Starship Asterisk*

http://photojournal.jpl.nasa.gov/catalog/PIA11396
http://apod.nasa.gov/apod/ap081119.html

What a mystery! It’s through APODs like these that I most enjoy being a sideline viewer of scientific phenomena. Even when something is outside the experienced/understood astrophysical window, scientists are still expected to have some sort of intelligent description of what ever is being witnessed. So the qualifying language translating the anomaly to us laymen is an art form to behold in my eyes.

I think it’s cool that Saturn not only has rings but appears to have gears and magnetos as well. (See, I don’t feel the professional pressure to be conservative in my observation)

Actually the hexagon cloud looks more like it could be concealing some sort of planetary nut... OK... I know what you're thinking... and yes... in a way Asterisk* is concealing me too... but I'm not alone... am I.

The caption to the APOD on 11.18.08 mentions the hexagonal shaped cloud band around the north pole of Saturn. It appears to me that the strange aurora also there overlays this same cloud band. It may be that whatever forces are creating the hexagonal cloud band are also effecting the strange aurora above it in the Saturnian atmosphere.

emc wrote:
http://apod.nasa.gov/apod/ap081119.html

What a mystery! It’s through APODs like these that I most enjoy being a sideline viewer of scientific phenomena. Even when something is outside the experienced/understood astrophysical window, scientists are still expected to have some sort of intelligent description of what ever is being witnessed. So the qualifying language translating the anomaly to us laymen is an art form to behold in my eyes.

I think it’s cool that Saturn not only has rings but appears to have gears and magnetos as well. (See, I don’t feel the professional pressure to be conservative in my observation)

Actually the hexagon cloud looks more like it could be concealing some sort of planetary nut... OK... I know what you're thinking... and yes... in a way Asterisk* is concealing me too... but I'm not alone... am I.

http://chaos.utexas.edu/research/annulus/apparatus.html

http://forums.ski.com.au/forums/ubbthre ... 999&page=1

brbear1 wrote:The caption to the APOD on 11.18.08 mentions the hexagonal shaped cloud band around the north pole of Saturn. It appears to me that the strange aurora also there overlays this same cloud band. It may be that whatever forces are creating the hexagonal cloud band are also effecting the strange aurora above it in the Saturnian atmosphere.

I don't think that it is any kind of aurora at all!

IMO, It is either some atmospheric phenomenum
akin to lightning or to blue jets or to red sprites:

http://www.spritesandjets.com/

Blue jets
http://en.wikipedia.org/wiki/Lightning#Blue_jets

<<Blue jets differ from sprites in that they project from the top of the cumulonimbus above a thunderstorm, typically in a narrow cone, to the lowest levels of the ionosphere 25 miles (40 km) to 30 miles (48 km) above the earth.[citation needed] They are also brighter than sprites and, as implied by their name, are blue in colour. They were first recorded on October 21, 1989, on a video taken from the space shuttle as it passed over Australia, and subsequently extensively documented in 1994 during aircraft research flights by the University of Alaska.

On September 14, 2001, scientists at the Arecibo Observatory photographed a huge jet double the height of those previously observed, reaching around 50 miles (80 km) into the atmosphere. The jet was located above a thunderstorm over the ocean, and lasted under a second. Lightning was initially observed traveling up at around 50,000 m/s in a similar way to a typical blue jet, but then divided in two and sped at 250,000 m/s to the ionosphere, where they spread out in a bright burst of light. On July 22, 2002, five gigantic jets between 60 and 70 km (35 to 45 miles) in length were observed over the South China Sea from Taiwan, reported in Nature.52] The jets lasted under a second, with shapes likened by the researchers to giant trees and carrots.[citation needed]

In 2001, the Arecibo scientists modeled the blue-jet phenomenon to better understand how it works. It is like an electron avalanche that can flood up toward the ionosphere or slide earthward, depending on the electric field direction. Intense hail may trigger the avalanche. The field accelerates the electrons and slams them into air molecules. The molecules break down into ions and free electrons and emit light. The newly generated electrons also accelerate.>>
-----------------------------------
Blue Jets
http://elf.gi.alaska.edu/#chrjet

