Properties of Turbulence in the Very Local Interstellar Clouds

Abstract

We have investigated the degree to which turbulence in the Very Local Interstellar Clouds resembles the highly-studied turbulence in the solar corona and the solar wind. The turbulence diagnostics for the Local Clouds are the absorption line widths measured along 32 lines of sight to nearby stars, yielding measurements for 53 absorption components (Redfield and Linsky 2004). We have tested whether the Local Cloud turbulence has the following properties of turbulence in the solar corona or the solar wind: (a) velocity fluctuations mainly perpendicular to the average magnetic field, (b) a temperature anisotropy in the sense that the perpendicular temperature is larger than the parallel temperature (or at least enhanced relative to expectation), and (c) an ion temperature which is dependent on the ion Larmor radius, in the sense that more massive ions have higher temperatures. Our analysis of the data does not show compelling evidence for any of these properties in Local Cloud turbulence, indicating possible differences with heliospheric plasmas. In the case of anisotropy of velocity fluctuations, although the expected observational signature is not seen, we cannot exclude the possibility of relatively high degrees of anisotropy (anisotropy parameter $\epsilon \sim 0.50-0.70$), if some other process in the the Local Clouds is causing variations in the turbulent line width from one line of sight to another. We briefly consider possible reasons for differences between coronal and solar wind turbulence and that in the Local Clouds.

Submitted to the Astrophysical Journal

References in corpus (8)

• The Structure of the Local Interstellar Medium V: Electron Densities
• A Model for the Sources of the Slow Solar Wind
• Modeling the Magnetic Field in the Galactic Disk using New Rotation Measure Observations from the Very Large Array
• Alfven Wave Turbulence and Perpendicular Ion Temperatures in Coronal Holes
• The Origin of Radio Scintillation In the Local Interstellar Medium
• Comparisons of the Interstellar Magnetic Field Directions obtained from the IBEX Ribbon and Interstellar Polarizations
• Ion-Neutral Collisions in the Interstellar Medium: Wave Damping and Elimination of Collisionless Processes
• Observational Tests of the Properties of Turbulence in the Very Local Interstellar Medium

Cited by in corpus (7)

• Gamma-ray Astrophysics in the MeV Range: the ASTROGAM Concept and Beyond
• Plasma Diagnostics of the Interstellar Medium with Radio Astronomy
• Alfven Wave Collisions, The Fundamental Building Block of Plasma Turbulence IV: Laboratory Experiment
• Inhomogeneity within Local Interstellar Clouds
• Evidence for Asymmetry in the Velocity Distribution of the Interstellar Neutral Helium Flow Observed by IBEX and Ulysses
• On the injection scale of the turbulence in the partially ionized very local interstellar medium
• The origin of Cosmic-Rays from SNRs: confirmations and challenges after the first direct proof