Environmental Engineering Reference
In-Depth Information
characteristic feature of the solar corona is its high temperature (approximately
10
6
K), and therefore the solar corona emits hard UV radiation.
The solar corona is not stable because of its high temperature and not low tem-
perature gradient. Expansion of the solar corona into space creates a plasma flow,
the solar wind, directed outward from the Sun. The solar wind creates interplane-
tary plasma and leads to various phenomena in the upper terrestrial atmosphere.
The solar wind interacts with dust from Saturn's and Jupiter's satellites and the
magneticfieldsoftheseplanetscreateSaturn'sandJupiter'srings(Section6.2.3).
Interaction of the solar wind with comet dust involving solar radiation and mag-
netic fields determines the properties of the comet tail (Section 6.2.3).
In the Sun there are a number of phenomena that result from interaction of
the solar plasma with its magnetic fields. Spicules - separated columns of mov-
ing plasma - are formed in the chromosphere and create chromospheric bushes.
Under typical solar conditions, approximately 10
6
spicules are observed simultane-
ously. Spicules result from reconnection of magnetic lines of force (Section 4.5.9).
An increase in the magnetic field strength in some zones of the solar atmosphere
leads to scattering of gas in these zones, and causes the formation of cylindrical
structures in the plasma motion. This mechanism is the basis for the generation
of spicules.
Another structure of the solar plasma observed in the solar corona is a promi-
nence. Prominences are clots of dense plasma of different forms with tempera-
turesoftheorderof10
4
K. They are generated as a result of interaction of plasma
streams with magnetic fields and propagate in the corona from the chromosphere.
Solar flares are observed in the upper chromosphere or in the corona. They are a
result of development of plasma instabilities, in particular, reconnection of magnet-
ic lines of force (Section 4.5.9). Solar flares last several minutes. A sharp increase
of the plasma temperature in flares causes an increase in emission of short-wave
radiation. Solar flares generate short intense fluxes of solar plasma and can strong-
ly enhance the solar wind. Such signals reach the Earth in 1.5-2 days, and cause
magnetic storms and auroras in the terrestrial atmosphere. In summary, there are
several varieties of terrestrial plasma and this plasma is responsible for various
phenomena which we observe.
In considering briefly plasma applications, we note the variety of plasma forms,
which also create the variety of plasma applications. Hence, there are a great num-
ber of applications, and this number is increasing with time. The most widespread
is a gas discharge plasma that is produced in the simplest way, and the main plas-
ma application corresponds to light sources on the basis of gas discharge. There are
many types of gas discharge lamps depending on their use. In particular, fluores-
cent gas discharge lamps are used now instead of incandescent lamps and provide
an efficacy of up to 100 lm/W, whereas sodium lamps of yellow color are used for
outdoor lighting. A plasma may be used for determination of additions in gases
or vapors of low concentrations of admixtures up to 10
10
10
9
g/g within the
framework of the optogalvanic method [1, 2]. In this determination, gas discharge
is burned, and a laser signal is tuned to a resonant line of a given element, which
