MODELING THE EARTH S IONOSPHERE: SAMI2 AND SAMI3

Transcription

1 MODELING THE EARTH S IONOSPHERE: SAMI2 AND SAMI3 J.D. Huba and G. Joyce Plasma Physics Division Naval Research Laboratory Washington, DC CEDAR Workshop Boulder, CO June, 2010 Icarus Research, Inc. (acknowledge M. Swisdak)

2 SAMI VERSIONS highlights SAMI2-0.98; SAMI2 MPI-0.98; SAMI3 MPI-0.98 SAMI2: 2D and SAMI3: 3D magnetic latitude: ±60 E B drifts specified (analytical or Fejer/Scherliess) magnetic field: IGRF-like SAMI3 MPI-1.68; SAMI3 MPI-1.68CR CR: includes corotational potential E B drifts calculated from potential equation magnetic field: tilted and untilted dipole SAMI3 MPI-2.68CR magnetic field: untilted dipole high-resolution longitudinal subgrid (for ESF studies) ( φ = ; x 7 km) SAMI3/LFM and SAMI3/RCM global code with electrodynamic coupling to the magnetosphere magnetic latitude: ±88

3 PLASMA DYNAMICS H +,O +,He +,N +,N + 2,NO+,O + 2 ion continuity ion velocity n i t + (n iv i ) = P i L i n i V i t + V i V i = 1 ρ i P i + e m i E + e m i c V i B + g ν in (V i V n ) j ν ij (V i V j ) ion temperature T i t + V i T i T i V i n i k Q i = Q in + Q ij + Q ie

4 PLASMA DYNAMICS electron momentum electron temperature 0 = 1 n e m e b s P e s e m e E s T e t n e k b2 s s κ T e e s = Q en + Q ei + Q phe + Q RF

5 NEUTRAL ATMOSPHERE MODELS empirical models NLRMSISE-00 (Picone et al.) provides neutral densities and temperature HWM93/HWM07 (Hedin/Drob) provides neutral wind first principle models TIME-GCM (Crowley)

6 PHOTOIONIZATION: SOLAR FLUX MODELS empirical models: flux φ (λ) is in 37 bins EUVAC (Richards et al., 1994) function of geophysical conditions φ i = F i[1 + A i(p 80)] where P = (F 10.7A + F 10.7)/2 data/model driven (100 bins: 10Å) NRLEUV (Lean, Warren, and Mariska) FISM (Chamberlin) photoionization/photoabsorption cross-sections tabulated

7 CHEMICAL REACTION RATES

8 HOW IS THE MODEL BUILT? Numerical Issues transport parallel perpendicular grid lagrangian eulerian

9 TRANSPORT magnetic field organizes plasma motion: and components continuity equation n i t + (n iv i ) = P i L i n i n i t + (n i V i ) + (ni V i ) = P i L i n i parallel motion (diffusion/advection) n i t + (n ) i V i = Pi L i n i for t t t perpendicular motion (advection) n i t + (n iv i ) = 0 for t t t + t

10 PARALLEL TRANSPORT conventional method: ignore ion inertia n i t + b2 s s n i V is b s = P i L i n i 0 = 1 (P i + P e ) b s + g s ν in (V is V ns ) n i m i s j ν ij (V is V js ) procedure: solve for ion velocity V is substitute into continuity expand density n i n i0 + n i1 obtain fully implicit differencing scheme iterate equations to obtain a solution advantage: large time steps ( 5 15 min) disadvantage: complexity, stability, limited species (e.g., no molecular transport)

11 PARALLEL TRANSPORT SAMI2/3 method: include ion inertia n i t + b2 s s n i V is b s = P i L i n i V is t +(V i )V is = 1 (P i + P e ) b s +g s ν in (V is V ns ) n i m i s j ν ij (V is V js ) procedure: diffusion terms backward biased (implicit) advection terms use donor cell method obtain semi-implicit differencing scheme disadvantage: small time steps ( 1 15 sec) advantage: simplicity, stability, flexibility, better description at high altitudes

12 PERPENDICULAR TRANSPORT grid: lagrangian vs eurlerian perpendicular dynamics (E B transport) lagrangian grid: follow flux tube motion eulerian grid: fixed mesh

13 LAGRANGIAN GRID Follow E B drift of a flux tube animate

14 EULERIAN GRID orthogonal

15 EULERIAN GRID nonorthogonal: finite volume, donor cell method

16 GRID COMPARISON lagrangian, orthogonal eulerian, nonorthogonal eulerian

17 SAMI3 EXAMPLE

18 OVERVIEW OF SAMI2/3 2D and 3D ionosphere models magnetic field: tilted and untilted dipole model / IGRF-like interhemispheric / global ±60 and ±88 nonorthogonal, nonuniform fixed grid seven (7) ion species (all ions are equal): H +, He +, N +, O +, N + 2, NO+, and O + 2 solve continuity and momentum for all 7 species solve temperature for H +, He +, O +, and e plasma motion E B drift perpendicular to B (both vertical and longitudinal in SAMI3) ion inertia included parallel to B neutral species: NRLMSISE00/HWM93/HWM07 and TIMEGCM chemistry: 21 reactions + recombination photoionization: daytime and nighttime

19 SAMI2 OPEN SOURCE PROJECT