Amateur telescope photographer Thierry Legault has gained renown in recent years taking photographs of spacecraft in orbit… from the ground, with them either reflecting sunlight as they cross the terminator, or silhouetted by the moon, or in recent days, silhouetted by a near spotless sun.
His most recent accomplishment is this solar silhouette of the International Space Station docked with Space Shuttle Atlantis on its STS-132 mission. While many have marvelled at his accomplishment, we’ve heard less about the continuing near-spotless state of the sun in his photograph. This one sunspot region counted enough on May 22nd to make the daily sunspot count be 15!
It appears that the sunspot and 10.7 progression for Solar Cycle 24 have hit a bit of a roadblock in recent months, according to NOAA’s Solar Cycle Progression and Prediction Center.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
oneuniverse says:
July 5, 2010 at 11:22 am
What are the anisotropies outside the heliopause for particles with 100 MeV -10 GeV ?
The anisotropy increases with increasing energy so those low-energy particles will have even lower anisotropy as they are scattered even stronger. We can’t easily measure what the precise number is because of solar modulation, but likely much less than the 1 in a 1000 for the higher energies. Enough to justify the assumption of constancy.
The densities will not be affected in this way
Perhaps a poor choice of word. Flux might have been better, although ‘density’ describes the same thing. Think of a cubic meter in space. GCRs flow through this cube. The density of GCRs inside the cube is a measure of the flux: twice as many GCRs in the cube, twice the flux.
The average 15 million light year journey is the full distance travelled by a particle. The random walk that you mentioned, and the spiralling movements usual to a charged particle traversing a magnetic field, mean the direct distance could be much shorter than that taken by the particle. It would be interesting to know if this has been quantified – it sounds like our detailed knowledge of the interstellar fields is insufficient, though.
The direct distance [presuming you mean between a supernova and us] is irrelevant as the GCR does not travel along that. Instead they roam through the Galaxy for millions of years. E.g. from the nearby supernova to the end of the Galaxy and back many times, as the scattering in direction is severe.
Leif Svalgaard (July 5, 2010 at 11:49 am):
We can’t easily measure what the precise number is because of solar modulation, but likely much less than the 1 in a 1000 for the higher energies.
This sounds mostly like a guess? Would you expect the anisotropy to be less outside the heliopause?
(Leif, from 10:03 am)There is no evidence for an increase of supernovae production. In general with time [billions of years] there will be fewer and fewer supernovae.
It’s not about increases in the galactic rate, but the uneven spatial and temporal distribution of particularly the more local supernovae, which will cause spikes in the flux, rather than being lost in the background.
The direct distance [presuming you mean between a supernova and us] is irrelevant as the GCR does not travel along that.
[Yes]. It’s relevant in the sense that a particle that’s travelled 15 million light years (measured along its traversed path) may not have travelled around the galaxy (with it’s span of ~100,000 light years), depending on the quantifications mentioned above.
oneuniverse says:
July 5, 2010 at 1:13 pm
“We can’t easily measure what the precise number is because of solar modulation, but likely much less than the 1 in a 1000 for the higher energies.”
This sounds mostly like a guess? Would you expect the anisotropy to be less outside the heliopause?
It is a justified and considered guess, as we find experimentally and expect theoretically that for lower and lower energies the anisotropy would be smaller and smaller. And we are discussing condition outside the heliopause. Inside, solar modulation further acts to erase any remaining anisotropy.
but the uneven spatial and temporal distribution of particularly the more local supernovae, which will cause spikes in the flux, rather than being lost in the background.
No spikes are observed in the low-energy GCRs.
The direct distance [presuming you mean between a supernova and us] is irrelevant as the GCR does not travel along that.
[Yes]. It’s relevant in the sense that a particle that’s travelled 15 million light years (measured along its traversed path) may not have travelled around the galaxy (with it’s span of ~100,000 light years), depending on the quantifications mentioned above.
