Presentation is loading. Please wait.

Presentation is loading. Please wait.

Multifluid models of the solar wind Leon Ofman Catholic University of America NASA GSFC, Code 612.1, Greenbelt, MD 20771, USA.

Similar presentations


Presentation on theme: "Multifluid models of the solar wind Leon Ofman Catholic University of America NASA GSFC, Code 612.1, Greenbelt, MD 20771, USA."— Presentation transcript:

1 Multifluid models of the solar wind Leon Ofman Catholic University of America NASA GSFC, Code 612.1, Greenbelt, MD 20771, USA

2 UVCS Observations of a coronal streamer (Strachan et al 2002)

3 Nonthermal motions in coronal holes (SOHO/SUMER) (Banerjee et al 1998) Nonthermal broadening of Si VIII Context image WKB Alfvén wave amplitude:  V~  -1/4

4 Three-fluid model vs. UVCS observations p O 5+ r=5R s r=1.8R s Co-latitude (deg) r=2.33R s V (km/s) 3f model (Ofman 2000) UVCS (Strachan et al 2002)

5 Slow Solar Wind UVCS observations vs. 3-fluid model (Ofman 2000) UVCS Observations O VI Ly  Oxygen (O VI) Protons (Ly  )

6 Three-fluid model equations where Z k is the charge number; A k is the atomic mass number of species k. Normalized three fluid equations for V<

7 Formation of a streamer: 3-fluid polytropic (  =1.05) model with He ++ RR  

8  1 R [R s ] J2J2 TeTe

9 Magnetic field and flow

10 O 5+ vs He ++ O 5+ He ++

11 Heat conductive three-fluid model (e, p, He ++ )

12 “Active region” streamer model

13 Alfvén wave source Alfvén wave driver is modeled by Where a i =i -1/2,  i is the i th mode, and  i (  ) is the i th random phase. The parameters are V d =0.034 or 0.05,  1 =1,  N =100, N=100,   <<  p Power spectrum:  -1

14 Heating terms Electron heating by current dissipation: Proton heating by viscous dissipation: Empirical heating term for ions: Heat Conduction is included for protons and electrons along the magnetic field. use  =10 -4 use   =10 -4,  0 ~0. Classical heat conduction is used up to 2R s with smooth cutoff to zero for r> 2R s

15 Alfvén wave driven fast solar wind with He ++ (Ofman 2004)

16 Alfvén wave driven fast solar wind: 2.5D 3-fluid model: e-p-He ++  R [Solar radii] VpVp V pr TeTe

17 Evolution of magnetic field Alfvénic fluctuations | F (  )| 2     Power spectrum at 18R s  -2  -5/3

18  -Averaged radial outflow speed:3-fluid model (Ofman 2004) p He ++ O 5+ p p p He ++ H 0p =0.5 H 0i =12 V d =0.034 H 0p =0 H 0i =12 V d =0.05 H 0p =0.5 H 0i =0.5 V d =0.034 H 0p =0.5 H 0i =10 V d =0.034

19 Linearized multifluid equations and dispersion relation Momentum: Inductance: Quasineutrality: Dispersion Relation:

20 Four-fluid dispersion relation

21 Velocity amplitude ratios |V i /V p | using three fluid dispersion He ++ O 6+ (Ofman, Davila, Nakariakov, and Viñas 2005, in press)

22 Vlasov dispersion relation for finite  plasma  (Ofman, Davila, Nakariakov, and Viñas 2005, in press)

23 Dispersion relation from three-ion (p, He ++,O 6+ ) hybrid simulations BB VpVp V He ++  V O 6+  (Ofman, Davila, Nakariakov, and Viñas 2005, in press)

24 Velocity amplitude ratios from hybrid simulation dispersion (Ofman, Davila, Nakariakov, and Viñas 2005, in press) V  He ++ /V  p V  O 6+ /V  p kC A /  p ~0 kC A /  p =0.6

25 Conclusions Recent observations of minor ion emission lines in coronal holes provide clues for the acceleration and heating mechanism of the fast wind, and require multi-fluid and kinetic modeling in order to interpret the results. The slow solar wind has been modeled with 2D three-fluid code, and the basic features of streamers and acceleration profiles are recovered for protons and heavy ions. Wave driven wind in coronal holes was modeled with the three-fluid code in a self-consistent model, and the different proton and heavy ions flow profiles are reproduced. High frequency waves (in the ion-cyclotron frequency range) produce different perpendicular velocities for protons and heavy ion in the multifluid model, as well is in the hybrid simulations.


Download ppt "Multifluid models of the solar wind Leon Ofman Catholic University of America NASA GSFC, Code 612.1, Greenbelt, MD 20771, USA."

Similar presentations


Ads by Google