From the UK Telegraph – source link
The protective bubble around the sun that helps to shield the Earth from harmful interstellar radiation is shrinking and getting weaker, NASA scientists have warned.
By Richard Gray, Science Correspondent
Last Updated: 9:23AM BST 19 Oct 2008
New data has revealed that the heliosphere, the protective shield of energy that surrounds our solar system, has weakened by 25 per cent over the past decade and is now at it lowest level since the space race began 50 years ago.
Scientists are baffled at what could be causing the barrier to shrink in this way and are to launch mission to study the heliosphere.
The Interstellar Boundary Explorer, or IBEX, will be launched from an aircraft on Sunday on a Pegasus rocket into an orbit 150,000 miles above the Earth where it will “listen” for the shock wave that forms as our solar system meets the interstellar radiation.
Dr Nathan Schwadron, co-investigator on the IBEX mission at Boston University, said: “The interstellar medium, which is part of the galaxy as a whole, is actually quite a harsh environment. There is a very high energy galactic radiation that is dangerous to living things.
“Around 90 per cent of the galactic cosmic radiation is deflected by our heliosphere, so the boundary protects us from this harsh galactic environment.”
The heliosphere is created by the solar wind, a combination of electrically charged particles and magnetic fields that emanate a more than a million miles an hour from the sun, meet the intergalactic gas that fills the gaps in space between solar systems.
At the boundary where they meet a shock wave is formed that deflects interstellar radiation around the solar system as it travels through the galaxy.
The scientists hope the IBEX mission will allow them to gain a better understanding of what happens at this boundary and help them predict what protection it will offer in the future.
Without the heliosphere the harmful intergalactic cosmic radiation would make life on Earth almost impossible by destroying DNA and making the climate uninhabitable.
Measurements made by the Ulysses deep space probe, which was launched in 1990 to orbit the sun, have shown that the pressure created inside the heliosphere by the solar wind has been decreasing.
Dr David McComas, principal investigator on the IBEX mission, said: “It is a fascinating interaction that our sun has with the galaxy surrounding us. This million mile an hour wind inflates this protective bubble that keeps us safe from intergalactic cosmic rays.
“With less pressure on the inside, the interaction at the boundaries becomes weaker and the heliosphere as a whole gets smaller.”
If the heliosphere continues to weaken, scientists fear that the amount of cosmic radiation reaching the inner parts of our solar system, including Earth, will increase.
This could result in growing levels of disruption to electrical equipment, damage satellites and potentially even harm life on Earth.
But Dr McComas added that it was still unclear exactly what would happen if the heliosphere continued to weaken or what even what the timescale for changes in the heliosphere are.
He said: “There is no imminent danger, but it is hard to know what the future holds. Certainly if the solar wind pressure was to continue to go down and the heliosphere were to almost evaporate then we would be in this sea of galactic cosmic rays. That could have some large effects.
“It is likely that there are natural variations in solar wind pressure and over time it will either stabilise or start going back up.”
(hat tip to Dvid Gladstone)
nobwainer (19:29:05) :
The 1790 maximum is perhaps the group that doesnt fit the SSB graph
The 1788.0 maximum is pretty well constrained by geomagnetic data going back to 1781. Little doubt about that one.
Ric Werme (19:50:50) :
“I am on the NASA panel of solar experts to predict solar cycle 24.”
Ah, a lesson in humility, eh? 🙂 At least SC24 is a great learning experience.
humility is always good. In this particular case I’m not the least humble as I’m predicting a cycle 24 that will be the lowest in a 100 years http://www.leif.org/research/Cycle%2024%20Smallest%20100%20years.pdf
I’ll feel really humble, though, should the NASA-crew turn out to be correct and SC24 is a supercycle.
That seems to conflict with the inverse square law.
Personally, I don’t think we can jump to the conclusion of a single study.
For all we know this is a natural cyclical thing.
nanny_govt_sucks (21:13:10) :
At the shock the solar wind is effectively stopped and there is no further fall-off
That seems to conflict with the inverse square law.
Once the plasma becomes part of the interstellar medium its connection with the Sun is effectively broken and its further movement is controlled by forces outside of the solar system. Considering again two Sun-centered spheres, but this time so large that they are completely and far outside the heliosphere. Now it no longer holds that the same amount of matter has to go through the surfaces of both spheres, because matter, moving independently of the solar system, could come ‘in from the side’.
So, no longer an inverse square law. Rather, the density will tend to be uniform, independent of distance to the Sun [at least as long as we are inside our ‘local’ interstellar bubble:
http://www.daviddarling.info/encyclopedia/L/Local_Bubble.html ]
Leif Svalgaard (20:02:38) :
The 1788.0 maximum is pretty well constrained by geomagnetic data going back to 1781. Little doubt about that one.
