1. Alfvén Wave Generation and Dissipation Leading to High-Latitude Aurora W. Lotko Dartmouth College Genesis Fate Impact A. Streltsov, M. Wiltberger Dartmouth College SM 52B-08

2. 20 60 182 549 1657 4999 Rayleighs 75 ILAT 70 65 30 Jan 1998 Substorm Onsets Rankin & Gillam MPA 135791113 UT, hours 557.7 nm VIS Low-Resolution Camera, 557.7 nm Lyons et al. ‘01

3. Equatorial Noon-Midnight ExEx ExEx Power at 1.3 mHz in electric field E x (GSM) from LFM global MHD. Fourier transforms are computed from time interval 0900-1200 UT. Wiltberger et al. ‘02 10 Jan 1997

4. Goodrich et al. ‘98

5. 1 0 “Fast Mode” Energy z z mp z z mp 6 543210 0 1 “Alfvénic” Energy x/z mp  Earthward Allan and Wright ‘00 t/  m p vzvz 10 Disturbance Time Step t = 6  mp Earthward Propagation of “Plasma Sheet” Disturbances Characteristics Parameters v Lobe = 2600 km/s z mp = 25 R E  mp = 1 min Fast-Alfvén mode coupling: k y = 1.3 Plasma  = 0 ! 0 1 1 0 0.5 v A /v Lobe z z mp Alfvén Speed Profile

6. Coupling Efficiency Allan–Wright Simulation 0246810 t/t mp 0.08 E AT /E FT 0.5 0 012 Absorption Kivelson and Southwood ‘86 L y  15 R E L y  60 R E Coupling Parameter,

7. Phase Mixing, Dispersion and E || Dispersive Alfvén Waves  / e E || /E  >> 1 Kinetic << 1 Inertial Dispersion Lengths Phase mixing: L ph Ion gyroradius:  =  i (1+T e /T i ) Inertial Length: e = c/  pe Phase Mixing Length 0 10.001 100 1 5 Altitude, R E  2 / e 2 0 1 0.1 100 z/z mp L ph, R E PSBL LOBE Lysak and Carlson ‘81 Allen and Wright ‘98 x/z mp = 4, t/t mp = 6

8. Low-Altitude Dissipation Streltsov et al. ‘01 = 0.4  ci (1 – v c /|v ||e |), |v ||e | > 0 = 0 Lysak and Dum ‘83

9. 100 10 E , mV/m 100515 Altitude, R E Low-Altitude Intensification Streltsov et al. ‘01

10. Reflection Coefficient J || = K  || J  =  P E  inc ref 0.11 10 1001000 Wavelength, km 1 0 Reflection Coefficient Absorption, % 0 100 Insulator Conductor v Am v Ai  d d 2 R E Vogt and Haerendel ’99 Lysak and Carlson ‘81

11. Alfvén Wave Absorption vs Wavelength Observed Width of Auroral Arcs 0.1110 100 Arc Width, km Knudsen et al. ‘01 Maggs and Davis ‘68 Number of Arcs 0.11 10 1001000 1 0 Reflection Coefficient Absorption, % 0 100 Wavelength, km ?

12. North-South Electric Field East-West Magnetic Field 2 mho5 mho M-I Interaction Alfvén wave FAC exceeds current- carrying capacity of lower m’sphere E || is induced to boost electron parallel flux Accelerated electrons nonuniformly ionize E-layer Gradients in  induce quasi-electrostatic, inertial Alfvén waves at low altitude Ionospheric Alfvénic fluctuations enhance Joule heating  P E 2 , ion outflow Reactive Ionosphere Lotko and Streltsov ‘99 Ionosphere Equator

13. Ponderomotive Ion Upwelling via Alfvén Waves a p|| = ¼  || (E  /B 0 ) 2 a p|| > a g at 1000 km altitude when E  > 200 mV/m Inertial M-I Coupling Strangeway et al. ‘00 Li and Temerin ’93

14. SUMMARY Genesis (magnetotail) – CPS compressional disturbances  shear Alfvén waves in PSBL – Phase mixing in PSBL gradient creates smaller scale structure Fate (low-altitude magnetosphere) – Small k   Ionospheric penetration, reflection – Moderate k   Strong absorption in collisionless E || layer – Large k   Reflection at E || layer, momentum transfer to electrons Impact (ionosphere/thermosphere) – Enhanced Joule heating – Electron acceleration, 10-km scale auroral arcs – Ionospheric activation  Small-scale resonator Alfvén waves – Ponderomotive lifting of ionospheric ions Theory Program