Hang on for a lesson in solar dynamics – Earth is experiencing a solar sector boundary crossing. Let me explain….
The sun produces wind (currently 410.9 Km/second) that blasts across the cosmos. Just like Earth, our Sun has a magnetic field – known as the interplanetary magnetic field (IMF). Whipped into a spiral rotation, wind driven IMF rotates in one direction. It divides into spiral sections pointing to and away from the sun along the ecliptic plane ( a direct line between Earth and the Sun). The edge of this swirling mass has a surface separating polarities of planetary and solar magnetism called the heliosphere current sheet.
Earth’s magnetic field points north at the magnetopause (the point of contact between our magnetosphere and the IMF). If the IMF happens to point south at contact (scientific term, southward Bz) the two fields link causing partial cancellation of Earth’s magnetic field – in other words, opening a temporary door for solar energy to enter our atmosphere. Welcome solar sector boundary crossing – a phenomenon born of high solar wind and coronal mass ejections (CME’s – aka solar flares).
It takes 3 or 4 days for magnetism to sort itself out – in the meantime, and barring the occasional high frequency radio disruption, wonky GPS and cell phones, peppered with sudden power grid failure events – we’re treated to kick ass auroras.
Ponder Earth’s magnetic field as a shield protecting us from harmful cosmic radiation. Known as “geomagnetic” because it starts at our solid iron outer core, (miles below the surface) and reaches to the outer atmosphere. (creating a magnetosphere, the point in space beyond the ionosphere where charged particles protect us from solar wind and radiation). Without it – our ozone layer would wither, and we would succumb to ultraviolet radiation. In other words, life could not exist.
When strong solar winds impact the magnetosphere, they “distort” our magnetic field creating “openings” – the near side to the sun being “compressed” and far side of the planetary field is bulged outward.
As the charged particles of solar winds and flares hit the Earth’s magnetic field, they travel along the field lines.
Some particles get deflected around the Earth, while others interact with the magnetic field lines, causing currents of charged particles within the magnetic fields to travel toward both poles — this is why there are simultaneous auroras in both hemispheres. (These currents are called Birkeland currents after Kristian Birkeland, the Norwegian physicist who discovered them — see sidebar.)
When an electric charge cuts across a magnetic field it generates an electric current (see How Electricity Works). As these currents descend into the atmosphere along the field lines, they pick up more energy.
When they hit the ionosphere region of the Earth’s upper atmosphere, they collide with ions of oxygen and nitrogen.
The particles impact the oxygen and nitrogen ions and transfer their energy to these ions.
The absorption of energy by oxygen and nitrogen ions causes electrons within them to become “excited” and move from low-energy to high-energy orbitals (see How Atoms Work).
When the excited ions relax, the electrons in the oxygen and nitrogen atoms return to their original orbitals. In the process, they re-radiate the energy in the form of light. This light makes up the aurora, and the different colors come from light radiated from different ions.
Two recent solar events – CME’s (coronal mass ejection) are poised to deliver Aurora magic in regions unaccustomed to their magnificence. Solar wind from the first eruption have arrived, with stronger consequences from the second ejection expected in the next few hours. What this means is Auroras could be visible far below normal latitudes. Some scientists project as far south as Mexico.
If you feel so inclined – go outside, cast your gaze northward, and watch for tell tale green ripples across the sky. Best time to view is between midnight and dawn – obviously clear skies away from city lights are advisable.
Our sun has been busy, purging plasma with the vengeance of Thor. A X-1 flare from sunspot AR1875 on Oct. 28 is the third X-class flare since Oct. 25. This follows three M-class flares since Oct. 20. None of the recent flares are likely to give any direct hits to our magnetic field; instead “glancing blows” are likely to stir up geo-magnetic storms, resulting in spectacular auroras.
For the next 24 hours, Solar Dynamics Observatory predicts a 75% chance of M-class and 30% chance of more X-class flares. My secret wish is for solar hiccups to last long enough for my trip next week to the Canadian prairies; the home of endless, dark, crystal clear skies. A place to take in the majesty of Northern Lights.
