Sun, Solar Missions & Solar Phenomenon

Context: This topic is important for UPSE Prelims and Mains GS Paper3.

Aurora

• An aurora also known as the polar lights or aurora Polaris, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals or dynamic flickers covering the entire sky.
• Auroras are the result of disturbances in the magnetosphere caused by solar wind. These disturbances alter the trajectories of charged particles in the magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere (thermosphere/exosphere).
• The resulting ionization and excitation of atmospheric constituents emit light of varying colour and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating particles.
• Most of the planets in the Solar System, some natural satellites, brown dwarfs, and even comets also host auroras.

Aurora borealis

• The northern lights, or the aurora borealis, are the beautiful dancing waves of light that have captivated people for millennia. But for all its beauty, this spectacular light show is a rather violent event.
• Energized particles from the sun slam into Earth's upper atmosphere at speeds of up to 45 million mph (72 million km/h), but our planet's magnetic field protects us from the onslaught.
• As Earth's magnetic field redirects the particles toward the North Pole, the dramatic process transforms into a cinematic atmospheric phenomenon that dazzles and fascinates scientists and skywatchers alike.
• Though it was Italian astronomer Galileo Galilei who coined the name "aurora borealis" in 1619 — after the Roman goddess of dawn, Aurora, and the Greek god of the north wind, Boreas — the earliest suspected record of the northern lights is in a 30,000-year-old cave painting in France.

Aurora australis

• Aurora australis (also known as the southern lights, and southern polar lights) is the southern hemisphere counterpart to the aurora borealis. In the sky, an aurora australis takes the shape of a curtain of light, or a sheet, or a diffuse glow; it most often is green, sometimes red, and occasionally other colors too.
• Like its northern sibling, the aurora australis is strongest in an oval centered on the south magnetic pole. This is because they are the result of collisions between energetic electrons (sometimes also protons) and atoms and molecules in the upper atmosphere … and the electrons get their high energies by being accelerated by solar wind magnetic fields and the Earth’s magnetic field (the motions are complicated, but essentially the electrons spiral around the Earth’s magnetic field lines and ‘touch down’ near to where those lines become vertical).
• So by far the best place to see aurorae in the southern hemisphere is Antarctica ,at night. When the solar cycle is near its maximum, aurora australis are sometimes visible in New Zealand (especially the South Island), southern Australia (especially Tasmania), and southern Chile and Argentina (sometimes in South Africa too).

Aditya-L1 Mission

The Indian Space Research Organisation (ISRO) is preparing for its first scientific expedition to study the Sun, Aditya-L1. It would be placed into a point in space known as the L1 Lagrange point.

Aditya L1 will be ISRO’s 2^nd space-based astronomy mission after AstroSat, which was launched in 2015.

Aditya 1 was renamed as Aditya-L1. The Aditya 1 was meant to observe only the solar corona.

AstroSat

• AstroSat, was launched in September, 2015, by PSLV-C30 from Sriharikota (Andhra Pradesh).
• It is the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, optical and UV spectral bands simultaneously.

Launch Vehicle:

Aditya L1 will be launched using the Polar Satellite Launch Vehicle (PSLV) XL with 7 payloads (instruments) on board.

Objective:

Aditya L1 will study the Sun’s corona (Visible and Near infrared rays), Sun's photosphere (soft and hard X-ray), chromosphere (Ultra Violet ), solar emissions, solar winds and flares, and Coronal Mass Ejections (CMEs), and will carry out round-the-clock imaging of the Sun.

Challenges:

1. The distance of the Sun from Earth ( approximately 15 crore kms on average, compared to the only 3.84 lakh kms to the Moon).This huge distance poses a scientific challenge.
2. Due to the risks involved, payloads in earlier ISRO missions have largely remained stationary in space; however, Aditya L1 will have some moving components which increases the risks of collision.
3. Other issues are the super-hot temperatures and radiation in the solar atmosphere. However, Aditya L1 will stay much farther away, and the heat is not expected to be a major concern for the instruments on board.

Lagrange Point 1

• Lagrange Points, named after Italian-French mathematician Josephy-Louis Lagrange, are positions in space where the gravitational forces of a two-body system (like the Sun and the Earth) produce enhanced regions of attraction and repulsion.
• The L1 point is about 1.5 million km from Earth, or about 1/100th of the way to the Sun.
• L1 refers to Lagrangian/Lagrange Point 1, one of 5 points in the orbital plane of the Earth-Sun system.
• These can be used by spacecraft to reduce fuel consumption needed to remain in position.
• A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) has the major advantage of continuously viewing the Sun without any occultation/ eclipses.
• The L1 point is home to the Solar and Heliospheric Observatory Satellite (SOHO), an international collaboration project of National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA).

Sun’s Corona

• Corona is a luminous envelope of plasma that surrounds the Sun and other celestial bodies.
• It is extended to millions of kilometres into space and is commonly seen during a total solar eclipse.
• The corona of the Sun is much hotter than its visible surface.
• The intense temperature of the Sun's corona is due to the presence of highly ionized ions which give it a spectral feature.

