Starship Asterisk*

Flowing Auroras Over Norway

Explanation: Have you ever seen an aurora? Auroras are occurring again with increasing frequency. With the Sun peaking at its eleven year maximum in aurora-triggering activity, it is exhibiting a greater abundance of sunspots, flares, and coronal mass ejections. Solar activity like this typically expels charged particles into the Solar System, some of which impact Earth's magnetosphere and trigger Earthly auroras. In late 2010, the above timelapse displays of picturesque auroras were captured above Tromsø, Norway. Curtains of auroral light, usually green, flow, shimmer and dance as energetic particles fall toward the Earth and excite atoms of air high up in the Earth's atmosphere. There may even be opportunities to see auroras tonight, as recent solar explosions have triggered numerous aurora sightings over the past few days.

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Ahhh... NICE!... Peaceful!!

Yes, very nice. And it is much more interesting to see how auroras change over time. But this leaves me wondering two things: What was the rate of time compression in these vids? And also how bright can auroras get?

Looks like a still picture turned into a vid than a real video. I've seen auroras and they distinctly move, no doubt about it.

Real Purdee....there pardnuh.....

:---[===] *

Could we ever see the aurora here in NW Florida? To be that strong, would it mess up radio/TV/satellite transmissions?

To answer your first question: No, I have never seen an Aurora. I'd like to know about the time base. From the appearance of some clouds, I think it has been speeded up. Has it? How much?

biddie67 wrote:Could we ever see the aurora here in NW Florida? To be that strong, would it mess up radio/TV/satellite transmissions?

Aurora over Florida in 2003.
http://www.4saleusa.net/sto/aurora.html
http://www.bigcigarastronomy.com/Chiefland2003.html

And a little bit of the latter: http://spacefellowship.com/news/art7183 ... riest.html

“The effects of these storms were ghoulish enough that [aircraft controllers] had to re-route aircraft, it affected satellite systems and communications, and it also caused a power outage in Sweden for about an hour,” said Dr. Holly Gilbert, a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.

So, yeah, when aurora reaches Florida, some disruptions probably happen but not necessarily those end-of-the-world scenarios that get hyped up. There are a lot of observatories watching the sun just in case a catastrophic flare and CME ever point straight toward earth. If it did happen we'd at least get a warning a few hours ahead of time. I wonder if there is any plan in place for if that were to happen? I mean, it would at least be prudent to tell people to go home from work and try not to freak out until things get fixed.

geckzilla ~~ thanks for taking the time to find the links ~~ I was living here in NW FL in 2003 ~~ really sorry that I missed the Oct 2003 aurora .....

I can still remember with delight the awe and pleasure I felt the night(I think 68 years ago) my father woke me and took me out to watch a grand display of northern lights. The shimmering filled most of the northern sky to the zenith-and occasionally past it. And the sound was like taffeta rustling.
Joyce

Beautiful Auroras over Norway.
It is a good work!

this one and the recent past APOD describing the relative size of planets and stars have won my " have an ice cold one " award. Simply sit back and enjoy the movement.

BDanielMayfield wrote:... What was the rate of time compression in these vids? ...

WWW wrote:... I'd like to know about the time base. From the appearance of some clouds, I think it has been speeded up. Has it? How much?

I looked at only two scenes where Vega is visible:
00:54 to 01:05 => Time-lapse rate ≈30X faster
1:33 to 1:55 => Time-lapse rate ≈230X faster

Auroras exhibit varying rates of shape, color and intensity change over time, so there isn't one time-lapse rate that best for all displays. The cases I chose were simply meant to show the (large) range of time-lapse rates in the video sequences.

alter-ego wrote:

BDanielMayfield wrote:... What was the rate of time compression in these vids? ...

WWW wrote:... I'd like to know about the time base. From the appearance of some clouds, I think it has been speeded up. Has it? How much?

I looked at only two scenes where Vega is visible:
00:54 to 01:05 => Time-lapse rate ≈30X faster
1:33 to 1:55 => Time-lapse rate ≈230X faster

Auroras exhibit varying rates of shape, color and intensity change over time, so there isn't one time-lapse rate that best for all displays. The cases I chose were simply meant to show the (large) range of time-lapse rates in the video sequences.

Thanks alter-ego. And nice skill too; locating a known star and measuring the elapsed time from its rotation angle.

BDanielMayfield wrote: ... And also how bright can auroras get?

This is a harder question, but I believe I have an answer you can relate to.

Like other natural phenomenon, auroral brightness does have a standard, and it has a logarithmic scale. It is the International Brightness Coefficient (IBC) standard. (You might find S&T article interesting: An Aurora Watcher's Guide where brightness and other characteristics are discussed)
The levels range from 0 - 4, on a logarithmic scale:
0 ≡ subvisual, detected only with instruments,
1 ≡ comparable to the Milky Way; whitish with no discernible color,
2 ≡ comparable to moonlit cirrus clouds; color is barely identifiable (usually yellow-green),
3 ≡ like brightly lit cirrus or moonlit cumulus clouds; colors are evident,
4 ≡ much brighter than three; may cast discernible shadows; good colors, many of them fleeting

The unit of auroral brightness is the Rayleigh intensity unit. This allows a quantitative assessment of sky brightness, and referencing this paper: Auroral contribution to sky brightness for optical astronomy on the Antarctic Plateau, a calculation of the brightness for an IBC 4 aurora using a V-Band (Green) filter, you get ≈+14 Magntudes/arcsec² sky brightness.

So, what does this mean?
The equivalent brightness of the full moon ≈ 3.5 Magntudes/arcsec², so the full moon brightness per unit area ≈10.5 magnitudes brighter than the brightest aurora! Asked another way, how big would a uniformly bright, IBC 4 aurora need to be such that its integrated brightness equals a full moon (mag = -12.5)? If you were directly under a uniformly bright, circular IBC 4 aurora with a diameter about 65°, you would experience a full-moon lighting condition!

By the way, this same aurora would not be visible with the naked-eye during the daytime. As a thought experiment, consider increasing the moons diameter by 130x without changing the integrated brightness - it would not be visible with the bare eye.

Thanks alter-ego. And nice skill too; locating a known star and measuring the elapsed time from its rotation angle.

Thank you! I love solving problems by using old tools in new ways

Truly peaceful and serene video!! Makes me wanna go to Tromso!!

is there noise associated with these events ?

ta152h0 wrote:is there noise associated with these events ?

Sometimes. Auroras, like meteors, can produce electrophonic noise. It's not well understood, but probably involves very low frequency EM waves being transduced to sound by something conductive near the observer, maybe even on or in the observer!

sounds like whales ! Wonder if they can hear those sounds ?

ta152h0 wrote:sounds like whales ! Wonder if they can hear those sounds ?

Well... keep in mind that the videos Art posted are not demonstrating the sound of the auroras. The sounds in those videos are just the audio output of radio receivers.

Auroras can produce actual sounds, and those don't sound like whales, but more like sizzling bacon, and occasionally pings or pops. A Finnish study last year produced audio recordings (and at least in their case, the evidence suggests the sounds were produced a hundred meters or so above the ground).

ta152h0 wrote:
sounds like whales ! Wonder if they can hear those sounds ?

• That would explain how they swim in synchrony.

Flying whales, eh Aurora Whaliealis

never know the treasures yet to be uncovered by asking questions.

ta152h0 wrote:never know the treasures yet to be uncovered by asking questions.

A question is one of the most powerful things there is.