Formation and impact of solar winds
Gibiser Kevin
Department of Physics, Karl Fanzens University, Graz, Styria, Austria
Our sun spends warmth and light and because of that very reason life would not be existent on planet earth. But
the sun has not only positive effects, it can become dangerous for life because it spreads matter non-stop into
space as well into the direction of earth. This emissions are called ‚solar winds‘and if those winds grow into a
‚solar storm‘, they can have tremendous effects on our modern technology. The theoretical effects could affect
all of humanity, because a strong solar wind could penetrate earth magnetic field, leading to breakdowns of
electricity and broadcasting systems. The emission of protons, electrons helium cores (alpha-parts) on the
surface of the sun, can have influences on the distribution of electromagnetic waves on earth during strong solar
wind, leading to disruption in satellite-communication.
Our magnetic field, which is constantly hit by solar winds, protects ours mostly from that energy-rich radiation.
But it gets also distorted because of the solar winds, on dayside it gets flattened – on the night side distorted to
the back. With the help of solar telescope these mass-emissions can be detected in the visual and ultraviolet
spectral range. A higher emission in the Radio – an x-ray-range can also be visualized.
Due to the sun, the earth gets warmth and light. The visual part of the radiation is only a very small
part of the sun’s emitted radiation. Besides photons, which are responsible for the light, the sun also
sends charged particles and those are the solar winds.
They are made up mostly from protons, electrons and helium-cores. Ocassionally there are also
oxygen- and iron-cores present, this part although is almost nonexistent compared to the other parts of
a solar wind. Because of its composition of its main parts and the small part of other atomic cores and
non-ionic atoms, a solar wind is a so called plasma. Although a solar wind originates on the surface of
the sun, it doesn’t represent the exact composition and abundance of elements of this outter layer. The
reason for this is, that the elements are only gathered in fractionation processes. Such fractionation
processes label the shift of frequency of isotopes of an element. They are triggered by chemical and
physical effects and are thermodynamic, independent of temperature. Because the sun has a turbulent
atmosphere and isn’t a steady ball of gas, a lot of extreme reactions occur. Such events are huge
plasma-bows on the sun‘s surface, so called flares. Such flares change the local configuration of the
sun‘s magnetic field and a magnetic reconnection happens. That means that in the reconnection-zone,
the field lines break up and join again, resulting in a kind of a magnetic short circuit. Because the
particles heat up in the most outter layer of the sun (corona), they become able to overcome the gravity
of the sun. During this phenomenon a lot of plasma is emitted into space. The density of solar wind
near earth is about 5*106 particles per cubic meter. The son loses around 1 million tons of mass per
second during the emission of a solar wind, which in hindsight of its total mass of 2*1030 kg extremely
slight. This event is called coronal mass ejection. The flares and coronal mass ejections can be seen in
the visual and ultraviolet spectral range with the help of solar telescopes.
The solar winds can be distributed into 2 types, the slow and fast solar winds. The slow solar winds
have a velocity of around 400 km/s, a temperature from von 1,4-1,6*106 K and a composition similar
to the coronas. Furthermore their density is twice as much and their intensity much more variable than
those of the faster type. They have also a more complex structure and more turbulent regions. The
slower solar winds come from the region around the sun‘s equator belt, the so called ‚streamer belt‘. In
this region the flares transport plasma alongside magnetic field lines. Observations of the sun between
1996 and 2001 show that the emission of slow solar winds occur mostly between latitudinal lines 3035° around the equator during the solar minimum (time of least sun activity) and less in direction of
the sun‘s poles. During the solar maximum, the poles were also points of emission for slow solar
winds.
The fast solar winds have a velocity of about 750 km/s, a temperature of 8*105 K and a composition
similar to the one of the sun‘s photosphere. They escape near the coronal holes (dark areas on the sun).
