Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Earth's magnetic field measured using artificial stars at 90 kilometers altitude

14.11.2018

An international collaboration uses laser-generated stars to determine the Earth's magnetic field in the sodium layer of the atmosphere

The mesosphere, at heights between 85 and 100 kilometers above the Earth's surface, contains a layer of atomic sodium. Astronomers use laser beams to create artificial stars, or laser guide stars (LGS), in this layer for improving the quality of astronomical observations.


The experiment on La Palma: The laser beam (yellow) generates an artificial guide star in the mesosphere. This light is collected in the receiver telescope (front left). The laser source and the receiver telescope are eight meters away from each other.

photo/©: Felipe Pedreros Bustos


The Observatorio del Roque de los Muchachos, located on the rim of an extinct volcano at 2,400 meters altitude in the island of La Palma, provides adequate conditions to perform the experiments described.

photo/©: Felipe Pedreros Bustos

In 2011, researchers proposed that artificial guide stars could also be used to measure the Earth's magnetic field at this altitude. An international group of scientists has recently managed to do this with a high degree of precision.

The technique may also help to identify magnetic structures in the solid Earth's lithosphere, to monitor space weather, and to measure electrical currents in the part of the atmosphere called ionosphere.

Astronomers have been using lasers to generate artificial stars for the past 20 years. A laser beam is directed from the ground into the atmosphere. In the sodium layer, it strikes sodium atoms, which absorb the energy of the laser and then start to glow.

"The atoms emit light in all directions. Such artificial stars are barely visible to the naked eye but can be observed with telescopes," explained Felipe Pedreros Bustos of Johannes Gutenberg University Mainz (JGU).

In connection with the work on his doctoral thesis, the Chilean-born physicist has spent four years working on the project, which besides JGU involves the European Southern Observatory (ESO), the University of California, Berkeley and Rochester Scientific in the USA, the Italian National Institute for Astrophysics (INAF-OAR), and the University of British Columbia in Vancouver, Canada.

The artificial guide stars help astronomers to correct the distortions of light that travels through the atmosphere. The light from the artificial guide star is collected on the ground by telescopes, and the information is used to adjust in real time state-of-the-art deformable mirrors, compensating the distortions and allowing astronomical objects to be imaged sharply, down to the optical resolution, the so-called diffraction limit, of the telescope.

The precession of sodium atoms reveals the strength of the magnetic field

The participants in the collaborative project are using laser guide stars to measure the Earth's magnetic field. An ESO LGS unit dedicated to Research and Development is housed in the Roque de los Muchachos Observatory on La Palma, the westernmost Canary Island.

The availability and use of the LGS unit has allowed to perform the reported joint experiments, which also aim at increasing the brightness of laser guide stars. From the observatory, a laser beam is directed at the sodium layer which excites and spin-polarizes the atoms making most of their atomic spin point in the same direction.

Due to the effect of the surrounding magnetic field, the polarized atomic spins rotate around the direction of the magnetic field similar to the motion of a gyroscope that is tilted from the vertical, a phenomenon known as Larmor precession. "A guide star becomes brighter when the modulation frequency of our laser coincides with the precession frequency of sodium," explained Pedreros Bustos. "As the Larmor frequency is proportional to the strength of the magnetic field, we can use this method to measure the Earth's magnetic field in the sodium layer." The detection scheme is similar to a stroboscope.

Hence, the group has succeeded in using a well-studied, fundamental laboratory technique to observe the natural world. It fills a gap in our knowledge of the Earth's magnetic field by allowing us to make ground-based observations of the mesosphere, which was previously difficult to access. Up to now, the magnetic field could only be directly measured on the ground, from airplanes, from balloons in the stratosphere, or from satellites.

In May 2018, a US-American research group had published similar findings. However, these latest measurements are much more precise, and scientists hope to improve them still further by using higher-energy lasers. "We can also use the technique to estimate atomic processes in the atmosphere, for example, how often sodium collides with other atoms such as oxygen or nitrogen. This is something that hasn't been done before," said Pedreros Bustos.

This artificial guide star measuring technique will be particularly useful in geophysics. It will make it possible to determine changes to the magnetic field of the Earth's ionosphere caused by solar winds. In addition, observation of oceanic currents and large-scale magnetic structures in the upper mantle would be feasible by means of continuous surveillance of the Earth's magnetic field at altitudes of 85 to 100 kilometers.

