Doubt regarding direction of current during lightning

[Puneeth423]

Main Question or Discussion Point

In which direction do current flow during lightning? If it is from cloud to earth, which charge gets accumulated in below part of the cloud?

 

[Naty1]

most lightning is cloud to cloud.

Check here for current description:

http://en.wikipedia.org/wiki/Lightning#Leader_formation_and_the_return_stroke

The leader current is from cloud to earth, the return stroke from earth to cloud; the latter is the most visible.

 

[davenn]

some interesting descriptions in that Wiki link but it could do with some expanding by some one :)

Having done storm chasing and photography for some 12 years I have seen and photo'ed some of the interesting variations.

Types
Some lightning strikes exhibit particular characteristics; scientists and the general public have given names to these various types of lightning. The lightning that is most-commonly observed is streak lightning. This is nothing more than the return stroke, the visible part of the lightning stroke. The majority of strokes occur inside a cloud so we do not see most of the individual return strokes during a thunderstorm.[citation needed]

Cloud-to-Ground lightning Cloud-to-Ground is the best known and second most common type of lightning. Of all the different types of lightning, it poses the greatest threat to life and property since it strikes the ground. Cloud-to-ground (CG) lightning is a lightning discharge between a cumulonimbus cloud and the ground. It is initiated by a leader stroke moving down from the cloud.

Yes ... as the most common is cloud to cloud strokes some buried in the clouds some visible along the base of the cloud .... the most spectactular being the "Anvil Crawlers" that spread out in all directions.

Bead lightning is a type of cloud-to-ground lightning which appears to break up into a string of short, bright sections, which last longer than the usual discharge channel. It is relatively rare. Several theories have been proposed to explain it; one is that the observer sees portions of the lightning channel end on, and that these portions appear especially bright. Another is that, in bead lightning, the width of the lightning channel varies; as the lightning channel cools and fades, the wider sections cool more slowly and remain visible longer, appearing as a string of beads.

Have caught this style on camera a number of times, mainly when the strike has been relatively close within 1 km (1000m)

Ribbon lightning occurs in thunderstorms with high cross winds and multiple return strokes. The wind will blow each successive return stroke slightly to one side of the previous return stroke, causing a ribbon effect.[citation needed]

Only seen photos, havent observed myself as yet

Staccato lightning is a cloud-to-ground lightning (CG) strike which is a short-duration stroke that (often but not always) appears as a single very bright flash and often has considerable branching.[41] These are often found in the visual vault area near the mesocyclone of rotating thunderstorms and coincides with intensification of thunderstorm updrafts. A similar cloud-to-cloud strike consisting of a brief flash over a small area, appearing like a blip, also occurs in a similar area of rotating updrafts.

Staccato is always spectactular, making a great photo. I have watched complete storms and not seen a staccato strike, yet in another storm they have been common

Ground-to-cloud Ground to cloud lightning is an artificially initiated, or triggered, category of ground flashes. Triggered lightning goes from tall structures on the ground, such as towers on mountains, to clouds.[42]

Not sure what to make of their comments on this one .... I really dont like that artificially initiated as it gives the impression that its man made. I have only captured 1 Ground to Cloud strike and it was NOT from any sort of tall man made structure. Tho many pix and videos I have see, that has been the case. The often are also inverted Staccato rather than a single channel stroke

Dave

 

[nsaspook]

This program has some very good video of ground to cloud strikes.

http://www.liveleak.com/view?i=b19_1268795779

 

[Puneeth423]

You know current will flow only when the path is complete and closed. In this case, that doesn't happen. Lightning dies after some time? Its not a complete or closed path. How can you tell that charges are flowing or current is flowing?

 

[davenn]

You know current will flow only when the path is complete and closed. In this case, that doesn't happen. Lightning dies after some time? Its not a complete or closed path. How can you tell that charges are flowing or current is flowing?

why would you say that ? of course the path is completed and massive amounts of current flows in those brief milliseconds :)
The path is between cloud and cloud or cloud and ground between regions of excessive positive and of excessive negative charges ... the flow of current balances that out

how can you tell ? you can see and hear the effects of the of the current flowing.
the brigh glow of the ionised air, the crash of the thunder, the buildings, trees electronics etc that get damaged/destroyed because of the huge current flow

Dave

 

[davenn]

..............which charge gets accumulated in below part of the cloud?

If you looked at any of the links provided by those that responded to you ....
you would have seen that usually the base of the storm cloud get strongly negatively charged and the ground below it positively charged

Dave

 

[Puneeth423]

I m asking, where can you see a closed path here? We know, current will flow in a closed path only. It will reach the the ground, but where is the closed path? Also, if there is negative charge below the clouds, negative charge will flow from cloud to ground, which makes current flowing from ground to clouds. What we see is lighting striking from cloud to earth. Will lightning show the direction of current or charge? Also, there are few lightnings in those videos striking from earth towards clouds. What can be the current flow direction in those cases?

 

[davenn]

the closed path is the ioniosed air channel between the cloud and the ground

it is probably difficult to tell in which direction the current flow is as it depends on the type of discharge because we wouldnt know what the polarity of the leader is from the ground see image .....

cheers
dave

 

[davenn]

The wiki link originally given by Naty1 gives you an answer

snippet from Wiki.....

As the field increases, the positive streamer may evolve into a hotter, higher current leader which eventually connects to the descending stepped leader from the cloud. It is also possible for many streamers to develop from many different objects simultaneously, with only one connecting with the leader and forming the main discharge path. Photographs have been taken on which non-connected streamers are clearly visible.[35]

Once a channel of ionized air is established between the cloud and ground this becomes a path of least resistance and allows for a much greater current to propagate from the Earth back up the leader into the cloud. This is the return stroke and it is the most luminous and noticeable part of the lightning discharge

so its tells you that the main discharge is in the return stroke from the positively charged area to the negatively charged area
which could be either cloud to ground or ground to cloud depending on how the charges are distributed as in the diagrams above

Dave