Geocorona
Encyclopedia
The geocorona is the luminous part of the outermost region of the Earth's atmosphere
, the exosphere
. It is seen primarily via far-ultraviolet
light
(Lyman-alpha
) from the Sun
that is scattered
from neutral hydrogen. It extends to at least 15.5 Earth radii. The geocorona has been studied from outer space
by the Astrid satellites
and the Galileo spacecraft
(among others), using its ultraviolet spectrometer
(UVS) during an Earth
flyby
.
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
, the exosphere
Exosphere
The exosphere is the uppermost layer of Earth's atmosphere. In the exosphere, an upward travelling molecule moving fast enough to attain escape velocity can escape to space with a low chance of collisions; if it is moving below escape velocity it will be prevented from escaping from the celestial...
. It is seen primarily via far-ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
(Lyman-alpha
Lyman series
In physics and chemistry, the Lyman series is the series of transitions and resulting ultraviolet emission lines of the hydrogen atom as an electron goes from n ≥ 2 to n = 1...
) from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
that is scattered
Scattering
Scattering is a general physical process where some forms of radiation, such as light, sound, or moving particles, are forced to deviate from a straight trajectory by one or more localized non-uniformities in the medium through which they pass. In conventional use, this also includes deviation of...
from neutral hydrogen. It extends to at least 15.5 Earth radii. The geocorona has been studied from outer space
Outer space
Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....
by the Astrid satellites
Astrid (satellites)
Astrid-1 and Astrid-2 were two microsatellites designed and developed by Swedish Space Corporation on behalf of the Swedish National Space Board. They were piggyback launched on a Cosmos-3M launch vehicle from Plesetsk, Russia...
and the Galileo spacecraft
Galileo spacecraft
Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. Named after the astronomer and Renaissance pioneer Galileo Galilei, it was launched on October 18, 1989 by the Space Shuttle Atlantis on the STS-34 mission...
(among others), using its ultraviolet spectrometer
Spectrometer
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
(UVS) during an Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
flyby
Flyby
Flyby may refer to:* Flypast or flyover, a celebratory display or ceremonial flight* Planetary flyby, a type of interplanetary spacecraft mission* Gravity assist, a spaceflight maneuver* "Fly by II", a single released by the UK band Blue...
.