Solar Cycle

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Context: Indian Institute of Astrophysics astronomers find new method to predict amplitude of upcoming solar cycle.

What Is Space Weather?

• The term space weather refers to events beyond the Earth's atmosphere that impact upon our technology and the near-Earth space environment.

Elements of Space weather.

• Solar source: Solar Activity.
• Non solar source: Galactic Cosmic Rays (GCR).

Solar Activity

• The primary agent of Space Weather is the Sun, which even 150 million kilometres away, can influence the Earth and its environment.
• The Sun is a dynamic and complex body continuously emitting radiation, a constant stream of particles known as the solar wind, and generates a large magnetic field that extends throughout solar system (Interplanetary Magnetic Field, IMF).
• Solar activities such as Solar Flares, Coronal Mass Ejections (CMEs) events and High-speed Solar wind Streams (HSS) that create changes in magnetic fields, radiation, particle flows in space, and interaction with the magnetosphere.
• The Sun undergoes an 11-year cycle, with solar activity rising and falling.

Galactic Cosmic Rays (GCR)

• These Non-solar sources can alter space environment conditions near the Earth.
• These high energy particles originate outside of our solar system in distant galaxies and may have been travelling millions of years before they reach near Earth.

Protection from space weather

• Earth has an area of magnetic force activity, called a magnetic field, protects from the majority of the solar wind blast.
• Most of the charged particles crash into Earth’s shield and flow around it.

• The particles squish and flatten the side of the magnetic field that faces the Sun.
• Sometimes charged particles sneak past Earth’s shield. When these particles hit the atmosphere, we are treated to glowing light shows known as auroras.

Space weather impacts Earth

• Strong solar storms can cause fluctuations of electrical currents in space, directly impacting the power grid on Earth and energizing electrons and protons trapped in Earth's varying magnetic field.
• These disturbances can cause problems with radio communications, Global Navigation Satellite Systems (such as Global Positioning Systems or GPS), power grids, and satellites.
• Space Weather activity is also responsible for the aurorae that are sometimes visible over the polar regions. (Northern Lights (or Aurora Borealis),Southern Lights (Aurora Australis).

Warnings of bad space weather forecast.

• NASA and other agencies operate a collection of instruments that keep an eye on the Sun and space weather.
• NASA’s Solar and Heliospheric Observatory (SOHO) observes coronal mass ejections.
• Other spacecraft, like the Solar Dynamics Observatory (SDO) and NOAA’s Geostationary Operational Environmental Satellite (GOES) R-series, monitor the Sun and detect solar storms and changes in the solar wind.

What Is the Solar Cycle?

The solar cycle is the cycle that the Sun’s magnetic field goes through approximately every 11 years.

How it works?

• Sun is a huge ball of electrically-charged hot gas.
• This charged gas moves, generating a powerful magnetic field.
• Every 11 years or so, the Sun's magnetic field completely flips. This means that the Sun's north and south poles switch places.
• Then it takes about another 11 years for the Sun’s north and south poles to flip back again.

Effect on Solar Activity

• As the magnetic fields change, so does the amount of activity on the Sun's surface.
• The solar cycle affects activity on the surface of the Sun, such as sunspots which are caused by the Sun's magnetic fields.

Solar minimum and solar maximum activity

• The beginning of a solar cycle is a solar minimum, or when the Sun has the least sunspots.
• Over time, solar activity—and the number of sunspots—increases.
• The middle of the solar cycle is the solar maximum, or when the Sun has the most sunspots.
• As the cycle ends, it fades back to the solar minimum and then a new cycle begins.

 

Maunder Minimum One interesting aspect of solar cycles is that the sun went through a period of near zero sunspot activity from about 1645 to 1715. This period of sunspot minima is called the Maunder Minimum. The "Little Ice Age" occurred over parts of Earth during the Maunder Minimum.

Sunspots Formation Sunspots are areas where the magnetic field is about 2,500 times stronger than Earth's, much higher than anywhere else on the Sun. Because of the strong magnetic field, the magnetic pressure increases while the surrounding atmospheric pressure decreases. This in turn lowers the temperature relative to its surroundings because the concentrated magnetic field inhibits the flow of hot, new gas from the Sun's interior to the surface. Umbra and Penumbra Sunspots tend to occur in pairs that have magnetic fields pointing in opposite directions. A typical spot consists of a dark region called the umbra, surrounded by a lighter region known as the penumbra. The sunspots appear relatively dark because the surrounding surface of the Sun (the photosphere) is about 10,000 degrees F (5,538 degrees C), while the umbra is about 6,300 degrees F (3482 degrees C). Sunspots are quite large as an average size is about the same size as the Earth.

 

Other activity

• Giant eruptions on the Sun, such as solar flares and coronal mass ejections, also increase during the solar cycle.
• These eruptions send powerful bursts of energy and material into space.

Tracking of Solar Cycle

• One way to track the solar cycle is by counting the number of sunspots.
• Some cycles have maximums with lots of sunspots and activity.
• Other cycles can have very few sunspots and little activity.

Effect

• Times of maximum sunspot activity are associated with a very slight increase in the energy output from the sun.
• Ultraviolet radiation increases dramatically during high sunspot activity, which can have a large effect on the Earth's atmosphere.

Solar Flares: https://www.iasgyan.in/daily-current-affairs/solar-flares-26#:~:text=Solar%20flares%20result%20from%20the,form%20of%20heat%20and%20radiation.

Coronal Mass Ejections (CMEs): https://www.iasgyan.in/daily-current-affairs/coronal-mass-ejections-cmes

Auroras: https://www.iasgyan.in/daily-current-affairs/aurora-borealis

Sources

https://www.noaa.gov/education/resource-collections/weather-atmosphere/space-weather#:~:text=Rather%20than%20the%20more%20commonly,by%20disturbances%20from%20the%20Sun.

https://spaceplace.nasa.gov/spaceweather/en/

https://www.weather.gov/fsd/sunspots#:~:text=Sunspots%3A%20One%20interesting%20aspect%20of,the%20surrounding%20atmospheric%20pressure%20decreases.

https://scijinks.gov/space-weather-and-us/

PRACTICE QUESTION Q. What is a Solar Cycle? How do they occur? Disuses it’s impact on Earth. 150 words.