Simple stochastic model for geomagnetic excursions and reversals reproduces the temporal asymmetry of the axial dipole moment.

We present a simple model for the axial dipole moment (ADM) of the geomagnetic field based on a stochastic differential equation for two coupled particles in a biquadratic potential, subjected to Gaussian random perturbations. This model generates aperiodic reversals and excursions separated by stable polarity periods. The model reproduces the temporal asymmetry of geomagnetic reversals, with slower decaying rates before the reversal and faster growing rates after it.

The magnetic properties of particles deposited on Platanus x hispanica leaves in Madrid, Spain, and their temporal and spatial variations.

Magnetic phases are a common component of atmospheric particles and as such are being increasingly exploited in air quality studies. In this context the magnetic properties of Platanus x hispanica leaves were determined during the spring and summer months of 2001 and 2004 in Madrid, Spain. The leaves exhibited a stable magnetic signal carried by partially oxidized magnetite grains.