Physikalisches Kolloquium: Dr. Martin Schrön (UFZ Leipzig - Helmholtz Centre for Environmental Research GmbH)

"Detecting Environmental Water with Ground Albedo Neutrons from Cosmic Rays"

28.05.2019 ab 16:15

Leibnizstr. 13, 24118 Kiel, Hans-Geiger Hörsaal

Abstract

A few years ago, researchers found a way to detect water in the shallow ground with the help of exploding stars. The cosmic rays generated by supernova remnants can create neutrons near the planetary surface, which are highly sensitive to its hydrogen content. While this principle has been used to find water on Mars, researchers have developed the method further for applications on Earth in order to tackle current questions in hydrology, agriculture, and climate science.
Conventional neutron monitors on Earth have been used for decades to track the dynamics of incoming cosmic-ray particles under the assumption that local environmental conditions do not influence the highly energetic signal. In contrast, the low-energy signal of reflected cosmic-ray neutrons
can be used to monitor local conditions, particularly the surrounding water content. Water in soil, air, snow, and vegetation determines the number of ground albedo neutrons in the sensitive energy range from 1 eV to 100 keV. Specialized neutron detectors have been introduced in 2012 as the
COsmic Ray Soil Moisture Observing System (COSMOS) and since that time, plenty of those instruments have been installed on natural or agricultural sites throughout the USA (>50), Europe (>80), Africa (>4), Asia (>2), and Australia (>5), and more to follow.
Climate research, hydrologic models and irrigation management rely on large-scale soil moisture data. In contrast to conventional water sensors, the COSMOS products can represent root-zone water content averaged within an area of tens of hectares due to the fast diffusion of neutrons in air.
However, many open questions regarding the physics of the signal are still to be solved, such as the modulation of the count rate by the dynamics of incoming cosmic rays. The talk presents recent developments in cosmic-ray neutron sensing and shows how hydrology, agricultural, and climate
sciences can benefit from astro-particle physics.

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