What is a leader stroke?

[′lēd·ər ‚strōk] (geophysics) The entire set of events associated with the propagation of any leader between cloud and ground in a lightning discharge.

What are Leader strokes in lightning?

Typically, a negative flash of lightning will be comprised of an initial stepped leader/return stroke followed by 2 or 3 subsequent dart leaders/return strokes. Multiple return strokes will cause the lightning to flicker.

What is stepped leader stroke?

In thunderstorm: Initial stroke. …to thousands of amperes, the stepped leader propagates toward the ground at an average velocity of 1.5 × 10⁵ metres per second, or about one two-thousandth the speed of light. It is called a stepped leader because of its downward-moving “stepped” pulses of luminosity.

What is the first stroke of lightning called?

Cloud-to-cloud and intracloud lightning

True cloud-to-cloud lightning is rare because most lightning flashes occur within a cloud. The first lightning flash in a thunderstorm is typically an intracloud discharge. When an intracloud discharge occurs, the cloud becomes luminous for approximately 0.2 to 0.5 second.

How does the return stroke happen?

In a typical flash, the first return stroke ascends as soon as the descending stepped leader makes electrical contact with the earth, often aided by short ascending ground streamers. The second and all subsequent return strokes differ only in that they are initiated by a dart leader and not a stepped leader.

What is a stroke?

Why do stroke victims sleep so much?

Excessive sleeping after stroke is common during the early stages of recovery as the brain works hard to heal itself. However, excessive daytime sleepiness could signify other problems that deserve a conversation with your doctor.

Why do you not give oxygen to stroke patients?

Giving oxygen to people who have had a stroke could plausibly help to prevent or reduce brain damage. However, high levels of oxygen can also be harmful – causing constriction of the blood vessels, reduced blood flow to the brain, damage to the lungs and restricting people's mobility.

What color lightning is the strongest?

White: most powerful lightning color

White is the most dangerous color of lighting. It suggests both a low concentration of moisture and a high concentration of dust in air. We all are aware that being hit by lightning can have serious consequences.

What is fork lightning?

Cloud-to-Ground (CG) Lightning

In CG lightning, a channel of negative charge, called a stepped leader, will zigzag downward in a 'forked' pattern - hence it is sometimes called forked lightning. This stepped leader is invisible to the human eye, and travels to the ground in a millisecond.

What are the 4 types of lightning?

There are three common types of lightning: cloud to ground, cloud to cloud and cloud to air. Cloud to ground lightning is the most dangerous.

What is a lightning streamer?

When a branch of the stepped leader reaches within about 50 meters of the ground or some object on the ground, it connects with an upward-developing positive charge, often referred to as an upward streamer. Upward streamers tend to develop from the taller objects beneath one or more branches of the stepped leader.

Is it possible to thunder without lightning?

No, it is not possible to have thunder without lightning. Thunder starts as a shockwave from the explosively expanding lightning channel when a large current causes rapid heating. However, it is possible that you might see lightning and not hear the thunder because it was too far away.

What is a dart leader?

(Also called continuous leader.) The leader which, after the first stroke, typically initiates each succeeding stroke of a multiple-stroke flash lightning. (The first stroke is initiated by a stepped leader.) The dart leader derives its name from its appearance on photographs taken with streak cameras.

Does all lightning hit the ground?

No, lightning does not always strike the ground. In reality, there are three main kinds of lightning in nature, which are distinguishable on the basis of where they occur. The lightning on the ground is seen in the case of cloud to ground lightning. Let us learn about it in detail.

What are the stages of a lightning strike?

Can lightning go sideways?

Lightning can also travel from one cloud to another, or cloud-to-cloud (CC). Spider lightning refers to long, horizontally traveling flashes often seen on the underside of stratiform clouds. Spider lightning is often linked to +CG flashes.

What is dark lightning?

Dark lightning is a burst of gamma rays produced during thunderstorms by extremely fast moving electrons colliding with air molecules. Researchers refer to such a burst as a terrestrial gamma ray flash.

What is bead lightning?

bead lightning, also called chain lightning, form of lightning of longer duration than more typical lightning that appears as a string of luminous segments instead of a continuous channel. It occurs infrequently but has been observed many times.

What is the rarest type of lightning?

ball lightning, also called globe lightning, a rare aerial phenomenon in the form of a luminous sphere that is generally several centimetres in diameter. It usually occurs near the ground during thunderstorms, in close association with cloud-to-ground lightning.

What is a Superbolt lightning?

“Superbolts” are the most powerful lightning on Earth, with discharges so strong that they cannot be reproduced in the laboratory. The bolts also display geographic and seasonal attributes opposite that of regular lightning, adding to their mystery.

Is Gold lightning real?

Yellow lightning is uncommon; however, they tend to be cooler than the blue, lilac and white. They're caused to due to a high concentration of dust in the air. And is an indication of a dry thunderstorm with low-precipitation.

Is red lightning real?

Red lightning doesn't exist in the literal sense, according to the National Weather Service. The closest known phenomena is something called a red sprite, which occurs high in the atmosphere “directly above an active thunderstorm,” NOAA says.

What are the three types of strokes?

What is the normal oxygen level for stroke patients?

In 2003, the American Stroke Association Guideline recommended keeping the oxygen saturation level at or above 95% [28].

What is your oxygen level during a stroke?

In a recent local study we found that the mean oxygen saturation in awake stroke patients was 94.5%, which was about 1% lower than in controls.