Energy transfer, discontinuities and heating in the inner solar wind measured with a weak and local formulation of the Politano-Pouquet law

The solar wind is a highly turbulent plasma for which the mean rate of energy transfer ε has been measured for a long time using the Politano-Pouquet (PP98) exact law. However, this law assumes statistical homogeneity that can be violated by the presence of discontinuities. Here, we introduce a new method based on the inertial dissipation D_I whose analytical form is derived from incompressible magnetohydrodynamics (MHD); it can be considered as a weak and local (in space) formulation of the PP98 law whose expression is recovered after integration is space. We used D_I to estimate the local energy transfer rate from the THEMIS-B and Parker Solar Probe (PSP) data taken in the solar wind at different heliospheric distances. Our study reveals that discontinuities near the Sun lead to a strong energy transfer that affects a wide range of scales σ. We also observe that switchbacks seem to be characterized by a singular behavior with an energy transfer varying as σ^−3/4, which slightly differs from classical discontinuities characterized by a σ⁻¹ scaling. A comparison between the measurements of ε and D_I shows that in general the latter is significantly larger than the former.

https://arxiv.org/pdf/2201.02377.pdf