<p>According to the American Geophysical Union and reported at <a href="https://phys.org/news/2013-04-scientists-dark-lightning-linked-visible.html" rel="nofollow noreferrer">phys.org</a>:</p>
<blockquote>
<p>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 (TGF).</p>
</blockquote>
<p>However, things are not quite so simple.  There are actually several gamma ray phenomena related to thunderstorms.</p>
<p>According to <a href="https://www.nature.com/articles/s42005-019-0168-y" rel="nofollow noreferrer">Gamma-ray glow preceding downward terrestrial gamma-ray flash</a>:</p>
<blockquote>
<p>Two types of high-energy events have been detected from thunderstorms.
One is “terrestrial gamma-ray flashes” (TGFs), sub-millisecond
emissions coinciding with lightning discharges. The other is
minute-lasting “gamma-ray glows”. Although both phenomena are thought
to originate from relativistic runaway electron avalanches in strong
electric fields, the connection between them is not well understood.</p>
</blockquote>
<p>The general thought is that electrons are accelerated to high speeds by the extreme electric field present around lighting but that's not yet a completely satisfying explanation.</p>
<p><a href="https://i.sstatic.net/9MLNa.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/9MLNa.png" alt="Gamma-Ray Factory" /></a><br/>
Image from <a href="https://media.nature.com/original/magazine-assets/d41586-021-00395-3/d41586-021-00395-3.pdf" rel="nofollow noreferrer">The Quest to Understand how Thunderstorms Create Gamma Rays</a></p>
<p>Capture of photonuclear neutrons is also a potential source of terrestrial gamma-ray flashes:</p>
<blockquote>
<p>These results challenge TGF theoretical models based on runaway
electron acceleration. The TGF discharge electric field accelerates
particles over the large distances for which maximal voltages of
hundreds of megavolts can be established. The combination of huge
potentials and large electric fields in TGFs can efficiently
accelerate particles in large numbers, and we reconsider here the
photon spectrum and the neutron production by photonuclear reactions
in the atmosphere. <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.106.018501" rel="nofollow noreferrer">Terrestrial Gamma-Ray Flashes as Powerful Particle Accelerators</a>)</p>
</blockquote>
<p><a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075552" rel="nofollow noreferrer">TGF Afterglows: A New Radiation Mechanism From Thunderstorms</a> considers three different mechanisms at different time scales.<br>
<a href="https://i.sstatic.net/zed0Fl.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/zed0Fl.png" alt="Sketch of the distribution of durations of TGFs, TGF afterglows, and gamma ray glows" /></a><br/></p>
<ul>
<li>&quot;TGFs originate from cold runaway where thermal electrons accelerate to tens of MeV in the strong electric fields of a propagating leader discharge.&quot;</li>
<li>&quot;Glows ... would originate from relativistic runaway electron avalanches (RREA) with feedback of photons and positrons creating new avalanches...&quot;</li>
<li>&quot;TGF afterglow ... when photons in the TGF are energetic enough to release neutrons from air molecules by a photonuclear reaction.... During thermalization they can be captured again by nuclei and sometimes with the release of a high-energy photon....&quot;</li>
</ul>

CC BY-SA 4.0
2022-02-13T22:00:57.703Z
https://en.wikipedia.org/wiki/Relativistic_runaway_electron_avalanche
uhoh
CC BY-SA 4.0
2022-02-11T17:55:08.987Z
2022-02-11T17:55:08.987Z
GrapefruitIsAwesome
<p>The Science at NASA video <a href="https://www.youtube.com/watch?v=hN0wGga5e0I" rel="noreferrer">ScienceCasts: Dark Lightning</a> describes observation of gamma rays from Earth by the <a href="https://en.wikipedia.org/wiki/Fermi_Gamma-ray_Space_Telescope" rel="noreferrer">Fermi Gamma-ray Space Telescope</a>.</p>
<p>These gamma rays are associated with weather that produces lightning, but the actual mechanism for gamma ray production <em>by weather</em> was still uncertain at the time.</p>
<p>The video explains that a discharge mechanism called &quot;Dark Lightning&quot; might produce the gamma rays without producing the same visible light signatures that normal lightning produces.</p>
<p><strong>Question:</strong> Did Dark Lightning turn out to be a real thing? Is this what produces gamma ray flashes from lightning storms?</p>
<hr />
<p>Screen shot from the video shows a graphic of a booklet with the following words on its cover:</p>
<blockquote>
<p>AGU Fall Meeting, San Francisco, 3-7 December 2012</p>
</blockquote>
<p><a href="https://i.sstatic.net/Yirip.jpg" rel="noreferrer"><img src="https://i.sstatic.net/Yirip.jpg" alt="AGU Fall Meeting, San Francisco, 3-7 December 2012" /></a></p>

<meteorology><lightning><electromagnetism><ionizing-radiation>
Did Dark Lightning turn out to be a real thing? Is this what produces gamma ray flashes from lightning storms?
uhoh
# Did Dark Lightning turn out to be a real thing? Is this what produces gamma ray flashes from lightning storms?

