Slashdot Mirror
Scientists Discover A New Kind Of Lightning
Exoman writes "Lightning that shoots upward up to 60 miles from the clouds? A team of researchers led by Han-Tzong Su of the National Cheng Kung University in Taiwan, videotaped the discharges last July from an observatory on the southern tip of the island. The lightning was firing from the top of thunderclouds more than 300 miles away across the South China Sea. The researchers reported their work Thursday in the journal Nature."
There are some pictures and video available at Nature.com - http://www.nature.com/nsu/020311/020311-6.html
Most notably, 19 times from space.
Lightning Jets Blow Sky High
Found their site (please be nice) and dug around enough to find a decent image of what this kind of lightning looks like.
Check for yourself here.
I gotta say, I'd think it was the end of the world if I saw something like this on a regular basis.
The nasa page the parent points to seems to be describing red sprites, first photographic evidence in 1988/1989. This looks to be something different.
From the article:
Other types of high-altitude lightning events also have been documented in the past decade using high-flying planes and cameras carried aboard the space shuttle fleet. One, called blue jets, also streams upward but does not rise as high or spread over as wide an area as the giant jets in the new study.
Red sprites, another form of high-altitude lightning, travel downward toward clouds but appear to stop short of reaching the top of thunderclouds.
Su noted that while the other types of jets seem to occur over most parts of the world, the six gigantic optical jets observed so far have all been connected to thunderstorms over the open sea.
Also, from the Wired article:
Scientists had found plenty of evidence of sprites in the 1990s, but the larger, upward streaming lightning jets had escaped detection -- possibly because they may only occur over oceans, Inan said.
One, called blue jets, also streams upward but does not rise as high or spread over as wide an area as the giant jets in the new study.
Here is a link to the two articles in the most recent Nature, though w/out a site license or subscription all you can see is the first paragraph of the paper by Su et al.
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
Yes, they are nice images, but oddly enough I found the same images in the same directory without the annoying lettering. The lettering tipped me off to the fact that the images were the front cover of an issue of Geophysical Research Letters from last year (a pdf copy can be found in the same directory). The images are of a type of sprite known as a carrot, although the top one could be columniform.
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
Current is actually defined as a flow of positive charge. In most systems it is the electrons that flow (mostly because they are so small), but there are many sytems where the charge carriers are positive; in some materials, charge is transported by "holes" which are positively charged.
Current flows from a negative source to a positive source... opposites attract, and since electrons are free (for the most part they can be though of as a "soup"), they flow to the positively charged particles. I'm not sure what charge the ground and the clouds have, but I think its the opposite I recall a debate about it in the 80's and 90's, and I recall the conclusion being that lightning goes from the ground to the cloud, and its just an illusion that it goes the other way, they used cameras with extremely high shutter speeds... so we could conclude that the ground is negative, and the clouds positive...
There's 3 types of lightning: Cloud to ground, ground to cloud, and cloud to cloud. I guess you can figure out which has the positive and negative charge if, as stated above, charge flows from - to +.
There are only 10 kinds of people in this world... those who understand binary and those who don't
Yes. When someone says current flows from A to B, they (usually) mean 'positive current'. And usually, it doesn't matter. Usually (always? I don't remeber that class very well), electrons are the majority carrier in metals, but in semiconductors it can be either way.
>Wether such a description can be used in >gasous/plasma environment I'm not sure.
For sure, in plasma physics, both types of carriers are very important, though in this case it is electrons and ions, rather than holes.
Here's a link which does a good job of giving a general overview of how lightning works:
http://wvlightning.com/cgdesc.html
I don't read Chinese, so it was difficult. Here are some colorized images superimposed on fanciful daytime scenes from this page. The original images are not in color, and they come from this mostly illegible (to me) page. Most of the other images appear to be of sprites. I'm not certain how they know the tops are red and the bottoms are blue.
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
If there is a positively charged object and a negatively charged object, they exert an equal attractive force on each other, right?
F = ma, or: a = F/m. The heavier the object, the slower it will accelerate due to the force.
Now, in a wire, the negatively charged electrons are significantly lighter than the positively charged nuclei they've detactched from. So it's the electrons that move in an electrical circuit.
However, we're not talking about an eletrical circuit here. We're talking about charged ions. Ions are atoms or molecules, not sub-atomic particles. It can be quite easy for positively charged ions to be lighter than the negatively charged ions, and thus the positive ions move instead. Even when the positive ions are heavier, they won't be so disproportionately heavy, so they'll still move.
Keeping up now?
"Software is too expensive to build cheaply"
Discalimer: IAASSP (I AM a solid state physicist)
:-P
Please ignore the parent of this post (the one with F=ma, etc.). If you've got some mod points, please mod it down, or at least label it as "Funny" because just about everything in it is dead WRONG.
Going over all the made-up physics would just waste space. Please mod it down! (and me up)
The reason why electrons (instead of nuclei) move in metals has nothing to do with relative accelerations. In a solid, the nuclei are fixed in place. They don't generate a positive electrical current at all, and the "equal and opposite" argument of the poster doesn't apply. (The fastenings on the wire take up the infinitesimal acceleration due to momentum change of the electrons.)
The poster is wrong again about "charged ions" (by which he should mean plasma). Plasma isn't a solid; both species (positive & negative) of ions move and contribute to the current.
I am not a plasma physicist but DID study university physics. The + and - carriers won't move in inverse proportion to their masses; they're not accelerating freely unless in a vacuum. They bump into stuff and can be treated as moving at constant velocity. Parent poster: look up "mean free path".
On the scale of individual ions, balancing charge is WAY more important than balancing masses when figuring the dynamics.
If you just say "F=ma" followed by anything you like, that's not a scientific explanation.
je ne suis pas un fou
One is called burning tree and is quite unique. This is a tree like discharge appearing to hover above the ground.
http://www.astronet.ru:8100/db/x/msg/1170947
I don't think its new.
I'd go on a Vegan diet but the delivery time from Vega is too long. --brownkitty