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A number of sources on the Internet claim that an asteroid impact in 2000 caused widespread power outages in Yukon, Canada. For example, according to the German-language Wikipedia page for the small town of Atlin in British Columbia (just south of Yukon):

Atlin war auch vom Impakt (Asteroideneinschlag) betroffen, der am 18. Januar 2000 Yukons Stromnetz lahmlegte. (translation: "Atlin was also affected by the asteroid impact that paralyzed Yukon's electricity grid on January 18, 2000.")

On AerospaceWeb, retired astronomer Justine Whitman makes a more specific version of the claim:

In January 2000, a meteor only 15 ft (5 m) across entered the atmosphere and exploded over the town of Whitehorse in the Canadian Yukon. The blast created an electromagnetic pulse (EMP) similar to that of a high-altitude nuclear detonation and disabled a third of the region's electrical power grid.

However, none of this seems plausible to me. The meteor in question was the Tagish Lake meteorite, which broke up more than 20 miles above the ground over an unpopulated area. Meteors of this size do not normally cause an EMP or damage the power grid, since they do not produce high-energy gamma rays like a nuclear explosion. Also, I can't find any references to a power outage in news reports from the time.

What is the origin of this story, and is there any truth to it?

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    While I can't address the specific issue, a boom 20 miles up certainly can cause EMP. Starfish Prime (1.4 megaton h-bomb) detonated 250 miles up--and caused EMP damage 900 miles away. (And that's not a max range--EMP at sea wouldn't be noticed.) May 21, 2021 at 2:55
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    @LorenPechtel Good point, thanks for commenting. However, don't nuclear EMP's require gamma radiation? A meteor would be able to ionize atoms in the upper atmosphere, but I wouldn't think it could give the electrons enough energy to produce significant cyclotron radiation and an EMP.
    – Thorondor
    May 21, 2021 at 3:10
  • EMP is actually a gigantic lightning bolt, it doesn't require cyclotron energies. May 21, 2021 at 3:39
  • @LorenPechtel Could you clarify what you mean by "EMP is actually a gigantic lightning bolt"? As I understand it, there are significant differences between EMP's and lightning bolts.
    – Thorondor
    May 21, 2021 at 3:46
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    Non-nuclear EMP is a thing en.wikipedia.org/wiki/… but I agree that an asteroid causing such an event seems pretty implausible. There was no suggestion of any EMP from the Chelyabinsk meteor, and that is estimated at 20m across with an energy of some 30 times the Hiroshima A-bomb. May 21, 2021 at 8:17

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Notably, the body that created the fireball was initially only ~4 meters in diameter with a mass of 200,000 kg prior to atmospheric entry, traveling around 16 km/s (Brown et al. 2000). This is substantially smaller than the object that caused the airburst over Chelyabinsk (see Popova et al. 2015), which I'll discuss later. This mass was reduced prior to the explosion, as much of it was ablated as it traveled through the atmosphere.

I'm extremely skeptical of the claim because we have evidence that much of the area's telecommunications equipment functioned perfectly normally in the aftermath of the blast. This Master's paper relates accounts of the Tagish Lake event from locals in the area, including northern British Columbia and much of the Yukon Territory. It appears that immediately after the explosion, the radio station in Whitehorse was broadcasting as normal to a wide area:

The phone calls started immediately. With the contrail still bright, eyewitnesses called friends; they called the authorities; they called scientists; they called the media. Authorities and scientists and media all called each other, trying to nail down what had just happened. The phone lines at the local radio station of the Canadian Broadcasting Corporation filled with witnesses anxious to share their stories, and it was up to Peter Novak's calm baritone to mediate discussion on his daily program, The Valley Voice.

Whitehorse is claimed to have been near the blast (well, tens of kilometers below it, vertically). While landlines and individual cell phones would not necessarily be affected by an EMP, cell towers and other infrastructure might be - rendering communications difficult. This presumably includes equipment needed to broadcast the aforementioned radio show. It would be a bit surprising if there was no effect on telecommunications nearby if the electrical grid had severe problems - and yet folks seem to have been able to communicate just fine, including in Whitehorse.

It's not implausible that a meteor could cause electromagnetic activity in the atmosphere, but there's a significant difference between electromagnetic activity and an electromagnetic burst. There are a couple known cases of electrophonic bursters (which have an unfortunately similar name), meteors which were accompanied by pops and clicks. It has been proposed (Beech & Foschini 1999) that the sounds are caused by shock waves propagating through the plasma caused by the ablation of the meteor as it travels through the atmosphere, causing pulses in the electric field of the plasma and in turn causing sounds, which can propagate through the atmosphere.

These pulses are distinct from EMPs in the typical sense, of course. Remember the Chelyabinsk burst I mentioned? It did cause electrophonic sounds, but it did not cause an EMP. It did affect telecommunications, but through shock waves, not an electromagnetic pulse (Popova et al. 2013):

Electrophonic sounds were heard (SM Sect. 1.6), but there was no evidence of an Electromagnetic Pulse (EMP) under the track in neighboring Emanzhelinka. Due to shock wave induced vibrations, electricity and cell phone connectivity was briefly halted in the Kunashaksky district at the far northern end of the damage area.

The shock wave from the explosion did damage - not any sort of electromagnetic activity. Moreover, the Chelyabinsk object was substantially more massive than the body that impacted at Tagish Lake. The above paper estimates a mass of about 13,000,000 kg and a diameter of around 20 meters, traveling at 19 km/s.

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    "a diameter of around 20 km" That should be 20m surely? (Edit is whining about the 6 character minimum.)
    – Harabeck
    May 21, 2021 at 19:25
  • @Harabeck You're absolutely right! Thank you.
    – HDE 226868
    May 21, 2021 at 19:29
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    Re Notably, this was not an asteroid impact. By most definitions of the distinction between an asteroid and a meteoroid, this was an asteroid. Asteroids are rocky (rather than icy) objects in space that are larger than one meter across. Meteoroids are objects (icy or not) that are smaller than one meter across. This object was not icy (it was a carbonaceous chondrite), and it was larger than a meter across (it was four to five meters). May 23, 2021 at 16:34
  • It also helps to remember the distinction between asteroid, meteoroid, comet, meteor, and meteorite. A meteor is any natural space object that enters the Earth's atmosphere. Asteroids, comets, and meteoroids can all become meteors. The huge dinosaur killer asteroid or comet became a meteor when it entered the Earth's atmosphere. A meteorite is a remnant of a meteor that lands on the Earth's surface. Meteoroids are smallish space objects, and the object in question was just above smallish. May 23, 2021 at 16:46
  • @DavidHammen Ah, fair. I had made my categorization based on the size of the body after the atmospheric ablation, at which point it was below ~1 meter across, and as it was likely originally a small fragment of a larger asteroid, I felt that "asteroid" in the original usage would bring to mind the idea of an object much larger than a few meters across, particularly given the claim of a large outage. But it does seem like it would be only be correct to use its size prior to atmospheric entry.
    – HDE 226868
    May 23, 2021 at 17:40

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