Beg to differ….I have plotted the aa numbers and as you can see the aa group that peaks around 1790 is far from settled. According to the aa records it has an extreme length and displays a most unusual trend as does the aa group that peaks around 1830. Also you might note the peaks do not match the sunspot counts in particular the 1830 and 1840ish peaks. To me it correlates with the SSB graph. I might add the sunspot numbers so we can see it better on one graph.
http://users.beagle.com.au/geoffsharp/aagraph.jpg
Will we see SC23 act in a similar way as it did around 1790, continuing for 15 years before SC24 finally starts and reaches a very low sunspot number like the Dalton? Did they have the technology to determine which cycle, sunspots belonged to in 1790?
[…] See the original post here: Comment on Sun’s protective ‘bubble’ is shrinking by Ric Werme […]
Just a question on the Dalton Minimum (min in terms of sunspots). Is there actually any evidence that the period covering the Dalton Minimum was significantly cooler than the period immediately before it.
The CET certainly doesn’t show it. There seems to be a sharp cooling around 1780 but this precedes the ‘long’ cycle (4) and the 2 weaker cycles (5&6). There is a cool(er) period in the mid-1810s but at least some of this can be explained by the Tambora eruption (1815).
Leif:
Interesting article of yours:
http://www.leif.org/research/Cycle%2024%20Smallest%20100%20years.pdf
! I must say i believe more your prediction than Hattaways.
Leif Svalgaard (18:00:29) :
It puzzles me that that should be puzzling. Using the laws of gravity, JPL [ http://ssd.jpl.nasa.gov/?ephemerides ] calculates theoretically the distance between any two solar system bodies, and the calculated distance between the Sun and the Earth is just what it should be from the Earth following a simple ellipse around the Sun [apart from very, very small planetary perturbations].
Most software are based on some assumptions, and it isn’t clear to me whether the above is designed to take the solar orbit onto account. It appears to have some approximations built in http://ssd.jpl.nasa.gov/?planet_pos
If it is really a full implementation of time integration of an N-body system where both the Sun and the planets are free to move according to the laws of gravity, I agree it would be a good test. But it seems to be an approximation based on orbital elements, like my own simulator?
Leif Svalgaard (18:28:19) :
From a previous thread:
Because the barycenter is mainly determined by Jupiter [apart from the sun, of course] it moves but slowly [12 years to go round – or if you like, the Sun moves but slowly]. Launch a spacecraft from the [almost stationary] barycenter such that the spacecraft’s circular orbit takes it around the Sun. Because of its proximity to the Sun, the spacecraft will move very fast, completing its orbit [and returning to the barycenter] every few hours. Its distance from the Sun’s center is constant, yet “every object in the solar system, no exception, orbits the barycenter”. What does the spacecraft do? does it go around the barycenter in a circular orbit every few hours? yet passes through the very barycenter every few hours. What would your simulator say?
And for clarification:
The spacecraft and the Earth are both planets [albeit of different size]. They are both ‘primary’ bodies of the solar system. Same gravity laws apply for both.
As noted, this has been visited in the earlier thread. My reply then was that my wording “every object in the solar system, no exception, orbits the barycenter” was imprecise, as I meant to communicate “every object directly gravitationally bound to the solar system, no exception, orbits the barycenter”. “Gravitationally bound” would mean that its speed is less than the escape velocity for the system in question. We all know that some objects, for example the moon (Luna) does not directly orbit the solar system barycenter, and the same is obviously true for the moons of Jupiter, Saturn etc. These moons are gravitationally bound to their parent planet.
So does the Earth orbit the solar system barycenter? Almost. The Earth has as we know a large moon (Luna), i.e. the Earth and Moon are gravitationally bound to each other. The Earth/Moon system has its own barycenter 1710 km below the Earth’s surface, around which the Earth and Moon orbit http://en.wikipedia.org/wiki/Earth-Moon_barycenter . It is the Earth/Moon system that orbits the solar system barycenter, or if you like: The Earth/Moon barycenter orbits the solar system barycenter.
Then back to your example with the spacecraft launched from the solar system barycenter and assuming a circular orbit around the Sun. This is a case similar to the Earh/Moon example above, except that the mass ratios are many orders of magnitude different. But it is still a 2-body subsystem with a common barycenter. It is just that the spacecraft is of such small mass that the Sun/spacecraft barycenter is extremely close to to the mass center of the Sun. But if I for example choose a bigger spacecraft with a mass similar to, say Jupiter, the principle is the same, just much more noticeable.
So the answer to your question “What does the spacecraft do? does it go around the barycenter in a circular orbit every few hours?” is that the spacecraft orbits the Sun/spacecraft barycenter since we must assume that the spacecraft is gravitationally bound to the Sun. The Sun/spacecraft barycenter is probably just a few nanometers from the mass centre of the Sun, but they are not identical points.
