Can radiocarbon in tree rings tell us what is happening on the Sun?

We live next to a large star, the Sun, which is not an unchanging source of energy with regular cycles of activity, but which also has occasional bursts of radiation that can arrive at the Earth. Solar flares are intense bursts of radiation from the Sun, where charged particles are ejected and can affect the Earth, and which are particularly common during solar maximum. These flares increase the flux of cosmic rays to the Earth and can cause changes in the ionization of the atmosphere as well as geomagnetic effects.

However, these are small events compared to some very large events recorded by radiocarbon (carbon-14) in tree-ring records. There are historical reports of intense events associated with solar activity; for example, a historical event recorded in 1859 called the “Carrington event” that caused massive disruption to telegraph communications and polar lights to be observed as far south as Cuba and Panama. Large changes in the radiocarbon concentration in tree rings have been linked to solar flare events in the past.

The best documented is the 774-775 AD “Miyake” event, recorded in over 34 different locations around the world, in both the northern and southern hemispheres.

Ancient chronicles from European and Asian civilizations describe strange atmospheric phenomena in the past as well at about this time. In addition to atmospheric and irradiation effects, these “spikes” in the radiocarbon record can also act as precise markers of time that can allow some archaeological questions to be resolved to a precision of about one year, where a tree-ring record in wood covers one of these excursions.