The Sun

The Sun is 150 million kilometers (93 million miles) away from the Earth (this distance varies slightly throughout the year, because the Earth’s orbit is an ellipse and not a perfect circle). It’s mostly made up of hydrogen (about 92.1% of the number of atoms, 75% of the mass). Helium can also be found in the Sun (7.8% of the number of atoms and 25% of the mass). The other 0.1% is made up of heavier elements, mainly carbon, nitrogen, oxygen, neon, magnesium, silicon and iron.

The Sun is neither a solid nor a gas but is actually plasma. This plasma is tenuous and gaseous near the surface, but gets denser down towards the Sun’s fusion core.

The Sun has a complicated and changing magnetic field, which forms things like sunspots and active regions. The magnetic field sometimes changes explosively, spitting out clouds of plasma and energetic particles into space and sometimes even towards Earth. The solar magnetic field changes on an 11 year cycle. Every solar cycle, the number of sunspots, flares, and solar stormsincreases to a peak, which is known as the solar maximum. Then, after a few years of high activity, the Sun will ramp down to a few years of low activity, known as the solar minimum. This pattern is called the “sunspot cycle”, the “solar cycle”, or the “activity cycle”.

We are currently (Jan 2012) in Solar cycle 24 – solar maximum for this solar cycle is expected occur in May, 2013. Note, this is a consensus opinion, as supermajority of The Solar Cycle 24 Prediction Panel did agree to this prediction.

What is space weather

Space weather, as our scientists understand it now, manifests on Earth when a solar storm from the Sun travels through space and impacts the Earth’s magnetosphere. Studying space weather is important because solar storms can affect the Earth conditions and the advanced technology.

Energy and radiation from solar flares and coronal mass ejections can:

Harm astronauts in space
Damage sensitive electronics on orbiting spacecraft
Cause colorful auroras, often seen in the higher latitudes
Create blackouts on Earth when they cause surges in power grids
…

Coronal Mass Ejection (CME)

If the magnetic “nets” stretch far into the corona before they break, we have a Coronal Mass Ejection (CME), a billion tons of solar plasma speeding at over a million miles per hour!

Two to four days later, if the storm is aimed at Earth, the results can be dramatic. Induced currents can corrode pipelines, destroy power grids, and cause blackouts. Navigation and communication satellites can be damaged. Astronauts may be exposed to high radiation doses.

Sunspots

Sunspots/Active regions show us where the Sun’s magnetic fields are most intense. Magnetic fields above sunspots act like invisible nets, blocking the escape of electrically charged gas, or plasma, that constantly boils away from the solar surface. When the pressure is too great, they burst. Solar storms then erupt with the power of millions of Hydrogen bombs!

Solar flare

If the explosion occurs low in the solar atmosphere, the blast is short but intense. It pours out ultraviolet light, x-rays and energetic particle radiation – a solar flare.

Aurora

The most beautiful effects of Earth-directed solar storms are aurora shimmering curtains and swirls of light in the night sky.