Solar Flare

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    • Recently, a solar flare that occurred on the Sun triggered a magnetic storm and it arrived at the Earth in the early hours of November 4.

    About

    • Scientists had predicted that the magnitude of this storm would be such as to trigger spectacular displays of aurora (the coloured bands of light seen in the North and South poles) in the high-latitude and polar regions, just in time for the Deepavali celebrations in India. 
    • This prediction, which was based on models built by them and data from NASA’s observatories, seems to have come true, as people from several countries were tweeting pictures of aurorae.

    Effect on atmosphere

    • Judging by data from the NASA DSCOVR satellite, the scientists observed a steep jump in transverse magnetic fields, density and speeds of the plasma wind that are tell-tale signatures of the arrival of a coronal mass ejection shock front
    • These observations are taken at Lagrange Point L1.

    Sunspots and Solar Flares

    • The solar magnetic cycle that works in the deep interior of the Sun creates regions that rise to the surface and appear like dark spots. These are the sunspots
    • Solar flares are highly energetic phenomena that happen inside the sunspots. 
      • In a solar flare, the energy stored in the sun’s magnetic structures is converted into light and heat energy
      • This causes the emission of high energy x-ray radiation and highly accelerated charged particles to leave the sun’s surface. 
    • Sometimes solar flares also cause hot plasma to be ejected from the Sun, causing a solar storm, and this is called Coronal Mass Ejection (CME)
      • Coronal Mass Ejections can harbour energies exceeding that of a billion atomic bombs.
      • Very powerful Earth-directed coronal mass ejections can cause the failure of power grids and affect oil pipelines and deep-sea cables. 
      • They can also cause spectacular aurorae in the high-latitude and polar countries. 
    • The energy and radiation and high energy particles emitted by flares can affect Earth bound objects and life on Earth – it can affect the electronics within satellites and affect astronauts. 

    Image Courtesy: TH 

    Solar Storm Prediction

    • The process of prediction takes place in two steps
      • Step 1: 
        • The researchers analyse the possibility of a strong solar flare from an active region – that is, clusters of sunspots – using a machine learning algorithm that has been developed in CESSI, IISER Kolkata.
        • This algorithm needs observations of the sunspot magnetic fields, from which we extract various parameters to train the algorithm. 
      • Step 2: 
        • Estimating the time of arrival on Earth of coronal mass ejections and forecasting the geomagnetic storm. 
        • The group uses the near-Sun evolution of the coronal mass ejections through European Space Agency’s SOHO satellite and NASA’s STEREO satellite to extract their speed. 

    Image Courtesy: NASA 

    Aurora

    • An aurora is a natural phenomenon that is characterised by a display of a natural-coloured (green, red, yellow or white) light in the sky. 
    • It is a light show which is caused when electrically-charged particles from the sun collide with particles from gases such as oxygen and nitrogen present in the Earth’s atmosphere.
    • Aurora is sometimes referred to as ‘polar light’
    • It is predominantly seen in regions of high altitudes like the Arctic and Antarctic. 
    • Caused by: 
      • An aurora is caused by the streams of electrified particles (which are emitted by the sun) trapped in the magnetic field of the earth. 
      • It is produced when this magnetosphere is disturbed by the solar wind carrying the charged particles. 
    • Auroras are seen in latitudes of around 70 degrees
    • They generally occur in a band known as the ‘auroral zone’. The auroral zone is 3 to 6 degrees wide in latitude. It lies between 10 and 20 degrees from the geomagnetic poles. 
    • This is visible quite clearly during the night. 
    • Auroras can sometimes be seen at latitudes below the actual auroral zone. They can appear in various forms like streamers, patches, arcs, scattered light, diffused light etc. 
    • The brightest and the most distinctive of all forms of auroras are the ones that are curtain-like in the shape of an arc, extending in the east-west direction. This natural light effect is known as ‘Aurora Borealis in northern altitudes, while the effect in the southern latitudes is known as ‘aurora australis
    • Aurora borealis is also known as ‘Northern lights’. Similarly, aurora australis is also known as ‘Southern lights’. 
    • FACT: 
      • Auroras are not just something that happens on Earth. If a planet has an atmosphere and magnetic field, they probably have auroras. Auroras on Jupiter and Saturn have been seen.

    Source: TH