Meteoroids continually bombard the Earth's atmosphere, depositing iron and other elements into the mesosphere and thermosphere. Although other metals are also deposited by these celestial objects, recent studies have shown that the iron layer extends to higher altitudes.
The dusty space plasmas can change our atmospheric chemistry as particles are introduced into the Earth's upper mesosphere. This can influence the formation, distribution, and duration of noctilucent clouds. One way to examine the surface of the Earth is through a remote sensing method known as light detection and ranging or lidar.
What is a Lidar?
A lidar employs a pulsed laser beam to locate and distinguish objects or targets at various distances within a specified range. It is similar to radar but uses light waves instead of radio waves. It uses laser spectroscopy to measure densities, temperatures, and winds in the upper atmosphere, which other methods cannot do.
There are two types of lidar currently available. One type detects a hard surface and can produce highly detailed 3D maps of buildings, terrains, vegetation, and other objects. Meanwhile, the other type detects the volume of a target, such as the atmosphere or a body of water.
Atmospheric lidars allow experts to determine wind direction and speed by analyzing the Doppler shift in the returned signals. The Doppler shift refers to the change in wavelength or frequency of a wave relative to an observer moving relative to the source of the wave.
The broadening of spectral lines in the returned light of the laser helps infer temperature. The thermal motion of particles causes this broadening. The hotter areas encourage faster-moving particles, resulting in broader spectral lines.
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Expanded Research Capability
At the University of Alaska Fairbanks (UAF), experts are developing a new light detection and ranging tool to understand better the space weather that envelopes the Earth. Also known as iron resonance wind-temperature lidar, the latest laser radar will be the third for the UAF Geophysical Institute.
UAF lidar is designed to measure temperature and neutrally charged iron in the Earth's upper atmosphere as high as 75 to 125 miles (121 to 201 kilometers), the altitude at which the layers of mesosphere and thermosphere meet.
Understanding the processes and influences at this altitude has become increasingly significant due to the proliferation of low-Earth orbit satellites. In addition, more nations are sending space probes to the Moon and are planning to send more to the other regions of the Solar System.
According to UAF research assistant professor Jintai Li, the research team's goal is to create a remotely operated iron lidar. This will complement the ongoing science investigations with the two established lidars of the Geophysical Institute.
The development of the new lidar is carried out in collaboration with a commercial laser partner. The instrument will be placed at the High-frequency Active Auroral Program (HAARP) facility of the Geophysical Institute near Gakona.
The new UAF lidar will support research studies at HAARP and will offer complementary measurements to the two lidars of Poker Flat. These include the Rayleigh density temperature lidar and sodium resonance wind-temperature lidar.
Instead of using the molecules of the atmosphere itself, the new lidar will measure neutrally charged iron atoms. The color the lidar light emits is precisely tuned to provide a strong echo from the iron atoms.
The construction of the new UAF lidar started in April 2021. It is financially supported by the National Science Foundation and is expected to be operational later this year.
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