Then you ask “What would your simulator say?”. My simulator would not have any opinion because it isn’t designed to answer such questions. It uses orbital elements for the planets to compute their positions for any given time, and from that deduce the position of the Sun, using the mass of the planets, their positions and the mass of the Sun. It is essentially a standard engineering-type centre of mass calculation. What it does not do, is perform time step integration to estimate the positions of all major solar system objects using Newton’s law of gravity. Thinking about it, it could be an interesting experiment to use an existing (or write an new) simulator that was 100% gravity based, not assume any special role for the Sun and provide initial conditions (mass, orbital positions and speed vectors) from my current simulator to make things realistic. Then one should be able to compute a theoretical sun-earth distance graph as a function of time and see if it agreed with observations.
Leif Svalgaard (20:02:38) :
The 1788.0 maximum is pretty well constrained by geomagnetic data going back to 1781. Little doubt about that one.
Here is the aa data compared to the sunspot data. Fairly close match in the main but not super reliable….interesting how it deviates from 1960 to 2000.
pink =ssn
black=aa
http://users.beagle.com.au/geoffsharp/aassn.jpg
Data sources.
ssn: ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SUNSPOT_NUMBERS/YEARLY.PLT
aa: http://www.gao.spb.ru/database/esai/aa_mod.txt
Dr Svalgaard
I followed this strand with the thought ‘Where is Leif Svalgaard’? And there you were, finally, with the usual refreshing dose of cold water!
John Finn
“How much longer would global temperatures need to remain at current relatively high levels for you to be convinced that the sun is not, in fact, a major factor in short-term climate shifts?”
‘Relatively high’ compared to what time period?
Also, ‘global temperature’, is one thing, ‘global temperatures’ are another. One can certainly point to regions where temperatures have not been increasing over the past 100 years e.g the Southeastern states of the U.S.
Carsten Arnholm, Norway (02:09:10) :
Most software are based on some assumptions, and it isn’t clear to me whether the above is designed to take the solar orbit onto account. It appears to have some approximations built in
I’m amazed how one can so desperately search for support. The JPL site also have approximate formula for those not needing the full accuracy. Here is what the site says:
Keplerian Elements for Approximate Positions of the Major Planets.
This page contains sufficient information and data to allow computation of approximate positions for the planets.[…]
You are reminded that these formulae and data provide approximate positions for the planets. They should not be used unless the errors (tabulated below) are acceptable for your application. High precision ephemerides for the planets are available via our HORIZONS system.
Even the error using the approximate formulae is small, e.g. 6000 km = 1% of a solar radius for the Earth’s orbit.
The HORIZONS system ephemerides are the best modern astronomy can do and have no approximations. The only assumption is that the laws of gravity are correct.
nobwainer (06:11:57) :
Here is the aa data compared to the sunspot data. Fairly close match in the main but not super reliable….interesting how it deviates from 1960 to 2000.
This is because the aa-index is wrong [too low] before 1957 as I have shown elsewhere, e.g. http://www.leif.org/research/Analysis%20of%20K=0%20and%201%20for%20aa%20and%20NGK.pdf
and
http://www.leif.org/research/IHV%20-%20a%20new%20long-term%20geomagnetic%20index.pdf
John Finn (01:01:28) :
Just a question on the Dalton Minimum (min in terms of sunspots). Is there actually any evidence that the period covering the Dalton Minimum was significantly cooler than the period immediately before it.
The CET certainly doesn’t show it. There seems to be a sharp cooling around 1780 but this precedes the ‘long’ cycle (4) and the 2 weaker cycles (5&6). There is a cool(er) period in the mid-1810s but at least some of this can be explained by the Tambora eruption (1815).
The standard AGW answer [ 🙂 ] is that CET is not global, so doesn’t count. I may note that the sharp cooling in the 1780s coincides with the very large solar cycle that peaked in 1788.
Carsten Arnholm, Norway (04:05:27) :
As noted, this has been visited in the earlier thread. My reply then was that my wording “every object in the solar system, no exception, orbits the barycenter” was imprecise, as I meant to communicate “every object directly gravitationally bound to the solar system, no exception, orbits the barycenter”. “Gravitationally bound” would mean that its speed is less than the escape velocity for the system in question.
Is still imprecise, or rather wrong. ‘Gravitationally bound’ has nothing to do with it. Consider two comets travelling side by side. One has an eccentricity of 0.999,999,999 [a parabola – thus bound] and the other has an eccentricity of 1.000,000,001 [a hyperbola – thus not bound]. These two objects will have almost identical orbits swinging around the barycenter. If not, we just through in some more 9s and 0s.
