aurora is the 557.7nm line from (green line) • This is a Forbidden Transition line • So, it takes a loooooong time to radiate compared to more common dipole transitions (like a million times longer) • So, instead of microseconds, the lifetime is more like ½ second! This contributes to the ponderously slow apparent motions of the aurora Radiation Belts of the inner magnetosphere Radiation Belts

Charged particles are organized by the dipole magnetic field: Gyration: each particle spins around the magnetic field Bounce: as a gyrating particle moves into a strong magnetic field, it is repulsed Drift: because the field is not uniform, radiation belt particles drift around the world single particle motion in radiation belts Two important concepts

1. Force on charged particles (Lorentz Force)

Or for no E-field, just: F = I dl x B 2. Frozen in condition: Plasma drags the magnetic field: From Lenz’s Law: Currents flow in a conductor to oppose the change in the magnetic field Why does magnetic force act perpendicular to particle motion? • Practical experience: Transformers, generators/alternators • Biot-Savart law • Cross Products , vector products • Cross_product_vector.svg • Right hand rule Remember your lab for the motor: Do you know how it I works?

B (magnetic field) points up I (current) runs through the coil so one side is closer to the magnetic, sees a larger force perpendicular to the wire. When the other side gets close, the current stops because the insulation is only ½ scraped off Any moving Free Charge is a current • So, like the motor, Lorentz Force causes a force on the current (charged particle) which is perpendicular to both the motion of the charge, and the Magnetic field.

N S We were talking about ionospheric variability – Aurora has a strong effect on ionosphere plasma density in some places

E F Lets talk about lightning. What do you know about Lightning? Did you know Lightning Produces Antimatter? Did you know that lightning perturbs space plasma? Did you know the peak wave energy is at a frequency which strongly resonates with particles in the Van Allen Radiation Belts? Did you know Lightning is one of the most powerful natural phenomena on Earth (up to 1013W or more) Do you know the importance of lightning for our independence? Did you know that Lightning has been discovered on other ? Ionosphere is a trap-door for lightning VLF waves

n4 (density) Ionosphhere n3 n2 n1

Snell’s law tells us if nm+1 > nm then wave vector k refracts towards the normal Nearly any angle of incidence gets through starting from below, but most most waves incident from above are reflected From Holzworth, Winglee, et al, JGR, 1999