1. The tribulations and exaltations in coupling models of the magnetosphere with ionosphere- thermosphere models Aaron Ridley Department of Atmospheric, Oceanic and Space Sciences Aaron Ridley Department of Atmospheric, Oceanic and Space Sciences

2. GEM/CEDAR Workshop July 1, 2005 Slide 2 of Ionosphere Thermosphere Modeling and coupling  A quick review.  The ionosphere and thermosphere.  High latitude electrodynamics.  Coupling the neutral winds to the magnetosphere  Ion outflow  Other couplings  Some that work  Some that may not be on the horizon, but should be.  Pontification time  A quick review.  The ionosphere and thermosphere.  High latitude electrodynamics.  Coupling the neutral winds to the magnetosphere  Ion outflow  Other couplings  Some that work  Some that may not be on the horizon, but should be.  Pontification time 39

3. GEM/CEDAR Workshop July 1, 2005 Slide 3 of [e - ] and T n Many Thermosphere/Ionosphere plots “stolen” from my student Yue Deng! All T/I results from the global ionosphere thermosphere model (GITM) 309

4. GEM/CEDAR Workshop July 1, 2005 Slide 4 of Temperature Altitude Distribution noon midnight 465

5. GEM/CEDAR Workshop July 1, 2005 Slide 5 of Low Altitude Temperature Distribution 739

6. GEM/CEDAR Workshop July 1, 2005 Slide 6 of High Altitude Temperature Distribution 1001

7. GEM/CEDAR Workshop July 1, 2005 Slide 7 of Electron Density Altitude Distribution 1304

8. GEM/CEDAR Workshop July 1, 2005 Slide 8 of Low Altitude Electron Distribution 1573

9. GEM/CEDAR Workshop July 1, 2005 Slide 9 of High Altitude Electron Distribution 1846

10. GEM/CEDAR Workshop July 1, 2005 Slide 10 of High Altitude Electron Distribution 2149

11. GEM/CEDAR Workshop July 1, 2005 Slide 11 of V i and V n with B z = -1 nT Ion flows driven primarily by potential Neutral winds driven by (a) Gradient in pressure; (b) Corriolis; (c) ion drag. Note dawn/dusk differences 2638

12. GEM/CEDAR Workshop July 1, 2005 Slide 12 of V i and V n with B z = -10 nT Ion flows driven primarily by potential Neutral winds driven by (a) Gradient in pressure; (b) Corriolis; (c) ion drag. Note dawn/dusk differences 3067

13. GEM/CEDAR Workshop July 1, 2005 Slide 13 of [e - ] and V n with HPI = 100 GW Significant increase in the electron density causes much larger ion drag effect Dawn cell “much” more defined. 3471

14. GEM/CEDAR Workshop July 1, 2005 Slide 14 of V i, V n, and how well they are coupled 4132

15. GEM/CEDAR Workshop July 1, 2005 Slide 15 of V i in F-region and E-region  Rotation of Vectors  Shortening of Vectors 4578

16. GEM/CEDAR Workshop July 1, 2005 Slide 16 of Would the real V i please step forward?  As the collision frequency becomes large, most people think of the ion velocity rotating away from ExB to E.  That is not really true. Since there is a neutral wind, the ion velocity rotates towards a combination of E and U n.  We can then think of this in a couple of different ways:  The current caused by E is divergenceless, but the current caused by U n is not, so we have to force the total current to be:  So, calculate the divergence of the neutral wind driven current (perpendicular to the magnetic field).  Integrate this current, to come up with a total wind driven current.  Solve a Poisson equation to find a potential that would cancel this current out.  The push the ions with the solved E-field.  This the methodology used by all modeling groups for solving for equatorial electrojet and coupling to magnetospheric codes.  Pushing ions with U n will cause a polarization electric field. We could map this polarization electric field along field lines to higher altitudes.  Should be equivalent.  Also applies to things like gravity and gradient pressure.  As the collision frequency becomes large, most people think of the ion velocity rotating away from ExB to E.  That is not really true. Since there is a neutral wind, the ion velocity rotates towards a combination of E and U n.  We can then think of this in a couple of different ways:  The current caused by E is divergenceless, but the current caused by U n is not, so we have to force the total current to be:  So, calculate the divergence of the neutral wind driven current (perpendicular to the magnetic field).  Integrate this current, to come up with a total wind driven current.  Solve a Poisson equation to find a potential that would cancel this current out.  The push the ions with the solved E-field.  This the methodology used by all modeling groups for solving for equatorial electrojet and coupling to magnetospheric codes.  Pushing ions with U n will cause a polarization electric field. We could map this polarization electric field along field lines to higher altitudes.  Should be equivalent.  Also applies to things like gravity and gradient pressure. 4931

17. GEM/CEDAR Workshop July 1, 2005 Slide 17 of  Test run of the Space Weather Modeling Framework.  IMF inputs shown.  Look at potential.  Look at currents caused by neutral winds.  Test run of the Space Weather Modeling Framework.  IMF inputs shown.  Look at potential.  Look at currents caused by neutral winds. 5577

