THE NORTHERN LIGHTS
THE NORTHERN LIGHTS AURORA
The Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights) are the result of electrons colliding with the upper reaches of Earth’s atmosphere. (Protons cause faint and diffuse aurora, usually not easily visible to the human eye.) The electrons are energized through acceleration processes in the downwind tail (night side) of the magnetosphere and at lower altitudes along auroral field lines. The accelerated electrons follow the magnetic field of Earth down to the Polar Regions where they collide with oxygen and nitrogen atoms and molecules in Earth’s upper atmosphere. In these collisions, the electrons transfer their energy to the atmosphere thus exciting the atoms and molecules to higher energy states. When they relax back down to lower energy states, they release their energy in the form of light. This is similar to how a neon light works. The aurora typically forms 80 to 500 km above Earth’s surface.
Earth’s magnetic field guides the electrons such that the aurora forms two ovals approximately centered at the magnetic poles. During major geomagnetic storms these ovals expand away from the poles such that aurora can be seen over most of the United States. Aurora comes in several different shapes. Often the auroral forms are made of many tall rays that look much like a curtain made of folds of cloth. During the evening, these rays can form arcs that stretch from horizon to horizon. Late in the evening, near midnight, the arcs often begin to twist and sway, just as if a wind were blowing on the curtains of light. At some point, the arcs may expand to fill the whole sky, moving rapidly and becoming very bright. This is the peak of what is called an auroral substorm.
Then in the early morning the auroral forms can take on a more cloud-like appearance. These diffuse patches often blink on and off repeatedly for hours, then they disappear as the sun rises in the east. The best place to observe the aurora is under an oval shaped region between the north and south latitudes of about 60 and 75 degrees. At these polar latitudes, the aurora can be observed more than half of the nights of a given year.
The northern lights (called the aurora borealis) and the southern lights (aurora australis) appear when tiny particles stream out from the Sun and hit Earth's atmosphere. The particles give some of their energy to atoms and molecules of gases in the upper atmosphere. But the atoms and molecules cannot hold the energy.
SOLAR WEATHER AND HOW THE AURORA IS FORMED
Coronal holes are regions where the sun's corona is dark. These features were discovered when X-ray telescopes were first flown above the Earth's atmosphere to reveal the structure of the corona across the solar disc. Coronal holes are associated with 'open' magnetic field lines and are often found at the sun's poles.
A coronal hole forms in the sun's outer atmosphere (or corona) where a gap in the magnetic field lets the solar wind (gases spewing from the sun's surface) flow out.
WHAT IS A CORONAL MASS EJECTION (CME)
A coronal mass ejection (or CME) is a giant cloud of solar plasma drenched with magnetic field lines that are blown away from the Sun during strong, long-duration solar flares and filament eruptions. When the sun blasts a Earth-directed coronal mass ejection (CME), a solar phenomenon that can send billions of tons of solar particles into space and can reach Earth one to three days later and affect electronic systems in satellites and on the ground.
Coronal mass ejections are explosions in the Sun's corona that spew out solar particles. A lot of material is thrown out into the solar wind. Coronal mass ejections can be dangerous when they hit the Earth. CME's can seriously disrupt the Earth's environment.
In a coronal mass ejection, magnetized plasma from the Sun's corona erupts into space.
A solar flare is a brief eruption of intense high-energy radiation from the sun's surface, associated with sunspots and causing radio and magnetic disturbances on the earth.
Solar flares produce high energy particles and radiation that are dangerous to living organisms. However, at the surface of the Earth we are well protected from the effects of solar flares and other solar activity by the Earth's magnetic field and atmosphere.
Sometimes areas of the Sun will suddenly appear much brighter. These bright spots are called solar flares. They are areas where a large amount of energy is released to the surface of the Sun. Solar flares emit bursts of electromagnetic radiation including high energy X-rays and gamma rays.
The Sun has a magnetic field that gets twisted around inside the Sun as it spins. There are places on the Sun where this magnetic field rises up from below the Sun's surface and pokes through, creating sunspots. Sunspots are magnetic and often have a north and south pole like a magnet.
Sunspots are dark areas that appear on the surface of the Sun. They are caused by strong magnetic activity within the Sun. Sunspots are not permanent and they can move slowly across the surface of Sun changing size as they move. The appearance of sunspots follows the solar cycle of eleven years.
The solar wind is a continuous outward stream of particles (mostly protons and electrons) from the sun's hot corona. Energized by high temperatures in the corona, these particles leave the sun at speeds ranging from 200 to 500 miles per second (300 to 800 kilometers per second).
The sun's magnetic field contains both open and closed field lines. ... The open field lines, however, spiral out from the sun like a pinwheel as the sun rotates, and along these field lines particles can travel easily, and even get accelerated to form the bulk of the solar wind.
The solar wind is a stream of energetic particles ejected by the Sun. These include electrons and protons from hydrogen, along with atomic nuclei like helium, otherwise known as alpha particles. There are also traces of 'heavy ions' and atomic nuclei of carbon, nitrogen, oxygen, neon and magnesium.
Solar Wind Particles - The Sun is sending very small particles (usually protons and electrons) into the Solar System. Those particles are called the solar wind. The flow of particles doesn't just go to Earth. The particles hit all of the planets in the Solar System and create an envelope that protects the system.
COLOURS OF THE AURORA
The colours most often associated with the aurora borealis are pink, green, yellow, blue, violet, and occasionally orange and white. Typically, when the particles collide with oxygen, yellow and green are produced. Interactions with nitrogen produce red, violet, and occasionally blue colours.
Aurora noise, similar to a hissing, or crackling noise, begins about 70 m (230 ft) above the Earth's surface and is caused by charged particles in an inversion layer of the atmosphere formed during a cold night. The charged particles discharge when particles from the Sun hit the inversion layer, creating the noise.