In that case your quantification is wrong, because the 15 millions years come about because the particles are scattered through large angles [like 180 degrees] each time and actually traverse the Galaxy hundreds of times.
This may help shed some light:
http://www.leif.org/research/McCracken JGR 2.pdf
You’ll have to cut’n’paste as wordpress doesn’t like spaces in filenames.
It is a justified and considered guess, as we find experimentally and expect theoretically that for lower and lower energies the anisotropy would be smaller and smaller. And we are discussing condition outside the heliopause. Inside, solar modulation further acts to erase any remaining anisotropy.
I’ve asked the variations of the question three times in a row – your replies have been conspicuously unresponsive.
No spikes are observed in the low-energy GCRs.
The period of instrumental observation has only been about half a century.
The mean time between galactic supernovae is ~50 years, longer for local SN. (There are spikes in the geological cosmogenic isotope record, although we’re not considering those at the moment. )
In that case your quantification is wrong, because the 15 millions years come about because the particles are scattered through large angles [like 180 degrees] each time and actually traverse the Galaxy hundreds of times.
I didn’t do a quantification, so how can it be wrong? I said it’d be interesting to quantify the ratio of a particle’s traversed path to the direct distance from its origin to its terminus.
The ratio will be > 1 . If the particles are frequently experiencing up to 180 degree deflections, then it’s possible that the ratio will be high. If it is of the order of 1000, then a particle that’s travelled 15 mly journey may have had its origin only 15 kly away, with no round trips being involved. For reference, the classical supernovae that have been observed by eye over the last couple of millenia are mostly ~ 5-10 kly away.
oneuniverse says:
July 6, 2010 at 8:15 am
I’ve asked the variations of the question three times in a row – your replies have been conspicuously unresponsive.
Then I give up too. What is the question?
If the particles are frequently experiencing up to 180 degree deflections, then it’s possible that the ratio will be high. If it is of the order of 1000, then a particle that’s travelled 15 mly journey may have had its origin only 15 kly away, with no round trips being involved.
The acceleration of the GCRs happens in space during their travel by encountering magnetic ‘mirrors’, so the deflections are always large [otherwise they don’t get accelerated much], so the GGRs scatter all over the galaxy. That is why the anisotropy is so small.
Ralph,
If it makes you feel better, your observation is logical and dismissed quite out of hand by many here. The scale of your mathematical null is probably quite small, however?
This statement makes sense regarding the isotropy issue, which would seem to be the result of many such changes in direction, but earlier in the conversation you mentioned that the GCR’s end up with very high energies as a result of their long journeys. Since GCR’s are, to my understanding, just individual charged particles, then when they interact with a magnetic field, the force on them should always be perpendicular to their direction of motion (qv x B), and thus can’t change their Kinetic Energy, so what mechanism is it that does so?
/dr.bill
dr.bill says:
July 6, 2010 at 1:13 pm
when they interact with a magnetic field, the force on them should always be perpendicular to their direction of motion (qv x B), and thus can’t change their Kinetic Energy, so what mechanism is it that does so?
That is BTW why the idea that they travel 15 million light years by spiraling about the the field line that connect the Earth with the nearby supernova is wrong, because as you say, there is no change in energy. But this only holds for a uniform, nice, magnetic field. If the field is turbulent [as it is in the shock waves filling interstellar space], then there can be random kinks in the field. Kinks with a size smaller than the gyro-radius. In that case the gyration proceeds in a new [random] direction and that is when the kinetic energy changes.
All of this has been known for half a century.
Must have happened while I was otherwise occupied. ☺ ☺ So I take it then, that it is the induced electric fields caused by these ‘nasty’ magnetic ones that actually do the longitudinal accelerating?
/dr.bill
Leif Svalgaard says:
July 5, 2010 at 12:05 am
tallbloke says:
July 4, 2010 at 1:18 pm
If you really believe in this, then there is a fertile hunting ground for you.
