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Reconnection in the Magnetotail and the Solar Corona

Reconnection in the Magnetotail and the Solar Corona. J. Birn, M. Hesse Ackn.: R. Nakamura, E. Panov. photo: M.Hesse. Reconnection in the Magnetotail and the Solar Corona. Overview Bouncing and vortex flows Role of entropy loss/reduction Energetic particle fluxes (test electrons)

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Reconnection in the Magnetotail and the Solar Corona

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  1. Reconnection in the Magnetotailand the Solar Corona J. Birn, M. Hesse Ackn.: R. Nakamura, E. Panov photo: M.Hesse

  2. Reconnection in theMagnetotailand the Solar Corona • Overview • Bouncing and vortex flows • Role of entropy loss/reduction • Energetic particle fluxes (test electrons) • Solar application (force-free initial state) (photos: M. Hesse)

  3. “photospheric” magnetic field z x Initial states: Low and high β Initial States & Initiation Phase y y z x low , large By (force-free) strong shear high , small By low shear thin current sheet formation Initiation phase: converging footpoint motion

  4. Current density Jy and magnetic field Current intensification, initiation of reconnection high  small By low  large By y critical state: loss of equilibrium, thin current sheet formation

  5. 3D Tail Simulations: Collapse of near tail field Bz z x

  6. 3D Magnetotail Simulations: Ey(t)

  7. 3D Magnetotail Simulations & Observations THEMIS observations (Panov et al., 2010) MHD simulations (Birn et al., 2011) Bouncing, pulsating, dipolarization sequences

  8. 3D Tail Simulations & Observations MHD simulations (Birn et al., 2011) THEMIS observations (Panov et al., 2010) reversed pattern Vortex patterns that reverse during rebound

  9. “Entropy” in the x,y plane -15 -10 x -5 Bz contours 0 -10 -5 5 10 y

  10. Onset of fast reconnection

  11. Test particle simulations (electrons) y x

  12. Energetic (180 keV) electrons at x = 0 and z = 0 t=132

  13. Test particle simulations (electrons) field lines connecting to flux peak at x=0 & separatrices

  14. Simulated and observed distribution functions geosynchronous observations test particle simulations electrons protons

  15. Source regions of accelerated particles • High energy, early: flank plasma sheet • Low energy, late: plasma sheet boundary layer (mantle) • initial: more distant plasma sheet • later: lobe source, may cause sudden flux decrease • Phase space mixing

  16. Evolution of initially force-free arcades (β0 = 0.01) z y x

  17. Pressure and Temperature Evolution (force-free initial state) Pressure Temperature “temperature” = average kin. energy in rest frame = p/n

  18. Energy Conversion (low beta case 0 = 0.01) Enthalpy flux H = (u+p) v = 2.5 pv Poynting flux S = EB Kin. energy fluxK = 0.5 v2v Incoming Poynting flux Up & down Poynting flux Up & down enthalpy flux Up & down kin. energy flux

  19. Time Variation: Integrated Energy Fluxes Down 30 low , large By Force-free initial state Poynting flux jn 20 10 Corona units: BN = 100 G = 0.01 T nN = 31015/m3 LN = 10,000 km VN = 4000 km/s kTN = 200 keV (kTeb = 0.5 keV) tN = 2.5 s energy flux = 41029 erg/s Poynting flux down Enthalpy flux down 0 50 100 0 high , small By 40 Poynting flux jn Enthalpy flux down 20 Shear-free initial state Poynting flux down 0 50 0 time

  20. Velocity vz in y, z Plane (force-free initial state) t = 90 t = 110 Breakup of initially straight separator into multiple reconnection sites, localized flows t = 130

  21. By and vz in y, z Plane (force-free initial state) By vz

  22. Ey and E|| in y, z Plane Ey E||

  23. Sz in x, z Plane at y=5 (force-free initial state)

  24. Temperature & Poynting flux, z = 1 plane (Force-free initial state) Temperature Poynting flux t = 107 t = 90 t = 110 t = 110 t = 130 t = 113

  25. Summary • Entropy & mass loss from plasmoid ejection • crucial in earthward transport • Vorticity, bouncing, pulsating, consistent with observations • Electron acceleration from betatron and Fermi: • - two main source regions: flanks, PSBL/lobes • - poleward expansion, yet earthward motion • Solar corona (low β, initial force-free): • - strong compression near reconnection site • and in collapsing loops • - breakup into multiple sites (interchange?) • - localized Alfvenic (& enthalpy) pulses

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