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| Effect of solar wind on the atmosphere of planets. Source: NASA |
between magnetic field and solar wind creates bow shock. Magnetosphere causes the particles to travel around the planet rather than bombarding the atmosphere and surface
What is solar wind?
Solar wind is a stream of charged particles released from
the upper atmosphere of the Sun. solar wind mostly consists of electrons and
protons, the temperature and speed of particles varies with time. The particles
are able to escape the Sun’s gravity because of their high kinetic energy and
the high temperature of the corona.
Since solar wind has high energy particles, these particles
can easily affect atmosphere of planets which are present very close to the
Sun. The solar wind usually has such a high energy that it shows its impact up
to the boundary of solar system where it creates the Heliosphere after
interaction with the particles of interstellar medium. There are many phenomena
caused by solar wind some of which are given below:
Formation of Aurora
due to Solar Wind
Solar wind consists of high energy particles when these
particles approach Earth they are trapped and dragged by the magnetic field of
Earth toward the poles. At poles these high energy particles collide with the
molecules of atmosphere and excite them. After sometime, these excited
molecules returns in their normal states and lose energy in the form of
emission of visible lights.
The emitted color depends on the molecule of the atmosphere;
the normally observed colors are red, green and blue. The combination of these
colors creates beautiful patterns in the form of curtains and diffused
patterns. These colored patterns are called aurora and these are found around
the region of poles.
Solar Wind blows some
part of the atmosphere of Earth into space
In September 1998, residents of the far north observed a massive display of the aurora borealis along with fountain of gas being accelerated into space by a powerful bubble of solar wind which pumped about 200 gigawatts of electrical power into the Earth.
At the same time, a special space weather research satellite
was taking measurement showing that solar events can directly affect our outer atmosphere.
“This is the first time we’ve been able to correlate these
solar coronal mass ejections (CMEs) with enhanced ion outflows from the upper
ionosphere”, said Dr. James span on NASA’s Marshall Space Flight Center.
Atmosphere of Earth
expands and contracts due to Solar Wind
When the high speed solar wind reaches Earth, they cause the
gases in upper atmosphere to heat up and expand, then cool down and contract.
It causes the change in density of the upper atmosphere and creates high and
low density regions.
Orbiting satellite when flies through the resulting “hills
and valleys of density” experiences more or less drag. Satellite faced with
denser atmosphere will slow down and need more energy to keep moving in given
orbit.
The changes in drag affect satellite’s ability to stay on
path; require more fuel and complex orbital adjustments to maintain the
predictable and safe path.
Escape of atmosphere
of Mars to space due to Solar Wind
Space physicists from the University of Leicester have
identified that the pressure of solar wind is a main contributor to Mars
atmospheric escape. It is observed that Mars atmosphere does not drift away at
a steady; instead, atmosphere escape occurs in bursts.
Corotating interaction regions (CIR) form when regions of
fast solar wind encounter slower solar wind, creating a high-pressure pulse.
When these CIR pulses pass by Mars, they can drive away particles from Mars
atmosphere.
The main reason of loss of atmosphere of Mars is the absence
of Magnetic field produced by the planet which helps in protection from solar
wind.
Changes in Sea-Level
Pressure over South Korea Associated with High-Speed Solar Wind Events
Heon Young Chang and his colleagues performed analysis on
data collected from 1986 to 2011 to explore a possible response of the Sea
Level Pressure (SLP) over South Korea to the high speed solar wind event. The
change in Sea Level Pressure shows an increase up to 2.5 hpa at day +1 and a
gradual decrease to its normal level, whose Key dates is defined such that
whose daily solar wind speed at maximum exceeds 800 Km/s. They find that the
SLP in a low latitude region shows a measurable response to an encounter of
the high-speed solar wind as seen in the high latitude region.
Effect of transient
solar wind pulses on heating the atmosphere of Jupiter
The Jovian upper atmosphere temperature is up to 700 K
higher than that predicted by solar heating alone. The energy crisis at Jupiter
and the other giant planets have puzzled scientists for over 40 years.
Clarke et al, (2009) and Nichols et al, (2000) studied the
effect of transient changes in solar wind dynamic pressure on Jovian auroral
parameters and thermospheric energy budget. The transient magnetospheric changes
simulated are of two types i) a transient compression event and ii) a transient
expansion event, both of which last for three hours. Observations by them find
the factor of two increases in auroral brightness as well as pole ward shifts
up to 1 degree due to the arrival of solar wind shocks. The magnetospheric
super-corotation results in 2000 TW resultant power being dissipated in thermosphere
which leads to local temperature change of 25 K.
All the above phenomena clearly show that solar winds are very
powerful. There are many other problems that are caused by solar wind like
damage of satellites, problem in communication, and damage to ozone layer.
Therefore it is very important to develop protection against solar wind in the
interplanetary space probe. Solar wind are harmful for both human as well as
instruments. With the development of technology, we will be able to protect us
against solar wind in the future interplanetary missions.
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