Mohawk Valley Astronomical Society

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The Electric Dragon

by Perry Pezzolanella, MVAS

The Sun is the closest star and deserves respect. Without it there would be no life on Earth. With it we have a planet flourishing with its heat and light because it is just the right distance away. Most people take it for granted as the sun is a quiet, stable star shining in the sky. It is guaranteed to rise every day, but is the Sun really a gentle giant?

A view of the Sun through a properly filtered or hydrogen-alpha (Hα) telescope reveals a Sun often peppered with dark spots along with several prominences streaming off the limb. On certain occasions a bright spot will flare up and fade away. All of this is due to the Sun’s powerful magnetic field and it has a huge, potentially disastrous effect to the Earth. The Sun rotates at different rates at different latitudes along with strong convection that also varies with depth. The solar material churns in a complex way, which generates electric currents. These electric currents are what create the magnetic fields that twist as they rise to the surface and trap ionized gas. These are seen on the surface of the Sun as sunspots and prominences. The magnetic fields are like giant electrical loops that possess a tremendous amount of energy, especially when they become tangled. Fortunately the Sun is usually capable of untangling these loops uneventfully, but sometimes the stress in the loops increase to a point where they snap and reconnect. This gives a rapid, nearly explosive, release of the stored energy and is seen from Earth as a brilliant solar flare.

The Sun has an atmosphere, but it is different from the atmosphere that we are familiar with. It is constantly flowing outward in a stream of particles and magnetic fields known as the solar wind. The wind is always blowing, even way out beyond Pluto. The strength of the wind affects the Earth’s magnetic field and is stronger after a solar flare. The particles from the Sun funnel downward through Earth’s magnetic field into the atmosphere near both poles. The particles collide with the gases in the Earth’s atmosphere with enough energy to produce light that we know as aurorae, or the northern and southern lights (aurora borealis and aurora australis). It is the oxygen, nitrogen and hydrogen atoms that glow in the atmosphere much like a neon sign and range in color from the more common green to the more rare pink, red, blue, and violet.

An aurora is a beautiful sight to behold as they can pulsate, radiate and shift in the sky like a breeze blowing a silk curtain. They can appear like arcs, flames, pillars, curtains, and patches. The more colorful and active an aurora, the more powerful was the solar flare that spewed out the ionized particles to create it. Aurorae have been visible as far south as the tropics during particularly severe flares, such as the one during March 1989. A solar flare can create magnetic storms that induce currents in communication and power transmission systems having long distance wires, disrupting radio communications and causing electrical blackouts. The severe flare of March 1989 caused massive blackouts in Quebec. Solar activity also heats the Earth’s upper atmosphere causing it to expand. This causes low-orbiting satellites to experience increased frictional drag that can shorten their lifetime as they re-enter Earth’s atmosphere sooner than expected. Flares can also cripple planetary spacecraft such as the Mars Odyssey, which ended up with one of its instruments permanently disabled after a severe solar flare during October 2003 while orbiting Mars. A solar flare at the wrong time can increase the risk of cancer or be instantly lethal to astronauts without proper shielding.

Proof of the Sun’s power and changeability was experienced on 10 September 2005 by the author through his Coronado 40mm, double-stacked Hα solar telescope. On that day there was an active sunspot, and then suddenly a brilliant white spot erupted and rippled around the spot - a solar flare. It faded away within a half an hour right before my eyes, but the next night when the particles reached Earth, a beautiful aurora was seen; proof that the Sun is a dynamic, fire-breathing star.