<<Blue jets are a ... high altitude optical phenomenon, distinct from sprites, observed above thunderstorms using low light television systems. As their name implies, blue jets are optical ejections from the top of the electrically active core regions of thunderstorms. Following their emergence from the top of the thundercloud, they typically propagate upward in narrow cones of about 15 degrees full width at vertical speeds of roughly 100 km/s (Mach 300), fanning out and disappearing at heights of about 40-50 km. Their intensities are on the order of 800 kR near the base, decreasing to about 10 kR near the upper terminus. These correspond to an estimated optical energy of about 4 kJ, a total energy of about 30 MJ, and an energy density on the order of a few mJ/m^3. Blue jets are not aligned with the local magnetic field.>>

http://elf.gi.alaska.edu/
http://umbra.nascom.nasa.gov/spd/sprites.html
--------------------------------------

Wow - leave it to Neufer!

It seems that many of the small, dark, 'holes' in the cloud band also seem to be hexagonal.

Also interesting to note, The aurora thickens (brightens) in the middle of the flat sides of the hexagon. I wonder if magnetic waves could propogate from the aurora and travel back to the planet with the strongest portion being in the brightest portion of the aurora and thereby affecting (creating) the Hexagonal shape through interaction with the atmosphere?

Hello Sputnick,

Leave it to neufer? I have no CHOICE!

Very intriguing photo. How about......hmmm.......let me see............there's got to be something.............
..................................................................OH! I KNOW!................no I don't.

Wait......the precession of the magnetic pole(s) wobbling back and forth while, at the same time trying to trace out a (normal?) circular pattern. Even though I know that magnetic poles can't "try".

astrolabe wrote:Leave it to neufer? I have no CHOICE!

Would you care to have an online chat with my scientific associate, Luca Brasi ?

astrolabe wrote:Wait......the precession of the magnetic pole(s) wobbling back and forth while,
at the same time trying to trace out a (normal?) circular pattern.
Even though I know that magnetic poles can't "try".

Note that Jupiter has a HUMONGOUS magnetic field
with interesting auroral effects driven by it's major moons:

• ----------------------------------------------------------------------
  NASA image of Jupiter aurora in UV, Hubble Space Telescope
  Credit: John T. Clarke (U. Michigan), ESA, NASA
  
  Bright streaks and dots are caused by magnetic flux tubes
  connecting Jupiter to its largest moons:
  * Io: bright streak on the far left
  * Ganymede: bright dot below center
  * Europa: dot right of Ganymede dot
  ----------------------------------------------------------------------

Whereas, Saturn's magnetic field is weaker than the earth's!

• ----------------------------------------------------------------------
  <<Saturn has an intrinsic magnetic field that has
  a simple, symmetric shape—a magnetic dipole.
  Its strength at the equator—0.2 gauss —is approximately one twentieth than
  that of the field around Jupiter and slightly weaker than Earth's magnetic field.>>
  .........................................................
  <<Jupiter's broad magnetic field is 14 times as strong as the Earth's,
  ranging from 4.2 gauss at the equator to 10–14 gauss at the poles,
  making it the strongest in the Solar System (with the exception of sunspots).>>
  ----------------------------------------------------------------------

Ultraviolet HST images of polar DAY aurora:
http://antwrp.gsfc.nasa.gov/apod/ap050222.html
http://antwrp.gsfc.nasa.gov/apod/ap001219.html

Infrared satellite images of polar NIGHT "aurora??":
http://antwrp.gsfc.nasa.gov/apod/ap081119.html

Hello neufer,

Hmmmmm. You are something. Fast too!

Hi Luca.
P.S. My thought wasn't so much about the aurora as the hexagonal cloud shape of the polar atmospheric cloud formation. Sorry if I was unclear.

astrolabe wrote:Hello neufer, Hmmmmm. You are something. Fast too!

And often wrong when fast...
e.g., 'A Bubble in Cygnus' being the 'echo' of a recent gamma ray burst
(in which case it would have to noticeably change in size on the order of days).

astrolabe wrote:Hi Luca.

