The Solar Wind Energy Flux

TL;DR

This study demonstrates that the solar wind energy flux remains nearly constant across different speeds, latitudes, and solar cycle phases, acting as a global solar constant, with implications for understanding solar wind properties.

Contribution

It provides the first comprehensive analysis showing the invariance of solar wind energy flux across various conditions using multi-spacecraft data.

Findings

Energy flux is independent of solar wind speed and latitude within 10%.

High-speed solar wind has the same mean energy flux as slower wind.

A relation between solar-wind speed and density is derived.

Abstract

The solar-wind energy flux measured near the ecliptic is known to be independent of the solar-wind speed. Using plasma data from Helios, Ulysses, and Wind covering a large range of latitudes and time, we show that the solar-wind energy flux is independent of the solar-wind speed and latitude within 10%, and that this quantity varies weakly over the solar cycle. In other words the energy flux appears as a global solar constant. We also show that the very high speed solar-wind (VSW > 700 km/s) has the same mean energy flux as the slower wind (VSW < 700 km/s), but with a different histogram. We use this result to deduce a relation between the solar-wind speed and density, which formalizes the anti-correlation between these quantities.