So the answer to your question “What does the spacecraft do? […] is that the spacecraft orbits the Sun/spacecraft barycenter
And so does the Earth orbit the Sun/Earth barycenter which is 1650 times closer to the center of the Sun than ‘the’ barycenter based on Jupiter, hence the distance to the Sun does not need to take the Jupiter barycenter into account.
Carsten Arnholm, Norway (02:09:10) :
Most software are based on some assumptions, and it isn’t clear to me whether the above is designed to take the solar orbit onto account. It appears to have some approximations built in
Excerpts from the JPL documetation [why didn’t you care to check – its online too]:
STATEMENT OF EPHEMERIS LIMITATIONS
To produce an ephemeris, observational data (optical, VLBI, radar & spacecraft) containing measurement errors are combined with dynamical models containing modeling imprecisions. A best fit is developed to statistically minimize those errors. The resulting ephemeris has an associated uncertainty that fluctuates with time.
[…]Uncertainties in major planet ephemerides range from 10cm to 100+ km in the state-of-the-art JPL/DE-405 ephemeris, used as the basis for spacecraft navigation, mission planning and radar astronomy.
,…] Relativistic effects are included in all planet, lunar and small body dynamics, excluding satellites. […]
Deflections due to other gravity fields can potentially have an effect at the 10^-4 arcsec level but are not currently included here. Satellites of other planets, such as Jupiter could experience deflections at the 10^-3 arcsec level as well. Light time iterations are Newtonian. This affects light-time convergence at the millisecond level, position at ~10^-6 arcsec level.
The JPL DE-406/LE-406 extended ephemeris covers the interval from 3000 B.C. to A.D. 3000. This ephemeris is identical to the shorter DE-405 in the sense it is the same data-fit (solution) and the same numerical integration as DE-405. However, it has been stored with slightly less accuracy to reduce its size.
For the Moon, DE-406 recovers the original integrator state to within 1 meter, other bodies within 25 meters (maximum error). This difference can be less than the uncertainty associated with the trajectory solution itself, thus is insignificant for all but the most specialized circumstances. The short-span version, DE-405, recovers the integrator state to the millimeter level.
[…]
There should be no doubt that a full [even including relativistic effects] numerical integration is carried out. The result is generally good to the meter level and is used for all spacecraft navigation.
Carsten Arnholm, Norway (02:09:10) :
Most software are based on some assumptions, and it isn’t clear to me whether the above is designed to take the solar orbit onto account. It appears to have some approximations built in
And here is how the ephemeris is computed:
http://iau-comm4.jpl.nasa.gov/de405iom/de405iom.pdf
The elements of the planets etc are obtained from radar ranging [which you so disparaged] taking into account even the shape of the planets [see especially the section on Mercury].
From the document:
“DE406, The New JPL Long Ephemeris.
The full precision numerical integration covered the interval 3000 BC to 3000 AD … ”
The unwieldy numerical results from the integration are then fitted to a large set of polynomials for interpolation [just like the tables you see in Meuus’ book] and actual use.
Can we now put this to rest?
Carsten Arnholm, Norway (02:09:10) :
It appears to have some approximations built in
Just in case you do not take the trouble to read the documentation, I’ll state the conclusion here:
“DE405 represents the most accurate planetary positions available”.
Leif Svalgaard (07:58:17) :
Allow me to correct myself:
‘Gravitationally bound’ has nothing to do with it. Consider two comets travelling side by side. One has an eccentricity of 0.999,999,999 [an ellipse – thus bound] and the other has an eccentricity of 1.000,000,001 [a hyperbola – thus not bound]. These two objects will have almost identical orbits swinging around the barycenter. If not, we just throw in some more 9s and 0s.
Leif Svalgaard (08:53:00) :
Can we now put this to rest?
Let me remind you that my comment was initiated by you referring to me by name. I really don’t see why my post on the issue appears to agitate, it surely was not designed to. I am going to review the information you have provided with interest and see what I make of it. Then I reserve the right to make thoughtful comments as and when I find it relevant.
Carsten Arnholm, Norway (09:18:38) :
I really don’t see why my post on the issue appears to agitate, it surely was not designed to.
I don’t think I implied that at any time.
I am going to review the information you have provided with interest and see what I make of it. Then I reserve the right to make thoughtful comments as and when I find it relevant.
One cannot ask for more than that.
Carsten
wow, gjett om jeg har lett etter en slik simulator.
Is this all about the solar system’s orbit around the center of the galaxy? When all the large planets move from between the sun and the galaxy center to the other side of the sun, the sun has to move closer to the galaxy center because the angular momentum of the system must be preserved. In other words, the radius of the solar system center of mass orbit around the center of galaxy can not change over a short timespan. And if the sun is moving like this it means it’s motion is changing direction, i.e the sun is beeing accelerated. Why then is it so unthinkable that this acceleration is causing turbulence in the sun?