Images:
http://www.uni-mainz.de/bilder_presse/08_physik_quantum_laser_leitstern_magnetfe...
The experiment on La Palma: The laser beam (yellow) generates an artificial guide star in the mesosphere. This light is collected in the receiver telescope (front left). The laser source and the receiver telescope are eight meters away from each other.
photo/©: Felipe Pedreros Bustos

http://www.uni-mainz.de/bilder_presse/08_physik_quantum_laser_leitstern_magnetfe...
The Observatorio del Roque de los Muchachos, located on the rim of an extinct volcano at 2,400 meters altitude in the island of La Palma, provides adequate conditions to perform the experiments described.
photo/©: Felipe Pedreros Bustos

Related links:
https://budker.uni-mainz.de/?page_id=38 – Magnetometry with Laser Guide Stars project of the Budker Group
https://budker.uni-mainz.de/ – Budker Group at HIM and JGU
https://www.hi-mainz.de – Helmholtz-Institute Mainz
http://eso.org/sci/facilities/develop/lgsf.html – Laser guide star developments at ESO

Wissenschaftliche Ansprechpartner:

Felipe Pedreros Bustos
Helmholtz Institute Mainz
Johannes Gutenberg University Mainz
55099 Mainz, GERMANY
phone +49 6131 39-29638
e-mail: pedreros@uni-mainz.de
https://www.researchgate.net/profile/Felipe_Pedreros_Bustos

Originalpublikation:

F. Pedreros Bustos et al., Remote sensing of geomagnetic fields and atomic collisions in the mesosphere, Nature Communications 9:3981, 28 September 2018,
DOI:10.1038/s41467-018-06396-7
http://www.nature.com/articles/s41467-018-06396-7

J. M. Higbie et al., Magnetometry with mesospheric sodium, Proceedings of the National Academy of Sciences of the United States of America (PNAS) 108:9, 3522-3525, 1 March 2011,
DOI:10.1073/pnas.1013641108
http://www.pnas.org/content/early/2011/02/07/1013641108

Weitere Informationen:

http://www.uni-mainz.de/presse/aktuell/6963_ENG_HTML.php – press release "Atomic parity violation research reaches new milestone" (13 Nov. 2018) ;
http://www.uni-mainz.de/presse/20266_ENG_HTML.php – press release "ERC Advanced Grant for experimental physicists Dmitry Budker" (12 May 2016) ;
http://www.magazin.uni-mainz.de/2452_ENG_HTML.php – JGU MAGAZINE: "Not everything in the universe is symmetrical" (9 Jan. 2015)

Petra Giegerich | idw - Informationsdienst Wissenschaft

More articles from Earth Sciences:

nachricht Shrinking of Greenland's glaciers began accelerating in 2000, research finds
12.12.2019 | Ohio State University

nachricht One-third of recent global methane increase comes from tropical Africa
11.12.2019 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Virus multiplication in 3D

Vaccinia viruses serve as a vaccine against human smallpox and as the basis of new cancer therapies. Two studies now provide fascinating insights into their unusual propagation strategy at the atomic level.

For viruses to multiply, they usually need the support of the cells they infect. In many cases, only in their host’s nucleus can they find the machines,...

Im Focus: Cheers! Maxwell's electromagnetism extended to smaller scales

More than one hundred and fifty years have passed since the publication of James Clerk Maxwell's "A Dynamical Theory of the Electromagnetic Field" (1865). What would our lives be without this publication?

It is difficult to imagine, as this treatise revolutionized our fundamental understanding of electric fields, magnetic fields, and light. The twenty original...

Im Focus: Highly charged ion paves the way towards new physics

In a joint experimental and theoretical work performed at the Heidelberg Max Planck Institute for Nuclear Physics, an international team of physicists detected for the first time an orbital crossing in the highly charged ion Pr⁹⁺. Optical spectra were recorded employing an electron beam ion trap and analysed with the aid of atomic structure calculations. A proposed nHz-wide transition has been identified and its energy was determined with high precision. Theory predicts a very high sensitivity to new physics and extremely low susceptibility to external perturbations for this “clock line” making it a unique candidate for proposed precision studies.

Laser spectroscopy of neutral atoms and singly charged ions has reached astonishing precision by merit of a chain of technological advances during the past...

Im Focus: Ultrafast stimulated emission microscopy of single nanocrystals in Science

The ability to investigate the dynamics of single particle at the nano-scale and femtosecond level remained an unfathomed dream for years. It was not until the dawn of the 21st century that nanotechnology and femtoscience gradually merged together and the first ultrafast microscopy of individual quantum dots (QDs) and molecules was accomplished.

Ultrafast microscopy studies entirely rely on detecting nanoparticles or single molecules with luminescence techniques, which require efficient emitters to...

Im Focus: How to induce magnetism in graphene

Graphene, a two-dimensional structure made of carbon, is a material with excellent mechanical, electronic and optical properties. However, it did not seem suitable for magnetic applications. Together with international partners, Empa researchers have now succeeded in synthesizing a unique nanographene predicted in the 1970s, which conclusively demonstrates that carbon in very specific forms has magnetic properties that could permit future spintronic applications. The results have just been published in the renowned journal Nature Nanotechnology.

Depending on the shape and orientation of their edges, graphene nanostructures (also known as nanographenes) can have very different properties – for example,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Supporting structures of wind turbines contribute to wind farm blockage effect

13.12.2019 | Physics and Astronomy

Chinese team makes nanoscopy breakthrough

13.12.2019 | Physics and Astronomy

Tiny quantum sensors watch materials transform under pressure

13.12.2019 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>