One of the many threats facing space travellers and indeed our own planet is that of Solar Storms. At their most minor they can grant polar latitudes with a gentle auroral display but at their most extreme they can pose a threat to technology in space, communications and even our atmosphere. Now a team of researchers have found that extreme space weather can leave its mark in tree rings, leaving evidence that can help guard against future severe events.
The term space weather is typically used to refer to the changing conditions and events occurring on the Sun that can effect the space surrounding Earth and the other planets. The events are driven by the Sun’s magnetic field and can include flares, coronal mass ejections, and the solar wind. When the events interact with our own magnetic field they can cause problems for satellite communication, GPS systems and power grids. They can also produce the somewhat enigmatic auroral displays that gently dance across the skies.
Space Weather often creates energetic particles that, through the interactions of gas in the atmosphere, can produce radiocarbon (an isotope of carbon that is unstable and radioactive.) The process of growth in trees uses carbon from the air to create more wood. This is the process that leads to the creation of rings in their trunks. The team of researchers led by Amy Hessl from the Eberly College of Arts and Sciences has been exploring correlations between the annual tree rings and solar activity.
Tree ring records date back hundreds of years and have revealed evidence of severe solar storms known as Miyake events. The events bring with them an increase in the amount of radiocarbon in the atmosphere and it is this that can be traced in trees. The first event occurred in 774AD and another in 993AD and evidence in tree rings occurred 12 years ago. To date, 7 more events have been found dating back over the last 14,000 years.
The space weather events are not just an inconvenience though. Humans should only receive a certain dose of radiation in their lifetime. If you’re unlucky enough to be on a high altitude aircraft flight at the time of a severe solar storm it could give you a lifetime dose of radiation in one hit. If you were in space, it would more than likely kill you!
Theories of tree growth have assumed that trees absorb radiocarbon at an even rate. The team believes that trees take up radiocarbon in a different way, in a more biased way. They even found that different trees absorb the carbon isotope differently and the same trees at different locations were also found to be absorbing differently.
They studied different species; the evergreen conifer from Utah, bristlecone pines also from Utah, the bald cypress from Northern Carolina and oak trees preserved in a riverbed in Missouri. Core samples were taken from the cross section of trees to enable the rings to be analysed and data. Trees that were alive during one of the Miyake events would have recorded the event in the chemistry of the rings but possibly differently for different trees.
Studying the tree rings may give us a better understanding of how trees interact with atmospheric carbon and help us to better understand how to prepare for future extreme events. Surviving such events can only be possible through advanced preparation and it is hoped the study will lay a solid foundation.
Source : WVU researcher says ancient tree rings may help Earth prepare for dangerous space weather