The University of Adelaide

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Buckland Park 3-field Photometer

The Space and Atmospheric Physics group's three-field photometer instrument observed atmospheric nightglow from the 557.7 nm atomic oxygen (O(1S)) and 730 nm hydroxyl (OH (8-3) Meinel) bands, at 97 and 87 km in altitude respectively, from April 1995 through to late 2010, at the Buckland Park field site about 40 km north of Adelaide. The instrument was designed initially to study the characteristics of internal gravity waves in the mesosphere with periods of up to several hours, but recently the dataset acquired by the instrument has been seen to allow the determination of some much longer-term and more fundamental atmospheric parameters on the global scale, as well as providing a useful means of comparison with the other instruments at Buckland Park studying the same region.

Atmospheric airglow and its origin

At any location, and even on the clearest and calmest of nights, the Earth's sky isn't completely dark. Many would instinctively think that a phenomenon like the Auorora Australis or Borealis may be responsible for this; this is true, but such a thing is only observed in the regions of higher latitudes. As a matter of fact, the Earth has its own natural light source ubiquitous in the upper atmosphere - a result of various chemical processes dependent on the atmosphere's temperature and dynamics. In the mesosphere-lower-thermosphere (MLT) region (altitude ~ 100 km), where the air pressure is roughly one millionth of that at the Earth's surface, the incoming solar radiation has sucient energy to dissociate (ionize) the molecules constituting the atmosphere, resulting in this region being composed mainly of free electrons and ions. Depending on the background temperature and pressure, these free electrons and ions may recombine to create neutral molecules. Given the large oscillations in temperature and pressure propagating through the atmosphere on a global scale at all altitudes (including those in the MLT) and the varying solar radiation intensity throughout a given 24-hour period, the composition of this region ends up being very dynamic.


Prof. Iain Reid
Dr. Jonathan Woithe
Andrew Spargo