Those coronal holes are funnel-like areas of the open magnetic field lines. They show a lower
temperature (around 2000°) and a lower density than the rest of the corona. Coronal holes occur
during the solar minimum near the poles, during the solar maximum they can be found at every
latitudinal line. The emission originates alongside narrow coronal funnels, which are located around
20.000 kilometres above the photosphere. This behaviour is explained with the help of pic.1
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Pic.1 shows the coronal emission
alongside a funnel (fast solar wind) on
one hand and on the other hand it
shows the emission of a slow solar
wind alongside a flare.
pic.2 shows the coronal mass emissions
from Jan 14. 2007, which were
recorded by the research-orbiter SOHO
(Solar and Heliospheric Observatory).
Approximately a mass the same as the
mass of Mount Everest were emitted
and accelerated to a speed of 3000 km/s
.
The solar winds spread far ahead of the
planetary orbits and creates through the
pushing of interplanetary matter a kind
of bubble, which is called heliosphere.
The border of the heliosphere, where
the particles of the solar wind get
slowed is called heliopause (pic.3) on
the border of the heliosphere a part of
the cosmic background radiation is
reflected. If the solar wind varies, the
additional protective layer also varies
and therefore the flow of cosmic
radiation.
Pic.2 heliosphere (blue), heliopause (green)
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If the solar wind hits the earth‘s magnetic field, it gets deformed. On the side which faces the sun it
gets flattened and on the side facing away from the sun it gets drawn into length. Strong solar winds
can penetrate earth’s magnetic field at the poles in spiral paths around the magnetic field lines and
create in high layers of the earth’s atmosphere, with ionisation of nitrogen atoms, so called aurora.
Usually the particles of the solar wind and the cosmic radiation get diverted from the magnetic field,
so that they orbit in a ring, the so called Van-Allen belt around the earth.
The field strength of the earth’s magnetic field declined in the last 150 years by 10%, which
measurements from NASA show. This strengthens the interaction between the solar wind and the
atmosphere and this again leads to more heat-creating reactions and reduction of the ozone layer.
According a measurement from NASA, in the year 2000 9% of ozone in a height of 15-50km and 70%
of ozone in the height of 50-90 km got destroyed by solar winds.
The reduced field strengths of earth’s magnetic field leads also to a higher ionisation of the
atmosphere and therefore to reflections of electromagnetic waves with higher frequencies. It is still
possible to receive distant high frequented sources, but the quality of the signal reduces a lot because
of the reflection. This can lead to disturbances with radio- and TV-signals in extreme cases.
Because the particles of cosmic radiation have also a ionisation impact, they are able to accidentally
charge circuits of computer chips. This leads to a wrong current and maybe to damage to the
component. Neutrons, which are not diverted by the earth’s magnetic field, can create crystallographic
defects in semiconductor elements and therefore to a malfunction of the device.
In the 1980’s the so called ‚Soft Error‘was discovered. At a ‚Soft Error‘the content of a memory-chip
gets changed without any specific reason and the higher the computer was located, the bigger the error
was, because of the cosmic radiation. With more and more memory-chips with smaller profiles, the
chance of a ‚Soft-Error ‘got declined against every expectation. Because the profiles of the
components were smaller, the chance to be hit by cosmic reaction was smaller too.
The danger of malfunctioning bits in memory units is higher with satellites, because of the higher
altitude. Because of t hat, specially protected components, which circuits are located on isolated
material, are built into satellites. In 1994 a solar storm leads to disturbances for about two hours in 2
communication-satellites and with that to the breakdown of the whole radio- and TV-signal in Canada.
The main problem from solar storms is not the ionisation of the atmosphere and the components, but
the changeable magnetic field of the earth. If a magnetic field changes, a high voltage gets indicated in
a conductor loop to enable the electric current. Because earth’s magnetic field changes on a global
scale, a solar storm can lead to extremely high voltages in bigger conductor loops (like high-tension
power lines) and this again can lead to disturbances and damages in conductions and transformers. In
2989 a flare leads to a breakdown in the whole city of Quebec for a few hours. In Sweden a far
stronger flare lead to such high electric currents in telegraphic conductions that they lead to a forest
fire in 1859. In 2003 a solar storm lead to an electrical breakdown in Malmö which lasted for an hour
Approximately every 11 years a solar storm occurs. The last one was in 2013, but before that, there
was also one in 2011. In fact, such events can’t be predicted accurately, but there are research-orbiters,
which can discover solar storms in advance, so that there are one to two days to get prepared.
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