APOD: Energetic Particle Strikes the Earth (2023 Dec 05)

[APOD Robot]

Energetic Particle Strikes the Earth

Explanation: It was one of the most energetic particles ever known to strike the Earth -- but where did it come from? Dubbed Amaterasu after the Shinto sun goddess, this particle, as do all cosmic rays that strike the Earth's atmosphere, caused an air shower of electrons, protons, and other elementary particles to spray down onto the Earth below. In the featured illustration, a cosmic ray air shower is pictured striking the Telescope Array in Utah, USA, which recorded the Amaterasu event in 2021 May. Cosmic ray air showers are common enough that you likely have been in a particle spray yourself, although you likely wouldn't have noticed. The origin of this energetic particle, likely the nucleus of an atom, remains a mystery in two ways. First, it is not known how any single particle or atomic nucleus can practically acquire so much energy, and second, attempts to trace the particle back to where it originated did not indicate any likely potential source.

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[AVAO]

Energetic Particle Strikes the Earth

Explanation: It was one of the most energetic particles ever known to strike the Earth -- but where did it come from? Dubbed Amaterasu after the Shinto sun goddess, this particle, as do all cosmic rays that strike the Earth's atmosphere, caused an air shower of electrons, protons, and other elementary particles to spray down onto the Earth below. In the featured illustration, a cosmic ray air shower is pictured striking the Telescope Array in Utah, USA, which recorded the Amaterasu event in 2021 May. Cosmic ray air showers are common enough that you likely have been in a particle spray yourself, although you likely wouldn't have noticed. The origin of this energetic particle, likely the nucleus of an atom, remains a mystery in two ways. First, it is not known how any single particle or atomic nucleus can practically acquire so much energy, and second, attempts to trace the particle back to where it originated did not indicate any likely potential source.

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Nice illustration. One could argue about the P in APOD - but what is real ...that has already been discussed enough
Perhaps a link to the original scientific publication or image (arxiv) would be helpful.

Click to view full size image

"The high-energy particle event observed by TA SD on 27 May 2021. (A) A map of the TA SD. Each dot indicates the location of a SD station. The black arrow indicates the shower direction projected on the ground. The landing shower core position is located at (−9471 ± 31 m, 1904 ± 23 m) from the central position of the SD. The size of the colored circles is proportional to the number of particles detected by each station and the color denotes the relative time from the earliest detector. (B) The corresponding detector waveforms of flash analog-to-digital converter (FADC) counts for each station are shown with total signal in units of the minimum ionizing particle (MIP) and distance from the shower axis indicated. Thick and thin lines are recorded signals in upper and lower layers for each station. Each SD is identified by a four digit number. The first two digits correspond to the column of the array in which the SD is located (numbered west to east) and the second two digits correspond to the row (numbered south to north). The coordinated universal time (UTC) is used for the date and time of the event. The size of particle density and color code of the relative time in (A) are quantitatively indicated for each detector. " https://arxiv.org/pdf/2311.14231.pdf

[RocketRon]

Do we know for certain that this was indeed a single high energy particle ?
And not a whole 'cohort' of particles - arriving together ??

Indeed, Photographing such an event is going to present some challenges

[VictorBorun]

Do we know for certain that this was indeed a single high energy particle ?
And not a whole 'cohort' of particles - arriving together ??

Indeed, Photographing such an event is going to present some challenges

This should snapshot individual high energy particles creating a shower in the atmosphere

[Christian G.]

Good lord, Amaterasu rivals with the oh my god particule! Had this particule been travelling with a clock and originated a billion light-years away, its clock would indicate a one day travel!

[Chris Peterson]

Do we know for certain that this was indeed a single high energy particle ?
And not a whole 'cohort' of particles - arriving together ??

There is no mechanism by which a group of particles would travel together. And the particle shower caused by multiple low energy collisions would be completely different from that created by a single high energy particle.

[johnnydeep]

Do we know for certain that this was indeed a single high energy particle ?
And not a whole 'cohort' of particles - arriving together ??

There is no mechanism by which a group of particles would travel together. And the particle shower caused by multiple low energy collisions would be completely different from that created by a single high energy particle.

So, no natural mechanism that could do for particles what a laser does for photons (sort of), or that a particle accelerator can do for protons?

Also, that unimpeachable source Wikipedia says:

Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light.

[Chris Peterson]

Do we know for certain that this was indeed a single high energy particle ?
And not a whole 'cohort' of particles - arriving together ??

There is no mechanism by which a group of particles would travel together. And the particle shower caused by multiple low energy collisions would be completely different from that created by a single high energy particle.

So, no natural mechanism that could do for particles what a laser does for photons (sort of), or that a particle accelerator can do for protons?

Also, that unimpeachable source Wikipedia says:

Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light.

If you take "cluster" to simply mean atoms, sure. Not groups of independent particles.

[johnnydeep]

There is no mechanism by which a group of particles would travel together. And the particle shower caused by multiple low energy collisions would be completely different from that created by a single high energy particle.

So, no natural mechanism that could do for particles what a laser does for photons (sort of), or that a particle accelerator can do for protons?

Also, that unimpeachable source Wikipedia says:

Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light.

If you take "cluster" to simply mean atoms, sure. Not groups of independent particles.

