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SUMMARY:Theory Keynote 1: Interpreting the Palaeomagnetic Field - Bruce Bu
 ffett (University of California\, Berkeley)
DTSTART:20221128T113000Z
DTEND:20221128T123000Z
UID:TALK192065@talks.cam.ac.uk
DESCRIPTION:Modern observations of the geomagnetic field allow us to peer 
 into the Earth&rsquo\;s interior and recover estimates of fluid motion at 
 the top of the core. Properties of the resulting flow guide our understand
 ing of the underlying dynamics. However\, duration of the modern record is
  relatively short.&nbsp\; The challenge is illustrated by a loose analogy 
 with the dynamics of the atmosphere. Four hundred years of historical magn
 etic observations is roughly equivalent to four days of sparse meteorologi
 cal observations. The daunting task of understanding the climate system wi
 th such a short atmospheric record is ample motivation for seeking longer 
 records. Unfortunately\, a longer record from geological observations come
 s with fewer spatial details. Our theoretical approach should be adapted t
 o exploit the available information.\nStochastic models are well suited to
  the study of the palaeomagnetic field because we can focus on the observa
 ble part of the field (i.e. the axial dipole) and represent the turbulent 
 generation process using a suitable statistical description. One illustrat
 ive example is motivated by the work of Eugene Parker. We let the turbulen
 t generation process be represented by a series of short-period convective
  events. The timing of these events follows a Poisson process and the ampl
 itude of the convective event is a random variable. Sufficient constraints
  to specify the model come from the mean and variance of the dipole moment
 \, as well as the time required for the dipole to reach the time-averaged 
 amplitude after a reversal. The resulting model is able to reproduce the o
 bserved reversal rate and offers useful predictions for other properties o
 f the paleomagnetic field.&nbsp\; Physical insights into the generation pr
 ocess can be drawn from the amplitude and average recurrence time of the c
 onvective events.
LOCATION:Seminar Room 1\, Newton Institute
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