1. Plasma Unbound: Coronal Heating and Steven R. Cranmer Harvard-Smithsonian Center for Astrophysics Solar / Stellar Winds New Insights into

2. Plasma Unbound: Coronal Heating and Steven R. Cranmer Harvard-Smithsonian Center for Astrophysics Solar/Stellar Winds New Insights into Outline: Overview and brief historical background Heating the coronal base (reconnection & turbulence) 3. Heating and accelerating the extended corona (waves & turbulence) 4. The young Sun accretion-powered winds?

3. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Motivations plasma physics nuclear physics non-equilibrium thermodynamics electromagnetic theory Space weather can affect satellites, power grids, and astronaut safety. The Sun’s mass-loss & X-ray history impacted planetary formation and atmospheric erosion. Solar corona & solar wind: The Sun is a “laboratory without walls” for many basic processes in physics, at regimes (T, P) inaccessible on Earth!

4. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The extended solar atmosphere Heating is everywhere...... and everything is in motion

5. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The extended solar atmosphere Heating is everywhere...... and everything is in motion

6. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Too-brief history Total eclipses let us see the vibrant outer solar corona: but what is it? 1870s: spectrographs pointed at corona: 1930s: Lines identified as highly ionized ions: Ca +12, Fe +9 to Fe +13  it’s hot! Fraunhofer lines (not moon-related) unknown bright lines 1860–1950: Evidence slowly builds for outflowing magnetized plasma in the solar system: solar flares  aurora, telegraph snafus, geomagnetic “storms” comet ion tails point anti-sunward (no matter comet’s motion) 1958: Eugene Parker proposed that the hot corona provides enough gas pressure to counteract gravity and accelerate a “solar wind.”

7. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 In situ solar wind: properties 1962: Mariner 2 detected two phases of solar wind: slow (mostly) + fast streams Uncertainties about which type is “ambient” persisted because measurements were limited to the ecliptic plane... Ulysses left the ecliptic; provided 3D view of the wind’s source regions. By ~1990, it was clear the fast wind needs something besides gas pressure to accelerate so fast! speed (km/s) T p (10 5 K) T e (10 5 K) T ion / T p O 7+ /O 6+, Mg/O 600–800 2.4 1.0 > m ion /m p low 300–500 0.4 1.3 < m ion /m p high fastslow

8. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Ulysses’ view over the poles McComas et al. (2008)

9. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Exploring the solar wind (1970s to present) Space probes have pushed out the boundaries of the “known” solar wind... Helios 1 & 2: inner solar wind (Earth to Mercury) Ulysses: outer solar wind (Earth to Jupiter, also flew over N/S poles) Voyager 1 & 2: far out past Pluto: recently passed the boundary between the solar wind and the interstellar medium CLUSTER: multiple spacecraft probe time and space variations simultaneously

10. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Particles are not in “thermal equilibrium” Helios at 0.3 AU (e.g., Marsch et al. 1982) WIND at 1 AU (Collier et al. 1996) WIND at 1 AU (Steinberg et al. 1996) …especially in the high-speed wind. mag. field

11. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Overview of coronal observations “Quiet” regions Active regions Coronal hole (open) Plasma at 10 6 K emits most of its spectrum in the UV and X-ray...

12. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Solar wind: connectivity to the corona High-speed wind: strong connections to the largest coronal holes Low-speed wind: still no agreement on the full range of coronal sources: hole/streamer boundary (streamer “edge”) streamer plasma sheet (“cusp/stalk”) small coronal holes active regions Wang et al. (2000)

13. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 1990s: SOHO’s new view of the corona

14. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The coronal heating problem We still don’t understand the physical processes responsible for heating up the coronal plasma. A lot of the heating occurs in a narrow “shell.” Most suggested ideas involve 3 general steps: 1.Churning convective motions that tangle up magnetic fields on the surface. 2.Energy is stored in tiny twisted & braided magnetic flux tubes. 3.Collisions between ions and electrons (i.e., friction?) release energy as heat. Heating Solar wind acceleration!

15. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Coronal heating mechanisms So many ideas, taxonomy is needed! (Mandrini et al. 2000; Aschwanden et al. 2001) Where does the mechanical energy come from? vs.

16. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Coronal heating mechanisms So many ideas, taxonomy is needed! (Mandrini et al. 2000; Aschwanden et al. 2001) Where does the mechanical energy come from? How rapidly is this energy coupled to the coronal plasma? waves shocks eddies (“AC”) vs. twisting braiding shear (“DC”) vs.

17. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Coronal heating mechanisms So many ideas, taxonomy is needed! (Mandrini et al. 2000; Aschwanden et al. 2001) Where does the mechanical energy come from? How rapidly is this energy coupled to the coronal plasma? How is the energy dissipated and converted to heat? waves shocks eddies (“AC”) vs. twisting braiding shear (“DC”) vs. reconnectionturbulence interact with inhomog./nonlin. collisions (visc, cond, resist, friction) or collisionless

18. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Turbulence It is highly likely that somewhere in the solar atmosphere, the fluctuations become turbulent and cascade from large to small scales. The original Kolmogorov (1941) theory of incompressible fluid turbulence describes a constant energy flux from the largest “stirring” scales to the smallest “dissipation” scales. Largest eddies have kinetic energy ~ ρv 2 and a turnover time-scale  =l/v, so the rate of transfer of energy goes as ρv 2 /  ~ ρv 3 /l. Dimensional analysis can give the spectrum of energy vs. eddy-wavenumber k: E k ~ k –5/3

19. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Turbulence in coronal loops? Many stochastic processes can be described roughly using a turbulent “language.” Coronal loops are always in motion, with waves & bulk flows propagating back and forth along the field lines. Counter-propagating Alfvén waves interact over shorter time intervals  thus the cascade takes longer to develop. However, the weaker character of the cascade makes it able to “send” more energy down the ladder of ever-smaller eddies, and thus lead to more dissipation! n = 0 (Kolmogorov), 3/2 (Gomez et al. 2000), 5/3 (Kraichnan), 2 (van Ballegooijen; Rappazzo et al.)

20. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Ultimately, the actual dissipation and heating in loops appears to occur in regions of magnetic reconnection. Reconnection & Turbulence Onofri et al. (2006) Dmitruk et al. (2004) Rappazzo et al. (2008) » break up into thin reconnecting sheets. » accelerate electrons along the field to generate currents. Even pre-existing current sheets are unstable in a variety of ways to growth of turbulent motions, which may dominate the energy loss & particle acceleration. This is still understandable from a turbulence paradigm, since on its smallest scales, MHD turbulence tends to:

21. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The need for extended heating The basal coronal heating problem is not yet solved, but the field seems to be “homing in on” the interplay between emerging flux, reconnection, turbulence, and helicity (shear/twist). Above ~2 R s, some other kind of energy deposition is needed in order to... » accelerate the fast solar wind (without artificially boosting mass loss and peak T e ), » produce the proton/electron temperatures seen in situ (also magnetic moment!), » produce the strong preferential heating and temperature anisotropy of ions (in the wind’s acceleration region) seen with UV spectroscopy. X

22. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Waves? Start in the photosphere... The photosphere shows convective motion on a broad range of time/space scales: β << 1 β ~ 1 β > 1

23. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Alfvén waves from cradle to grave In dark intergranular lanes, strong-field photospheric flux tubes are shaken by an observed spectrum of horizontal motions. In mainly open-field regions, Alfvén waves propagate up along the field, and partly reflect back down (non-WKB). Nonlinear couplings allow a (mainly perpendicular) turbulent cascade, terminated by damping → gradual heating over several solar radii.

24. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 MHD turbulence: two kinds of “anisotropy” Outside closed loops, we can revert to “standard” Kolmogorov (1941) scaling, but with two modifications: With a strong background field, it is easier to mix field lines (perp. to B) than it is to bend them (parallel to B). Also, the energy transport along the field is far from isotropic. Z+Z+ Z–Z– Z–Z– (e.g., Hossain et al. 1995; Matthaeus et al. 1999; Dmitruk et al. 2001, 2002; Oughton et al. 2006)

25. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 “The kitchen sink” Cranmer, van Ballegooijen, & Edgar (2007) computed self-consistent solutions of waves & background one-fluid plasma state along various flux tubes... going from the photosphere to the heliosphere. Ingredients: Alfvén waves: non-WKB reflection with full spectrum, turbulent damping, wave-pressure acceleration Acoustic waves: shock steepening, TdS & conductive damping, full spectrum, wave-pressure acceleration Radiative losses: transition from optically thick (LTE) to optically thin ( CHIANTI + PANDORA ) Heat conduction: transition from collisional (electron & neutral H) to collisionless “streaming”

26. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Results: turbulent heating & acceleration T (K) reflection coefficient Goldstein et al. (1996) Ulysses SWOOPS

27. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Multi-fluid collisionless effects?

28. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 protons electrons O +5 O +6 Multi-fluid collisionless effects?

29. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Exploring the extended corona “Off-limb” measurements (in the solar wind acceleration region ) allow dynamic non-equilibrium plasma states to be followed as the asymptotic conditions at 1 AU are gradually established. Occultation is required because extended corona is 5 to 10 orders of magnitude less bright than the disk! Spectroscopy provides detailed plasma diagnostics that imaging alone cannot. The Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO combines these features to measure plasma properties of coronal protons, ions, and electrons between 1.5 and 10 solar radii.

30. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Preferential ion heating & acceleration UVCS observations have rekindled theoretical efforts to understand heating and acceleration of the plasma in the (collisionless?) acceleration region of the wind.

31. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Preferential ion heating & acceleration UVCS observations have rekindled theoretical efforts to understand heating and acceleration of the plasma in the (collisionless?) acceleration region of the wind. Alfven wave’s oscillating E and B fields ion’s Larmor motion around radial B-field Ion cyclotron waves (10–10,000 Hz) suggested as a “natural” energy source that can be tapped to preferentially heat & accelerate heavy ions. MHD turbulence cyclotron resonance- like phenomena something else?

32. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The Young Sun... Kelvin-Helmholz contraction: ISM cloud fragment becomes a protostar; gravitational energy converted to heat. Hayashi track: protostar reaches approx. hydrostatic equilibrium, but slower gravitational contraction continues. Observed as the T Tauri phase. Henyey track: T core reaches ~10 7 K and hydrogen burning dominates; some accretion and gravitational contraction remain, but both slow to a halt at ZAMS.

33. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 T Tauri stars: active accretion & outflows (Matt & Pudritz 2005, 2008) (Romanova et al. 2007) T Tauri stars exhibit signatures of disk accretion (outer parts), “magnetospheric accretion streams” & X-ray corona (inner parts), and various (polar?) outflows. Nearly every observational diagnostic varies in time, sometimes with stellar rotation, but often more irregularly.

34. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Accretion-driven T Tauri winds Cranmer (2008) extended the solar wave/turbulence models to outer atmospheres of young, solar-type stars. The impact of inhomogeneous “clumps” on the stellar surface generates MHD waves that propagate horizontally (like solar Moreton & EIT waves!). These “extra” waves input orders of magnitude more energy into a turbulent MHD cascade, and can give rise to stellar winds with dM/dt up to 10 6 times solar!

35. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Accretion-driven T Tauri winds Results: wind mass loss rate increases ~similarly to the accretion rate. For high enough densities, radiative cooling “kills” coronal heating!

36. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Synergy with other systems Pulsating hot (O, B, Wolf-Rayet) stars: Pulsations “leak” outwards as non-WKB waves and shocks. New insights from solar wave theory are being extended. Red giants & supergiants: Strong pulsations & shocks, with dense/slow winds (radiatively cooled?) and variability from dust, thermal instabilities, etc. AGN accretion flows: A similarly collisionless (but pressure-dominated) plasma undergoing anisotropic MHD cascade and kinetic wave-particle interactions... Freytag et al. (2002)

37. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Conclusions For more information: http://www.cfa.harvard.edu/~scranmer/ The Sun/heliosphere system is a nearby “laboratory without walls” for studying plasma physics in regimes of parameter space inaccessible in Earth-based laboratories. Theoretical advances in MHD turbulence continue to feed back into global models of coronal heating and the solar wind. The extreme plasma conditions in coronal holes (T ion >> T p > T e ) have guided us to discard some candidate processes, further investigate others, and have cross-fertilized other areas of plasma physics & astrophysics.

38. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Extra slides...

39. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 First observations of “stellar outflows” Coronae & Aurorae seen since antiquity... “New stars” 1572: Tycho’s supernova 1600: P Cygni outburst (“Revenante of the Swan”) 1604: Kepler’s supernova in “Serepentarius”

40. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The solar activity cycle Yohkoh/SXT

41. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 What produces “emission lines” in a spectrum? There are 2 general ways of producing extra photons at a specific wavelength. A free electron from some other ionized atom (“collisional excitation”) A photon at the right wavelength from the bright solar disk (“resonant scattering”) Both mechanisms depend on the quantum nature of atoms: “bound” electrons have discrete energies... The incoming particle can be either: Incoming particle Electron absorbs energy Energy re-emitted as light There is some spread in wavelength

42. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Mirror motions select height UVCS “rolls” independently of spacecraft 2 UV channels: 1 white-light polarimetry channel LYA (120–135 nm) OVI (95–120 nm + 2 nd ord.) The UVCS instrument on SOHO 1979–1995: Rocket flights and Shuttle-deployed Spartan 201 laid groundwork. 1996–present: The Ultraviolet Coronagraph Spectrometer (UVCS) measures plasma properties of coronal protons, ions, and electrons between 1.5 and 10 solar radii. Combines “occultation” with spectroscopy to reveal the solar wind acceleration region! slit field of view:

43. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 UVCS results: over the poles (1996-1997 ) The fastest solar wind flow is expected to come from dim coronal holes. In June 1996, the first measurements of heavy ion (e.g., O +5 ) line emission in the extended corona revealed surprisingly wide line profiles... On-disk profiles: T = 1–3 million K Off-limb profiles: T > 100 million K !

44. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Emission lines as plasma diagnostics Many of the lines seen by UVCS are formed by resonantly scattered disk photons. If profiles are Doppler shifted up or down in wavelength (from the known rest wavelength), this indicates the bulk flow speed along the line-of-sight. The widths of the profiles tell us about random motions along the line-of-sight (i.e., temperature) The total intensity (i.e., number of photons) tells us mainly about the density of atoms, but for resonant scattering there’s also another “hidden” Doppler effect that tells us about the flow speeds perpendicular to the line-of-sight. If atoms are flow in the same direction as incoming disk photons, “Doppler dimming/pumping” occurs.

45. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Doppler dimming & pumping After H I Lyman alpha, the O VI 1032, 1037 doublet are the next brightest lines in the extended corona. The isolated 1032 line Doppler dims like Lyman alpha. The 1037 line is “Doppler pumped” by neighboring C II line photons when O 5+ outflow speed passes 175 and 370 km/s. The ratio R of 1032 to 1037 intensity depends on both the bulk outflow speed (of O 5+ ions) and their parallel temperature... The line widths constrain perpendicular temperature to be > 100 million K. R < 1 implies anisotropy!

46. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Coronal holes: over the solar cycle Even though large coronal holes have similar outflow speeds at 1 AU (>600 km/s), their acceleration (in O +5 ) in the corona is different! (Miralles et al. 2001) Solar minimum: Solar maximum:

47. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Waves: remote-sensing techniques The following techniques are direct… (UVCS ion heating was more indirect) Intensity modulations... Motion tracking in images... Doppler shifts... Doppler broadening... Radio sounding... Tomczyk et al. (2007)

48. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Alfvén waves: from Sun to Earth Velocity amplitudes of fluctuations measured (mainly) perpendicular to the background magnetic field.

49. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Why is the fast (slow) wind fast (slow)? vs. What determines how much energy and momentum goes into the solar wind?  Waves & turbulence input from below?  Reconnection & mass input from loops? Cranmer et al. (2007) explored the wave/turbulence paradigm with self-consistent 1D models of individual open flux tubes. Boundary conditions imposed only at the photosphere (no arbitrary “heating functions”). Wind acceleration determined by a combination of magnetic flux-tube geometry, gradual Alfvén-wave reflection, and outward wave pressure.

50. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Do blobs trace out the slow wind? The blobs are very low- contrast and thus may be passive “leaves in the wind.” Sheeley et al. (1997)

51. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Polar plumes and jets Dense, thin flux tubes permeate polar coronal holes. They live for about a day, but can recur from the same footpoint over several solar rotations. Short-lived “polar jets” are energetic events that appear to eject plasma into the solar wind. Hinode/XRT (DeForest et al. 1997)

52. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The solar chromosphere

53. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 The need for chromospheric heating Not huge in radial extent, but contains order of magnitude more mass than the layers above...

54. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 “Traditional” chromospheric heating Vertically propagating acoustic waves conserve flux (in a static atmosphere): Amplitude eventually reaches V ph and wave-train steepens into a shock-train. Shock entropy losses go into heat; only works for periods < 1–2 minutes… New idea: “Spherical” acoustic wave fronts from discrete “sources” in the photosphere (e.g., enhanced turbulence or bright points in inter-granular lanes) may do the job with longer periods. Bird (1964) ~

55. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Time-dependent chromospheres? Carlsson & Stein (1992, 1994, 1997, 2002, etc.) produced 1D time-dependent radiation-hydrodynamics simulations of vertical shock propagation and transient chromospheric heating. Wedemeyer et al. (2004) continued to 3D...

56. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Runaway to the transition region (TR) Whatever the mechanisms for heating, they must be balanced by radiative losses to maintain chromospheric T. Why then isn’t the corona 10 9 K? Downward heat conduction smears out the “peaks,” and the solar wind also “carries” away some kinetic energy. Conduction also steepens the TR to be as thin as it is. When shock strengths “saturate,” heating depends on density only:

57. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Strongest fields in supergranular “funnels?” Peter (2001) Tu et al. (2005) Fisk (2005)

58. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Streamers with UVCS Streamers viewed “edge-on” look different in H 0 and O +5 Ion abundance depletion in “core” due to grav. settling? Brightest “legs” show negligible outflow, but abundances consistent with in situ slow wind. Higher latitudes and upper “stalk” show definite flows (Strachan et al. 2002). Stalk also has preferential ion heating & anisotropy, like coronal holes! (Frazin et al. 2003)

59. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Coronal mass ejections Forbes & Priest (1995) and Lin & Forbes (2000) developed a theory of CMEs as a loss of magnetostatic equilibrium in a twisted “flux rope.” The current sheet energizes both the CME (above) and a “two-ribbon flare” (below)

60. Plasma Unbound: New Insights Coronal Heating and Solar/Stellar WInds Steven Cranmer, CfA HAO Colloquium, March 4, 2009 Overview of “in situ” fluctuations Fourier transform of B(t), v(t), etc., into frequency: The inertial range is a “pipeline” for transporting magnetic energy from the large scales to the small scales, where dissipation can occur. f -1 “energy containing range” f -5/3 “inertial range” f -3 “dissipation range” 0.5 Hzfew hours Magnetic Power How much of the “power” is due to spacecraft flying through flux tubes rooted on the Sun?