<p>I found the paper you initially referred to here:</p>

<p><a href="http://onlinelibrary.wiley.com/doi/10.1029/JB073i006p01889/full" rel="noreferrer">http://onlinelibrary.wiley.com/doi/10.1029/JB073i006p01889/full</a></p>

<p>based on the hyperlink by the xkcd webpage you referred</p>

<p><a href="http://www.agu.org/pubs/crossref/1968/JB073i006p01889.shtml" rel="noreferrer">http://www.agu.org/pubs/crossref/1968/JB073i006p01889.shtml</a></p>

<p>The full reference for this paper is: Oetzel, G. N. (1968), Computation of the diameter of a lightning return stroke, J. Geophys. Res., 73(6), 1889–1896, <a href="http://dx.doi.org/10.1029/JB073i006p01889" rel="noreferrer">doi:10.1029/JB073i006p01889</a>.</p>

<p>In the abstract:</p>

<blockquote>
  <p>The diameter of a first return stroke is found to lie in the range <strong>1–4 cm</strong>. Subsequent return strokes are smaller, with diameters in the range <strong>0.2–0.5 cm</strong>. In many cases, strokes to towers have shown evidence of the smaller strokes occurring alone. These are explained as strokes initiated by an upward leader.</p>
</blockquote>

<p>This paper is quite old - but is relevant nevertheless.</p>

<p>A more recent paper review the physics of lightning in this review paper, titled 'The Physics of lightning' by <a href="http://www.sciencedirect.com/science/article/pii/S037015731300375X" rel="noreferrer">Dwyer and Uman (2014)</a>. They present the various steps implied when a lightning form, illustrated by this illustration <a href="https://i.sstatic.net/9mVGG.jpg" rel="noreferrer">(Figure 1)</a>:</p>

<p><img src="https://i.sstatic.net/9mVGG.jpg" alt="Fig. 1.3 in [Dwyer and Uman (2014)"></p>

<p>Basically, there is several stages when a lightning strike. There is the stepped leader component, that somewhat lead the way for the exchanges that will follow. In the figure, we notice the positive and negative signs (+ / -) and how they change position depending on the discharge.</p>

<p>The stepped leader can be followed by return strikes and so on. In this paper they mention diameters for the stepped leader, which may appear to be much larger than the return stroke, such as in the range of one to ten meter in diameter:</p>

<blockquote>
  <p>The luminous diameter of the stepped leader has been measured photographically to be between 1 and 10 m. </p>
</blockquote>

<p>But - this is by using photography - yet the core of the lightning at the center (the core) seem to be a few centimeter in diameter:</p>

<blockquote>
  <p>It is thought, however, that most of the stepped-leader current flows down a narrow conducting core a few centimeters in diameter at the center of the observed leader. </p>
</blockquote>

<p>So in the end both papers tend toward similar centimeter-scale measurements for the lightning core.</p>

<hr>

<p>The core: aforementioned literature refer to the component of the actual lightning as a 'current carrying core' surrounded by a corona sheath. The sheath is what appear to be 1 to 10 m in diameter, where the actual 'electricity channel' is centimeter wide; </p>

<p>so this core as the centimeter wide channel is the electron pathway.</p>

CC BY-SA 3.0
2016-11-18T16:48:24.993Z
Is the term *lightning core* or *the core of lightning* widely used among researchers? Also, if we have *electron pathway* as its name already, why do we need to have another name for it?
Ooker
CC BY-SA 3.0
2016-11-18T17:07:53.223Z
@Ooker 'electron pathway' was a simple way to express and illustrate the concept of core - I don't think this is in use in the literature. Lightning core seem used by a few, such as https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/new-model-and-estimation-of-the-danger-of-ball-lightning/054B6D10646954B07F3AB033F5E1BB56 and http://onlinelibrary.wiley.com/doi/10.1002/qj.49708134809/abstract but I can guess other expressions are used too for the same concept.
marsisalie
CC BY-SA 3.0
2016-11-17T17:46:51.773Z
2016-11-17T19:38:22.100Z
2016-11-17T19:38:22.100Z
marsisalie
<p>The post <a href="http://what-if.xkcd.com/16/" rel="noreferrer">Lightning</a> mentions about "the core of a lightning bolt":</p>

<blockquote>
  <p>The core of a lightning bolt is a <a href="http://www.agu.org/pubs/crossref/1968/JB073i006p01889.shtml" rel="noreferrer">few centimeters in diameter</a>.</p>
</blockquote>

<p>I couldn't find any article discussing about this. The reference link has been changed, so I couldn't read the original post. So what is it?</p>

<lightning>
What is the core of the lightning?
Ooker
# What is the core of the lightning?