Alright. I wasn't considering a nucleus as a cluster, but obviously it is, and was also thinking there might be other "cluster" possibilities. I suppose neutrons could travel together in a group since they don't repel each other, but since they have no charge, presumably it would also be difficult to accelerate them. Hmm, how IS a nucleus cosmic ray accelerated anyway?

[Rauf]

So, no natural mechanism that could do for particles what a laser does for photons (sort of), or that a particle accelerator can do for protons?

Also, that unimpeachable source Wikipedia says:

If you take "cluster" to simply mean atoms, sure. Not groups of independent particles.

Alright. I wasn't considering a nucleus as a cluster, but obviously it is, and was also thinking there might be other "cluster" possibilities. I suppose neutrons could travel together in a group since they don't repel each other, but since they have no charge, presumably it would also be difficult to accelerate them. Hmm, how IS a nucleus cosmic ray accelerated anyway?

I don't know. But, it says here:

Lower-energy cosmic ray particles that strike the earth come from within our own Milky Way Galaxy. They may originate, directly or indirectly, from the supernova icon info explosions that mark the deaths of many stars. These explosions throw out fast-moving magnetic fields which reflect charged particles. Cosmic ray nuclei gain energy when they collide with such a moving reflector. At a magnetic shock, where the magnetic field slows abruptly, particles can become trapped between two reflectors. Like a ping-pong ball caught between two converging paddles, the nuclei make many reflections, and the energy gained in each reflection grows as their energy increases. This "magnetic shock acceleration" model was first proposed by the great physicist Enrico Fermi as an explanation for the acceleration of most cosmic rays. The process has been observed in magnetic shocks in the solar wind that flows out from our sun, producing cosmic rays of modest energy. The stronger moving magnetic fields produced in supernova explosions could provide the energy for most other cosmic rays.

[johnnydeep]

If you take "cluster" to simply mean atoms, sure. Not groups of independent particles.

Alright. I wasn't considering a nucleus as a cluster, but obviously it is, and was also thinking there might be other "cluster" possibilities. I suppose neutrons could travel together in a group since they don't repel each other, but since they have no charge, presumably it would also be difficult to accelerate them. Hmm, how IS a nucleus cosmic ray accelerated anyway?

I don't know. But, it says here:

Lower-energy cosmic ray particles that strike the earth come from within our own Milky Way Galaxy. They may originate, directly or indirectly, from the supernova icon info explosions that mark the deaths of many stars. These explosions throw out fast-moving magnetic fields which reflect charged particles. Cosmic ray nuclei gain energy when they collide with such a moving reflector. At a magnetic shock, where the magnetic field slows abruptly, particles can become trapped between two reflectors. Like a ping-pong ball caught between two converging paddles, the nuclei make many reflections, and the energy gained in each reflection grows as their energy increases. This "magnetic shock acceleration" model was first proposed by the great physicist Enrico Fermi as an explanation for the acceleration of most cosmic rays. The process has been observed in magnetic shocks in the solar wind that flows out from our sun, producing cosmic rays of modest energy. The stronger moving magnetic fields produced in supernova explosions could provide the energy for most other cosmic rays.

Thanks, that's pretty interesting! I'm still not sure how an electrically neutral(*) nuclei can be "reflected" though, except by kinetically impacting other particles. Unless that's just what is meant here, which could explain the paddle analogy. Guess I might have to (try to) actually read the paper.

EDIT: (*) - D'oh! A bare nucleus composed of only protons and neutrons is obviously VERY positively charged!

[Bird_Man]

Thanks, that's pretty interesting! I'm still not sure how an electrically neutral nuclei can be "reflected" though, except by kinetically impacting other particles. Unless that's just what is meant here, which could explain the paddle analogy. Guess I might have to (try to) actually read the paper.

If cosmic rays are either electrons, nuclei, or individual protons, they would be either negatively or positively charged. Therefore easily reflected by the magnetic waves.

[johnnydeep]

Thanks, that's pretty interesting! I'm still not sure how an electrically neutral nuclei can be "reflected" though, except by kinetically impacting other particles. Unless that's just what is meant here, which could explain the paddle analogy. Guess I might have to (try to) actually read the paper.

If cosmic rays are either electrons, nuclei, or individual protons, they would be either negatively or positively charged. Therefore easily reflected by the magnetic waves.

Yeah, you're right. For some dumb reason I was thinking a bare nuclei - with only protons and neutrons - was somehow neutral in charge! D'oh!!

[aneedham]

Too many "likely"s in this article. Only the last one is used correctly, as an adjective.

[johnnydeep]

Too many "likely"s in this article. Only the last one is used correctly, as an adjective.

Well, "likely" can also be used as an adverb, meaning "in all probability", or "probably" and in that usage, it makes sense in the other contexts here.

See https://www.merriam-webster.com/diction ... ry-entry-2

[ However, IANAL (I am not a linguist)! ]

[Chris Peterson]

Too many "likely"s in this article. Only the last one is used correctly, as an adjective.

I'd say the word has been used quite correctly throughout the caption. And likely most English language experts would agree with me!

[johnnydeep]

Too many "likely"s in this article. Only the last one is used correctly, as an adjective.

I'd say the word has been used quite correctly throughout the caption. And likely most English language experts would agree with me!

Yes. See my reply posted at the same time!