"Don astrolabe, I am honored and grateful that you have invited me to your home on the wedding day of your daughter.
And may their first child be a masculine child."

astrolabe wrote:P.S. My thought wasn't so much about the aurora as the hexagonal cloud shape of the polar atmospheric cloud formation. Sorry if I was unclear.

The polygonal shape of polar night Rossby wave jet stream flows is something that I've actually given talks on at American Geophysical Union meetings. It is tighter & better defined on Saturn than on earth simply due to Saturn's rapid 10 hour rotation.

Hello neufer,

Thank you for the graphic, and, a little off topic here, but in learning more about L.R. forecasting of Earth weather I've been aware of the polar front dynamic from trying to study patterns at the 500mb level. Too bad I'm not an AGU guy so I could sit in. Any lectures appearing on the www?

astrolabe wrote:Hello neufer,

Thank you for the graphic, and, a little off topic here, but in learning more about L.R. forecasting of Earth weather I've been aware of the polar front dynamic from trying to study patterns at the 500mb level.

500mb is the mass center of the atmosphere.

400mb is near the dynamic center of the atmosphere and close to where my water vapor channel shows motion:
http://tinyurl.com/5vx3g4

My last AGU talk actually involved the 1mb. level of the stratopause
where the 11 year solar cycle actually has a significant physical effect
which (IMO) cascades down through the stratosphere & may even affect the troposphere.

astrolabe wrote:Too bad I'm not an AGU guy so I could sit in. Any lectures appearing on the www?

No lectures by me but I recommend:
-----------------------------------------------
http://mediaman.gsfc.nasa.gov/colloquia ... 080509.asx
http://scicolloq.gsfc.nasa.gov/
http://scicolloq.gsfc.nasa.gov/Spring08.html
http://scicolloq.gsfc.nasa.gov/Fall07.html
http://scicolloq.gsfc.nasa.gov/Spring07.html
http://scicolloq.gsfc.nasa.gov/Fall06.html
http://scicolloq.gsfc.nasa.gov/Spring06.html
http://scicolloq.gsfc.nasa.gov/Fall05.html
http://scicolloq.gsfc.nasa.gov/Spring05.html

Hello neufer,

Terrific. Thanks a mil.

BTW the bubble-in-Cygnus admission went a long way. Honesty in the Forum in general promotes good will.

I knew there was a good reason for the hexagon shape! It does correspond so well to our jet stream and other streams on the spinning earth.

So what variables affect its periodic pattern? Temperature? Planet rotation speed? Day length (summer or winter)?

rigean wrote:I knew there was a good reason for the hexagon shape! It does correspond so well to our jet stream and other streams on the spinning earth.

So what variables affect its periodic pattern? Temperature? Planet rotation speed? Day length (summer or winter)?

Fundamentally:

1) The periodicity is determined by the
temperature difference between the pole and the equator.

The higher the temperature difference => the longer the wavelength.

2) The stability is determined by the rotational rate.

The higher the rotational rate => the stronger the stability (and smaller the amplitude).

If the effective rotational rate is too small
(like it is in the tropical regions of the earth)
then the periodic patterns quickly become unstable
and the flow reverts to a Hadley type circulation.

So let me make a prediction for Saturn:

The hexagon shape leads to a small amplitude of the waves = fast speed of rotation.
The rotational time I know is 10 hours: pretty fast! Especially considering the circumference of Saturn is 10 times our circumference.

The earth had 5-6 peaks, and saturn currently has 6 peaks.
So the temperature relationship between the equator and the pole seems to be similar if comparing Earth and Saturn.

Another prediction:
During the Northern Hemisphere Summer, the pole will be warm (tilted towards sun) and the equator will be warm,
and so there will be fewer peaks along the Northern Hemisphere wave.

During the Northern Hemisphere Winter, the pole will be cold (tilted away from sun) and the equator will not have changed,
still be warm, so there will be more peaks along the Northern Hemisphere wave.

Sound reasonable?

EDIT: Does this also cause the gas giants (or the sun for that matter) to form the banding stripes that they have around the equator?
b/c they spin quite a lot faster than we do.

