A Summary of the Evidence in Favor of the Idea that the Solar Wind is Accelerated by

Waves and/or Turbulence

S. R. Cranmer1 & B. D. G. Chandran2

1 Harvard-Smithsonian CfA,2 University of New Hampshire

• The empirical evidence points to there being strong coronal Alfvénic fluctuations, an active turbulent cascade, and wave damping consistent with measured plasma heating rates.

SHINE session: Pinning Down the Physical Processes that Generate the Solar Wind

Hinode/SOT

G-band bright points

SUMER/SOHO

Helios & Ulysses

UVCS/SOHO

Undamped (WKB) wavesDamped (non-WKB) waves

A Summary of the Evidence in Favor of the Idea that the Solar Wind is Accelerated by Waves and/or Turbulence

Are eclipse/coronagraph images consistent with the presence of Alfvén waves of the magnitude to heat the corona?

Yes. The predicted “wiggles” in the field lines should not be exaggerated enough to see in existing “snapshot” images in the corona.

i.e., it’s not surprising that we see this, not this:

Modeled field-line displacements from

the Cranmer et al. (2007) model:

A Summary of the Evidence in Favor of the Idea that the Solar Wind is Accelerated by Waves and/or Turbulence

Are the measured MHD fluctuations undergoing turbulent cascade & dissipation?

Probably. In situ measurements of the plasma heating rate ≈ statistical estimates of the turbulent dissipation rate. We also have empirical constraints on the plasma heating rate in the corona (from parameter-study models of solar wind acceleration):

We can estimate how much dissipation is consistent with the empirical heating rate. Integrate downward, with and without dissipation. “With” is more consistent with Helios and coronal measurements.

(All data here are for polar

coronal holes & high-latitude wind streams)

FIT to empirical

constraints