# Tag Info

## Hot answers tagged cosmic-rays

13

Great question. The electric field creates such a strong force that it would be very hard to move large amounts of just one type of charge. So astrophysical systems do generally eject equal numbers of protons and electrons. In particular, the solar wind is electrically neutral. So these cosmic rays are created in very nearly equal numbers, but by the ...

8

Ultra-high energy cosmic rays all come from a very, very long way away (anything with the power to create them nearby would constitute a danger to life as we know it). I think the preferred mechanism these days is dynamic acceleration in the jets formed by active galactic nuclei, but don't quote me. Anyway, ultra-relativistic though they are, that means ...

8

The OMG particle was observed by the Fly's Eye experiment located on Dugway Proving Ground in Utah. The Fly's Eye experiment was the first experiment to successfully employ the air fluorescence technique developed by Dr. Alan Bunner (Cosmic Ray Detection by Atmospheric Fluorescence, Ph. D. Thesis, Cornell University, 1967). The air fluorescence technique ...

8

The short answer is you can't, or at least not at all easily. Your detector has only a single detection plane, and almost all muons are minimum ionizing, so you get essentially the same energy deposition from every muon (well, there is a factor from the angle of incidence the detection plane). The usual mechanism for measuring the energy of a particle are ...

7

OK, here is something concrete and quantitative, "Guidelines for predicting single-event upsets in neutron environments": Neutrons in the atmosphere result from cosmic-ray spallation interactions with nitrogen and oxygen nuclei. A typical reaction is a 1 GeV proton fragmenting a nitrogen necleus into lighter charged particles and simultaneoously emitting ...

7

Ultra-high energy cosmic rays create enormous cascades of charged particles as they and interact and re-interact and re-re-interact in the atmosphere. This generates a lot of Cerenkov radiation and nitrogen fluorescence in the atmosphere and many of the charged particles reach the ground in a cone that may be miles wide. So you build an array of ground ...

6

It isn't needed in a rocket, however if you are going to the effort of sending something up outside the atmosphere (or even just high up within the atmosphere) you might as well try and get some useful data out of it. This might even help you get sponsorship for your rocket, as data from climbs through altitude is useful to a number of academic institutions. ...

6

The short answer is "we do" (see Pierre Auger Observatory and others1), but it's not like you can build a CMS equivalent at the one spot in the whole atmosphere where a $10^{19}\text{ eV}$ cosmic ray is going to hit next year, so we do a different kind of particle physics there. A typical ultra-high energy cosmic ray observatory combines an array of ...

6

Happens all the time. Low background neutrino detectors have to contend with the products: short lived, light isotopes that are created in after cosmic rays knock some neutrons loose from other material (neutron spallation). See (to chose an example I'm an author on) DOI 10.1103/PhysRevC.81.025807 (also at arXiv:0907.0066). You can also find simlar papers ...

6

We can make a reasonable guess by taking a look at the Hillas criterion. The gist of this criterion is that the maximum energy of the particle, $E$, is limited by the size of the accelerator, $R$ ($\sim R_L$ the Larmor radius), and the strength of the magnetic field, $B$. The relation gives $$E_{max}=10^{18}\,Z\beta B_{\mu G}R_{kpc}\,{\rm eV}$$ where ...

5

Between what I've learned about cosmic rays and what I can find online (example: http://www.fisica.unlp.edu.ar/~veiga/experiments.html), it seems that the primary source of neutrons in cosmic ray showers is the disintegration of the atomic nuclei that are struck by the cosmic ray or its decay products. As you may know, cosmic rays enter the atmosphere with ...

4

One must keep in mind also that it is the particle, not the shower that goes through the astronaut in dmckee's estimate above, where he treats the relativistic particle going through matter. The shower in your question which gave the energy estimate of the parent particle is generated by cascade/sequential collisions of deep angle scattering over a ...

4

Roughly yes. Radiation is broadly divided into two from a safety point of view. Ionising radiation can break chemical bonds and so has an obvious way to cause damage to your body - how much depends on the energy, how much radiation you absorb and where in your body it gets to. Both X-Rays and particles from radioactive material are ionising, as is the ...

4

There is the ground based observatory ( nice picture) Veritas. VERITAS (Very Energetic Radiation Imaging Telescope Array System) is a major ground-based gamma-ray observatory located at the basecamp of the Fred Lawrence Whipple Observatory in southern Arizona, designed to observe and study very-high-energy (VHE) gamma-rays (energies above ~100 GeV). ...

