New search with data from NasaThe Global Extremity and Disc Observation, or GOLD, mission revealed unexpected behavior in the expanse of charged particles connecting the Earth’s equator – perhaps thanks to GOLD’s long-term global vision, the first of its kind for its kind . measure.
Gold is in geostationary orbit, which means that it orbits the earth at the same speed as the planet and that it “floats” in the same place. This allows GOLD to see the same region for changes over time across latitude and longitude, which most satellites that study the upper atmosphere cannot.
“Since GOLD is on a geostationary satellite, we can capture a two-dimensional evolution of these dynamics over time,” said Dr. Xuguang Cai, a researcher at the High Altitude Observatory in Boulder, Colorado, and lead author of a new paper. of research.
GOLD targets parts of Earth’s upper atmosphere that extend to a height of about 50 to 400 miles, including a neutral layer called the thermosphere and the electrically charged particles that make up the ionosphere. Unlike neutral particles in most of the Earth’s atmosphere, charged particles in the ionosphere react to electric and magnetic fields passing through the atmosphere and into neighboring Earth. But because charged and neutral particles are mixed together, something that affects one population can affect another.
This means that the ionosphere and the upper atmosphere are formed by a complex combination of factors, including space weather conditions – such as geomagnetic storms fueled by the sun – and terrestrial meteorology. These areas also serve as highways for many of our communication and navigation signals. Changes in the density and composition of the ionosphere can distort signals passing through it, such as radio and GPS.
From its vantage point on a commercial communications satellite in geostationary orbit, GOLD makes hemispherical observations of the ionosphere every 30 minutes or so. This unprecedented sight gives scientists new information on the evolution of this region.
One of the most distinctive features of the nocturnal ionosphere are the double bands of densely charged particles straddling the Earth’s magnetic equator. These bands, called equatorial ionization anomalies or EIAs, can change in size, shape, and intensity depending on conditions in the ionosphere.
The bands can also move their position. So far, scientists have relied on data captured by satellites crossing the region, measuring averages over months to see how the range might change in the long term. But short-term changes are harder to follow.
Before GOLD, scientists suspected that rapid band changes would be symmetrical. As the north band moves north, the south band reverses south. One night in November 2018, GOLD saw something that challenged this idea: the southern band of particles drifted south, while the northern band remained stable, all in less than two hours.
The shape of Earth’s magnetic field (indicated by the orange lines in this data visualization) near the equator pulls charged (blue) particles away from the equator, creating two dense bands north and south of the equator known as the name of equatorial ionic anomaly. Credit: NASA Science Visualization Studio
This isn’t the first time scientists have seen bands move in this way, but this shorter event – only around two hours, compared to the more typical six to eight hours seen previously – was first seen. and could have only been observed previously OR. The notes are set out in an article published on December 29, 2020 at: Geophysical Research Journal: Ruimtefysica.
The symmetrical drift of these tires is caused by the height of the air which carries the charged particles. As night falls and temperatures cool, pockets of warmer air arise. The charged particles carried in these hotter air pockets are connected by magnetic field lines, and for pockets near the Earth’s magnetic equator, the shape of Earth’s magnetic field means that the upward motion also pushes the charged particles horizontally. . This creates the symmetrical north-south drift of the two bands of charged particles.
The exact cause of the asymmetric aberration seen by GOLD remains a mystery – although Cai suspects the answer lies in a combination of the many factors that determine the movement of electrons in the ionosphere: ongoing chemical reactions, electric fields, and wind on the planet. altitude in the area.
Surprisingly, however, these findings could help scientists look behind the curtain of the ionosphere and better understand what is causing the changes. Because every process cannot be followed with a satellite or a ground sensor, scientists rely heavily on computer models to study the ionosphere, such as those that allow meteorologists to predict the weather. on earth. To create this simulation, scientists code what they suspect the underlying physics is at work and compare the model’s prediction with the observed data.
Before GOLD, scientists obtained this data from occasional transiting satellites and limited observations on the ground. Now GOLD gives scientists the full picture.
Reference: “Observation of Post-Sunset OI 135.6 nm Radiation Enhancement Over South America by the Gold Expedition” carries Xuguang Cai, Alan G. Burns, Wenbin Wang, Liying Qian, Jing Liu, Stanley C. Solomon, Richard W. Eastes , Robert E. Danielle, Carlos R. Martins, William E. McClintock and Inez S. Batista, December 29, 202, yesterday beschikbaar. Geophysical Research Journal: Ruimtefysica.
doi: 10.1029 / 2020JA028108
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