The Sun

à 24 avril

The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona.This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV.The composition of the solar wind plasma also includes a mixture of materials found in the solar plasma: trace amounts of heavy ions and atomic nuclei C, N, O, Ne, Mg, SiThis week we're celebrating the launch of a new series on Energy.gov: How Energy Works.Join us today on Twitter at 2 p.m. ET for our How Energy Works live Q&A answering everything you want to know about microgrids.The solar wind is a fast-moving part of the Sun's outer atmosphere. The solar corona, with a temperature greater than one million degrees C, is so hot that the Sun's gravity can't hold it down. It flows away in all directions traveling 400 to 800 km/s. Every planet in the solar system is immersed in this gusty breeze of charged particles.The biggest problem wind production faces is the cost of transporting the energy generated, as the windiest areas are usually remote. In addition, like solar, wind is an intermittent power source, so you can't count on turbines to provide energy around the clock. Also, wind is less ideal for residential use for two reasons. One, turbines makeSolar energy is generally collected with solar panels while wind energy is generated when the wind turns wind mill like structures that in turn, turn turbines that generate electricity.

How Microgrids Work | Department of Energy

What is solar wind? The solar wind is a stream of energized, charged particles, primarily electrons and protons, flowing outward from the Sun, through the solar system at speeds as high as 900 km/s and at a temperature of 1 million degrees (Celsius). It is made of plasma.Solar and wind power use has grown at a rapid rate over the past decade or so, but as of 2018 those sources accounted for less than 4% of all the energy used in the U.S. (That's the most recent full year for which data is available.) As far back as we have data, most of the energy used in the U.S. has come from coal, oil and natural gas.Wind turbines convert wind energy into electricity. Biomass was the source of about 1.4% of total U.S. electricity generation in 2020. Biomass is burned directly in steam-electric power plants, or it can be converted to a gas that can be burned in steam generators, gas turbines, or internal combustion engine generators.Solar wind is a constant stream of plasma and particles emanating from the sun. Fortunately, Earth's magnetic field protects us from its harmful effects.

The Solar Wind at Mars | Science Mission Directorate

Solar wind is an ionized gas made up primarily of protons and electrons with minor ions in amounts similar to those in the corona. The electrons and ions are very tightly bound to lines of magnetic flux, again like the coronal plasma in streamers. However, the magnetic field in the solar wind is relatively weak and thus is carried along by the solar wind.The Sun's outer atmosphere, the super-hot corona, is the source of the solar wind, a steady outflow of charged particles from the Sun.These particles have gained enough energy to fill the heliosphere, a region of space that extends well past the orbit of Pluto.In fact, one wind turbine can generate the same amount of electricity per kWh as about 48,704 solar panels. But the enormous power-generating capacity of wind turbines doesn't make wind energy a clear winner. Wind turbines are an eyesore. They take up a lot of space. They can hurt wildlife.Solar radiation, often called the solar resource or just sunlight, is a general term for the electromagnetic radiation emitted by the sun.Solar radiation can be captured and turned into useful forms of energy, such as heat and electricity, using a variety of technologies.Start studying Solar Wind. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

The solar wind streams plasma and particles from the sun out into space. Though the wind is constant, its properties aren't. What causes this stream, and how does it affect the Earth?

Windy star

The corona, the sun's outer layer, reaches temperatures of up to 2 million degrees Fahrenheit (1.1 million degrees Celsius). At this level, the sun's gravity can't hold on to the rapidly moving particles, and they stream away from the star.

The sun's activity shifts over the course of its 11-year cycle, with sun spot numbers, radiation levels, and ejected material changing over time. These alterations affect the properties of the solar wind, including its magnetic field, velocity, temperature and density. The wind also differs based on where on the sun it comes from and how quickly that portion is rotating.

The velocity of the solar wind is higher over coronal holes, reaching speeds of up to 500 miles (800 kilometers) per second. The temperature and density over coronal holesare low, and the magnetic field is weak, so the field lines are open to space. These holes occur at the poles and low latitudes, reaching their largest when activity on the sun is at its minimum. Temperatures in the fast wind can reach up to 1 million F (800,000 C).

At the coronal streamer belt around the equator, the solar wind travels more slowly, at around 200 miles (300 km) per second. Temperatures in the slow wind reach up to 2.9 million F (1.6 million C).