(Asked by: username_0 on 2016-11-17)

The post [Lightning](http://what-if.xkcd.com/16/) mentions about "the core of a lightning bolt":

> The core of a lightning bolt is a [few centimeters in diameter](http://www.agu.org/pubs/crossref/1968/JB073i006p01889.shtml).

I couldn't find any article discussing about this. The reference link has been changed, so I couldn't read the original post. So what is it?

**Tags:** lightning


---

## 1 answers

### Answer by username_1 on 2016-11-17. Score: 5 | Accepted answer

I found the paper you initially referred to here:

<http://onlinelibrary.wiley.com/doi/10.1029/JB073i006p01889/full>

based on the hyperlink by the xkcd webpage you referred

<http://www.agu.org/pubs/crossref/1968/JB073i006p01889.shtml>

The full reference for this paper is: Oetzel, G. N. (1968), Computation of the diameter of a lightning return stroke, J. Geophys. Res., 73(6), 1889–1896, [doi:10.1029/JB073i006p01889](http://dx.doi.org/10.1029/JB073i006p01889).

In the abstract:

> The diameter of a first return stroke is found to lie in the range **1–4 cm**. Subsequent return strokes are smaller, with diameters in the range **0.2–0.5 cm**. In many cases, strokes to towers have shown evidence of the smaller strokes occurring alone. These are explained as strokes initiated by an upward leader.

This paper is quite old - but is relevant nevertheless.

A more recent paper review the physics of lightning in this review paper, titled 'The Physics of lightning' by [Dwyer and Uman (2014)](http://www.sciencedirect.com/science/article/pii/S037015731300375X). They present the various steps implied when a lightning form, illustrated by this illustration [(Figure 1)](https://i.sstatic.net/9mVGG.jpg):

![Fig. 1.3 in [Dwyer and Uman (2014)](https://i.sstatic.net/9mVGG.jpg)

Basically, there is several stages when a lightning strike. There is the stepped leader component, that somewhat lead the way for the exchanges that will follow. In the figure, we notice the positive and negative signs (+ / -) and how they change position depending on the discharge.

The stepped leader can be followed by return strikes and so on. In this paper they mention diameters for the stepped leader, which may appear to be much larger than the return stroke, such as in the range of one to ten meter in diameter:

> The luminous diameter of the stepped leader has been measured photographically to be between 1 and 10 m.

But - this is by using photography - yet the core of the lightning at the center (the core) seem to be a few centimeter in diameter:

> It is thought, however, that most of the stepped-leader current flows down a narrow conducting core a few centimeters in diameter at the center of the observed leader.

So in the end both papers tend toward similar centimeter-scale measurements for the lightning core.

---

The core: aforementioned literature refer to the component of the actual lightning as a 'current carrying core' surrounded by a corona sheath. The sheath is what appear to be 1 to 10 m in diameter, where the actual 'electricity channel' is centimeter wide;

so this core as the centimeter wide channel is the electron pathway.

> **Comments:**
> **username_0**: Is the term *lightning core* or *the core of lightning* widely used among researchers? Also, if we have *electron pathway* as its name already, why do we need to have another name for it?  
> **username_1**: @username_0 'electron pathway' was a simple way to express and illustrate the concept of core - I don't think this is in use in the literature. Lightning core seem used by a few, such as https://www.cambridge.org/core/journals/journal-of-plasma-physics/article/new-model-and-estimation-of-the-danger-of-ball-lightning/054B6D10646954B07F3AB033F5E1BB56 and http://onlinelibrary.wiley.com/doi/10.1002/qj.49708134809/abstract but I can guess other expressions are used too for the same concept.  

---

