Extended Data Fig. 2: Schematic of an S-shaped magnetic structure creating a field reversal, heat-flux reversal and a spike in velocity.
From: Alfvénic velocity spikes and rotational flows in the near-Sun solar wind
This figure illustrates the possible geometry of an S-shaped propagating Alfvénic disturbance (grey box) and how it would appear to the spacecraft (black square) as it flew through the spike on the green trajectory. The pink lines with arrows indicate the configuration of the magnetic field, with all field lines ultimately pointing back to the Sun. Arrows at each black square indicate the vector velocity (blue), electron strahl (orange) and magnetic field (red) seen by the spacecraft. If this was a purely Alfvénic structure, then the spike would move away from the Sun in an antiparallel direction to B at the local Alfvén speed, CA. In the frame of the spike, the shape of the structure would be static, with plasma flowing in along field lines on the upper left and through the spike and emerging at the lower right, always flowing at CA. In the frame of the spacecraft, the constant flow along field lines in the propagating spike frame would translate into a radial increase of V by CA when B is perpendicular to the R direction, and a maximum jump of 2CA when B is completely inverted. Because the heat flux flows away from the Sun along magnetic field lines, it would rotate so as to always be antiparallel to B and appear locally to be flowing back to the Sun at the centre of this disturbance.
