The Galactic cosmic-ray Sun shadow observed by HAWC

Understand

The magnetic field of the Solar corona is difficult to measure directly.

• However, indirect observations of the solar corona are possible using the deficit in flux of cosmic rays coming from the direction of the Sun.
• Low-energy cosmic rays (~GeV) are deflected by the inner magnetic field of the Sun and the interplanetary magnetic field frozen into the solar wind.
• In contrast, high-energy cosmic rays (~TeV and above) are absorbed in the Sun's photosphere producing a shadow in the Sun's nominal position viewed from Earth.