Researchers analyzed tree rings from six trees in Finland, dating from 1853 to 1871, and found a statistically significant increase in carbon-14 in the polar trees compared with those in mid-latitudes during the year of the Carrington event. This suggests that polar trees are more sensitive to solar storms than their mid-latitude counterparts, possibly due to how solar particles interact with Earth’s magnetic field. Solar flares cause bursts of particles that get deflected toward the poles when they encounter Earth’s magnetic field, producing auroras and potentially disrupting radio signals. As these particles enter the stratosphere, they react with atmospheric molecules to produce carbon-14, which gets absorbed into tree rings.
Miyake Events and Improved Understanding of Solar Activity
Carbon-14 spikes in tree rings, known as Miyake events, have been linked to solar storms. Previously, scientists believed that carbon-14 would mix evenly into the atmosphere, making it difficult to distinguish between latitudes. However, recent studies suggest that there is faster air exchange between the stratosphere and the troposphere in the Arctic, allowing polar trees to receive a slightly bigger infusion of carbon-14 during solar storms. This discovery could help scientists better understand radiocarbon spikes in the tree ring record and improve our understanding of past solar activity.
The discovery of the Carrington event in Finnish tree rings offers valuable insights into the frequency of moderate-sized solar storms and highlights the importance of studying these events to better predict and mitigate their impacts. Historical archives suggest that there were other flares in 1582, 1730, and 1770 that have not yet been detected in mid-latitude tree rings. Uusitalo’s team plans to search for these events closer to the north pole. Additionally, this finding underscores the need to study tree rings that span longer periods to account for the sun’s influence on carbon-14 production in the atmosphere.