Le vent solaire peut sembler être une brise inoffensive, mais il peut en réalité être assez dangereux pour la Terre. Lorsque le soleil émet ces particules à haute énergie, elles peuvent perturber le champ magnétique de notre planète. Cela pourrait entraîner des perturbations majeures dans nos réseaux électriques et nos systèmes de communication. De plus, dans les cas extrêmes, cela pourrait même mettre en danger les astronautes et les vols à haute altitude. Donc oui, ces vents solaires sont plus que de simples curiosités spatiales — ils pourraient sérieusement bouleverser les choses ! Animation créée par Sympa.
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FunTranscript
00:00In May 2024, the amazing auroras that illuminated the night sky
00:05demonstrated all the power of the radiation emitted by solar storms.
00:09But sometimes, our sun does much more destructive things.
00:13I'm talking about events related to solar particles.
00:16During this time, protons explosions coming directly from the sun's surface
00:21can burst like gigantic cosmic projectors.
00:26According to the surveys, an extreme particle eruption strikes the Earth every thousand years.
00:31It often causes serious damage to the ozone layer
00:34and increases the levels of ultraviolet radiation on the surface of our planet.
00:39Fortunately, the Earth's magnetic field is a powerful protective cocoon.
00:44It repels radiation charged with electricity from the sun.
00:48In its normal state, this field functions like a huge magnet
00:52with field lines that start from one pole, go around the planet and end up at the other pole.
00:58This diagram is sometimes called inverted pamplemousse.
01:02This vertical orientation of the magnetic field at the poles
01:06allows some ionizing cosmic radiation to cross the field to the high atmosphere.
01:12There, it interacts with the gas molecules
01:15and produces the glows we know as auroras.
01:19But over time, the Earth's protective bubble changes.
01:23During the last century, the North magnetic pole moved at a speed of about 40 km per year
01:29through northern Canada.
01:31In addition, it weakened by more than 6%.
01:34Even more shocking, according to the geological archives,
01:38there were periods of several centuries and millennia
01:41during which the magnetic field of our planet was very weak or totally absent.
01:45But we will come back to these tragic periods later.
01:50It is easy to imagine what our planet would look like without its protective bubble while observing Mars.
01:56The red planet lost its global magnetic field a long time ago.
02:00And when this field disappeared, most of Mars' atmosphere also became volatile.
02:06In May 2024, the planet was hit by a powerful solar particle bombardment.
02:11This phenomenon disrupted the operation of the Mars-Odyssey probe
02:15and led to an increase in radiation levels on the surface of the red planet.
02:19They were 30 times higher than what a person receives during a thorax x-ray.
02:25The upper atmosphere of the Sun constantly emits a flux changing electrons and protons, the solar wind.
02:32At the same time, the surface of the star produces energy bubbles,
02:35mainly made up of protons, during events involving solar particles.
02:40These energy bubbles are linked to solar eruptions,
02:43extremely powerful explosions of electromagnetic radiation that can last from a few minutes to a few hours.
02:49Protons are much heavier than electrons and carry more energy.
02:53This is why they can reach the lower levels of the Earth's atmosphere
02:57and activate the gas molecules present in the air.
03:00These activated molecules emit invisible x-rays to the naked eye.
03:05Tens and hundreds of events of relatively weak solar particles occur during each solar cycle.
03:13Let's talk a little about these cycles.
03:15From a distance, the Sun seems calm and stable.
03:19But if you zoom in, you will see that its surface is constantly boiling and moving.
03:25It is constantly transforming,
03:27from a uniform ocean of fire to a chaos of deformed plasmas,
03:30and vice versa, according to a continuous cycle.
03:33Every 11 years or so, the magnetic field of our star literally gets mixed up.
03:38Imagine a ball made of tight elastic bands,
03:41and you will have an idea of what it looks like.
03:44And then, at some point, the field breaks and turns completely,
03:48transforming the North Pole into the South Pole.
03:52Just before this event, the Sun accelerates its activity.
03:56It starts to spit out gigantic balls of inflamed plasma,
03:59emitting powerful radiation flows,
04:01and releases spots the size of a planet to its surface.
04:05This period is called the Solar Maximum.
04:08It is a rather dangerous period for the Earth,
04:11because it is then regularly hit by solar storms.
04:14These storms can disrupt communications and damage electrical infrastructure.