SOLAR FLARES AND HOW THERE CLASSED
Solar flares are classified according to their strength. The smallest ones are A-class, followed by B, C, M and X, the largest. Solar flares are giant explosions on the sun that send energy, light and high speed particles into space.
X-class flares are big; they are major events that can trigger planet-wide radio blackouts and long-lasting radiation storms. M-class flares are medium-sized; they can cause brief radio blackouts that affect Earth's polar regions. Minor radiation storms sometimes follow an M-class flare.
THE CARRINGTON EVENT – THE BIGGEST SOLAR STORM IN HISTORY TO BE RECORDED
The auroras that resulted from the "great geomagnetic storm" on both 28 August and 2 September 1859, however, are thought to be the most spectacular in recent recorded history. In a paper to the Royal Society on 21 November 1861, Balfour Stewart described both auroral events as documented by a self-recording magnetograph at the Kew Observatory and established the connection between the 2 September 1859 auroral storm and the Carrington-Hodgson flare event when he observed that, "It is not impossible to suppose that in this case our luminary was taken in the act." The second auroral event, which occurred on 2 September 1859 as a result of the exceptionally intense Carrington-Hodgson white light solar flare on 1 September 1859, produced auroras, so widespread and extraordinarily bright, that they were seen and reported in published scientific measurements, ship logs, and newspapers throughout the United States, Europe, Japan, and Australia. It was reported by The New York Times that in Boston on Friday 2 September 1859 the aurora was "so brilliant that at about one o'clock ordinary print could be read by the light". One o'clock EST time on Friday 2 September, would have been 6:00 GMT and the self-recording magnetograph at the Kew Observatory was recording the geomagnetic storm, which was then one hour old, at its full intensity. Between 1859 and 1862, Elias Loomis published a series of nine papers on the Great Auroral Exhibition of 1859 in the American Journal of Science where he collected worldwide reports of the auroral event.
The associated "white light flare" in the solar photosphere was observed and recorded by British astronomers Richard C. Carrington (1826–1875) and Richard Hodgson (1804–1872).
In June 2013, a joint venture from researchers at Lloyd's of London and Atmospheric and Environmental Research (AER) in the United States used data from the Carrington Event to estimate the current cost of a similar event to the U.S. alone at $0.6–2.6 trillion.
That aurora is thought to have been produced by one of the most intense coronal mass ejections in history. It is also notable for the fact that it is the first time where the phenomena of auroral activity and electricity were unambiguously linked. This insight was made possible not only due to scientific magnetometer measurements of the era, but also as a result of a significant portion of the 125,000 miles (201,000 km) of telegraph lines then in service being significantly disrupted for many hours throughout the storm. Some telegraph lines, however, seem to have been of the appropriate length and orientation to produce a sufficient geomagnetically induced current from the electromagnetic field to allow for continued communication with the telegraph operator power supplies switched off.
The following conversation occurred between two operators of the American Telegraph Line between Boston and Portland, Maine, on the night of 2 September 1859 and reported in the Boston Traveler:
Boston operator (to Portland operator): "Please cut off your battery [power source] entirely for fifteen minutes."
Portland operator: "Will do so. It is now disconnected."
Boston: "Mine is disconnected, and we are working with the auroral current. How do you receive my writing?"
Portland: "Better than with our batteries on. – Current comes and goes gradually."
Boston: "My current is very strong at times, and we can work better without the batteries, as the aurora seems to neutralize and augment our batteries alternately, making current too strong at times for our relay magnets. Suppose we work without batteries while we are affected by this trouble."
Portland: "Very well. Shall I go ahead with business?"
Boston: "Yes. Go ahead."
A solar storm of this magnitude occurring today would cause widespread disruptions and damage to a modern and technology-dependent society. The solar storm of 2012 was of similar magnitude, but it passed Earth's orbit without striking the planet
On Saturday, September 3, 1859, the Baltimore American and Commercial Advertiser reported:
Those who happened to be out late on Thursday night had an opportunity of witnessing another magnificent display of the auroral lights. The phenomenon was very similar to the display on Sunday night, though at times the light was, if possible, more brilliant, and the prismatic hues more varied and gorgeous. The light appeared to cover the whole firmament, apparently like a luminous cloud, through which the stars of the larger magnitude indistinctly shone. The light was greater than that of the moon at its full, but had an indescribable softness and delicacy that seemed to envelop everything upon which it rested. Between 12 and 1 o'clock, when the display was at its full brilliancy, the quiet streets of the city resting under this strange light, presented a beautiful as well as singular appearance.]
In 1909, an Australian gold miner C.F. Herbert retold his observations in a letter to The Daily News in Perth:
"I was gold-digging at Rokewood, about four miles from Rokewood township (Victoria). Myself and two mates looking out of the tent saw a great reflection in the southern heavens at about 7 o'clock p.m., and in about half an hour, a scene of almost unspeakable beauty presented itself, lights of every imaginable colour were issuing from the southern heavens, one colour fading away only to give place to another if possible more beautiful than the last, the streams mounting to the zenith, but always becoming a rich purple when reaching there, and always curling round, leaving a clear strip of sky, which may be described as four fingers held at arm's length. The northern side from the zenith was also illuminated with beautiful colours, always curling round at the zenith, but were considered to be merely a reproduction of the southern display, as all colours south and north always corresponded. It was a sight never to be forgotten, and was considered at the time to be the greatest aurora recorded... The rationalist and pantheist saw nature in her most exquisite robes, recognising, the divine immanence, immutable law, cause, and effect. The superstitious and the fanatical had dire forebodings, and thought it a foreshadowing of Armageddon and final dissolution."