Solar Winds and Flares

• The solar wind is a continuous stream of charged particles that flows out of the Sun in all directions.
• The strength of the solar wind varies depending on the activity on the surface of the Sun.
• The Earth is mostly protected from the solar wind by its strong magnetic field.
• However, some types of activity, like solar flares, can cause high energy particles to emit from the Sun which can be dangerous to astronauts and can cause damage to satellites orbiting Earth.

Coronal Mass Ejection

• A Coronal Mass Ejection (CME) is a significant release of plasma and accompanying magnetic field from the solar corona.
• They often follow solar flares and are normally present during a solar prominence eruption.
• Prominences are clouds of incandescent, ionized gas ejected from the Sun's surface.
• The plasma is released into the solar wind, and can be observed in coronagraph imagery.
• An ARIES team has recently developed an algorithm to study the accelerating solar eruptions in the lower corona called CMEs Identification in Inner Solar Corona (CIISCO).

Other Missions to the Sun

• Japan’s Solar-C EUVST: The EUVST (Extreme Ultraviolet High-Throughput Spectroscopic Telescope Epsilon) would be studying the solar wind released by the solar atmosphere, as well as studying how this atmosphere drives solar material eruption.
• NASA’s EZEI Mission: The EZEI (Electrojet Zeeman Imaging Explorer) Mission would study the atmosphere of the earth and electric currents in it, which link the aurora to the magnetosphere.
• NASA’s Parker Solar Probe’s aim is to trace how energy and heat move through the Sun’s corona and to study the source of the solar wind’s acceleration.

It is part of NASA’s ‘Living With a Star’ programme that explores different aspects of the Sun-Earth system.

• The earlier Helios 2 solar probe, a joint venture between NASA and space agency of erstwhile West Germany, went within 43 million km of the Sun’s surface in 1976.

ARIES-

• ARIES facility (Aryabhata Research Institute for Observational Sciences) will host the support centre for Aditya-L1 mission, which is due to be launched next year (2022).
• ARIES is an autonomous institute under the Department of Science & Technology and is located in Nainital (Uttarakhand).

Aditya-L1 Support Centre (ASC):

• The main aim of this centre is to let every researcher in India perform analysis over scientific data obtained from Aditya-L1. It will expand the visibility of Aditya-L1 beyond India at the international level.
• It will host a compendium of the location and duration of different features on the solar surface such as coronal holes, prominences, flares, CMEs and sunspots.
• Continuous monitoring of the location and duration of these features will help in monitoring the Earth directed CMEs and thereby, the space weather.

Editorial-The Sun lights up aurorae in high-latitude countries

Kolkata-based researchers had predicted this ‘Solar Deepavali’ using a home-grown model and data from NASA’s observations

A solar flare that occurred on the Sun triggered a magnetic storm which scientists from Center of Excellence in Space Sciences India (CESSI), in Indian Institutes for Science Education and Research, Kolkata, had predicted will arrive at the Earth in the early hours of November 4, and they said 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.

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 (CME) shock front, according to Dibyendu Nandi of CESSI Kolkata whose team predicted the event.
• “This happened at 1.00 AM IST. We will know whether this is the CME flux based on its evolution as it passes through. These observations are taken at Lagrange Point L1,” .
• Dipankar Banerjee, a solar physicist and Director of Aryabhata Research Institute of Observational Sciences (ARIES) based in Nainital, who was not involved in this work, said about the prediction, “This is quite promising. It appears their predictions are matching the observations.”

Sunspots seed storms

• 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.
• The energy, radiation and high-energy particles emitted by the flares can affect Earth-bound objects and life on Earth – it can affect the electronics within satellites and affect astronauts. Very powerful Earth-directed coronal mass ejections can cause 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 last time a major blackout due to a coronal mass ejection was recorded was in 1989 – a powerful geomagnetic storm that took down the North American power grid, plunging large parts of Canada into darkness and triggering spectacular aurorae beyond the polar regions.

Predicting solar storms

• The process of prediction takes place in two steps: First the researchers analyse the possibility of a strong solar flare from an active region – that is, clusters of sunspots – using a machine learning algorithm which has been developed in CESSI, IISER Kolkata.
• The second step is 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. There is an associated flare, and its position on the Sun is used to extract the location of origin of the CME.
• The location of the source of the CME and the velocity are used as inputs by the group in a publicly available model widely called the Drag Based Ensemble Model to calculate the CME arrival times and speed.
• “This latter step has uncertainties as the physics of CME propagation is quite complex, but this is treated in a simplified manner in this model,” explains prof. Nandi. “When ISRO’s Aditya-L1 satellite is launched, we would be receiving similar data on solar storms from this observatory,” he adds.
• Some have been tweeting pictures of the aurorae seen in places such as Alberta in Canada, and Alaska, to name just a few.