1. 12 00 12 00 0 2 3 4 1 Prob, % WinterSummer Probability of observing downward field-aligned electron energy flux >10 mW/m 2 in winter and summer hemispheres. Newell et al., 1996 18 06

2. Carlson et al. ‘01 Three Characteristic Acceleration Regions  Direction of J ||

3. Carlson et al. ‘01 Alfvén Wave Induced Outflow

4. Average Thermal Plasma Density Near 1R E Altitude (Polar EFI) Johnson et al. ‘01

5. Polarization  Field-Aligned Current Ionospheric Feedback Atkinson ’70, Sato ‘78 Lysak

6. Two-fluid Alfvénic Response of the Magnetosphere Electron parallel momentum Density continuity Current continuity v ||e - electron parallel speed; IC - electron collision frequency; AR - effective collision frequency representing wave-particle interactions. ρ i - ion Larmour radius.

7. Coupling to Auroral E-Region Density Continuity Equation n = n 0 + n 1 E-region plasma number density; S 1 =  n 0 2 ionization source maintaining equilibrium n 0 j || field-aligned current;  recombination coefficient. Current Continuity Equation  P,  H height-integrated Pedersen and Hall conductances.

8. “Feedback” Unstable Alfvén Waves IAR Growth Rate  larger for – smaller  P – larger E  – larger k  Two resonant cavities Field Line Resonator Ionospheric Alfvén Resonator Pokhotelov ‘02

9. Feedback Instability Ionospheric Alfvén Resonator E Layer J   J    N e +–  N e 2 +–  P +–  E  – + Stable? yesno 125 s 297 s 281 s 266 s 251 s 235 s 220 s 204 s 188 s 173 s 157 s 141 s E NS 670 mV/m equator ionosphere L = 7.258.25

10. E NS (mV/m) L = 8.25 7.25 Animation sequence from 0 < t < 300 s

13. Occurrence of Upward Ion Beams Near 1R E Altitude (Polar TIMAS) Collin et al. ‘98

14. Auroral Electrodynamics Opgenoorth et al. ‘02