NASA’s Parker Solar Probe ‘touches’ the sun for the first time ever

NASA's Parker Solar Probe has successfully flown through the Sun's upper atmosphere, marking a significant milestone. This achievement occurred during the probe's eighth flyby on April 28th. The probe is set to make 21 close approaches over seven years. The Sun lacks a solid crust, but its alpha and critical surface define its atmospheric boundary. Outside this boundary, solar wind particles move faster than magnetic waves, while inside, the opposite occurs. The Parker Probe collected data on zigzag structures in the solar wind, known as switchbacks, which are created by convection cells at the Sun's surface.

What is the significance of the boundary marked by the alpha and critical surface of the Sun's atmosphere?

Describe the relationship between solar wind particles and magnetic waves inside and outside the Sun's atmosphere.