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Today:1. Finish Ionosphere Conductivity2. Relate Auroral Currents with Ionospheric currents
What is Conductivity?
• The scalar conductivity σ is defined as the ratio of the current density to the electric field strength σ = J/E. For a resistive medium this is just the Spitzer conductivity:
• To get the components look at • So, σ can have many components:
(Another way to derive scalar conductivity)
Conductivity when particles gyrate
σ becomes a matrix
Now lets relate the ionospheric currents, to the field aligned magnetosphericcurrents:To start: How does the Aurora Work?
Substormstarts here
DE aurora
The Auroral Currents
Today
• Review Aurora and substorm• Begin atmospheric electrodynamics
• Cosmic rays• Lightning and thunderstorms
Note, missed classes can be made up by writing a 1-2 page summary of the material presented on that day, based on the on-line pdf file for the missed lecture: see http://earthweb.ess.washington.edu/bobholz/ess471-503/lectures/
Current Conditions: SuperDarn radars
http://superdarn.jhuapl.edu/rt/map/index.html
Substorm starts
Southward E-field before substorm (and after)
After substorm starts, B-field determined by Hall Currents
Energetic Electron beam
Discovery paper (Mozer et al, 1978)
Parallel
Electric
fields
Great Red Aurora
Jupiter aurora
Cosmic Radiation
June 2006
Astronomy Picture of the Day 2006 August 14
Solar Flare can produce 1030 ergs
• But a single Galactic Cosmic Ray can be over 1020 eV allby itself
30
neutron monitors
Cosmic Rays are the prime source for ions in the atmosphere
+,- ions generated per second per cubic centimeter
Cosmic Ray energy fluxcomparisons