Transcript Slide 1
M-I Coupling Physics: Issues, Strategy, Progress Dartmouth William Lotko, John Gagne, David Murr, John Lyon, Paul Melanson The “Gap” Issues “Knight” Dissipation founded 1769 Cosponsored by NASA SECTP EM Power In Ions Out Empirical “Causal” Relations A 2 RE spatial “gap” exists between the upper boundary of TING and TIEGCM and the lower boundary of LFM. FO+ = 2.14x107·S||1.265 The gap is a primary site of plasma transport where electromagnetic power is converted into fieldaligned electrons, ion outflows and heat. r = 0.755 Modifications of the ionospheric conductivity by the electron precipitation is included in global models via the “Knight relation”; but other crucial physics is missing; Strangeway et al. ‘05 Progress – 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. Reconciled E mapping and collisionless Joule dissipation with Knight relation in LFM Conductivity Modifications O +. Developed and implemented empirical outflow model – O+ flux indexed to EM power and electron precipitation flowing into gap from LFM (S|| Fe||) The mediating transport processes occur on spatial scales smaller than the grid sizes of the LFM and TING/TIEGCM global models. Initiated validation of LFM Poynting fluxes with global statistical results from DE, Astrid, Polar and Iridium/SuperDARN events (Gagne thesis + student poster by Melanson) Evans et al., ‘77 Challenge: Develop models for subgrid processes using the dependent, large-scale variables available from the global models as causal drivers. r = 0.721 Chaston, C.C., J. W. Bonnell, C. W. Carlson, J. P. McFadden, R. E. Ergun, and R. J. Strangeway, Properties of small-scale Alfvén waves and accelerated electrons from FAST, J. Geophys. Res. 108(A4), 8003, doi:10.1029/2002JA009420, 2003 Cran-McGreehin, A.P., and A.N. Wright, Current-voltage relationship in downward field-aligned current region, J. Geophys. Res. 110, A10S10, doi:10.1029/2004JA010870, 2005 Evans, D.S., N. Maynard, J. Trøim, T. Jacobsen, and A. Egeland, A., Auroral vector electric field and particle comparisons 2. Electrodynamics of an arc, J. Geophys. Res. 82(16), 2235–2249, 1977 Keiling, A., J.R. Wygant, C.A. Cattell, F.S. Mozer, and C.T. Russell, The global morphology of wave Poynting flux: Powering the aurora, Science 299, 383-386, 2003 Lennartsson, O.W., and H.L. Collin, W.K. Peterson, Solar wind control of Earth’s H+ and O+ outflow rates in the 15-eV to 33-keV energy range, J. Geophys. Res. 109, A12212, doi:10.1029/2004JA010690, 2004 Paschmann, G., S. Haaland and R. Treumann, Auroral Plasma Physics, Kluwer Academic Publishers, Boston/Dordrecht/London, 2003 Strangeway, R.J., R. E. Ergun, Y.-J. Su, C. W. Carlson, and R. C. Elphic, Factors controlling ionospheric outflows as observed at intermediate altitudes, J. Geophys. Res. 110, A03221, doi:10.1029/2004JA010829, 2005 Zheng, Y., T.E. Moore, F.S. Mozer, C.T. Russell and R.J. Strangeway, Polar study of ionospheric ion outflow versus energy input, J. Geophys. Res. 110, A07210, doi:10.1029/2004JA010995, 2005 Priorities Energization Regions Strategy Zheng et al. ‘05 Implement multifluid LFM (!) Global Effects of O+ Outflow Implement CMW (2005) current-voltage relation in downward currents (four transport models) Include electron exodus from ionosphere conductivity depletion 1. Current-voltage relation in regions of downward field-aligned current; Accommodate upward electron energy flux into LFM No outflow With outflow Advance empirical outflow model 2. Electron energization and collisionless Joule dissipation in Alfvénic regions – mainly cusp and the auroral BPS regions; Develop model for particle energization in Alfvénic regions (scale issues!) Need to explore frequency dependence of fluctuation spectrum at LFM inner boundary 3. Ion transport in regions 1 and 2 above; and Equatorial plane Paschmann et al., ‘03 Parallel transport model for gap region (long term) 4. Ion outflow in the polar cap, essentially a polar wind. Alfvénic Electron Where does the mass go? Energization Percent Change in Mass Density Ionospheric Parameters (issues!) 1010 O+ / m2-s Alfvénic Ion Energization IMF 0 2 4 6 mW/m2 Energy Flux T > 1 keV > 0.5 Mean Energy keV n < 0.2/cm3 Northern Outflow P < 0.01 nPa Chaston et al. ‘03 A/m2 J|| Alfvén Poynting Flux, mW/m2 IMF 12:00 UT Keiling et al. ‘03 Lennartsson et al. ‘04 8 10