Parker Spiral in 3D
Field lines from solar wind leaving at latitude +λ (north) and −λ (south) at the same time, drawn in three dimensions. Every setting of λ plots both hemispheres. Drag to turn the scene. The two grey walls show the shadows of the field lines on the x-y and x-z planes. These are the same two views as the flat panels in UCLA's Parker Spiral Model module, so you can match the 3D shape to each flat view.
Things to try
- Set λ to 0 and click Side (x-z). Why does the spiral turn into a straight line? Then click Top (x-y).
- Keep the cone surface on and sweep λ from 0 to 90. What does the cone turn into at each end? What do those two shapes look like from the side?
- Set λ to 80 and r to 1. Read the distance to the axis and the height. Which trig function of λ gives each one? Which wall shows which?
- Fix V and note ψ at λ = 0, 45 and 80. Divide each tan ψ by the value at λ = 0. What do you get?
- Press Play rotation. Each parcel moves straight outward and never changes longitude. Why do the parcels still end up lying along a spiral? Why is that spiral looser at high latitude? (Think about how fast the footpoint moves.)
Terms
- Latitude λ: angle measured up from the Sun's equator. 0° is the equator, 90° is the pole.
- Rotation axis: the z-axis here. The Sun spins about it once every 25.4 days (sidereal).
- Footpoint: where a field line is anchored on the Sun. It turns with the Sun.
- Garden-hose angle ψ: the angle between the field line and the straight-out (radial) direction at a given point.