Solar corona heating and solar wind

5 problems

• What heats the solar corona above $10^{6}\ \mathrm{K}$?

  Open

  Energy from churning gas below the surface must be carried up by magnetic fields and released in the corona; how it is released is unknown.

• What supplies the energy and momentum of the fast solar wind?

  Open

  The fast solar wind leaves the Sun at about $7.5 \times 10^{7}\,\mathrm{cm/s}$, and it is not settled whether waves in the magnetic field or bursts of magnetic reconnection push it to that speed.

• Wave versus nanoflare heating fraction in active-region coronal loops

  Open

  Heating could come as countless tiny explosions (nanoflares) or as a steady trickle from waves; each leaves a different temperature fingerprint.

• Where on the Sun does the slow solar wind originate?

  Open

  The slow solar wind could leak from the edges of coronal holes (dark regions of open magnetic field) or be released from closed magnetic loops when they reconnect with open field.

• Do magnetic switchbacks form at the Sun or in the wind?

  Contested

  Parker Solar Probe found that the Sun's magnetic field in the wind often flips back on itself for seconds to hours; these switchbacks may be launched from the solar surface or grow out of waves as the wind expands.