Kinetic physics of the solar wind

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1 "What science do we need to do in the next six years to prepare for Solar Orbiter and Solar Probe Plus?" Kinetic physics of the solar wind Eckart Marsch Max-Planck-Institut für Sonnensystemforschung

2 Complementary heliophysics missions In-situ plasma measurements Remote-sensing solar observations Views on the Sun s poles from 34 Corotation (>8 /d) observations < 30 R s 2150 h < 10 R s 30 h Solar Orbiter (SO), launch 2017, ESA, perihelion 48 R s Solar Probe Plus (SPP), launch 2018, NASA, perihelion 9.5 R s

3 Solar Probe Plus: How does the Sun produce the solar wind? Determine the structure and dynamics of the magnetic fields at the sources of the fast and slow solar wind Trace the flow of energy that heats the corona and accelerates the solar wind Determine what mechanisms accelerate and transport energetic particles Explore dusty plasma phenomena in the near-sun environment and their influence on the solar wind and energetic particle formation

4 Solar Probe Plus goes progressively closer 24 passes < 0.2 AU 20 1st perihelion (~0.16 AU) 3 months after launch 19 passes < 20 R s 1.2 Perihelion (Rs) R s 5 1 Solar Distance (AU) Time (days from launch) Time (days from launch) Courtesy, McComas, 2009

5 Solar Orbiter: How does the Sun create and control the Heliosphere? How and where do the solar wind plasma and magnetic field originate in the corona? How do solar transients drive heliospheric variability? How do solar eruptions produce energetic particle radiation that fills the heliosphere? How does the solar dynamo work and drive connections between the Sun and the heliosphere?

6 Solar Orbiter goes progressively higher AU 2017 Courtesy, Marsden, 2010

7 Correlative observations Sun Solar Probe Plus V sw B Solar Orbiter Radial alignments: SO and SPP observe the same SW plasma IMF alignments: SO and SPP connect to the same IMF footpoint Quadratures: SO remote-sensing and SPP 9.5 Rs Courtesy, Marsden, 2010

8 Sun-Heliosphere connections SPP in-situ observations near the Sun within ~1 mean free path of SEP acceleration site (< 0.3 AU) in fields of view of wide-angle coronagraph and heliospheric imager of SO before stream-stream interaction dominates (< 0.3 AU) SO and SPP multi-point in-situ observations 2 varying inner-heliosphere vantage points, enabling the separation of radial, longitudinal and temporal variations 3-point observations possible with another Earth-bound spacecraft in extended mission phases, simultaneous observations out of and in the ecliptic plane at different helio-latitudes (global magnetic connectivity) SO concurrent remote sensing of solar sources for SPP synoptic and extended photospheric magnetic fields synoptic coronal plasma imaging (structure) and diagnostics (composition, flow and temperature) for heliospheric context

9 "What science do we need to do in the next six years to prepare for Solar Orbiter and Solar Probe Plus?" Read and digest recent references: 1. Echim, Marius M., Joseph Lemaire, Øystein Lie-Svendsen, A review on Solar Wind Moodeling: Kinetic and Fluid Aspects, Surv. Geophys. (2011) 32, Ofman, Leon, Wave Modeling of the Solar Wind, Living Rev. Solar Phys. 7, (2010), Cranmer, Steven R., Coronal Holes, Living Rev. Solar Phys. 6, (2009), Marsch, Eckart, Kinetic physics of the solar corona and solar wind, Liv. Rev. Solar Phys 3, (2006),

10 Approaches in theory/modeling 1. Single-fluid MHD (heating functions) 2. Multi-fluid models (anisotropic, higher-order, multi-species, differential heating/acceleration) 3. Hybrid models (kinetic ions, fluid electrons, simulation) 4. Vlasov-Boltzmann (exospheric, collisions, waves) F r =(V A /V ) 2 ; F V = viscous force S h, S l = heating, losses (conduction, radiation) = 5/3; = 8 p/b 2 ; S= A / R Ofman, Space Sci. Rev., 2005

11 Collisional fluid versus exosphere Parameter Chromo -sphere Corona (1R S ) n e (cm -3 ) Solar wind (1AU) T e (K) Pierrard et al., JGR, 2004 V 3 kv (km) Total energy and magnetic moment are conserved:

12 Suprathermal coronal electrons interacting with whistler waves Boltzmann equation A(s) area function s= R s s= 6.5 R s Mirror force focusing -> strahl Pitch-angle scattering -> shell formation Vocks and Mann, Ap. J., 593, 1134, 2003

13 Magnetic funnel - source of fast wind polar hole funnel Tu, Zhou, Marsch, et al., Science and SW11, 2005

14 Coronal mass and energy supply Sketch to illustrate the scenario of the solar wind origin and mass supply through reconnection. The supergranular convection is the driver of solar wind outflow in coronal funnels. Sizes and shapes of funnels and loops shown are drawn to scale. He, Tu and Marsch, Solar Phys., 2008

15 Alfvén waves from reconnection in magnetic network Simulations of Alfvén waves: Self-consistent 3D radiative MHD simulation, ranging from the convection zone up to the corona. The field lines (red) are continuously shaken and carry Alfvén waves. The coloring shows the plasma temperature from lower chromospheric (red) to higher transition-region values (green). De Pontieu et al., Science, 2007

16 HIS and SPICE studying heavy-ion kinetics SPICE provides generally plasma diagnostics of corona on disk and off limb (also for Solar Probe Plus) SPICE with HIS (SWA) provides (via composition) key links of Sun with Heliosphere SPICE will scrutinize the solar wind acceleration region by observing line broadenings (temperatures versus height) of minor ions with different charge/mass ratios. UVCS/SOHO