(Asked by: username_0 on 2021-08-07)

The Science at NASA video [ScienceCasts: Dark Lightning](https://www.youtube.com/watch?v=hN0wGga5e0I) describes observation of gamma rays from Earth by the [Fermi Gamma-ray Space Telescope](https://en.wikipedia.org/wiki/Fermi_Gamma-ray_Space_Telescope).

These gamma rays are associated with weather that produces lightning, but the actual mechanism for gamma ray production *by weather* was still uncertain at the time.

The video explains that a discharge mechanism called "Dark Lightning" might produce the gamma rays without producing the same visible light signatures that normal lightning produces.

**Question:** Did Dark Lightning turn out to be a real thing? Is this what produces gamma ray flashes from lightning storms?

---

Screen shot from the video shows a graphic of a booklet with the following words on its cover:

> AGU Fall Meeting, San Francisco, 3-7 December 2012

[![AGU Fall Meeting, San Francisco, 3-7 December 2012](https://i.sstatic.net/Yirip.jpg)](https://i.sstatic.net/Yirip.jpg)

**Tags:** meteorology, lightning, electromagnetism, ionizing-radiation


---

## 1 answers

### Answer by username_1 on 2022-02-11. Score: 4 | Accepted answer

According to the American Geophysical Union and reported at [phys.org](https://phys.org/news/2013-04-scientists-dark-lightning-linked-visible.html):

> 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 (TGF).

However, things are not quite so simple. There are actually several gamma ray phenomena related to thunderstorms.

According to [Gamma-ray glow preceding downward terrestrial gamma-ray flash](https://www.nature.com/articles/s42005-019-0168-y):

> Two types of high-energy events have been detected from thunderstorms.
> One is “terrestrial gamma-ray flashes” (TGFs), sub-millisecond
> emissions coinciding with lightning discharges. The other is
> minute-lasting “gamma-ray glows”. Although both phenomena are thought
> to originate from relativistic runaway electron avalanches in strong
> electric fields, the connection between them is not well understood.

The general thought is that electrons are accelerated to high speeds by the extreme electric field present around lighting but that's not yet a completely satisfying explanation.

[![Gamma-Ray Factory](https://i.sstatic.net/9MLNa.png)](https://i.sstatic.net/9MLNa.png)  
Image from [The Quest to Understand how Thunderstorms Create Gamma Rays](https://media.nature.com/original/magazine-assets/d41586-021-00395-3/d41586-021-00395-3.pdf)

Capture of photonuclear neutrons is also a potential source of terrestrial gamma-ray flashes:

> These results challenge TGF theoretical models based on runaway
> electron acceleration. The TGF discharge electric field accelerates
> particles over the large distances for which maximal voltages of
> hundreds of megavolts can be established. The combination of huge
> potentials and large electric fields in TGFs can efficiently
> accelerate particles in large numbers, and we reconsider here the
> photon spectrum and the neutron production by photonuclear reactions
> in the atmosphere. [Terrestrial Gamma-Ray Flashes as Powerful Particle Accelerators](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.106.018501))

[TGF Afterglows: A New Radiation Mechanism From Thunderstorms](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075552) considers three different mechanisms at different time scales.  
[![Sketch of the distribution of durations of TGFs, TGF afterglows, and gamma ray glows](https://i.sstatic.net/zed0Fl.png)](https://i.sstatic.net/zed0Fl.png)

* "TGFs originate from cold runaway where thermal electrons accelerate to tens of MeV in the strong electric fields of a propagating leader discharge."
* "Glows ... would originate from relativistic runaway electron avalanches (RREA) with feedback of photons and positrons creating new avalanches..."
* "TGF afterglow ... when photons in the TGF are energetic enough to release neutrons from air molecules by a photonuclear reaction.... During thermalization they can be captured again by nuclei and sometimes with the release of a high-energy photon...."

> **Comments:**
> **username_0**: https://en.wikipedia.org/wiki/Relativistic_runaway_electron_avalanche  

---