18. GEM/CEDAR Workshop July 1, 2005 Slide 18 of Potential 6300

19. GEM/CEDAR Workshop July 1, 2005 Slide 19 of NW driven current 39

20. GEM/CEDAR Workshop July 1, 2005 Slide 20 of Ionospheric outflow  Outflow is also very important in MI coupling.  Can control the density in the plasma sheet.  Oxygen outflow can significantly change the mass density in the magnetosphere.  Lowers the Alfven velocity.  Adds to the ring current.  Outflow is also very important in MI coupling.  Can control the density in the plasma sheet.  Oxygen outflow can significantly change the mass density in the magnetosphere.  Lowers the Alfven velocity.  Adds to the ring current. 5238

21. GEM/CEDAR Workshop July 1, 2005 Slide 21 of What controls Outflow?  It seems like outflow is a two step process:  Raise the ionospheric plasma up.  Suck it out into magnetosphere  Joule heating is one of the primary mechanisms thought to control the raising of the ionosphere.  It seems like outflow is a two step process:  Raise the ionospheric plasma up.  Suck it out into magnetosphere  Joule heating is one of the primary mechanisms thought to control the raising of the ionosphere. 4872

22. GEM/CEDAR Workshop July 1, 2005 Slide 22 of Effect of heating on electron density 4321

23. GEM/CEDAR Workshop July 1, 2005 Slide 23 of Outflow Experiments  Examine what the influence of the ion outflow is on the magnetosphere  Use simple constant boundary conditions at the inner boundary of the magnetosphere  diffusion lifts the density off the boundary a few cells  Gradient in pressure brings the plasma out into the magnetosphere  These experiments are meant to show what the most simple thing possible will do to the magnetosphere  Run to steady-state Northward IMF, flip to Southward IMF at t=0, and see what happens.  Examine what the influence of the ion outflow is on the magnetosphere  Use simple constant boundary conditions at the inner boundary of the magnetosphere  diffusion lifts the density off the boundary a few cells  Gradient in pressure brings the plasma out into the magnetosphere  These experiments are meant to show what the most simple thing possible will do to the magnetosphere  Run to steady-state Northward IMF, flip to Southward IMF at t=0, and see what happens. 3965

24. GEM/CEDAR Workshop July 1, 2005 Slide 24 of N=1000; Grid 4; No RCM

25. GEM/CEDAR Workshop July 1, 2005 Slide 25 of CPCP variations for 3 runs Changing the density seems to: Increase the cross polar cap potential Make the transition take longer N=10N=100 N=1000

26. GEM/CEDAR Workshop July 1, 2005 Slide 26 of But……  The cross polar cap increasing doesn’t make much sense. Why does it do this???? After thinking a bit…  Our numerical solver has to add diffusion for stability.  That diffusion is controlled by the fastest wave speed in the cell… roughly the Alfven speed.  Which is controlled by the density.  So, turning the density up means turning the diffusion down.  Turning the diffusion down allows more current to make it to the inner boundary, and hence to the ionosphere.  The cross polar cap potential goes up.  Purely numerical.  Crap.  The funny thing is that this is true for (a) grid resolution, (b) where you put the boundary, and (c) Artificially reducing the speed of light (Boris) also.  The cross polar cap increasing doesn’t make much sense. Why does it do this???? After thinking a bit…  Our numerical solver has to add diffusion for stability.  That diffusion is controlled by the fastest wave speed in the cell… roughly the Alfven speed.  Which is controlled by the density.  So, turning the density up means turning the diffusion down.  Turning the diffusion down allows more current to make it to the inner boundary, and hence to the ionosphere.  The cross polar cap potential goes up.  Purely numerical.  Crap.  The funny thing is that this is true for (a) grid resolution, (b) where you put the boundary, and (c) Artificially reducing the speed of light (Boris) also. 3180

27. GEM/CEDAR Workshop July 1, 2005 Slide 27 of What Coupling Should Be Magnetosphere Model Field-aligned Currents Heat Flux Electron & Ion Precipitation Plasmasphere Density Potential Electrodynamics Model Ionosphere-Thermosphere Model Neutral wind FACs Conductances Upward Ion Fluxes TidesGravity Waves Solar Inputs PhotoelectronFlux 2713

28. GEM/CEDAR Workshop July 1, 2005 Slide 28 of What we have discussed so far Magnetosphere Model Field-aligned Currents Potential Electrodynamics Model Ionosphere-Thermosphere Model Neutral wind FACs Upward Ion Fluxes 2525

29. GEM/CEDAR Workshop July 1, 2005 Slide 29 of Electron and Ion Precipitation Magnetosphere Model Electron & Ion Precipitation Electrodynamics Model Ionosphere-Thermosphere Model Conductances This is the hardest part of the coupling T-I models use energy deposition codes to determine ionization and heating rates as a function of altitude, given input (ion and electron) spectra at the top of the model. This is sort of a major weakness if not done well, or if distributions are assumed to be Maxwellian and are not. Need to have both ion and neutral densities correct to get conductances 2189

