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.
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RACookPE1978 says:
July 10, 2010 at 10:21 am
Certainly, that would be a “local” effect – like an eclipse is a small local effect compared to the size of the sun. But in that local area under the eclipse shadow zones, there is a very drastic sudden effect that can vary in effect significantly (complete darkness, umbra, annulus, duration, and temperature effects) all changing based on where the observer happens to be.
We seem to be going around in circles here.
It there were those sudden effects, we would see that in the intensity of the GCRs having a spike in the direction of the source. But no such spikes are seen in todays map of the GCR intensity across the sky: http://imagine.gsfc.nasa.gov/Images/science/galaxy_cr.gif
If there century-scale variations in the production, e.g ten supernovae exploding within a short time of another, we would still expect an anisotropy [albeit broader than a spike] because centuries are short compared to the millions of years of travel time.
rbateman says:
July 10, 2010 at 10:28 am
And then there is the theory of shock waves in the spiral arms causing star formation. Do the GCR’s pile up ahead of the theoretical shock wave?
The GCRs are much too energetic for that [move too fast compared to the shock wave]. They are scattered by the shock waves, and generally gain energy by this. The Galaxy is ‘filled’ with old shock waves from long-ago supernovae.
Leif Svalgaard says:
July 10, 2010 at 10:47 am
How fast do we currently understand GCR’s to travel compared to the speed of light?
A decimal based number would be great.
rbateman says:
July 10, 2010 at 11:04 am
How fast do we currently understand GCR’s to travel compared to the speed of light?
depends on their energy, but at 10 GeV, they travel at 99.6% of the speed of light.
A decimal based number would be great. ?
Leif Svalgaard says:
July 10, 2010 at 11:25 am
99.6% is .996 of c.
So if a SN goes off 1,000 ly distant, it takes 1004 years for the 10 GeV GCR’s to get here.
And they get here with the inverse square quantity, assuming a spherical outburst.
If it were aimed right, and looking at SN remnants, that spherical assumption of output would be a poor one.
Then one has to figure what % of the output is 10 GeV.
That’s a lot of unknowables already.
We could get splashed with a load of GCR’s, or we could sit here for the next 10 million years and wonder.
I’m going back to my measured data sets.
rbateman says:
July 10, 2010 at 4:27 pm
So if a SN goes off 1,000 ly distant, it takes 1004 years for the 10 GeV GCR’s to get here.
No, it takes some 15 million years, because the CR bounces all over the place, being scattered by the many shock waves [from many different supernovae] that fill the Galaxy.
Leif Svalgaard says:
July 10, 2010 at 4:40 pm
Is there empirical data on these 10 GeV CR’s, that we know their behavior well enough to say that a SN 1000 ly away will produce GCR’s that arrive in 15 million years? The numbers seem to be rather bizzare for something moving near the speed of light.
rbateman says:
July 10, 2010 at 7:49 pm
The numbers seem to be rather bizarre for something moving near the speed of light.
As a CR move along it collides with other atoms and splinter them into pieces [other atoms] that then move along also as CRs [called secondary CRs]. This means that the chemical composition of the CRs change as they move along: they get enriched in the pieces knocked out. For Beryllium, the enhancement is more than a factor of a hundred. Clearly, the overabundance depends on how many atoms there are to collide with in the first place. From the observed overabundance one can calculate the number of such atoms encountered, which in turn depends on two numbers: the path length and the density of interstellar material. Since the latter is known in other ways, the path length can be calculated to be 15 million light years. Moving at the speed of light, that takes 15 million years.
Since 10Be is also produced in this way [same as in the Earth’s atmosphere], we would expect to see some of that. We do not see any, so whatever is produced must have decayed away [half life 1.6 million years], so they must have traveled far. Same goes for 14C and other radioactive nuclei with short half life.
rbateman says:
July 10, 2010 at 4:27 pm (Edit)
That’s a lot of unknowables already.
We could get splashed with a load of GCR’s, or we could sit here for the next 10 million years and wonder.
It sounds like another of those things where the degree of smoothed-outness or spikiness will depend partly on how isotropic you want your universe to look.
I’m going back to my measured data sets.
Probably a smart move. I think I’ll leave it in my pending tray too.
tallbloke says:
July 10, 2010 at 9:31 pm
It sounds like another of those things where the degree of smoothed-outness or spikiness will depend partly on how isotropic you want your universe to look.
Whne it comes to cosmic rays, there is not much choice, as we have direct observations. Here is the observed cosmic ray map of the sky: http://imagine.gsfc.nasa.gov/Images/science/galaxy_cr.gif
Leif Svalgaard says:
July 10, 2010 at 10:29 pm
Looks more like the perfect flatfield on the perfect optical system with the perfect detector.
If I were to take a picture like that, I’d be looking to see what went wrong.
Even the cosmic microwave background has some variation.