FIGURE 4.

Pulsed-field remanence measurements on MMPs. (Top) Remanence magnetization curves of individual organisms resulting from a sequence of remanent moment measurements and pulses applied opposite to a weak alignment field. The remanent magnetic dipole moment is expressed in terms of the escape frequency ω_crit (see Eq. 5). Note that the initial values of ω_crit (MMPs in the natural state) are close to the final values in each curve (after treatment with a pulse of 1000 Oe). The DMO is obtained from the ratio between the initial and the final ω_crit values, as 90%. (Bottom) Distribution of ω_crit from ensemble measurements. The frequency distribution n(ω_crit) in the natural state is centered at and increases only slightly after pulsing (100 mT), with a new mean of (n = 109). The ensemble DMO amounts to 85% (Eq. 6).