Plasma Turbulence in the Local Bubble

TL;DR

This paper reviews recent observational progress in measuring turbulence within the Local Bubble using radio scintillation of pulsars, highlighting the variability and need for further detailed analysis of interstellar plasma turbulence.

Contribution

It provides an updated overview of pulsar scintillation measurements in the Local Bubble and discusses potential improvements through secondary spectrum analysis.

Findings

Some pulsars show lower turbulence levels than typical.

Measurements suggest magnetic field and density are smaller but not as much as expected.

Further analysis of secondary spectra could clarify turbulence characteristics.

Abstract

Turbulence in the Local Bubble could play an important role in the thermodynamics of the gas that is there. The best astronomical technique for measuring turbulence in astrophysical plasmas is radio scintillation. Measurements of the level of scattering to the nearby pulsar B0950+08 by Philips and Clegg in 1992 showed a markedly lower value for the line-of-sight averaged turbulent intensity parameter $<C_N^2>$ than is observed for other pulsars, consistent with radio wave propagation through a highly rarefied plasma. In this paper, we discuss the observational progress that has been made since that time. At present, there are four pulsars (B0950+08, B1133+16, J0437-4715, and B0809+74) whose lines of sight seem to lie mainly within the local bubble. The mean densities and line of sight components of the interstellar magnetic field along these lines of sight are smaller than nominal values for pulsars, but not by as much expected. Three of the four pulsars also have measurements of interstellar scintillation. The value of the parameter $<C_N^2>$ is smaller than normal for two of them, but is completely nominal for the third. This inconclusive status of affairs could be improved by measurements and analysis of ``arcs'' in ``secondary spectra'' of pulsars.