Flux conservation, radial scalings, Mach numbers, and critical distances in the solar wind: magnetohydrodynamics and Ulysses observations

Abstract

One of the key challenges in solar and heliospheric physics is to understand the acceleration of the solar wind. As a super-sonic, super-Alfvénic plasma flow, the solar wind carries mass, momentum, energy, and angular momentum from the Sun into interplanetary space. We present a framework based on two-fluid magnetohydrodynamics to estimate the flux of these quantities based on spacecraft data independent of the heliocentric distance of the location of measurement. Applying this method to the Ulysses dataset allows us to study the dependence of these fluxes on heliolatitude and solar cycle. The use of scaling laws provides us with the heliolatitudinal dependence and the solar-cycle dependence of the scaled Alfvénic and sonic Mach numbers as well as the Alfvén and sonic critical radii. Moreover, we estimate the distance at which the local thermal pressure and the local energy density in the magnetic field balance. These results serve as predictions for observations with Parker Solar Probe, which currently explores the very inner heliosphere, and Solar Orbiter, which will measure the solar wind outside the plane of the ecliptic in the inner heliosphere during the course of the mission.

13 pages, 9 figures

References in corpus (9)

• The Solar Orbiter mission -- Science overview
• Origins of the Ambient Solar Wind: Implications for Space Weather
• The Effect of Combined Magnetic Geometries on Thermally Driven Winds I: Interaction of Dipolar and Quadrupolar Fields
• Strong Preferential Ion Heating is Limited to within the Solar Alfven Surface
• Global solar magnetic field organization in the outer corona: influence on the solar wind speed and mass flux over the cycle
• Deceleration of Alpha Particles in the Solar Wind by Instabilities and the Rotational Force: Implications for Heating, Azimuthal Flow, and the Parker Spiral Magnetic Field
• Direct Detection of Solar Angular Momentum Loss with the Wind Spacecraft
• The Solar Wind Angular Momentum Flux as Observed by Parker Solar Probe
• Application of a MHD hybrid solar wind model with latitudinal dependences to Ulysses data at minimum

Cited by in corpus (7)

• Prediction and Verification of Parker Solar Probe Solar Wind Sources at 13.3 R${}_{\odot }$
• Exploring the Solar Wind from its Source on the Corona into the Inner Heliosphere during the First Solar Orbiter - Parker Solar Probe Quadrature
• A hydrodynamic study of the escape of metal species and excited hydrogen from the atmosphere of the hot Jupiter WASP-121b
• An Extended and Fragmented Alfvén Zone in the Young Solar Wind
• On the Generation and Evolution of Switchbacks and the Morphology of Alfvénic Transition: Low Mach-number Boundary Layers
• The solar-wind angular-momentum flux observed during Solar Orbiter's first orbit
• Reconstructing the Sun's Alfvén surface and wind braking torque with Parker Solar Probe