M-I Coupling Physics: Issues, Strategy, Progress

1. M-I Coupling Physics: Issues, Strategy, Progress William Lotko, John Gagne, David Murr, John Lyon, Paul Melanson 1010 O+ / m2-s Dartmouth 0 2 4 6 8 10 founded 1769 Cosponsored by NASA SECTP FO+ = 2.14x107·S||1.265 Energization Regions Percent Change in Mass Density EM Power In  Ions Out • A 2 RE spatial “gap” exists between the upper boundary of TING (or TIEGCM) and the lower boundary of (LFM). • The gap is a primary site of plasma transport where electromagnetic power is converted into field-aligned electrons, ion outflows and heat. • Modifications of the ionospheric conductivity by the electron precipitation is included global MHD models via the “Knight relation”; but other crucial physics is missing: • Collisionless dissipation in the gap region; • Heat flux carried by upward accelerated electrons; • Conductivity depletion in downward current regions; • Ion parallel transport outflowing ions, esp. O+. Evans et al., ‘77 r = 0.755 r = 0.721 Equatorial plane Where does the mass go? Progress 12:00 UT Conductivity Modifications The “Gap” Issues • Reconciled E mapping and collisionless Joule dissipation with Knight relation in LFM • Developed and implemented empirical outflow model – O+ flux indexed to EM power and electron precipitation flowing into gap from LFM (S|| Fe||) • Initiated validation of LFM Poynting fluxes with Iridium/SuperDARN events (student poster by Melanson) and global statistical results from DE, Astrid, Polar (Gagne thesis) IMF T > 1 keV  > 0.5 No outflow n < 0.2/cm3 P < 0.01 nPa The mediating transport processes occur on spatial scales smaller than the grid sizes of the LFM and TING/TIEGCM global Zheng et al. ‘05 Challenge: Develop models for subgrid processes using dependent, large-scale variables available from the global models as causal drivers. Global Effects of O+ Outflow With outflow IonosphericParameters(issues!) Priorities • Current-voltage relation in regions of downward field-aligned current; Strategy (Four transport models) • Ion transport in regions 1 and 3; • Implement multifluid LFM (!) • Implement CMW (2005) current-voltage relation in downward current regions • Include electron exodus from ionosphere  conductivity depletion • Accommodate upward electron energy flux into LFM “Knight”Dissipation Paschmann et al., ‘03 Alfvénic Electron Energization Advance empirical outflow model • Collisionless Joule dissipation and electron energization in Alfvénic regions – mainly cusp and auroral BPS regions; IMF Alfvénic Ion Energization • Ion outflow model in the polar cap (polar wind). Energy Flux mW/m2 Empirical “Causal” Relations • Develop model for particle energization in Alfvénic regions (scale issues!) • Need to explore frequency dependence of fluctuation spectrum at LFM inner boundary • Full parallel transport model for gap region (long term) Mean Energy keV Northern Outflow J|| A/m2 Strangeway et al. ‘05 Keiling et al. ‘03 Alfvén Poynting Flux, mW/m2 Chaston et al. ‘03 Lennartsson et al. ‘04