Storms causing an exhaust of the Earth’s upper atmosphere

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Researchers from the LPC2E (OSUC-CNRS/Université Orleans) and IRAP (OMP-CNRS/Université Paul Sabatier Toulouse 3) have observed for the very first time significant density perturbations of the Earth’s upper atmosphere of the ionospheric plasma above very intense atmospheric storms. The researchers used the DEMETER satellite, first of the scientific micro-satellites developed by CNES 1. These results were recently published in the Journal of Geophysical Research.

To achieve this outcome, the researchers took measurements of the electromagnetic field in a wide range of frequencies and analyzed the ionized medium (using a particle detector, a plasma analyzer and a Langmuir probe). Studies on the effects of storm activity were undertaken since bursts of waves caused by lightning strikes are commonly observed overnight at the satellite altitude. By studying the plasma, it was found that when the thunderstorm activity is very important it can create increases in ion and electron densities of the order of 130% at 650 km altitude. The most intense lightning are moreover generally associated with transient luminous phenomena called “sprites”. A storm event with many “sprites” observed by a ground camera on November 17, 2006 in the south of France, has been more particularly studied with DEMETER. It was thus possible to show that lightning induce a precipitation of energetic electrons from the radiation belts which reach altitudes of 70-100 km where they locally heat the electron gas. These heated electrons can then escape out of the upper atmosphere, driving the heavier components, such as oxygen. This chain of processes that leads to the swelling of the upper atmosphere and to the ionosphere coupling has been detected for the first time.

Data recorded by the DEMETER satellite June 30, 2005 as it passes over a storm between 2:33 p.m. 2:27 p.m. ET TU. The top panel shows the spectrogram of a component of the electric field between 0 and 20 kHz. The signal intensity is color coded according to the scale on the right. Each vertical line corresponds to a wavelength due to atmospheric lightning that has spread to the altitude of the satellite. The lower panel shows the variation of the density of the O + ion (the densities of the other ions are much lower). We can see an increase in ion density when the wave intensity is the most important. The information at the bottom of the figure gives the universal time, local time, geographical latitudes and longitudes, and McIlwain L parameter which is related to the magnetic field. Credits: Parrot et al.

This research is to better prepare the TARANIS2 mission dedicated to the study of energy transients observed above atmospheric storms.

Note(s): 

1. DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) : It was launched in 2004 on a sun-synchronous polar and circular orbit, at an altitude of 650 km (http://smsc.cnes.fr/DEMETER/Fr/)

2. The primary goal of the TARANIS mission to be launched in 2016 is the study of transient phenomena which are observed above atmospheric storms. These phenomena like “sprites” result from a coupling between the atmosphere and ionosphere. They occur between 20 and 100 km altitude. The study will be extended to the precipitation and the transient acceleration of energetic electrons, that these electrons are directly related or not to these optical phenomena. The main partners are the the LPC2E, CEA, IRAP, LATMOS, APC and foreign laboratories in the Czech Republic and Poland (http://smsc.cnes.fr/TARANIS/Fr/).

Further Details: 

Source(s): 

IRAP Contact :

  • Jean-André Sauvaud

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