It’s not a question of belief, it’s a matter of following where the data leads.
Data does not led anywhere. They are seen though the model, hypothesis, theory, etc that you believe they represent.
____________________________________________________
Not data, rather rules or laws that lead to highly precise and deterministic short term temperature change forecasts. You could bet on that.
Leif Svalgaard to Dr. Bill:
That is BTW why the idea that they travel 15 million light years by spiraling about the the field line that connect the Earth with the nearby supernova is wrong, because as you say, there is no change in energy. But this only holds for a uniform, nice, magnetic field
This is a strawman – what I wrote was : “The random walk that you mentioned, and the spiralling movements usual to a charged particle traversing a magnetic field, mean the direct distance could be much shorter than that taken by the particle”
That’s significantly different to your description of particles “spiraling about the the field line that connect the Earth with the nearby supernova” – that’s your imagination at work.
Leif: Kinks with a size smaller than the gyro-radius. In that case the gyration proceeds in a new [random] direction and that is when the kinetic energy changes.
As I understand it. a moving magnetic field will do work on a charged particle, a static (non-moving) one won’t.
Magnetic interactions can in general accelerate or deccelerate charged particles. Given the tangled nature of the magnetic fields you describe, which implies a degree of randomness, what is it about them that causes a net acceleration of the particles ?
dr.bill says:
July 6, 2010 at 2:36 pm
So I take it then, that it is the induced electric fields caused by these ‘nasty’ magnetic ones that actually do the longitudinal accelerating?
That is one way of looking at it. Reading Fermi’s original paper on this is illuminating:
http://fermi.lib.uchicago.edu/notebook_104_excerpt.pdf
A more accessible treatment is here: http://www-ttp.particle.uni-karlsruhe.de/GK/Workshop/parizot_CRAP_2.pdf
oneuniverse says:
July 6, 2010 at 7:51 pm
what I wrote was : “The random walk that you mentioned, and the spiralling movements usual to a charged particle traversing a magnetic field, mean the direct distance could be much shorter than that taken by the particle”
since what you wrote is irrelevant [‘the direct distance’] as we were discussing the bouncing around in the Galaxy of a cosmic ray particle, I took the liberty of injecting some sense into your statement and interpret it in a way that made sense. Sorry, if that was unjustified.
As I understand it. a moving magnetic field will do work on a charged particle, a static (non-moving) one won’t.
Moving? the particle moves at high speed through a magnetic field…
Magnetic interactions can in general accelerate or deccelerate charged particles. Given the tangled nature of the magnetic fields you describe, which implies a [‘high’ – my insert] degree of randomness, what is it about them that causes a net acceleration of the particles ?
I think I have already answered that [the kinks], but here is a longer explanation: http://www-ttp.particle.uni-karlsruhe.de/GK/Workshop/parizot_CRAP_2.pdf It will be interesting to see if you consider this another strawman.
oneuniverse says:
July 6, 2010 at 7:51 pm
what I wrote was : “The random walk that you mentioned, and the spiraling […]
Come to think about it. The other chapters are good too:
http://www-ttp.particle.uni-karlsruhe.de/GK/Workshop/parizot_CRAP_1.pdf
http://www-ttp.particle.uni-karlsruhe.de/GK/Workshop/parizot_CRAP_2.pdf
http://www-ttp.particle.uni-karlsruhe.de/GK/Workshop/parizot_CRAP_3.pdf
Leif Svalgaard: July 6, 2010 at 11:34 pm
Thanks very much Leif. I’m afraid that Fermi and Parizot will have to submit to a bit of time-sharing with Salmo salar and Salvelinus fontinalis for the next month or so, but I presume that they didn’t abuse Maxwell’s Equations too much, and I’m looking forward to getting an extension to my education. The workshop topics list for Parizot’s “Lectures on Cosmic Acceleration” seems to cover a lot of ground.