30. GEM/CEDAR Workshop July 1, 2005 Slide 30 of Photoelectrons Magnetosphere Model Ionosphere-Thermosphere Model PhotoelectronFlux Photoelectron are created by sunlight. These electrons flow along field lines from the sunlit hemisphere to the dark hemisphere, causing soft electron precipitation. This can effect the F-region density in the winter hemisphere. Photoelectron codes are relatively “expensive” to run, so they are typically ignored. Photoelectron flux could be parameterized with a transmission coefficient through the plasmasphere. 1939

31. GEM/CEDAR Workshop July 1, 2005 Slide 31 of Plasmaspheric Density Magnetosphere Model Plasmasphere Density Ionosphere-Thermosphere Model Many global circulation models have a hard time getting the F- region densities correct, because the pressure gradient at the top of the model is unknown. With an accurate plasmaspheric model, the gradient could be determined and an inflow or outflow would be self-consistently derived. 1776

32. GEM/CEDAR Workshop July 1, 2005 Slide 32 of Electron Heat Flux Magnetosphere Model Heat Flux Ionosphere-Thermosphere Model Magnetospheric electron heat flux causes the electron to heat up in the ionosphere. This changes the height distribution of the electron pressure, which causes the ions to lift. 1492

33. GEM/CEDAR Workshop July 1, 2005 Slide 33 of Electron Heat Flux Magnetosphere Model Heat Flux Ionosphere-Thermosphere Model Wait. Did you say lift? 1100

34. GEM/CEDAR Workshop July 1, 2005 Slide 34 of Electron Heat Flux Magnetosphere Model Heat Flux Ionosphere-Thermosphere Model The electron energy heat flux may cause changes in the amount of ion outflow. Upward Ion Fluxes Therefore, passing the heat flux from magnetospheric codes (that are capable of computing it - like RAM) to the IT models may be crucial for accurately specifying outflow regions 999

35. GEM/CEDAR Workshop July 1, 2005 Slide 35 of Electron heat flux experiment  Simulations done by Alex Glocer, a graduate student at UM.  Using updated version of the Gombosi et al. [1645, I think] polar wind code.  Do two ion outflow runs  80 o latitude  noon  Summer conditions  low f 10.7  Run 1 nominal heat flux  Run 2 double heat flux  Simulations done by Alex Glocer, a graduate student at UM.  Using updated version of the Gombosi et al. [1645, I think] polar wind code.  Do two ion outflow runs  80 o latitude  noon  Summer conditions  low f 10.7  Run 1 nominal heat flux  Run 2 double heat flux 675

36. GEM/CEDAR Workshop July 1, 2005 Slide 36 of Electron heat flux experiment  By changing the electron heat flux by a factor of two:  increase H+ outflow by a little bit.  Increase O+ by a factor of two.  While the polar wind code is still being developed and validated, the results are intriguing.  By changing the electron heat flux by a factor of two:  increase H+ outflow by a little bit.  Increase O+ by a factor of two.  While the polar wind code is still being developed and validated, the results are intriguing. 472

37. GEM/CEDAR Workshop July 1, 2005 Slide 37 of What Coupling Should Be Magnetosphere Model Field-aligned Currents Heat Flux Electron & Ion Precipitation Plasmasphere Density Potential Electrodynamics Model Ionosphere-Thermosphere Model Neutral wind FACs Conductances Upward Ion Fluxes TidesGravity Waves Solar Inputs PhotoelectronFlux 281

38. GEM/CEDAR Workshop July 1, 2005 Slide 38 of Summary  The thermosphere and ionosphere are overlapping, tightly coupled regions of space that do influence the magnetosphere. And Vise-versa.  We sort of understand the neutral wind coupling to the ion flows.  We sort of understand what happens to electrons and ions from the magnetosphere (if the magnetosphere could specify them correctly…)  We really don’t understand outflow  Joule heating effects can last a LONG time.  Electron energy flux could play a role - no one has coupled this yet.  Plasmasphere?  Photoelectrons?  Wouldn’t it be great is we could model the system without the numerics getting in the way?  The thermosphere and ionosphere are overlapping, tightly coupled regions of space that do influence the magnetosphere. And Vise-versa.  We sort of understand the neutral wind coupling to the ion flows.  We sort of understand what happens to electrons and ions from the magnetosphere (if the magnetosphere could specify them correctly…)  We really don’t understand outflow  Joule heating effects can last a LONG time.  Electron energy flux could play a role - no one has coupled this yet.  Plasmasphere?  Photoelectrons?  Wouldn’t it be great is we could model the system without the numerics getting in the way? 78

39. GEM/CEDAR Workshop July 1, 2005 Slide 39 of Thank You! 39