During July of this year, researchers from the Center for Research in Nuclear Physics and Neutron Spectroscopy, CCHEN, visited the Las Campanas Observatory, LCO, with the purpose of finding relationships between the energy of the background neutrons with the local variables of the place where the observatory is located, in the Atacama region. These variables are ambient temperature, atmospheric pressure, relative humidity, soil moisture, wind speed and soil composition.
There are about 60 neutron monitors in the world. These instruments are dedicated to counting high-energy neutrons which, in conjunction with satellite measurements, make it possible to predict solar activity.
The neutrons that reach the Earth’s surface come from the interaction of cosmic rays – charged particles originating from astrophysical events involving high energy, such as supernova explosions – with the atomic nuclei of chemical elements present in the atmosphere. These particles travel through the vacuum and interact, on their way, with the electromagnetic fields of galaxies and stars.
Those that reach the vicinity of the Solar System, if they enter, interact with the Earth’s atmosphere and then follow a trajectory that depends on their energy and eventually produce a nuclear reaction with the nuclei of the atmosphere. In this reaction, a series of particles called secondary cosmic rays are produced.
“Neutrons are very particular because since they have no electric charge they can only interact with the atomic nuclei, not with the whole atom. So, measuring neutrons on the Earth’s surface gives us information on the occurrence of interactions with the Earth’s atmosphere and, in turn, information on solar activity due to all the obstacles that the cosmic ray has to enter the solar magnetic field,” says Francisco Molina, Director of the Center for Research in Nuclear Physics and Neutron Spectroscopy (CEFNEN) of the Chilean Nuclear Energy Commission.
The monitor used detects high-energy neutrons and can be corrected by finding relationships between local variables and neutron energy, thus improving space weather prediction.
“Chile is the ideal country to make these neutron spectroscopic measurements, since it is a longitudinal country that is relatively close to the equator and relatively close to the south pole. In addition, we have a great diversity of climates and soil types and, finally, in a few hundred kilometers we can go from high mountain areas to sea level,” emphasizes Molina, who is also an Associate Researcher at the SAPHIR Millennium Institute.
The first of six measurements to be made in the group’s third experimental campaign was carried out at LCO. During this measurement, the area had great climatic variability, which, according to Molina, was highly relevant for the purposes of the experiment.
“Because of its location, altitude, infrastructure and sky quality, Las Campanas Observatory offers the ideal conditions for this type of experiments. We are very happy that this team of researchers from CCHEN has chosen our observatory for such important research”, says Leopoldo Infante, Director of LCO.
This project is sponsored by the Chilean Nuclear Energy Commission and the Millennium Institute for Physics at the High Energy Frontier SAPHIR. The institutions involved in the development of the project are Universidad de Tarapacá, Universidad Católica de Antofagasta, Universidad de Atacama, Universidad de La Serena, Las Campanas Observatory, Universidad de Valparaíso, Universidad Santa María, Pontificia Universidad Católica de Chile, Universidad Andrés Bello, Universidad de O’Higgins, Universidad de Talca, Universidad Católica del Maule, Universidad de Concepción, Universidad de la Frontera, Universidad Austral, Universidad de Aysén and Universidad de Magallanes.