17 Turbulence broadening of UV lines Limits on Alfvén wave amplitude v: km/s Coronal plasma diagnostics in solar transition region with emission line broadenings Wilhelm, Marsch, Dwivedi, Feldman, Space Sci. Rev., 2008

18 Key issues in solar wind kinetic physics Electric field and electron kinetics (heat conduction) Perpendicular coronal heating of (heavy) ions Magnetic-mirror and wave forces in solar corona Differential ion acceleration (faster minor ions) Turbulence (MHD and kinetic): origin, evolution, anisotropy, cascading and disspation Plasma waves and instabilities (wave emission and absorption, wave-particle interactions) Heavy ion composition (i.e., elemental abundances and charge states, FIP effect) of fast and slow streams

19 Breakdown of classical transport theory Helios Strong electron heat flux tail Collisonal free path larger than temperature gradient scale Expansion about a local Maxwellian does not converge Pilipp et al., JGR, 92, 1075, 1987 Maksimovic et al., JGR, 2005

20 Heat flux carried by halo and strahl Locally, q is well correlated with B -> regulation by Whistler waves! Scime et al., 1994

21 Proton kinetics and plasma waves Free energy source Proton anisotropy Proton beam Ion differential streaming Kinetic wave mode Ion cyclotron wave Ion acoustic wave Magnetosonic wave Marsch, Liv. Rev. Solar Phys. 2006

22 Cyclotron-resonant pitch-angle diffusion Helios V A =109 km/s core beam v y v y 0.9, 0.7, 0.5, 0.3, 0.1, 0.03, 0.01, Plateau formation v x (km/s) V=614 km/s Heuer and Marsch, JGR, 2007 v x (km/s) Ω p = 1.1 Hz

23 Transverse Alfvén/cyclotron waves Proton anisotropy (T /T ll >1) is strongly correlated with wave power. Bourouaine et al., GRL, 2010

24 Anisotropic turbulence cascade ions Simulations and analytic models predict cascade from small to large k, leaving k unchanged. Critical balance assumes A = k V A NL = k V (Goldreich and Sridar, ApJ. 1995, 1997) Kinetic Alfven wave (KAW) with large k does not necessarily have high frequency A. electrons In a low-beta plasma, KAWs are Landau-damped, heating electrons preferentially. Courtesy, Cranmer, 2010

25 "What science do we need to do in the next six years to prepare for Solar Orbiter and Solar Probe Plus?" Continue data analysis of ongoing and past missions: 1. Messenger (0.38 AU) 2. STEREO (1 AU) 3. ACE, Wind (1 AU) 4. SOHO (1 AU) 5. SDO, Hinode (1 AU) 6. Ulysses and Helios ( AU)

26 Kinetic theory/modeling of solar wind Kinetic models (collisions) of solar wind electrons Kinetic models of coronal ion heating Derivation (beyond WKB) of fluid-wave forces Ion acceleration by nonlinear MHD effects, and by plasma waves Theory of anisotropic spectral transfer of turbulence, and its cascading and dissipation Understanding wave-particle interactions, beyond quasi-linear theory and from numerical simulation

27 SPICE is indispensable for kinetic physics In situ composition (M/q) data show that solar wind stream composition varies with structure. SPICE measurement ranges are shown by black boxes. Measure temperatures and densities of ions and electrons in corona Determine bulk flows and overall plasma motions in corona Probe (mass/charge related) differential kinetic and wave effects in solar corona Determine heavy ion composition (elemental abundances, charge states) SPICE will relate outflow velocities of magnetic surface features to solar wind structures.

28 SPICE is indispensable for coronal physics Analyse coronal shocks (CME related and off limb) Probe waves and turbulence (MHD) through ultraviolet line intensities, shifts, and broadenings Study morphology of coronal magnetic field by correlating emission patterns with extrapolated field

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30 Particles and fields - measurements and theory Characterize and explain the solar wind micro-state Measure heavy ion distributions, for probing waves and identifying plasma sources from abundances and charges Determine the k vectors (propagation directions) of plasma waves and their polarization Develope a microturbulence-mediated transport theory Simulate the effects of wave-particle interactions numerically and validate theory empirically Analyse the dissipation of MHD turbulence Determine the diffusion tensor for SEP propagation

31 Sun/solar corona - observations and theory Establish the magnetic Sun-heliosphere connections, i.e. measure magnetic flux in photosphere and heliosphere Use SEPs as tracers for magnetic connectivity Detect and characterize sources of solar wind streams Diagnose the coronal plasma state off limb and on disk Determine composition from ultraviolet spectroscopy Remotely sense and identify coronal waves Detect origin of and classify coronal shocks Study flux emergence and eruption as cause of activity Trace the evolution of CMEs and model them

32 Required SPICE observations: How and where do the solar wind plasma and magnetic field originate in the corona? - Composition of source regions and in-situ (SWA) - Full-Sun, high-resolution and spectral images of corona and chromosphere (EUI, METIS) - High-resolution spectral images of coronal loops, funnels and evolving magnetic structures (EUI) - Coronal wave propagation and heating - Off-limb observations of ion temperature, flows and nonthermal velocities (METIS) - Imaging of solar wind source regions in Doppler-broadened lines in correlation with magnetic-field maps

33 Required SPICE observations: How do solar transients drive heliospheric variability? - Study CME source location, expansion, rotation (helicity), and composition through corona maps (EUI, SPICE,STIX) - Map source regions to in-situ properties and analyse magnetic connectivity, polarity, and helicity (EUI, METIS, SoloHI, SWA, MAG, EPD) - Determine position and speed of coronal shocks (METIS, SoloHI, RPW, EUI) - Provide full-sun and high-resolution coronal and chromospheric images (EUI, STIX, METIS)