On the Interpretation of Magnetic Helicity Signatures in the Dissipation Range of Solar Wind Turbulence

TL;DR

This paper shows that the observed right-handed magnetic helicity in solar wind turbulence's dissipation range can be explained by kinetic Alfven waves, challenging the idea that ion cyclotron damping is the main cause.

Contribution

It demonstrates that kinetic Alfven waves can produce the observed magnetic helicity signature, questioning previous interpretations linking it to ion cyclotron damping.

Findings

Kinetic Alfven waves produce a right-handed magnetic helicity signature.

The observed helicity does not necessarily indicate ion cyclotron damping.

Energy in solar wind turbulence mainly resides in low frequency anisotropic fluctuations.

Abstract

Measurements of small-scale turbulent fluctuations in the solar wind find a non-zero right-handed magnetic helicity. This has been interpreted as evidence for ion cyclotron damping. However, theoretical and empirical evidence suggests that the majority of the energy in solar wind turbulence resides in low frequency anisotropic kinetic Alfven wave fluctuations that are not subject to ion cyclotron damping. We demonstrate that a dissipation range comprised of kinetic Alfven waves also produces a net right-handed fluctuating magnetic helicity signature consistent with observations. Thus, the observed magnetic helicity signature does not necessarily imply that ion cyclotron damping is energetically important in the solar wind.