The sun and its atmosphere are made up of plasma, a mix of positively and negatively charged particles at extremely high temperatures. But as the material leaves the sun, carried by solar wind, it becomes more gas-like.

"As you go farther from the sun, the magnetic field strength drops faster than the pressure of the material does," Craig DeForest, a solar physicist at the Southwest Research Institute (SwRI) in Boulder, Colorado, said in a statement. "Eventually, the material starts to act more like a gas, and less like a magnetically structured plasma."

Affecting Earth

As the wind travels off the sun, it carries charged particles and magnetic clouds. Emitted in all directions, some of the solar wind is constantly buffeting our planet, with interesting effects.

If the material carried by the solar wind reached a planet's surface, its radiation would do severe damage to any life that might exist. Earth's magnetic field serves as a shield, redirecting the material around the planet so that it streams beyond it. The force of the wind stretches out the magnetic field so that it is smooshed inward on the sun-side and stretched out on the night side.

Sometimes the sun spits out large bursts of plasma known as coronal mass ejections (CMEs), or solar storms. More common during the active period of the cycle known as the solar maximum, CMEs have a stronger effect than the standard solar wind. [Photos: Stunning Photos of Solar Flares & Solar Storms]

"Solar ejections are the most powerful drivers of the sun-Earth connection," NASA says on its website for the Solar Terrestrial Relations Observatory (STEREO). "Despite their importance, scientists don't fully understand the origin and evolution of CMEs, nor their structure or extent in interplanetary space." The STEREO mission hopes to change that.

When the solar wind carries CMEs and other powerful bursts of radiation into a planet's magnetic field, it can cause the magnetic field on the back side to press together, a process known as magnetic reconnection. Charged particles then stream back toward the planet's magnetic poles, causing beautiful displays known as the aurora borealisin the upper atmosphere. [Photos: Amazing Auroras of 2012]

Though some bodies are shielded by a magnetic field, others lack their protection. Earth's moon has nothing to protect it, so takes the full brunt. Mercury, the closest planet, has a magnetic field that shields it from the regular standard wind, but it takes the full force of more powerful outbursts such as CMEs.

When the high- and low-speed streams interact with one another, they create dense regions known as co-rotating interaction regions (CIRs) that trigger geomagnetic storms when they interact with Earth's atmosphere.

The solar wind and the charged particles it carries can affect Earth's satellites and Global Positioning Systems (GPS). Powerful bursts can damage satellites, or can push GPS signals to be off by tens of meters.

The solar wind ruffles all of the planets in the solar system. NASA's New Horizons mission continued to detect it as it traveled between Uranus and Pluto.

"Speed and density average together as the solar wind moves out," Heather Elliott, a space scientist at SwRI in San Antonio, Texas, said in a statement. "But the wind is still being heated by compression as it travels, so you can see evidence of the sun's rotation pattern in the temperature even in the outer solar system.

Studying the solar wind

We've known about the solar wind since the 1950s, but despite its extensive effects on Earth and on astronauts, scientists still don't know how the it evolves. Several missions over the last few decades have sought to explain this mystery.

Launched on Oct. 6, 1990, NASA's Ulysses mission studied the sun at various latitudes. It measured the various properties of the solar wind over the course of more than a dozen years.

The Advanced Composition Explorer (ACE) satellite orbits at one of the special points between Earth and the sun known as the Lagrange point. In this area, gravity from the sun and the planet pull equally, keeping the satellite in a stable orbit. Launched in 1997, ACE measures the solar wind and provides real-time measurements of the constant flow of particles.

NASA's twin spacecraft, STEREO-A and STEREO-B study the sun's edge to see how the solar wind is born. Launched in October 2006, STEREO has provided "a unique and revolutionary view of the sun-Earth system," according to NASA.

A new mission hopes to shine light on the sun and its solar wind. NASA's Parker Solar Probe, planned to launch in the summer of 2018, aims to "touch the sun." After several years of closely orbiting the star, the probe will dip into the corona for the first time, using a combination of imaging and measurements to revolutionize understanding of the corona and increase understanding of the origin and evolution of the solar wind.

"Parker Solar Probe is going to answer questions about solar physics that we've puzzled over for more than six decades," Parker Solar Probe Project scientist Nicola Fox of the Johns Hopkins University Applied Physics Laboratory, said in a statement. "It's a spacecraft loaded with technological breakthroughs that will solve many of the largest mysteries about our star, including finding out why the sun's corona is so much hotter than its surface."

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