Solar activity makes me giddy; I prickle with school girl excitement at the mere mention of an earth directed CME. I knew the sun was getting a little uppity – a visit to http://spaceweather.com/ when I got home from work set my heart a flutter. Our sun has been busy – three flares between Oct. 20 – 22 have apparently merged into one; promising to light up our magnetic field with auroras. Another powerful M-9 class flare hurled earthward yesterday, arrival time as yet unknown.
Courtesy NASA – Solar Dynamics Observatory
Sunspots AR1875 and 1877 are ready to speak their minds – both strutting their stuff – ready to make a statement. Predictions of activity in the next 24 hours may not be earth shattering – 40% chance of M-class and 10% chance of X-class flares – still enough of a magnetic storm for ridiculous northern lights.
Meanwhile, Comet C/2012X1 exploded 450 million Km’s from earth. Of little significance to our little corner of the universe, yet worthy of a look low on the eastern horizon an hour or so before sunrise if you happen to have a telescope.
It appears our sun is about to flip poles. I was stunned to learn this happens every 11 years; or at least that seems to be the pattern since the Wilcox Solar Observatory at Stanford started paying attention in 1976. The sun’s magnetic influence is called the heliosphere, reaching outwards for billions of kilometres , directly impacting space weather in every corner of our galaxy.
The “current sheet” radiates outwards from the equator of the sun. Slow rotation of the sun’s magnetic field produces an electrical current, when the sun’s inner core tidies itself up, reorganizing the closets, a pole shift takes place making the current sheet “wavy”. As Earth passes in and out of this wavy charge, space weather can be a little bonkers.
Hardly a prediction of catastrophe, solar pole reversal is a normal part of the solar cycle. My only wish is for people to start paying attention to the sky. As I write Perseids blaze across the night sky, solar wind rages at 460 Km/second – down from the blast of solar wind striking earth yesterday, responsible for the geomagnetic storm igniting auroras. Asteroid 2013PJ10 just passed earth, a mere Lunar Distance away; at just over 50 metres, capable of wiping out an entire city.
A little cosmic pondering is good for the soul; it helps put things in perspective.
Massive sunspot AR 1785 – eleven times the diameter of earth – now faces our planet with potential for some nasty flares. Space weather forecasters at NOAA predict a 55% chance of M-class and 10% X-class for today.
Luckily earth has the magnetosphere which deflects solar wind and concentrates solar energy at the magnetic pole. Scientists have known for a long time the magnetosphere wasn’t perfect; just as the ozone layer develops “holes”, our magnetic shield is prone to “cracks”. Anyone lucky enough to see an aurora has witnessed the power of electrically charged solar winds.
In 1961 scientist Jim Dungey theorized these cracks occurred when the solar energy arrived packing a magnetic field that travelled in the opposite direction from our magnetic field. We now know these cracks can remain open for hours, allowing billions of electrically charged particles to light up the sky. Severe solar storms can wipe out satellites, communication, and power.
AR 1785 will most likely blast tons of plasma into space before fading away. Geomagnetic storms will rage – airplanes might change course to avoid radiation, auroras will dazzle, and few will be the wiser. I don’t lose sleep over space weather, I just wish more people understood the implications of a direct hit through an unlucky crack that could plunge us into darkness for months.
Photo by Taichi Nakamura of Dunedin New Zealand – southern hemisphere auroras when earth passed through a region of southward magnetic field, opening a crack in the magnetosphere on July 6.
Historical and scientific records indicate many earth shattering events are long overdue. The “big one”, referring to a mega earthquake in the pacific north west, the Yellowstone super volcano, and apparently – a magnetic pole reversal.
I always believed theories of pole reversal lived only on the pages of books. Discovering this event is not only probable, but has happened in our history on more than one occasion, gave birth to this ponder.
Andrew Biggin from the University of the Netherlands in Utrecht, analyzed rock to determine how they were magnetized at formation. This allowed him to pin point the location of the magnetic pole at the time. His research showed a reversal every 400,00 years or so; the last one taking place about 800,000 years ago. He suggests that a pattern of weakening in the earth’s magnetic field takes place for around 2000 years prior to the complete reversal. Archaeological evidence indicates our magnetic field was considerably stronger in Roman times.
Pole reversal doesn’t happen overnight; overdue, in earth terms could be hundreds, thousands, or millions of years. Just one more reason to ponder our time on earth. One more reason to embrace each day, not sweating the little stuff.