Telescoping in on the Microscopic Origins of the Fast Solar Wind Steven R. Cranmer & Adriaan van Ballegooijen Harvard-Smithsonian Center for Astrophysics

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Magnetic connectivity of the open field Cranmer & van Ballegooijen (2005) Tu et al. (2005) Fisk (2005)

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Is a time-steady approach doomed? Open-field regions show frequent jet-like events. Evidence of magnetic reconnection between open and closed fields? How much of the solar wind is ejected like this? Hinode/SOT: Nishizuka et al. (2008) Is there enough mass & energy released to heat/accelerate the entire solar wind? Antiochos et al. (2011)

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 What processes drive solar wind acceleration? No matter the relative importance of reconnection events, we do know that waves and turbulent motions are present everywhere... from photosphere to heliosphere. How much can be accomplished by only these processes? (Occam’s razor?) Hinode/SOT G-band bright points SUMER/SOHO Helios & Ulysses UVCS/SOHO Undamped (WKB) waves Damped (non-WKB) waves

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Turbulence-driven solar wind models A likely scenario is that the Sun produces MHD waves that propagate up open flux tubes, partially reflect back down, and undergo a turbulent cascade until they are damped at small scales, causing heating. Cranmer et al. (2007) explored the wave/turbulence paradigm with self-consistent 1D models, and found a wide range of agreement with observations (including composition!) Z+Z+ Z–Z– Z–Z– (e.g., Matthaeus et al. 1999) Ulysses (see also, e.g., Suzuki & Inutsuka 2006; Verdini et al. 2010; Usmanov et al. 2011; Matsumoto & Suzuki 2011; Chandran et al. 2012)

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Turbulent heating scales with field strength Mean field strength in low corona: If the regions below the merging height can be treated with approximations from “thin flux tube theory,” then:... and the turbulent heating in the low corona scales directly with the mean magnetic flux density there (e.g., Pevtsov et al. 2003; Schwadron et al. 2006; Kojima et al. 2007; Schwadron & McComas 2008). Thus,

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Increase the complexity of the field... Existing models used low-resolution magnetic fields. What will happen when we solve for the time-steady plasma conditions along higher-resolution field structures (with higher rates of shear, more QSLs, etc.)? SOLIS Vector SpectroMagnetograph on Kitt Peak + PFSS 8727 field lines: Δt = 1 min. Δφ = 0.01 o Δx on surface = 100 km 1 SOLIS pixel ≈ 800 km Overkill? \ Maybe not... (Borovsky 2008)

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Expectations from flux-tube expansion Wang & Sheeley (1990) found an anticorrelation between flux tube expansion and wind speed at 1 AU... low f FAST high f SLOW

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Adjusting the field strength Unmodified SOLIS potential fields :Add photospheric component... is it enough? Black curves: Cranmer et al. (2007)

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Extremely preliminary results Cranmer et al. (2007) ZEPHYR output ~WS90 scaling SOLIS B-field insufficient coronal heating!? ACE

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Do the “flux tubes” survive to 1 AU? Fast/slow wind stream structure leads to corotating interaction regions (CIRs) and shocks in the heliosphere. We applied the upwind differencing method of Riley & Lionello (2011) to the empirical u–f relationship. The finest-scale flux tube variations may be swept away at 1 AU, but SPP & Orbiter may see much higher variances in plasma parameters in the inner heliosphere! r = 20 R s r = 40 R s r = 1 AU

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Conclusions There is still a lot that can be done with “time-steady” wave/turbulence models. Some “spaghetti-like” time variability may be generated from high-resolution lower boundary structure in the magnetic field. (more expected closer to Sun) AIA/SDO Magnetically complex regions may generate more waves. (ZEPHYR models used identical wave boundary conditions.) Take into account how turbulence “shreds” flux tubes. Collisionless kinetic physics (T p ≠ T e ≠ T ion ) Confront models with actual data! (present & future) Next steps...

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 extra slides...

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Cranmer et al. (2007): other results Ulysses SWICS Helios ( AU) Ulysses SWICS ACE/SWEPAM Wang & Sheeley (1990)

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 What is the source of solar wind mass? Until relatively recently, the dominant idea was that a steady rate of “evaporation” is set by a balance between downward conduction, upward enthalpy flux, and local radiative cooling (Hammer 1982; Withbroe 1988). On the other hand, new observations of spicules and jets (e.g., Aschwanden et al. 2007; De Pontieu et al. 2011; McIntosh et al. 2011) fuel the idea that a lot of the corona’s mass is injected impulsively from below. heat conduction radiation losses — ρvkT 5252 Schrijver (2001)

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Controversies about waves & turbulence Where does the turbulent cascade begin? Chromosphere? Low corona? Some say it doesn’t become “fully developed” turbulence until < 1 AU. (van Ballegooijen et al. 2011) Simple motions input at photospheric lower boundary. In simulations that include flux-tube expansion, complex turbulent motions are induced, even down in the middle chromosphere! ~

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 Other questions to address Origin of lowest-frequency (1/f) waves seen at 1 AU:  The self-consistent product of a turbulent cascade?  Spacecraft passage through “spaghetti-like” flux tubes rooted on the solar surface? (Borovsky 2008) Coronal heating from MHD turbulence:  Does damping of turbulence produce the right mixture of collisionless kinetic effects?  How can we better constrain the frequency spectrum of waves/turbulence in the corona? (crucial for non-WKB reflection) Do reconnection/loop-opening events generate enough mass, momentum, & energy to power the solar wind?

SH43F-01: Telescoping in on the Microscopic Origins of the Solar WindS. R. Crarnmer, Dec. 8, 2011 How are ions preferentially heated? MHD turbulence may have some kind of “parallel cascade” that gradually produces ion cyclotron waves in the corona and solar wind. When MHD turbulence cascades to small perpendicular scales, the small-scale shearing motions may be unstable to generation of cyclotron waves (Markovskii et al. 2006). Dissipation-scale current sheets may preferentially spin up ions (Dmitruk et al. 2004). If MHD turbulence exists for both Alfvén and fast-mode waves, the two types of waves can nonlinearly couple with one another to produce high-frequency ion cyclotron waves (Chandran 2005). If nanoflare-like reconnection events in the low corona are frequent enough, they may fill the extended corona with electron beams that would become unstable and produce ion cyclotron waves (Markovskii 2007). If kinetic Alfvén waves reach large enough amplitudes, they can damp via wave-particle interactions and heat ions (Voitenko & Goossens 2006; Wu & Yang 2007). Kinetic Alfvén wave damping in the extended corona could lead to electron beams, Langmuir turbulence, and Debye-scale electron phase space holes which could heat ions perpendicularly (Matthaeus et al. 2003; Cranmer & van Ballegooijen 2003). UVCS results (mainly in coronal holes) have spurred a lot of theoretical work... but observations still haven’t allowed the exact mechanisms to be pinned down!

CPI is a large-aperture ultraviolet coronagraph spectrometer that has been proposed to be deployed on the International Space Station (ISS). The primary goal of CPI is to identify and characterize the physical processes that heat and accelerate the plasma in the fast and slow solar wind. CPI follows on from the discoveries of UVCS/SOHO, and has unprecedented sensitivity, a wavelength range extending from 25.7 to 126 nm, higher temporal resolution, and the capability to measure line profiles of He II, N V, Ne VII, Ne VIII, Si VIII, S IX, Ar VIII, Ca IX, and Fe X, never before seen in coronal holes above 1.3 solar radii September 29: NASA selected CPI as an Explorer Mission of Opportunity project to undergo an 11-month Phase A concept study.