The Sun: Composition, Structure, and Solar Cycle

• The Sun is the star of our solar system, holding Earth and other planets in orbit with its gravity.
• It's the largest object in the solar system, with a diameter of 865,000 miles (1.4 million km).
• Its influence affects Earth's weather, seasons, and climate.

Sun Composition and Structure

• The Sun is a yellow dwarf star, approximately 4.5 billion years old, and in its main sequence phase.
• It's primarily made of hydrogen and helium gases, undergoing nuclear fusion of hydrogen into helium at its core, producing heat and light.
• Energy moves outward through the radiative and convective zones.
• The photosphere is the visible surface and lower atmosphere
• The chromosphere forms the middle atmosphere.
• The corona is the Sun’s outermost atmosphere.

Solar Cycle

• The Sun experiences a magnetic activity pattern known as the solar cycle.
• The solar cycle includes an active period called "solar maximum" and a less active period called "solar minimum."
• Sunspots, which are darker, cooler spots, increase during solar maximum due to heightened magnetic activity.
• The number of sunspots indicates the Sun's level of activity.
• The solar cycle, driven by the Sun’s magnetic polarity flipping, lasts about 11 years.
• The Sun's magnetic poles flip every 11 years
• The full magnetic cycle, where the poles return to their original positions, takes 22 years.

Space Weather

• Space weather includes phenomena like solar wind, solar storms, and solar flares.
• Increased solar activity can significantly impact Earth and space.

Solar Wind

• Solar wind is a stream of charged particles flowing from the Sun’s corona, extending beyond the planets' orbits.
• When solar wind interacts with Earth’s magnetic field, it creates auroras at the north and south poles.
• Earth's magnetic field protects the planet from the solar wind's charged particles.

Solar Storms, Solar Flares, and Coronal Mass Ejections

• Solar storms result from the twisting and reconnection of the Sun’s magnetic fields, releasing energy.
• Solar storms include solar flares and coronal mass ejections, occurring more often during solar maximum.
• Solar flares are intense bursts of light and energy.
• Solar flares originate near sunspots where magnetic fields are strongest.
• Coronal mass ejections are massive clouds of material ejected from the Sun, occurring independently or with solar flares.

Effects on Earth

• Earth’s atmosphere and magnetic field protect it from significant harm from solar storms.
• Strong solar storms can cause power outages and radio blackouts.
• Solar storms can disrupt GPS signals and affect satellite electronics.
• Astronauts outside the International Space Station face radiation risks during solar storms.
• NASA monitors and forecasts space weather to protect astronauts and spacecraft.
• Interactions between charged particles from solar storms and Earth’s magnetic fields can cause auroras.