Alfven Waves Drive Coronal Heat + Solar Wind

In summary, recent satellite observations have revealed that Alfven waves, which were first observed in 2007, are much stronger than previously thought. These waves, which carry energy from the Sun's surface into its corona, are powerful enough to heat the corona to temperatures of over a million degrees and drive the solar wind. This discovery brings us closer to understanding the mystery of the Sun's extreme heat and its impact on Earth. The next step is to study how these waves lose their energy, which could lead to a better understanding of the Sun's 11-year sunspot cycle.
  • #1
Dotini
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One of the all-time great science mysteries is now a step closer to explanation. The surface of the sun, known as the photosphere, can reach temperatures of 5,000 degrees. To many it would seem logical that the temperature would lower further away from the sun. But, the outer atmosphere, known as the corona, has been shown to reach temperatures of over a million degrees.

http://www.physorg.com/news/2011-07-power-sun-intense.html
The study uses satellite observations to reveal that magnetic oscillations carrying energy from the Sun's surface into its corona are far more vigorous than previously thought. These waves are energetic enough to heat the corona and drive the solar wind, a stream of charged particles ejected from the Sun that affects the entire solar system.

Alfven waves were directly observed for the first time in 2007. Scientists recognized them as a mechanism for transporting energy upward along the Sun's magnetic field into the corona. But the 2007 observations showed amplitudes on the order of about 1,600 feet (0.5 kilometers) per second, far too small to heat the corona to its high levels or to drive the solar wind. http://www.sciencemag.org/content/317/5842/1192.abstract

General info on Alfven waves: http://en.wikipedia.org/wiki/Alfvén_wave

Respectfully submitted,
Steve
 
Astronomy news on Phys.org
  • #2
Interesting!
 
  • #3
Drakkith said:
Interesting!

Yes, interesting from an intellectual point of, but possibly important, too.

Not only has this question been at the forefront of astrophysics for 50 years, but now Dr Richard Fisher, the director of NASA’s Heliophysics division, warned in an interview of a once-in-a-lifetime ‘space storm’ after the sun wakes ‘from a deep slumber’ sometime around 2013, causing ‘20 times more economic damage than Hurricane Katrina’.

http://www.sciencedaily.com/releases/2011/07/110727131404.htm
http://www.thehindu.com/sci-tech/article2296011.ece

"Alfven waves were directly observed for the first time in 2007. Scientists recognized them as a mechanism for transporting energy upward along the Sun's magnetic field into the corona. But the 2007 observations showed amplitudes on the order of about 1,600 feet (0.5 kilometers) per second, far too small to heat the corona to its high levels or to drive the solar wind.

The new satellite observations used in the current study reveal Alfven waves that are over a hundred times stronger than previously measured, with amplitudes on the order of 12 miles (20 km) per second -- enough to heat the Sun's outer atmosphere to millions of degrees and drive the solar wind. The waves are easily seen in high-resolution images of the outer atmosphere as they cause high-speed jets of hot material, called spicules, to sway.

Now that the real power of the waves has been revealed in the corona, the next step in unraveling the mystery of its extreme heat is to study how the waves lose their energy, which is transferred to plasma. To do that, scientists will need to develop computer models that are fine enough in detail to capture how the jets and waves work together to power the atmosphere. By studying the Sun's underlying physics with these tools, scientists could better understand the Sun's 11-year sunspot cycle and its impacts on Earth."


Respectfully submitted,
Steve
 

1. What are Alfven Waves and how do they drive coronal heat and solar wind?

Alfven waves are a type of electromagnetic wave that can propagate through plasma, such as the solar corona. These waves are caused by the interaction between charged particles and the magnetic field in the corona. As they travel through the plasma, they transfer energy and momentum, which can heat up the corona and accelerate the solar wind.

2. How do Alfven Waves impact the temperature of the corona?

Alfven waves can heat up the corona through a process called wave-particle interactions. As the waves travel through the plasma, they can collide with charged particles, transferring energy and increasing their temperature. This process is known as Joule heating and is one of the main drivers of coronal heating.

3. What role do Alfven Waves play in the generation of solar wind?

Alfven waves are thought to be one of the main mechanisms for accelerating the solar wind. As the waves transfer energy and momentum to the plasma, they can push it outwards, creating the high-speed solar wind streams that flow from the Sun. This process is known as wave-driven wind acceleration.

4. How do scientists study Alfven Waves and their effects on the Sun?

Scientists use a variety of instruments, such as radio telescopes and spacecraft, to study Alfven waves and their impact on the Sun. These instruments can measure properties of the waves, such as their frequency and amplitude, as well as observe the changes they cause in the corona and solar wind.

5. What are the potential implications of understanding Alfven Waves and their role in solar activity?

Understanding Alfven waves and their effects on the Sun can help scientists better predict solar activity, such as solar flares and coronal mass ejections. This knowledge can also aid in the development of more accurate space weather forecasting, which is crucial for protecting satellites, astronauts, and Earth's power grids from the effects of solar storms.

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