There is a Amateur Jupiter/Saturn group claiming for many years to sometimes see Saturn off color, sometimes blue tinted.

"real astronomers" ridiculed them.

The recent Aurora picture of Saturn has verified that this "blue Saturn" phenomenon DOES have a basis in fact Score one for the Amateurs .........

Lewis Brackett

lewishb wrote:... The recent Aurora picture of Saturn has verified that this "blue Saturn" phenomenon DOES have a basis in fact ...

The photo was infrared, not visible light, and in "falsecolor".

rigelan wrote:So let me make a prediction for Saturn:

The hexagon shape leads to a small amplitude of the waves = fast speed of rotation.
The rotational time I know is 10 hours: pretty fast! Especially considering the circumference of Saturn is 10 times our circumference.

The earth had 5-6 peaks, and saturn currently has 6 peaks.
So the temperature relationship between the equator and the pole seems to be similar if comparing Earth and Saturn.

Another prediction:
During the Northern Hemisphere Summer, the pole will be warm (tilted towards sun) and the equator will be warm,
and so there will be fewer peaks along the Northern Hemisphere wave.

During the Northern Hemisphere Winter, the pole will be cold (tilted away from sun) and the equator will not have changed,
still be warm, so there will be more peaks along the Northern Hemisphere wave.

Sound reasonable?

By George, you've got it, rigelan!

However, what I gave you was basically a very simplified version of rotating flat dishpan (or annulus) fluid convection experimental results.

While it, more or less, seems to give reasonable qualitative results when applied to complex spherical planetary atmospheres one shouldn't get too carried away making blanket assumptions without also checking them out.

rigelan wrote:EDIT: Does this also cause the gas giants (or the sun for that matter) to form the banding stripes that they have around the equator?
b/c they spin quite a lot faster than we do.

I believe so.

Check out:

Slowly rotating (once every 4 earth days as regards the atmosphere)
Venus Hadley (spiral) circulation:
http://antwrp.gsfc.nasa.gov/apod/ap070501.html

http://mediaman.gsfc.nasa.gov/colloquia ... 070216.asx

http://mediaman.gsfc.nasa.gov/colloquia ... 080502.asx

bystander wrote:

lewishb wrote:... The recent Aurora picture of Saturn has verified that this "blue Saturn" phenomenon DOES have a basis in fact ...

The photo was infrared, not visible light, and in "falsecolor".

One more reason for authenticity.

Sputnick wrote:

bystander wrote:

lewishb wrote:... The recent Aurora picture of Saturn has verified that this "blue Saturn" phenomenon DOES have a basis in fact ...

The photo was infrared, not visible light, and in "falsecolor".

One more reason for authenticity.

Yeah, I'd much rather see NOTHING in "true" color.

And we can only view photos rendered in visible wavelengths. And that's all our monitors will display. So how could we show an infrared photo in true color?

apodman wrote: Yeah, I'd much rather see NOTHING in "true" color.

And we can only view photos rendered in visible wavelengths. And that's all our monitors will display. So how could we show an infrared photo in true color?

False colour should be much more clearly indentified in alterations.

Sputnick wrote:False colour should be much more clearly indentified in alterations.

The caption clearly stated "... Infrared images by the robotic Cassini spacecraft of the north pole of Saturn ...". Following the provided link gives detailed information about the composition.

I guess it is pretty standard that if you see the term: infrared or microwave or xray, then you know it is a false color image.

But that is generally only noticed by audiences that are trained to see that sort of thing.

To the random wanderer on the internet - The connected is not always made. It might be better to make mention of it.

But then again, many if not most pictures here on APOD are false color. We don't get the extraordinary detail in images if we don't use very specific wavelengths and correspond a color to them. The 'natural color' images are actually more rare here than anywhere else on the internet, I suppose.

And to neufer: thanks! This meteorological stuff is pretty fantastic!

Test your color vision here:

http://www.xrite.com/custom_page.aspx?PageID=77

Apodman took 5 or 10 minutes and thought he got a 0 (perfect score), but he actually got an 8 (not terrible).