/dr.bill
since what you wrote is irrelevant [‘the direct distance’] as we were discussing the bouncing around in the Galaxy of a cosmic ray particle, I took the liberty of injecting some sense into your statement and interpret it in a way that made sense.
The direct distance is relevant to the analysis I described, which was merely explaining how the path length of the particles journey may be much longer than the final (direct) distance travelled. Depending on the level of the path-folding that takes place, this may mean that the radius of the envelope described by the dispersing particles may be small as well compared to their travelled path length. This result would be highly relevant to the discussion.
Also, I didn’t describe a scenario of particles spiralling along the field line of a uniform magnetic field connecting Earth to the supernova, yet you put forward this incorrect representation, and then pronounce that it’s wrong. That’s a classic ‘strawman’ manouevre, isn’t it?
I think I have already answered that [the kinks], but here is a longer explanation:
Thanks – the phenomenon appears to be referred to as second-order Fermi acceleration. According to Fermi, it’s the slightly higher probability of a particle colliding head-on with a moving cloud (both moving towards each other) compared to a read-end collision (with the cloud moving in same direction as the particle) that causes the net accelaration [second-order Fermi acceleration] – I’m not sure if kinks come into it. Do the kinks refer to magnetic inhomogenieties present for first-order Fermi acceleration ?
oneuniverse says:
July 7, 2010 at 4:39 am
The direct distance is relevant to the analysis I described, which was merely explaining how the path length of the particles journey may be much longer than the final (direct) distance travelled. Depending on the level of the path-folding that takes place, this may mean that the radius of the envelope described by the dispersing particles may be small as well compared to their travelled path length. This result would be highly relevant to the discussion.
I think that is what I have been trying to get across to you, that no matter how small the distance, the actual path is very much longer, so all information about the original location is lost [isotropy], and that therefore the distance does not matter.
That’s a classic ‘strawman’ manouevre, isn’t it?
A strawman implies deliberate attempt of deception, so that is what you accuse me of. ah well, discussions often end with something like that. Too bad.
I’m not sure if kinks come into it. Do the kinks refer to magnetic inhomogenieties present for first-order Fermi acceleration ?
The ‘kinks’ was a short hand for field lines changing direction on a scale comparable to the gyroradius, see the bottom panel in slide 16 of http://www-ttp.particle.uni-karlsruhe.de/GK/Workshop/parizot_CRAP_2.pdf
The important result of all this is the resulting isotropy. The GCRs may themselves smooth out any anisotropies, see e.g. slide 40.
A strawman implies deliberate attempt of deception, so that is what you accuse me of.
Only you know whether you’d manufactured the strawman unwittingly or on purpose.
I showed that you had misrepresented my argument, and that you’d argued against the easily-dismissed misrepresented version – that’s what a strawman argument is.
I think that is what I have been trying to get across to you, that no matter how small the distance, the actual path is very much longer, so all information about the original location is lost [isotropy], and that therefore the distance does not matter.
The flux density may be affected by the proximity (or lack of) of sources of GCR. The flux density is a more important metric in practice than the isotropy, and is far more relevant to the geological 10Be & 14C record than the isotropy of arriving cosmic rays. (Astronaut and equipment safety is determined more by the flux than the isotropy too).
oneuniverse says:
July 7, 2010 at 8:13 am
I showed that you had misrepresented my argument
Your argument was not clearly stated and didn’t make sense. I tried to make sense of it, but apparently failed.
The flux density may be affected by the proximity (or lack of) of sources of GCR.
May be? The distance to the sources [unless they are really close, in which case we’ll all die anyway] and what flux they produce do not matter as we don’t get anything directly from them, rather we get the averaged out effect from the whole Galaxy. Isotropy in space also means isotropy in time.
