Solar Jets

Context:

Recently, Scientists at Indian Institute of Astrophysics (IIA) have unravelled the science behind the jets of plasma on the Sun’s chromosphere.

What is Solar Jets:

• Solar jets are bursts of plasma coming off the Sun. Studying solar jets contributes to better understanding of our closest star, the Sun, and how its energy impacts conditions on Earth.
  • Solar jets, or spicules, appear as thin grass-like plasma structures that constantly shoot up from the surface and are then brought down by gravity.
• These jets rise and fall back under the influence of the Sun’s gravity, which is 20 to 30 times greater than Earth.
• Some jets are so energetic that they propel into the solar corona and beyond.
• The amount of energy and momentum that these spicules can carry is of fundamental interest in solar and plasma astrophysics.
• The four key ingredients favouring solar jets are the plasma’s fluid nature, gravity, strong quasi periodic triggers to eject the plasma and most importantly, the Sun’s powerful magnetic field giving it specific direction for ejection.
• What is sun’s chromosphere: It is the atmospheric layer just above the Sun’s visible surface.
• What is photosphere: The photosphere is the deepest layer of the Sun that we can observe directly.

Key findings

• Scientists found that the physics underlying paint jets when excited on a speaker is analogous to the solar plasma jets.
• The scientists elaborated that the plasma right below the visible solar surface (photosphere) is perpetually in a state of convection, much like boiling water in a vessel heated at the bottom.
• This is ultimately powered by the nuclear energy released in the hot-dense core.
• The convection serves almost periodic but strong kicks to the plasma in the solar chromosphere, the shallow semi-transparent layer right above the visible solar disk.
• The chromosphere is 500 times lighter than the plasma in the photosphere.
• Therefore, these strong kicks from the bottom, not unlike alligator bellowing, shoot the chromospheric plasma outward at ultrasonic speeds in the form of thin columns or spicules.

Significance

• Spicules come in all sizes and speeds. The existing consensus in the solar community has been that the physics behind the short spicules is different from that of taller and faster spicules.
• The study challenges this widespread belief to show that solar convection can by itself form all kinds of jets – short as well as tall.

What is Plasma?

• Plasma is a hot, charged gas made of positive ions and free-moving electrons that has unique properties distinct from solids, liquids and gases.
• At high temperatures, electrons are ripped from atom’s nuclei and become a plasma or an ionised state of matter.
• Plasma is also known as the fourth state of matter.

Various Solar Missions till now are as follows:

1. In between 1959 and 1968 the first satellites were launched by NASA’s Pioneers 5,6,7,8 and 9 to observe the Sun. These had made the first detailed measurements of the solar wind and the solar magnetic field and these probes were orbited the Sun at the same distance as that of Earth.
   1. Mission: To measure solar wind and solar magnetic field.
2.  NASA in 1980 launched the Solar Maximum Mission.
3. Mission: This spacecraft was designed to observe gamma rays, X-rays and UV radiation from solar flares during the time of high solar activity and solar luminosity.
4. In 1991, Japan’s Yohkoh (Sunbeam) satellite was launched.
5. Mission: To observe the solar flares at X-ray wavelengths.
6. The Solar and Heliospheric Observatory (SOHO) which was jointly built by European Space Agency and NASA, the most important solar mission launched on 2^nd December 1995.
7. Mission: It was designed to study the internal structure of the Sun, its extensive outer atmosphere and the origin of the solar wind.
8. In October 2006, The Solar Terrestrial Relations Observatory (STEREO) mission was launched by NASA.
9. Mission: To capture unseen images of Sun i.e. Stereo A and B will enable stereoscopic imaging of the Sun and solar phenomena such as coronal mass ejections, the acceleration of particles in interplanetary space, and terrestrial consequences.
10. NASA’s Interface Region Imaging Spectrograph (IRIS) spacecraft was launched in June 27, 2013.
11. Mission: To study the solar atmosphere which was placed in orbit by an Orbital Sciences Corporation Pegasus XL rocket.
12. NASA has tapped the Johns Hopkins University Applied Physics Laboratory (APL) to develop the ambitious Solar Probe Plus mission. Mission: To study the streams of charged particles the Sun hurts into space from inside the Sun’s corona-its outer atmosphere from where the solar wind is produced and the material it carries into our solar system. It will be launched on 31 July, 2018.
13. Aditya-L1 is the first Indian mission to study the Sun.
14. Mission: Its main objective is to study the solar dynamics in the chromosphere and corona with a suite of instruments including a coronagraph and a UV imager. The orbit around L1 provides continuous solar observations without any eclipse/occultation and is an excellent outpost outside Earth’s magnetic field to make in-situ measurements of incoming charged particles.

Source: PIB

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