04:20Worse still, solar storms can harm astronauts working in space
04:25and even crush satellites on the planet.
04:28When the cycle is over,
04:30they fade away to leave room for the Solar Minimum,
04:33and then a new cycle begins.
04:36Let's go back to our solar particle events.
04:39Researchers have found extremely powerful traces of this throughout the history of the Earth.
04:45Some of these events were thousands of times more powerful
04:48than anything our modern instruments have ever recorded.
04:52These extreme solar events occur every few millennia.
04:56The most recent is around the year 993 of our era.
05:02Beyond their immediate effect,
05:04solar particle events can trigger a chain of chemical reactions in the high atmosphere.
05:10These processes often lead to a decrease in ozone,
05:14which is not a good thing.
05:16Ozone absorbs UV rays that can damage not only our vision,
05:20but also the DNA of all living beings.
05:24In addition, changing the amount of ozone in the atmosphere can have an impact on the climate.
05:29In a recent study,
05:31researchers used large computer models
05:34to examine how extreme solar particle events affect the Earth.
05:38They discovered that if a proton bomb hits us
05:41at a time when the magnetic field of our planet is very weak,
05:45the damage caused to ozone can last six years.
05:48In addition, the level of UV radiation can increase by 25%,
05:53which increases the damage caused by solar energy by about 50%.
05:59Apparently, this spectacular combination of a weak magnetic field
06:03and a proton eruption occurs quite often.
06:07Some researchers think that this could even explain some mysterious events
06:11that occurred in the past of our planet.
06:14For example, the most recent period of weak magnetic field
06:18began 42,000 years ago and lasted about 1,000 years.
06:23This period led to a temporal inversion of the north and south poles.
06:27Several major events of evolution occurred during this period.
06:31For example, the last Neanderthals disappeared in Europe
06:35and the marsupial megafauna went extinct in Australia.
06:39Yes, unfortunately, we will no longer see wombats or giant kangaroos.
06:44Another event related to evolution, even more important,
06:48could also have been associated with the geomagnetic field of the Earth.
06:52Multicellular animals appeared at the end of the Ediacarian period,
06:56which began about 635 million years ago.
07:00This appearance took place after a period of 26 million years,
07:03during which the magnetic field was extremely weak, even non-existent.
07:08The rapid evolution of different groups of animals during the Cambrian explosion
07:12about 539 million years ago
07:15could also have been linked to high levels of UV and geomagnetism.
07:20The simultaneous evolution of hard and hard-shelled shells
07:23in many non-related groups
07:25could be the result of the need to detect UV rays and protect against them.
07:30A complete inversion of the magnetic poles of the Earth
07:33could have a serious impact on the climate of our planet.
07:36Fortunately, such revolutions do not occur overnight.
07:41The process extends over thousands of years.
07:43In addition, even if the magnetic field weakens during an inversion of the poles,
07:47it does not disappear completely.
07:49This is why the magnetosphere continues to protect the planet
07:52against cosmic rays and charged solar particles,
07:56even if a certain amount of particular radiation reaches the surface of the Earth.
08:00The magnetic fields of our planet are generated by electric charges in motion.
08:05If a material allows these charges to move easily,
08:08it is called a conductor.
08:10Metal is an excellent conductor
08:12and we often use it to transfer electric currents from one place to another.
08:17In this case, the electric current is made up of negative charges
08:21called electrons that move in the metal.
08:23The current is what generates a magnetic field.
08:26The outer core of the Earth is made up of iron and liquid nickel.
08:30In other words, there are layers and layers of conductive materials inside our planet.
08:35Charging currents move constantly in the core
08:39and liquid metal moves there and also circulates there, generating the magnetic field.
08:44This magnetic field then forms like a bubble around the planet.
08:48This is the magnetosphere, located above the upper part of the atmosphere.
08:53This layer protects us by deflecting cosmic high-energy radiation
08:58which, without it, would be extremely dangerous for all forms of life on Earth.
09:03The magnetosphere also interacts with the ionosphere.
09:07This layer of the atmosphere of our planet contains a large amount of free ions and electrons
09:12and is able to reflect radio waves.
09:15The interaction between these two layers and the magnetized solar winds
09:18is what scientists call the space weather.
09:22But the solar wind is generally moderate and time remains at a constant pace.