Aeronomy is the scientific study of the

upper atmosphere Upper atmosphere is a collective term that refers to various layers of the atmosphere of the Earth above the troposphere and corresponding regions of the atmospheres of other planets, and includes: * The mesosphere, which on Earth lies between th ...

of the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

and corresponding regions of the atmospheres of other planets. It is a branch of both

atmospheric chemistry Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earth's atmosphere and that of other planets is studied. It is a multidisciplinary approach of research and draws on environmental chemistry, physics, meteorol ...

and

atmospheric physics Within the atmospheric sciences, atmospheric physics is the application of physics to the study of the atmosphere. Atmospheric physicists attempt to model Earth's atmosphere and the atmospheres of the other planets using fluid flow equations, chem ...

. Scientists specializing in aeronomy, known as aeronomers, study the motions and chemical composition and properties of the Earth's upper atmosphere and regions of the atmospheres of other planets that correspond to it, as well as the interaction between upper atmospheres and the

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consi ...

environment. In atmospheric regions aeronomers study, chemical dissociation and

ionization Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecul ...

are important phenomena.

History

The mathematician Sydney Chapman introduced the term ''aeronomy'' to describe the study of the Earth's upper atmosphere in 1946 in a

letter to the editor A letter to the editor (LTE) is a letter sent to a publication about an issue of concern to the reader. Usually, such letters are intended for publication. In many publications, letters to the editor may be sent either through conventional ma ...

of ''

Nature Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...

'' entitled "Some Thoughts on Nomenclature." The term became official in 1954 when the

International Union of Geodesy and Geophysics The International Union of Geodesy and Geophysics (IUGG; french: Union géodésique et géophysique internationale, UGGI) is an international non-governmental organization dedicated to the scientific study of Earth and its space environment us ...

adopted it. "Aeronomy" later also began to refer to the study of the corresponding regions of the atmospheres of other planets.

Branches

Aeronomy can be divided into three main branches: terrestrial aeronomy, planetary aeronomy, and comparative aeronomy.Mendillo, Michael, Andrew Nagy, and J .H. Waite, "Introduction," ''Atmospheres in the Solar System: Comparative Aeronomy'', Geophysical Monograph Series Volume 130, 2002, unpaginated Accessed 23 March 2021
/ref>

Terrestrial aeronomy

''Terrestrial aeronomy'' focuses on the Earth's upper atmosphere, which extends from the

stratopause The stratopause (formerly mesopeak) is the level of the atmosphere which is the boundary between two layers: the stratosphere and the mesosphere. In the stratosphere, the temperature increases with altitude, and the stratopause is the region where ...

to the atmosphere's boundary with

outer space Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...

and is defined as consisting of the

mesosphere The mesosphere (; ) is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as altitude increases. This characteristic is used to define its limits: it ...

thermosphere The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere. Within this layer of the atmosphere, ultraviolet radiation causes photoionization/photodissociation of molecules, creating ions; the ...

, and

exosphere The exosphere ( grc, ἔξω "outside, external, beyond", grc, σφαῖρα "sphere") is a thin, atmosphere-like volume surrounding a planet or natural satellite where molecules are gravitationally bound to that body, but where the densi ...

and their ionized component, the

ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...

.Mendillo, Michael, Andrew Nagy, and J .H. Waite, "Preface," ''Atmospheres in the Solar System: Comparative Aeronomy'', Geophysical Monograph Series Volume 130, 2002, unpaginated Accessed 23 March 2021
/ref> Terrestrial aeronomy contrasts with

meteorology Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did no ...

, which is the scientific study of the Earth's lower atmosphere, defined as the

troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. Fro ...

and

stratosphere The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air h ...

."Planetary Aeronomy," Imperial College London Accessed 23 March 2021
/ref>An alternative definition divides the atmosphere into three rather than two parts, with the "upper atmosphere" limited to the exosphere and thermosphere, the mesosphere and stratosphere making up the "middle atmosphere," and the "lower atmosphere" consisting only of the troposphere. Use of this definition does not change the focus of aeronomy, which is all of the earth's atmosphere above the stratopause, or of meteorology, which is all of the earth's atmosphere below the stratopause. Although terrestrial aeronomy and meteorology once were completely separate fields of scientific study, cooperation between terrestrial aeronomers and meteorologists has grown as discoveries made since the early 1990s have demonstrated that the upper and lower atmospheres have an impact on one another's

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which ...

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, proper ...

, and

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...

