Feed aggregator

First principles understanding of single domain magnetizations - Part II: Non-ideal magnetic behavior in ideal single domain titanomagnetite

Geophysical Journal International - Thu, 03/05/2026 - 00:00

SummaryLouis Néel’s theory of magnetism, which describes a rock’s magnetization as being carried by “ideal” uniformly magnetized or single domain (SD) particles, has been a cornerstone of paleomagnetic studies for over seven decades and has enabled paleomagnetists to make plate tectonic reconstructions, date geological and archaeological materials, and recover the history of Earth’s magnetic field. Unfortunately, many geological samples produce experimental results that disagree with the predictions made by Néel theory. This “non-ideal” behavior is often associated with larger particles that are non-uniformly magnetized. In this paper, we use simulations based on Néel theory to demonstrate that non-ideal behavior is also expected in assemblages of SD particles with a range of sizes and shapes previously assumed to be ideal. This effect occurs over a relatively small range of shapes and sizes for magnetite, but a much wider range for titanomagnetites. Our results call into question the typical interpretation of SD particles as ideal magnetic carriers. Instead, we suggest that the geological stability of a rock’s magnetization is influenced not only by the domain state of the magnetic carriers, but also by their shape and composition. This has important implications for paleointensities (and cooling rate corrections thereof), paleodirections, and the dating of viscous magnetizations.

A wide-range thermodynamically consistent constitutive model for dynamic loading of partially saturated porous media

Geophysical Journal International - Thu, 03/05/2026 - 00:00

SummaryThis paper presents a novel thermodynamically consistent constitutive model for partially saturated porous rocks across a wide range of conditions. The material states generated behind the shock wave from an explosive source can vary significantly, ranging from crushed and melted rock near the source to a poroelastic medium in the far field. In the model, rock strength is determined by the effective pressure, which is calculated using two independent equations of state: one for the solid rock and another for the pore fluid. The model accounts for shock-induced liquefaction resulting from fluid pressure buildup in the pore spaces near the explosive source. Simultaneously, it describes the increase in wave propagation speed due to elastic pore contraction in both dry and partially saturated rocks. This model is applied to investigate how fluid saturation affects the amplitude and shape of the generated waves, as well as the residual stress surrounding the cavity formed by spherical explosions.

Irrigation gaps in weather models could skew air quality forecasts, study finds

Phys.org: Earth science - Wed, 03/04/2026 - 23:30

Outdoor air pollution is estimated to contribute to more than 100,000 premature deaths in the United States each year, according to the National Weather Service. Accurate air quality forecasts—designed to protect public health, alerting communities to dangerous levels of pollutants linked to asthma attacks, heart disease and premature death—are critical for helping people limit exposure and for guiding regulatory action.