Brane Space: Powerful Geomagnetic Storm Triggers Auroral Displays in Colorado and Across U.S.

Some of the auroral displays captured in Colorado Tuesday night

A wave of new solar activity has triggered marvelous light shows in Colorado skies - and across the nation - the last few nights. Two of those energy bursts arrived Tuesday evening painting the skies of Colorado cities pink, blue and green. Coloradans across the state reported being able to see the colors with their naked eye, and the effect was boosted by phone cameras.

The magnetic field of Tuesday night's storm was estimated to be eight times stronger than normal and favorable to "continued activity," NOAA space forecasters said in a video update. A new storm then was forecast to arrive Wednesday, according to space weather forecasters. We looked out toward the northern horizon just after sunset but cloudy conditions prevented us from seeing anything.

Unfortunate, because the energy burst expected to arrive would likely have generated a spectacular aurora. I.e. hitting the "severe" G4 category, and possibly reaching the "extreme" G5 levels, forecasters said in one NASA video. An extreme G5 storm can collapse power grids, cause blackouts and disrupt satellite navigation and radio frequencies, according to the NOAA.

For reference, the five-step ranking scale e,g,

SANSA Space Weather - Geomagnetic Storm Scale

predicts how the storm will impact Earth -- not just in the vibrancy of the aurora borealis, but in the potential disruption or damage to power grids and communications systems.

The brightness of auroras and how far south they can be observed depends on when the solar bursts arrive and how they interact with Earth’s atmosphere. If the Wednesday night storm is as strong as Tuesday's, as forecasted, Coloradans should once again be able to see it on the horizon just after sunset.

What causes these magnificent multi-colored displays?

One can visualize the Earth as a giant spherical magnet, with magnetic field lines extending from its north to south magnetic poles. These magnetic field lines, have the property that any charged particles (+protons, - electron or ions) that approach, will spiral along them.

The Earth itself, is "bathed" in the solar wind, a stream of high speed
charged particles that flows into space, originating from the Sun's
corona. (A hot, gaseous envelope that spews these particles out continuously – more so when there is a violent explosion known as a Solar Flare)

Around the Earth the speed of these particles can reach 400- 500
km/second. Because of its high temperature, over a million degrees, we know the corona gas is ionized so must consist of charged particles, mainly (+) protons, and (-) electrons).

During high solar activity (e.g. near sunspot maximums) a higher flux of these charged particles inundates the solar wind, and the region around the Earth. The Earth's magnetic field then traps these charged particles, and the highest density occurs around the polar regions. We refer to as the "auroral ovals". In these ovals, very high electric currents are set up, as the charged particles start moving in unison about the magnetic field lines.

As this discharge occurs, one or more outer electrons is stripped from the atoms, for example from oxygen in the atmosphere - then recombines to form new e.(g. oxygen) atoms.

With this recombination there is emission of light, for a certain part
of the visible spectrum. For example, in the case of recombination of oxygen atoms - the emitted light is in the GREEN region of the spectrum. The aurora or northern lights we see displays a kind of green curtain-like shimmering.

The remarkable red aurora, visible in Colorado skies the past two nights, is produced by emission at the 630 nm (nanometer) line of oxygen and at relatively high altitudes (e.g. 200-600 km) compared to green - which tends to form below 100 km when the oxygen line at 557 nm is excited.

Auroras can display as both diffuse and discrete. In the first case the shape is ill-defined and the aurora is believed to be formed from trapped particles originally in the magnetosphere which then propagate into the lower ionosphere via wave-particle interactions.
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A great analogy by Prof. Syun Akasofu (Univ. of Alaska-Fairbanks) compares the aurora to images on a TV screen. In this case the (polar) upper atmosphere corresponds to the screen and the aurora to the image that would be projected on it, say for a TV. The electron beam in the TV (remember we are talking about the old-style cathode ray jobs!) corresponds the electron beam in the magnetosphere.

In the conventional TV motions of the image are generated by the changing impact points of the electron beam on the screen. Similarly, with the aurora, its motions – such as moving sheets or curtains- are produced by moving impact points of the magnetospheric electron beams.

In gauging the power and intensity of auroras at different times, it is useful to remember that ultimately the aurora derives its power and potential from the Sun and specifically the charged particles of the solar wind. This is why the most spectacular displays are usually near sunspot maximum. Around those times the currents which I noted earlier are “amped” up – no pun intended- to 1 million amps or more.

To give an example, during a quiet Sun interval the residual power for the magnetospheric generator is on the order of maybe a tenth of a megawatt. If we see a new cycle coming on and solar wind activated –as it is now - we may get that power up to a million megawatts for a few hours.

If intense enough, such solar storms can herald the onset of enormous induction currents such as caused parts of the Ottawa grid to melt down in 1989.

See Also:

Latest Auroral Display - From G4 Level Solar Storm- Lights Up Skies As Far South As AL, MS, TX

And:

A Threat To U.S. Power Grids? Solar X-Ray Flares Presage Active Solar Cycle 25 And Potential Earlier CMEs As Well As Aurora

And:

The Northern Colorado Aurora - And Why Space Physicists Were Less Obsessed With Appearance Than Effects

And: