Jupiter's Giant Red Spot

zoobyshoe

I'm interested in finding out more about how this is generated. I recently learned it is believed to be caused by the Coriolis effect, but I don't have a clear picture of how that would generate the spot. My understanding of the Coriolis effect is limited to its usefullness in north/south airplane trips.

Mentat

Well, I don't know exactly how this is explained, but I do know that the "spot" is actually a giant windstorm (the size of like 4 Earths, IIRC), and giant windstorms can be generated by the coriolis effect (which is something like the effect of the centripetal force of the spin of the planet coupled with the force of it's gravity, IIRC).

Labguy

Mentat is correct. The GRS "storm has been seen for 300 years+ and has undergone many changes.

The north-south airplane trip trick is about flying "Great Circles", not the Coriolis Effect.

zoobyshoe

The information presented at the site linked below indicates the coriolis effect plays an important part in north/south airplane travel.

Coriolis Effect
Address:http://zebu.uoregon.edu/~js/glossary...is_effect.html

I am having a difficult time envisioning how it contributes to the storm on Jupiter.

Labguy

Unless I can't read, that site says absolutely ZERO about aircraft flight. It does state that:

"The Coriolis effect has great significance in astrophysics and stellar dynamics, in which it is a controlling factor in the directions of rotation of sunspots. It is also significant in the earth sciences, especially meteorology, physical geology, and oceanography, in that the Earth is a rotating frame of reference, and motions over the surface of the Earth are subject to acceleration from the force indicated. Thus, the Coriolis force figures prominently in studies of the dynamics of the atmosphere, in which it affects prevailing winds and the rotation of storms, and in the hydrosphere, in which it affects the rotation of the oceanic currents."

It would have an effect on the path of anything in orbit, and atmospheric and oceanographic motions, just as it says. Except for very "local" atmospheric conditions, the atmosphere is also rotating with the Earth's surface, and an airplane flying a Great Circle would be the shortest N-S path, like the current "over-the pole" flights to Russia. An over-the-pole ballistic missle would, of course, have to take the effect into account or miss. It leaves the atmosphere. IF there is an effect on aircraft flight in the atmosphere, it would be very small.

The part stating that: "Thus, the Coriolis force figures prominently in studies of the dynamics of the atmosphere, in which it affects prevailing winds and the rotation of storms, and in the hydrosphere, in which it affects the rotation of the oceanic currents." directly affects the formation and intensity of hurricanes. The GRS on Jupiter is just considered a large "hurricane" that maintains energy from the Coriolis force of winds of several hundred miles per hour, vs. our puny 150 MPH stuff.

zoobyshoe

The word "airplane" is not used at that site. It speaks of how the coriolis effect figures in to the apparent trajectory of projectiles fired north from the equator, and south from the pole.

This indicates it plays an important part in north/south airplane travel.

I am having a hard time envisioning how it figures in to the creation of the big red spot on Jupiter.

Labguy

Yes, it affects airplanes. How could an airplane fly in a Great Circle without navigating toward or against any Coriolis effect?? That is how they fly a Great Circle.

Maybe it doesn't! I'm not a weatherman, and don't study much planetary stuff.

zoobyshoe

Jupiter's Giant Red Spot

I'm interested in finding out more about how this is generated. I recently learned it is believed to be caused by the Coriolis effect, but I don't have a clear picture of how that would generate the spot. My understanding of the Coriolis effect is limited to its usefullness in north/south airplane trips.

Phobos

from http://www.seds.org/billa/tnp/jupiter.html
So, a high pressure region forms it, perhaps the Coriolis effect spins it (layers of clouds rotating at different speeds), and the lack of significant friction (no land form beneath to slow it down) allows it to keep going for 300+ years.

Although I have to wonder about the different cloud bands being as, or more important, than the Coriolis effect. Would a differential in the velocity of the upper and lower cloud bands keep the GRS going? Anyone have info on this?

zoobyshoe

Here is the brief, undetailed statement I read:

"The planet spins fast, each day flashing by in ten earth hours. The spin produces a strong Coriolis force, the sidelong force that shoves against a person walking across a merry-go-round, and the Coriolis force drives the spot."

Chaos
-James Gleick

Now it mentions in a prior passage that the Voyager photos indicate the spot is stable, not, itself, rotating hurricane-like, and that the hurricane model is believed to be erroneous.

I'm having a hard time getting this all straight in my mind.

Your source, Phobos, seems to say they have, indeed, determined it to be rotating. (They refer to the direction of its rotation.)

Phobos

The Hubble site says it rotates...
http://heritage.stsci.edu/1999/29/caption.html

Here is a possible video of it (but I don't want to download quicktime to check it)...
http://www.solarviews.com/cap/jup/vjupitr3.htm

Nereid

Here's a nice set of collected images etc of the GRS, from the Galileo mission:
http://galileo.jpl.nasa.gov/images/jupiter/grs.html

From the JPL website (http://www.jpl.nasa.gov/) you can get data from many solar system spacecraft missions, including all the raw and processed images. Easy to lose yourself.

zoobyshoe

O.K. I found out the answer. You were on the verge of it here, Phobos.

Here is how the coriolis effect figures into the GRS:

As Phobos uncovered, the GRS is a high pressure island. This would imply, by earth weather standards that it is a subsiding, sinking area of cooler temperature gas that is thereby denser. This is what differentiates it from the surrounding lower pressure atmosphere to begin with.

It should dissipate into the lower pressure and disappear but it doesn't. Some dynamic is keeping it contained, or perhaps feeding it roughly in proportion to whatever high pressure it may lose.
(That's a different topic. My question is about how the coriolis effect figures in.)

As the presumedly more dense atmosphere rotates beneath it, the edge of the spot closer to the equator is subjected to greater surface speeds, running along beneath, than the edge farther away from the equator. If we say, for instance, that one edge is just touching the equator and the other is touching a tropic, the edge at the equator will have a greater circumference running beneath it than the edge at the tropic. This imbalance of force between the two edges is, obviously, what torques the GRS.

I was having a hard time figuring out where the torque was coming from. I see now that it is the result of two different surface speeds arising from the spherical shape of the planet.

(I discovered, too, that winds will take a different route around a high pressure area than they do around a low pressure area, and that these directions are flopped, mirror-like; Those in the northern hemisphere are enantiomorphs, so to speak, of those in the southern.)

-Zooby

FZ+

Actually, no... The previous passage says that the voyager probe showed the spot to be rotating anticyclonically, rather than cyclonically like earthbound hurricanes do. And the stability refers to the non-transient quality of the dynamic behaviour.

zoobyshoe

Yes, because a hurricane is a low pressure driven system, and as Phobos uncovered, the GRS is a high pressure system. It is rotating, but is not a hurricane. Wind goes the opposite direction around a high pressure island than it does a low pressure island.


Edit: I misapprehended what you were saying. You were saying I had incorrectly characterized what the previous passage in the Gleick book said. I have checked it and you are correct. It does say it was rotating but not from hurricane dynamics. My error.