The ‘kinks’ was a short hand for field lines changing direction on a scale comparable to the gyroradius, see the bottom panel in slide 16
Thank you for pointing out this material again. For slide 16, is that actually the slide you mean (with the image of Boris Becker) ? It makes no mention of scales or gyroradii, just the analogy of the tennis racket & ball.
By the way, please see the trajectory plots on slides 12-15 of the 3rd pdf of the set.
Prima facie, these provide support for what I’d written concerning the long path lengths of CRs but a small radius of the envelope of exploration. The convoluted nature of the paths will increase for lower energies 10^9 – 10^12 eV than plotted. Also, the magnetic field strength for those plots is 10 nG (0.001 nT), which is smaller than estimates of (local) interstellar field strength of approx. 0.1-1 nT.
[ I just realised that my earlier hyperlink to Opher et al.’s paper had a trailing ‘/’, which stopped it from working. The preceding link works, though ].
oneuniverse says:
July 7, 2010 at 9:19 am
For slide 16, is that actually the slide you mean (with the image of Boris Becker)?
Sorry, slide 6 of
http://www-ttp.particle.uni-karlsruhe.de/GK/Workshop/parizot_CRAP_3.pdf
By the way, please see the trajectory plots on slides 12-15 of the 3rd pdf of the set.
Note that the scale there is in Megaparsec, because the energies depicted are enormous [10^18 eV and higher]
Also, the magnetic field strength for those plots is 10 nG (0.001 nT), which is smaller than estimates of (local) interstellar field strength of approx. 0.1-1 nT.
For a stronger magnetic field the scattering will be even larger. And the local field strength does not matter one whit, as we see the integrated effect of the whole Galaxy.
The mainstream view as put forward by NASA, is that supernovae and their remnants are able to accelerate particles to GCR energies, if not to rare ultra-high energies (>= 10^20 eV):
Since SN (SNR) are considered to be the main sources of GCRs for the relevant energies, their proximity will make a difference .
Missing link to NASA article in last post.
oneuniverse says:
July 7, 2010 at 10:03 am
“Eventually they build up enough speed that the remnant can no longer contain them, and they escape into the Galaxy.”
And once they have escaped [the very small SNR] they begin their tortured bounce [and some further acceleration] all over the Galaxy, which completely [as observed] obliterates the signature of their origin, near or far, to give us the isotropy in space [and hence in time] that we see for ‘normal’ energy GCRs. There are two accelerations that occur: one to escape the SNR and one thereafter that destroys information about the location, near or far, of the source.
Since SN (SNR) are considered to be the main sources of GCRs for the relevant energies, their proximity will make a difference
No, because the scattering occurs mainly after the GCRs have entered the Galaxy. We have no evidence [observational or theoretical] that there are any differences, no matter how many times you say that, or how badly you want it to be true. I suggest that this would be fitting point for you to accept that.
The mainstream view …
By the way, Webber and company are the formers of the mainstream view. They are the experts on this.
The diffusion process will lead to isotropy for all but the high energy particles, true, but the GCR flux density experienced by our solar system will change in the presence of proximate GCR sources such as SNR.
As an analogy, to show that isotropy doesn’t imply a homogenous density, consider a scenario where gas molecules of type A are released in a jet into an existing gas of molecules type B. The A molecules will rapidly lose any isotropy due to the random action of Brownian motion, so the isotropy will remain constant, yet the density of A molecules in the gas will increase . Volumes closer to the source will have a higher density of A than those further away. Similarlty, the density will change again when the source is stopped.
By the way, Webber and company are the formers of the mainstream view. They are the experts on this.
Why not address the discrepancy between the mainstream view, which I quoted at 10:03 am just above, and your description, which was :
The particles ejected by a supernova explosion are not GCRs [yet] because they move way to slowly.During millions of years some of these particles will encounter ‘magnetic mirrors’ [tangled magnetic fields] and some will be accelerated by that, each time a little bit more until the particles move almost at the speed of light. This takes time, so proximate supernovae does not add to the GCR flux that we can observe.