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Current Affairs

Sunspots

Date: 11 August 2020 Tags: Space

Issue

A massive Sunspot group, AR2770, was observed last week using images of the Sun’s surface from NASA’s Solar Dynamics Observatory (SDO).

 

Background

A few minor space flares have been emitted by this particular Sunspot group already, which has not caused anything major other than minor waves of ionization to ripple through Earth’s upper atmosphere.

 

Details

  • Solar flares, when powerful enough, can disrupt satellite and radio transmission, and more severe ones can cause ‘geomagnetic storms’ that can damage transformers in power grids.

  • A Sunspot is an area on the Sun that appears dark on the surface and is relatively cooler than surrounding parts. These spots are the visible markers of the Sun’s magnetic field, which forms a blanket that protects the solar system from harmful cosmic radiation.

  • On the photosphere– the outer surface of the Sun which radiates heat and light– Sunspots are the areas where the star’s magnetic field is the strongest; around 2,500 times more than the Earth’s magnetic field.

  • Most Sunspots appear in groups that have their own magnetic field, whose polarity reverses during every solar cycle, which takes around 11 years. In every such cycle, the number of Sunspots increases and decreases.

  • Because Sunspots have high magnetic pressures, the atmospheric pressure in the surrounding photosphere reduces, inhibiting the flow of hot gases from inside the Sun to the surface.

  • The temperatures of Sunspots are thousands of degrees lower than the surrounding photosphere, which has a temperature of 5,800 degrees Kelvin. Sunspots temperatures are around 3,800 degrees Kelvin.

  • Because they stop the convective flow of heat and light, Sunspots appear dark. They typically consist of a dark region called the ‘umbra’, which is surrounded by a lighter region called the ‘penumbra’.

  • At times, solar flares are accompanied by Coronal Mass Ejections (CME), large bubbles of radiation and particles emitted by the Sun that explode into space at high speed. CMEs can trigger intense light in the sky on Earth, called auroras.

  • Solar flares can have a major effect on radio communications, Global Positioning Systems (GPS) connectivity, power grids, and satellites.

  • The current solar cycle, which began in 2008, is in its ‘solar minimum’ phase, when the number of Sunspots and solar flares is at a routine low.

  • Recently, scientists have developed a new model that can successfully predict seven of the Sun’s biggest flares from the last solar cycle, out of a set of nine with the help of NASA’s Solar Dynamics Observatory.

Sunspots

Date: 08 March 2020 Tags: Space

Issue

A group of researchers from IISER Kolkata has shown that the next sunspot cycle has begun and the Sun has indeed woken.

 

Background

Sun spots are relatively cooler spots on the Sun’s surface. Their number waxes and wanes in cycles that last 11 years approximately.

 

Details

  • From our safe distance of about 148 million km, the Sun appears to be sedate and constant. However, huge solar flares and coronal mass ejections spew material from its surface into outer space.

  • They originate from sunspots, an important phenomenon that people have been following for hundreds of years.

  • Sunspots occur in pairs, with a leader and a follower. They originate deep within the Sun and become visible when they pop out.

  • Their number is not constant but shows a minimum and then rises up to a maximum and then falls again in what is called the solar cycle. So far, astronomers have documented 24 such cycles, the last one ended in 2019.

  • Following a weakening trend in activity over the last few cycles, there were predictions that the Sun would go silent into a grand minimum in activity, with the disappearance of cycles.

  • Researchers used the data from the instrument Helioseismic and Magnetic Imager aboard NASA’s space-based Solar Dynamics Observatory for their calculations.

  • Sunspot activity may be correlated with climate on earth. In the period between 1645 and 1715, sun spot activity had come to a halt on the Sun, a phenomenon referred to as the Maunder minimum.

  • This coincided with extremely cold weather globally. So sunspots may have a relevance to climate on earth. Such links are tenuous, but definitely solar activity affects space weather, which can have an impact on space-based satellites, GPS, power grids and so on.

Formation of Sunspot cycle

  • Given the high temperatures in the Sun, matter exists there in the form of plasma, where the electrons are stripped away from the nuclei.

  • The Sun is made of hot ionised plasma whose motions generate magnetic fields in the solar interior by harnessing the energy of the plasma flows. This mechanism is known as the solar dynamo mechanism.

  • Because of the nature of the solar dynamo, the part of its magnetic field that gives rise to sunspots reverses direction when it moves from one solar cycle to another.