Every year, the UK magnetism community gets together at a conference to showcase the most recent advances in the field, establish collaborations and discuss (sometimes heatedly) new projects and findings.
This year, Magnetic Interactions, was hosted by the Lancaster Environment Center. They certainly did a great job! An interesting program of talks was put together, alongside a good poster session and an excellent curry for dinner!
All of us at Liverpool Geomagnetism attended the conference, with much of our recent work on display (more on that later). Labs from other Universities were represented too, including Oxford, Imperial, Plymouth, Leeds and Cambridge. Talk and poster topics ranged from discussion on geomagnetic excursions and jerks, through nanopalaeomagnetism and magnetic tracing of particulate pollutants.
Work from other labs
For the most part, the attendees are based at UK Labs, but this year, the invited speaker was none other than Ted Evans (University of Alberta, Canada) who gave a very interesting talk on what he has called the cryptonchron enigma. So what is a cryptonchron? It is described as a tiny wiggle seen in the Geomagnetic Polarity Time Scale (GPTM) which is smaller than the major chrons, a small feature of dimensions on the scale of:40-80nT, 10-20Km. Their underlying cause is currently unexplained, although recent studies suggest they might be attributed to short reversal periods or intensity fluctuations of the geomagnetic field (Boulingand et al. 2006). But the enigma remains: what are cryptochrons? With his collaborator G.Hoye, Ted has developed a computer model which calculates the magnetic anomaly over a section of oceanic crust. The output of this model suggests that cyptochrons could be considered subchrons which could indicate that the field might be reversing more regularly than was previously thought.
A pick of other interesting talks and posters included: Sarah Dodd (Imperial) & Conall Mac Niocaill, (Oxford), who propose that magentostratigraphic data can help in understanding the eruption rate and exact chronology of Large Igneous Provinces (LIPs), which a particular focus on the Etendeka Flood Basalts of Namibia. Richard Harrison, from Cambridge, presented his new approach to palaeomagnetic measurements, where the source of uncertainty introduced during bulk rock measurements, is removed by performing paleomagnetic measurements at sub micron length scales, in what is being called: nanopalaeomagnetism. One of the hosts, Barbara Maher talked about how magnetic particles found in particulate pollutants which accumulate on tree leaves allows monitoring of pollution in urban areas.
What the Geomag Lab has been up to
As I mentioned earlier, the Liverpool Geomagnetism Lab had a strong presence at the conference:
• Andy gave a talk in which he discussed the findings of his recently published article in Nature Geoscience were he and his collaborators link long term variations of the geomagnetic field to whole-mantle convection processes.
• I also presented the latest findings of my research on Archean age rocks of the Barberton Greenstone Belt. Combined with data previously published by Andy (Biggin et al. 2011), I’ve been able to constrain the age of the magnetic signal recorded in the rocks of the Hooggenoeg Formation, to 3.2Gyr.
• Emma Hodgson has been researching non-ideal behaviour in interacting single and multi-domain grains, using synthetic magnetic samples. She presented a poster with experimental results from her recent work which indicates that there is violation of Néel’s Laws of thermoremanent behaviour in interacting single domain samples.
• Wilbor Poletti (a visiting student from the University of Sao Paulo, Brazil) has compared classical Thellier-Thellier(TT), Triaxe (TR) and Microwave (MW) methods for determining palaeointensities using Brazilian baked clays. In his work, he has improved the experimental protocol for the MW method. He also shows that the MW method is significantly affected by the “cooling-rate effect” and a pseudo-single domain bias, but these are easily accounted for, performing an experimental correction, which means all three methods for determining palaeointensities are now comparable.
• Keeping with the paleointensity theme; Megan (who also contributes to the blog) has been working on determining the past geomagnetic field intensity using Turkish pottery fragments has found that, as is well known, experiment success rate is very variable. Putting aside methodology issues, she discussed other potential issues e.g. dating uncertainty, pottery compositional variability and kiln design.
• Andy also presented the PINT database (which has been recently updated with 227 new records taken from 14 references) with the aim to reach a consensus on what the properties of the most reliable paleointensity measurements are.
• In his work, Andreas Nilsson, has used data from the Pint database, using archaeological artefacts/lavas and lake/marine sediments, has constructed a new continuous spherical harmonic model for the geomagnetic filed over the past 9000 years.
• Finally, Neil has been questioning if how we calculate pole positions (from Fisher distribution statistics) is actually the best way to go about things? He proposes a new method which defines the virtual geomagnetic pole (VGP) from the expectation of angle between VGP and spin-axis of the Earth, adopting a spherical exponential distribution. This method consistently gives confidence limits that are smaller than those derived from Fisher, yet more likely to contain the true pole position.
The conference was a huge success. The conference organisers did a brilliant job, and it provides a great platform for us all to showcase the best of our work. Already looking forward to the next one – Cambridge here we come!