Comparing Poynting flux dominated magnetic towers with kinetic-energy dominated jets

1. Comparing Poynting flux dominated magnetic towers with kinetic-energy dominated jets Martín Huarte-Espinosa, Adam Frank and Eric Blackman, U. of Rochester NY Andrea Ciardi, LERMA Paris, Patrick Hartigan, Rice U. TX Sergey Lebedev and Jeremy Chittenden, Imperial College London HEDLA 2012, Tallahassee FL, 3 May

2. Motivation Lebedev et al. From the AGN Atlas of ^ NGC 326, Murgia et al.

3. Q(X,t) = Magnetic flux / kinetic-energy flux ? ? ? ? ? ? ?

4. Outline 1. Magnetic jet launch scenarios 2. Lab jets 3. Our models

5. Astro jet launch Ingredients: -1 compact object -some accreted plasma -some magnetic fields Preparation: Stir (rotation) vigorously until a hot disk is formed and the magnetic fields are helical & strong Enjoy! Begelman & Rees

6. A) Magnetocentrifugaljets (Blandford & Payne 1982; Ouyed & Pudritz 1997; Ustyugova et al. 1999; Blackman et al. 2001) Bonly dominates out to the Alfvén radius B) Poynting flux dominated jets (PFD; Shibata & Uchida ’86, Lynden-Bell 1996; Ustyugova et al. ‘00; Li et al. ‘01; Lovelace et al. ‘02; Nakamura & Meier ‘04) B dominates the jet structure

7. Lab astro experiments Radial wire array (Lebedev et al. ’05) 1MA pulse current flows radially through 16 x 13μm tungsten metallic wires a central electrode. ~1 MG toroidal magnetic field produced below the wires. MAGPIE generator, Imperial College London.

8. Evolution with XUV wire ablation + JxB force produce background plasma resistive diffusion keeps current close to wires Lebedev et al. 2005 Suzuki-Vidal et al. 2010

9. Evolution with XUV Full wire ablation near the central electrode forms a magnetic cavity. Lebedev et al. 2005 Suzuki-Vidal et al. 2010

10. Evolution with XUV Lebedev et al. ‘05 Suzuki-Vidal et al. ‘10 • Expanding magnetic tower jet driven by toroidal magnetic field pressure • Jet Collimation by hoop stress • Magnetic bubble Collimation by ambient medium • Consistent with Shibata & Uchida ‘86, Lynden-Bell ‘96, ’03.

11. Jets corrugate becoming a collimated chain of magnetized “clumps”. Lebedev et al. 2005 Suzuki-Vidal et al. 2010

12. Our models (Huarte-Espinosa et al. 2012, 1204.0800, submitted to ApJ) • Solve hyperbolic PDE with elliptic constraints: MHD • Source terms for energy loss/gain, ionization dynamics • Operator splitting: gravity, heat conduction (HYPRE)

13. Simulations PFD magnetic tower jet kinetic-energy dominated jet 1. adiabatic 4. adiabatic 2. cooling 5. cooling 3. adiabatic & rotating 6. adiabatic & rotating

14. Assumptions HD jets are collimated at sub-resolution scales. jets have same time averaged max speed: Equal injected energy fluxes: where ρj is the jet’s density and a (= πrj2) is the area of the energy injection region.

15. Initial conditions z Stellar jets. Density = 100 cm-3 Temperature = 10000 K γ =5/3 V = 0 km s-1 Magnetic fields only within the central region. This is different from other models, e.g. Li et al. ’06. r rt <----------1200 AU ---------->

16. Continuous pure magnetic energy injectionnew current initial = +

17. Adiabatic

18. 42 yr 84 yr Keplerian 118 yr adiabatic rotating

19. 42 yr 84 yr 118 yr Dalgarno & McCray (1972). Ionization of both H and He, the chemistry of H2 and optically thin cooling. adiabatic rotating cooling

20. 42 yr 84 yr 118 yr adiabatic rotating cooling hydro

21. Field line maps adiabatic cooling rotating Only 2 central field lines for clarity

22. Field geometry and perturbations

23. Instability: z x Relative strength:

24. Jet velocities: Alfvén speed highest inside tower Adiabatic Rotating Cooling βz~1 Z

25. Jet velocities: Alfvén speed highest inside tower Adiabatic Rotating Cooling βz~1 Z

26. Beam energy flux Cooling case (but rotating is similar) 120yr Poynting Kinetic 42yr 120yr

27. Summary • PFD jets more unstable and structurally different than purely HD jets with same energy flux. • -Base rotation amplifies Bφ exacerbating a pressure unbalance and leading to kink instability. • -Cooling reduces the thermal energy of the core and rjet thus it’s insufficient to damp magnetic pressure kink perturbations. • -PFD jet beams eventually yield a series of collimated clumps which may then evolve into kinetic-energy dominated jets at large distances from the engine. Relevant for YSO and possibly other jets too. • -Our model towers agree with MAGPIE lab experiments, even though no tuning was made. I.e. robust results which reveal generic properties of PFD outflows.

28. Summary -PFD jets more unstable and structurally different than purely HD jets with same energy flux. -Base rotation amplifies Bφ exacerbating a pressure unbalance and leading to kink instability. -Cooling reduces the thermal energy of the core and rjet thus it’s insufficient to damp magnetic pressure kink perturbations. -PFD jet beams eventually yield a series of collimated clumps which may then evolve into kinetic-energy dominated jets at large distances from the engine. Relevant for YSO and possibly other jets too. -Our model towers agree with MAGPIE lab experiments, even though no tuning was made. Thanks! Find this talk at: http://www.pas.rochester.edu/~martinhe/talks.html

29. Current consistent  Lebedev et al. 2005 Adiabatic Rotating Cooling