I am a PhD student at the University of Liverpool Geomagnetism Laboratory. My current research project is the palaeomagentic study of 3.5-3.2 billion year old rocks from South Africa. The aim of my research is to improve our understanding of the long term evolution of the Earth and the surface conditions under which the first forms of life originated through using palaeomagnetic records. The rocks of the Barberton Greenstone Belt are excellently preserved and have only been subjected to low grade metamorphism (greenschist facies), making them good candidates for paleomagnetic studies. I also undertook my undergraduate studies at Liverpool University, where I studied monogenetic volcanism on Tenerife. Between my undergraduate and PhD I had a brief stint in the world of industry as an environmental consultant. I’m a keen science communicator and am involved in a number of outreach projects.
An article last month in the U.K’s Guardian Newspaper reported on the findings of the Royal Academy of Engineers who warned the U.K government of the need to set up an expert panel which could generate plans on how the country should prepare and cope in the event of a large solar storm or corona mass ejection (CME). What was not reported in the article and is often unknown, is that we already have a shield that goes some way to protect us from the harmful effects of out giant neighbour; but I’m getting ahead of myself. Let start with a few basics.
In essence, a solar flare is a large release of energy at the Sun’s surface, which can be followed by a CME. Solar flares tend to be short lived events and eject a cloud of charged particles, including protons, electrons and atoms. CMEs often follow flares and tend to emit considerable gusts of solar wind and magnetic fields. When the winds and charged particles reach the proximity of planet Earth, they interact with the Earth’s magnetic field causing a magnetic storm with the charged particles being preferentially deflected towards the Earth’s magnetic poles. Magnetic storms can cause disruption to electronic grids and communication systems, including satellites, aircraft, GPS navigation systems and mobile phone networks, amongst others. The Royal Academy of Engineer’s report was making reference to these potential harmful effects and arguing that the U.K. should prepare itself against them. In truth, they don’t exaggerate, the damage that solar flares can cause is not negligible: In September 1859, a large solar flare caused telegraph wires in both the United States and Europe to spontaneously short circuit, causing numerous fires; Northern Lights were seen as far south as Rome, Havana and Hawaii, with similar effects at the South Pole. More recently, in March 1989, a large solar flare caused a blackout in the whole of the Quebec province of Canada, whilst the Canadian television network and newspapers were disrupted by damage caused by a solar flare to communication satellites orbiting the Earth in 1994. I won’t go into the details of how and what we ought to be doing to protect ourselves against these (this is not my field!). Instead, I’ll tell you about the Earth’s Magnetic field and its role in protecting us against the harmful storm winds and particulate clouds.
My research focuses on some of the oldest rocks in the world. I study the Barberton Greenstone Belt (BGB), which is located in North Eastern South Africa and is one of a few Archean aged terrains located across the globe.
The BGB is characterised by volcanic sequences which are interspersed with layers of sediments. It has been subjected to a number of tectonic events which have led to folding and low-grade metamorphism in the area. The world famous type-section of Komatiite lavas, as discovered by the Viljoen brothers in 1969, is exposed in the BGB. My research is concentrated on three Complexes of the Onvenwacht Suite, with rocks showing ages between 3.5 and 3.2 billion years (geological map modified from de Wit et al. 2011). But, how can these rocks tell us anything about solar storms, CMEs and the Earth’s magnetic field?
We now that the Earth’s magnetic field acts a shield against the harmful particles ejected by solar flares, deflecting them pole wards. In addition, it protects us against atmospheric erosion and water loss caused by solar wind. The lack of a magnetic field on Mars (generate by a geodynamo in the core), leaves the planet barren with no atmosphere or water. The early Earth was able to retain its atmosphere and water and so became habitable (with early forms of life being reported in the BGB). However, we know little about the Earth’s magnetic field during this time. Studying the paleomagnetic signature of the rocks of the BGB might enlighten us about the processes that were taking place in the core, mantle and crust during the Archean. My research focuses on the directions of the magnetic field recorded in the BGB during its formation. Recent studies (Tarduno et al, 2010) have attempted to understand the strength of the field during the Archean and what bearing that might have on the ability of the planet to protect itself against solar winds. In their study, Tarduno and collegues, report paleointensities (obtained from single silicate crystal bearing magnetic inclusions) that are ~50-70% lower than the intensity of the present day field. How much then, could the Earth’s magnetic field reasonably be expected to shield the planet from the Sun? Tarduno et al. argue that solar particles would have greater access to the Earth’s atmosphere during this period, due to an increased polar cap area. During the Archean, the stand-off distance between the Sun and the Earth could also be estimated to be smaller. These two facts combined would promote loss of volatiles and water, suggesting that the early Earth had a larger water inventory than presently. Overall, the young Earth was able to produce a magnetic field strong enough to protect the planet from large scale atmospheric erosion and water loss, it is likely that there were important changes to these in the first billion years of the Earth’s history.
I find it reassuring that there is this invisible shield that is protecting us humans, (perhaps not our technology), and has been doing for most of the Earth’s history. The Magnetic field has contributed to the conditions being right for evolution to happen. I think we should give it a lot more credit!
Please see below for a selection of links that might be of interest for those who might want a bit more reading on the subject!
http://www.geomagnetism.org/
http://www.peeringintobarberton.com/project.html
http://news.bbc.co.uk/1/hi/sci/tech/8659019.stm
http://www.nasa.gov/topics/earth/features/sun_darkness.html
http://science.nasa.gov/science-news/science-at-nasa/2003/23oct_superstorm/
Laura Roberts Artal
