The Aditya-L1 mission follows the space weather enigma

On a cold winter’s night on March 13, 1989, a power plant in Quebec, Canada, went down without warning, plunging the province into darkness. The subway in the city of Montreal has come to a halt and the work of the airport has been disrupted. In the neighboring southern United States, the night was lit up with beautiful aurorae as far south as Texas, which is unaccustomed to seeing such displays. Several sensors on the Discovery spacecraft began to misbehave. Radio Free Europe’s transmission over Russia went silent, prompting fears of a jammed connection.

More than three decades later, in the first week of February 2022, almost the entire batch of SpaceX Starlink communication satellites unexpectedly fell from their orbit, as if sunk by a storm.

Despite the diversity of events on all continents, they all have one cause: bad weather in space.

Sun, meet Aditya

On September 2 this year, the Indian Space Research Organization (ISRO) launched the Aditya-L1 satellite, the first space mission to observe solar activity. After hovering a few times in increasingly distant orbits, the spacecraft will be boosted to the Lagrange L1 region – a strategic point in space about 1.5 million kilometers from Earth. From here, the spacecraft can keep looking at the sun and monitor the changing environment, or space weather, before Earth hears about it – giving us tens of minutes of early warning.

The path Aditya-L1 will take to L1. | Photo credit: ISRO

The sun is a huge ball of burning plasma. Energy is generated by nuclear fusion at its core, where temperatures reach 15 million degrees Celsius and a density more than 20 times that of iron. From the center to the surface of the sun, the temperature drops and energy flows outward. Inside the sun, the temperature is high enough that atoms disintegrate into negatively charged electrons and positively charged ions – a state of matter called plasma. Beneath the surface of the sun is a convection zone, where the warm liquid rises and spreads its energy as sunlight reaches the surface. The light from the sun that reaches us sustains life and drives the processes that control the earth’s climate.

After the solar plasma releases its energy from the Earth’s surface, it cools and sinks back down, similar to a cyclonic flow in the Earth’s atmosphere. This swirling motion of the plasma inside the sun creates large electric currents and, as a result, strong magnetic fields. This process, known assolar dynamo, produces earth-sized dark spots on the sun’s surface known as sunspots, and magnetism that emanates as large vents that pierce the star’s atmosphere, the corona.

A storm in space

While the visible part of the sun, or photosphere, has a temperature of about 6,000 degrees Celsius, the temperature in the corner of the sun rises to a million degrees. How does it get so hot – in clear contradiction to the laws of thermodynamics, which state that heat energy can only flow from a higher temperature to a lower temperature?

We know that other novel processes, such as the currents circulating in those large coronal magnetic fields, superheated plasma jets rising from the surface into the coronal layer, and a process known as magnetic reconnection, are at the heart of coronal heating. The hot magnetic corona of the sun is also responsible for the supersonic outflow of plasma air that washes all the planets in the solar system and creates the background atmosphere of the atmosphere. Sometimes that environment can be violently disrupted.

The PSLV C57 launch vehicle in its XL configuration inside the Vehicle Assembly Building, prior to launch. | Photo credit: ISRO

The magnetic poles rotating in the sun’s corona are constantly being stirred by the turbulent plasma flowing below the surface, where they are embedded. These loops, strengthened by the serpentine motion of the plasma, maintain large currents of electricity, and sometimes, in their frenzied circuit, they cross paths. When the conditions are right, this causes a magnetic coupling event that destroys the loops. The magnetic energy they emit is bound to create the most violent events we see in our star: solar flares, and the energy output can exceed 100 billion nuclear bombs.

The energy from that solar storm further heats the sun’s atmosphere, producing intense X-ray radiation and accelerating charged particles to a tiny fraction of the speed of light. The most powerful events can throw material from the coronal magnetic plasma into outer space at a speed exceeding several million kilometers per hour, which causes a coronal mass ejection – a storm that, when viewed from Earth, seriously disrupts the environment of our space.

New infrastructure dependencies

Severe weather can produce geomagnetic storms that create beautiful aurorae on the one hand and cause power grid failures at high altitudes, disrupt communications and GPS navigation networks, affect air traffic on polar paths, and jam radar signals. They can fry a satellite’s fragile electronics and sometimes cause catastrophic orbital decay, such as the loss of the Starlink satellites in 2022.

Aurorae are the product of disturbances in the Earth’s magnetic field due to the solar wind. | Photo Credit: The Hindu

With our increasing reliance on space-based infrastructure, a dangerous solar storm could lead to a trillion dollar economic impact. However, we still don’t have a way to accurately predict space weather.

ISRO’s Aditya-L1 mission will explore how magnetism results in changes in the sun’s ultraviolet radiation, which plays an important role in controlling the Earth’s atmosphere and climate change. It will look at the flow of energy in the sun’s outer atmosphere to test competing theories about the heating of the sun’s corona. By analyzing X-ray radiation, it will be necessary to understand how powerful solar storms are born. Aditya-L1 will also track the initial movement of magnetic storms near the Sun and monitor the local environment in the vicinity of the Lagrange point L1, the environment that eventually affects Earth.

National cooperation

Aditya-L1 was originally intended as a basic science research target. In 2020, ISRO formed a committee to examine how mission data can be used to extract relevant information for space weather monitoring and forecasting. I chaired that committee; wrote a set of recommendations specific to the board’s intelligence on space weather warnings and to support data analysis and predictive modeling initiatives to create more space climate information.

More than 60 scientists from about 20 academic institutions participated in the mission, and many scientists, engineers, and students contributed to the mission – reflecting the collaborative national effort that produced Aditya-L1.

If the mission is successful, it will be a tangible proof of India’s investment in space science research, which can on one hand promote basic research about our cosmos and on the other hand generate solid knowledge of human importance. Today, we wake up about the weather forecast. The day is not far when we will wake up location weather forecast. Ever since we fired our first rocket off the distant coast of Thumba the people of India have been very excited about space.

Dr. Dibyendu Nandi is a professor of physics and head of the Center of Excellence for Space Sciences India at IISER Kolkata. He is an expert in understanding and predicting space weather.

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