In a new study, a team of physicists led by the University of Iowa has revealed definitive evidence showing that the brightest auroras are produced by powerful electromagnetic waves during geomagnetic storms. Let’s find out then what is the true origin of the Aurora Borealis.
Aurora Borealis: after more than 40 years the definitive proof of its origin is revealed
The phenomenon, known as Alfvén waves , is a particular magnetohydrodynamic wave that accelerates electrons towards Earth , causing the particles to produce the well-known atmospheric light show that characterizes the Northern Lights.
The study, published in the journal Nature Communications , concludes a decade-long investigation to experimentally demonstrate the physical mechanisms that determine the acceleration of electrons by Alfvén waves under conditions corresponding to the Earth’s auroral magnetosphere.
Professor Greg Howes , study co-author and professor in the Iowa Department of Physics and Astronomy, said : » The measurements found that this small population of electrons undergoes a resonant acceleration of the Alfven wave electric field, similar to a surfer caught by a wave that is continually accelerating while moving simultaneously with it ‘.
Scientists already knew the basis of the phenomenon , in which energized particles emitted by the sun, such as electrons traveling at 45 million miles per hour, hurtling along the lines of the Earth’s magnetic field, collide with molecules. of oxygen and nitrogen, thus shooting through the atmosphere in an excited state (when the electrons are at a higher energy level than normally occupied). Once relaxed, these molecules emit light, producing the colorful hues of the Northern Lights.
This theory was also supported by space missions that often found Alfvén waves crossing the planet in the vicinity of auroras, presumably accelerating electrons along the way. However, the inherent limitations of spacecraft and rocket measurements had always prevented a definitive test to support these hypotheses.
However now, physicists were able to find confirmatory evidence in a series of experiments carried out on the Large Plasma Device (LPD) at UCLA’s Basic Plasma Science Facility, a national research center that is backed by the US Department of Energy. . UU, as well as by the National Science Foundation.
‘ The idea that these waves can energize the electrons that create the aurora dates back more than four decades, but this is the first time that we can prove it. The experiments have allowed us to make key measurements that explain how theory and ancient data collected can describe the fundamental way in which auroras are created , ‘said study co-author Professor Kletzing.
The experiment required a measurement of a very small population of electrons (less than 1/1000 of the electrons in plasma) moving through the UCLA LPD chamber, almost at the same speed as Alfvén waves, which which yields direct evidence that electrons cause auroras.
