Inner Structure of CME Shock Fronts Revealed by the Electromotive Force and Turbulent Transport Coefficients in Helios-2 Observations

Abstract

Electromotive force is an essential quantity in dynamo theory. During a coronal mass ejection (CME), magnetic helicity gets decoupled from the Sun and advected into the heliosphere with the solar wind. Eventually, a heliospheric magnetic transient event might pass by a spacecraft, such as the Helios space observatories. Our aim is to investigate the electromotive force, the kinetic helicity effect ($\alpha$ term), the turbulent diffusion ($\beta$ term) and the cross-helicity effect ($\gamma$ term) in the inner heliosphere below 1 au. We set up a one-dimensional model of the solar wind velocity and magnetic field for a hypothetic interplanetary CME. Because turbulent structures within the solar wind evolve much slower than this structure needs to pass by the spacecraft, we use a reduced curl operator to compute the current density and vorticity. We test our CME shock-front model against an observed magnetic transient that passes by the Helios-2 spacecraft. At the peak of the fluctuations in this event we find strongly enhanced $\alpha$, $\beta$ and $\gamma$ terms, as well as a strong peak in the total electromotive force. Our method allows us to automatically identify magnetic transient events from any in-situ spacecraft observations that contain magnetic field and plasma velocity data of the solar wind.

10 pages, 14 figures, published

References in corpus (1)

• The role of the Yoshizawa effect in the Archontis dynamo

Cited by in corpus (5)

• Investigating Mercury's Environment with the Two-Spacecraft BepiColombo Mission
• Application of the electromotive force as a shock front indicator in the inner heliosphere
• Electromotive field in space and astrophysical plasmas
• Turbulent dynamo in the terrestrial magnetosheath
• Ill-posedness of the mean-field dynamo equations with a linear electromotive force