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.
This is not a warning, hysterical plea to take cover or recruiting post for the tin foil hat club – simply a heads up for Northern hemisphere sky watchers. Sunspot AR1865 sent an M1 class flare our way, it should reach earth’s magnetic field this evening. Not powerful enough to cause a bad day – even though it was earth directed – the magic is expected to unfold in spectacular auroras.
Those who have witnessed Aurora’s spell understand her soul restoring powers. Those who haven’t can only hope that one day she will allow you to witness her dance across the northern sky. If you happen to find yourself in a dark place, away from city lights; gaze upwards tonight – if you’re lucky, Aurora will dance for you.
AR1748 is one pesky sunspot; still beating its chest, and threatening to show us who’s boss. With odds of eruptions now up to 80% for M-class and 60% for X in the next 24 hours – 1748 unleashed another X class flare today – in case the three X flares of 1.7, 2.8, and 3.2 the previous day hadn’t made us stand up and take notice. As AR1748 turns towards earth, today’s X-1 is expected to deliver a little slap – most likely in the form of geo-magnetic disturbances responsible for crazy beautiful auroras. Ar1748 has produced more X-class flares in the last few days than all other sunspots this year combined.
NASA Solar Dynamics Observatory – photo of AR 1748 taken on May 16
I’ve been a space weather nerd for a while and have never seen an 80% chance of M-class and 40% chance of X-class flares in the next 24 hours. Our sun is flexing muscle with the most intense solar activity this year. Sunspot AR 1748 let loose significant X class eruptions of 1.7, 2.8, and 3.2 in the last 24 hours. Take it from me – this is crazy. The good news is none were “earth directed”, no incoming CME (coronal mass ejection) is anticipated for now. The bad news – while researching when 1748 will face earth I stumbled upon a wordpress blog proclaiming it the beginning of the “rapture”. My decision to retreat, despite every fibre in my being screaming “post a comment” – left me shaking, incensed, reaching for a cocktail, and ultimately validated in my AR1748 raised eyebrow. When all is said and done – not only have I never seen such crazy solar activity in a short period of time, I’ve never seen it attributed to the rapture. All the affirmation I need to know I’m not pondering fairy dust. FYI -AR1748 will be earth directed in a few days.
Bookmark this link to spaceweather, start paying attention to solar reports, and send your tin foil hats to those anticipating the “rapture”, just be sure to tuck a little tin foil into that emergency kit at the top of your “to do” list.
I wouldn’t be a particularly responsible space weather geek if I neglected to report on uppity sunspots. Sunspots AR 1730 and 1731 are getting cranky; currently a 40% chance of M-class and 5% chance of X-class flares in the next 24 hours. Ho hum you say? Most likely the case – but never fear, I’m on the job and will let you know if any spectacular eruptions take place.
I just heard from my sister in Saskatchewan; feeling green with envy as she’s sitting on her front steps watching the Northern Lights dance. Auroras are a magical gift – they find you, wrap their arms around you, and feed your soul. Argh – so jealous.
Solar eruption on the far-side of the sun – courtesy NASA