. Terrestrial aeronomers study

atmospheric tide Atmospheric tides are global-scale periodic oscillations of the atmosphere. In many ways they are analogous to ocean tides. Atmospheric tides can be excited by: *The regular day–night cycle in the Sun's heating of the atmosphere (insolation) *T ...

s and

upper-atmospheric lightning Upper-atmospheric lightning and ionospheric lightning are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmo ...

discharges such as red sprites, sprite halos, blue jets, and ELVES. They also investigate the causes of dissociation and

processes in the Earth's upper atmosphere. Terrestrial aeronomers use ground-based

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to obse ...

balloons A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, and air. For special tasks, balloons can be filled with smoke, liquid water, granular media (e.g. sand, flour or rice), or light s ...

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...

s, and

sounding rockets A sounding rocket or rocketsonde, sometimes called a research rocket or a suborbital rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to ...

to gather data from the upper atmosphere.

Atmospheric tides

Atmospheric tides are global-scale periodic oscillations of the Earth′s atmosphere, analogous in many ways to ocean

tides Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables c ...

. Atmospheric tides dominate the dynamics of the mesosphere and lower thermosphere, serving as an important mechanism for transporting energy from the upper atmosphere into the lower atmosphere. Terrestrial aeronomers study atmospheric tides because an understanding of them is essential to an understanding of the atmosphere as a whole and of benefit in improving the understanding of meteorology. Modeling and observations of atmospheric tides allow researchers to monitor and predict changes in the Earth's atmosphere.Volland, H., "Atmospheric Tidal and Planetary Waves", Kluwer Publ., Dordrecht, 1988

Upper-atmospheric lightning

"Upper-atmospheric lightning" or "upper-atmospheric discharge" are terms aeronomers sometimes use to refer to a family of electrical-breakdown phenomena in the Earth's upper atmosphere that occur well above the altitudes of the

tropospheric The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From t ...

lightning Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an average ...

observed in the lower atmosphere. Currently, the preferred term for an electrical-discharge phenomenon induced in the upper atmosphere by tropospheric lightning is "

transient luminous event Upper-atmospheric lightning and ionospheric lightning are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmo ...

" (TLE) . There are various types of TLEs including red sprites, sprite halos, blue jets, and ELVES (an acronym for “ Emission of Light and Very-Low-Frequency perturbations due to

Electromagnetic Pulse An electromagnetic pulse (EMP), also a transient electromagnetic disturbance (TED), is a brief burst of electromagnetic energy. Depending upon the source, the origin of an EMP can be natural or artificial, and can occur as an electromagnetic f ...

Sources”) .

Planetary aeronomy

''Planetary aeronomy'' studies the regions of the atmospheres of other planets that correspond to the Earth's mesosphere, thermosphere, exosphere, and ionosphere. In some cases, a planet's entire atmosphere may consist only of what on Earth constitutes the upper atmosphere, or only a portion of it. Planetary aeronomers use ground-based telescopes,

space telescope A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launch ...

s, and

space probe A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; o ...

s which fly by,

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

, or land on other planets to gain knowledge of the atmospheres of those planets through the use of instruments such as

interferometer Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber o ...

optical spectrometer An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mate ...

magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...

s, and plasma detectors and techniques such as

radio occultation Radio occultation (RO) is a remote sensing technique used for measuring the physical properties of a planetary atmosphere or ring system. Atmospheric radio occultation Atmospheric radio occultation relies on the detection of a change in a radio ...

. Although planetary aeronomy originally was confined to the study of the atmospheres of the other planets in the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

, the discovery since 1995 of

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

s has allowed planetary aeronomers to expand their field to include the atmospheres of those planets as well.Abstract of Bauer, Siegfried J, and Helmut Lammer, ''Planetary Aeronomy: Atmosphere Environments in Planetary Systems''
Berlin: Springer-Verlag, 2004, Accessed 23 March 2021

Comparative aeronomy

''Comparative aeronomy'' uses the findings of terrestrial and planetary aeronomy — traditionally separate scientific fields — to compare the characteristics and behaviors of the atmospheres of other planets with one another and with the upper atmosphere of Earth. It seeks to identify and describe the ways in which differing chemistry,

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

s, and

thermodynamics Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws ...

on various planets affect the creation, evolution, diversity, and disappearance of atmospheres.

Notes

References

External links

*
The NOAA Aeronomy Laboratory
{{Authority control Atmospheric chemistry Atmospheric physics Electrical phenomena Lightning Space physics Atmospheric sciences

History

Branches

Terrestrial aeronomy

Atmospheric tides

Upper-atmospheric lightning

Planetary aeronomy

Comparative aeronomy

Notes

See also

References

External links