4

Energetic cosmic rays are rare, as @John Rennie states in his answer, and the detectors to measure their effect cover kilometers. One high energy entrant creates what is called an air shower and it is measured as @dmckee describes. It is not possible to use them as an incoming beam because we do not know what they are ( except in the case of gamma rays and ...

3

We actually use cosmic rays to study fundamental physics. Thanks to them we discovered the muon and the positron many years ago, as you probably know, and currently they imposes severe constraints on violations of Lorentz invariance. The tension between cosmic ray physics and accelerator physics is the tension between observations and experiments. In the ...

3

First of all terminology: When physicists speak of radiation they primarily speak of electromagnetic radiation. When health physicists speak of radiation they include radiations of other types, alpha and beta and neutrons in addition to gamma and xrays. They have developed a system where radiation is given in Becquerel ignoring the particular source. So ...

3

Muons are the main cosmic rays reaching sea level with a possibility of interacting with matter. Neutrinos interact very weakly and need special detectors to be seen at all. Rule of thumb when I was working with counters is that the flux of muons at sea level is 1 per cm^2 per second, wikipedia gives this number for over 1 Gev The number of particles ...

3

Cosmic rays do have noticeable affect on electronics. The most prevalent effect is from memory bit flips (known as "soft errors"). The degree of significance of the effect depends on the application. A typical soft error rate for static RAM is in the region of 400 FITs/Mbit [1]. (Failures in time=failures per billion device hours) So if you have 1 Gb of ...

3

For the most part cosmic rays do nothing to consumer electronics. This is not to say that they can't flip bits or even damage elements, but the rate for such effects is very, very low. Radiation effects are routinely observed in electronics placed in accelerator experimental halls (where the radiation levels are at lethal-dose-in-minutes levels when the ...

3

Muon catalyzed fusion needs the muons to be low enough energy to replace an electron and stay in a stable orbit. Since the reason the catalysis happens is because the atom is much smaller and two protons can get close together enhancing the probability of overlap and fusion, one needs a large number of low energy muons so that the probability of two muonic ...

3

Moun catalyzed fusion requires very specific kinematics, but cosmic muons come in all energies from stopped to tens of GeV at any particular spot. Care to work out the cross-section for having the right kinematics? If you're having trouble I know a graduate student who is familiar with several of the common cosmic muon Monte Carlo generators.

3

These are rare, on the order of one per square mile per century. See Ultra-high-energy cosmic ray (Wikipedia). So a human, with a cross sectional area less than 1 square meter might get hit about once per each 100 million years. I think that the risk of life due to spacecraft malfunction is significantly greater than this. And when they do hit the Earth's ...

3

JEM-EUSO is designed to look for air showers caused by extremely high energy cosmic rays (>$10^{19}$ eV). According to the website, it will be attached to the International Space Station in 2016.

3

I'm a bit outside of my expertise here, and perhaps someone who knows in detail will be along, but here goes... The composition of UHE cosmic rays is not directly measured because they are too rare to justify putting a spectrometer sufficient to test them in space. The composition of normal cosmic rays has been tested and they are mostly protons with a few ...

3

To address the actual question of how we know the composition of UHECR without relying on source information (of which we have none), we have to look at their extensive air showers (EAS). After an UHECR hits the top of the atmosphere an EAS is created in the air, but p and Fe will create EAS with different shapes. Properties of hadronic interactions are ...

3

You are assuming the Big Bang happened at a point, so the CMB is a shell of radiation expanding outwards from that point. However the Big Bang happened everywhere so every point in the universe is a source of the CMB. The CMB radiation we are detecting today comes from regions of the universe that were about 13.8 billion light years away at the moment the ...

2

Spallation of air atoms' nuclei is the easiest way - there are neutrons kicked out of the nucleus directly or emmited by radioactive elements, which were activated by cosmic rays. Also neutrons can be produced upon hadronization of quark-gluon-plasma or from electron capturing in air nuclei.

2

2012-07-11 Addendum Based on excellent inputs, in particular from @annav, my answer is now "no, even a direct worst-case hit by the Oh-My-God particle would not kill you, even by radiation, because there is insufficient distance and angle to generate a fatal radiation cone. Thanks all, and be sure to look at the earlier answer that @dmckee pointed out. ** ...

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