The NOAA SWPC monthly solar cycle update has been published here, and after a big spike last month, the sunspot count is down again. There’s an even bigger drop though in the Ap geomagnetic index, as seen and discussed below the Continue reading line.
10.7 centimeter radio flux was down slightly too.
But here’s the really interesting part, the Ap geomagnetic index plummeted to a value of 2, equal to the previous 12 year minimum set in November 2009.
Source data: http://www.swpc.noaa.gov/ftpdir/weekly/RecentIndices.txt
Dr. Leif Svalgaard offers these comments via email:
Ap is based on mostly Northern Hemisphere stations [11 North, 2 South] and is somewhat biased [having less activity in northern winter]. This is in addition to a general semiannual variation http://www.leif.org/research/Semiannual-Comment.pdf
with minima at the solstices. The definitive Ap values are determined by Potsdam and can be found here: http://isgi.latmos.ipsl.fr/lesdonne.htm
Real-time values [preliminary the last 15 days] are available here http://www.geomag.bgs.ac.uk/data_service/data/magnetic_indices/apindex.html
SWPC [NOAA] also compute preliminary real-time values. These computed values are truncated, so if, for instance, Ap = 9.99 it is reported [and plotted] as 9.00. SWPC is not very good at updating their graphs with definitive values, so one should not make too strong statements based on their graphs. The value for December, 2011 is a case in point. It is plotted as 2, but the real value is estimated [by BGS] to be 4.1.
The Aa index is based on one northern and one southern station, so does not suffer from some of the problems Ap has. The index can also be calculated from solar wind data: Aa = 1/6 BVo^2, where the solar wind magnetic field B is in nT and the solar wind speed Vo is in units of 100 km/s. Here is computed [blue and green curves] vs. observed [red curve] values since 2005: http://www.leif.org/research/Aa-Since-2005.png
You can see that geomagnetic activity is low, but not as low as at the end of 2009.
The reason for the low activity is that the solar wind speed is low [365 km/s]. This often happens near solar maximum.
UPDATE: David Archibald adds this graph and narrative –
Dr Svalgaard’s comment re solar wind and solar maximum might be misinterpreted to suggest that Ap Index is lowest at solar maximum. The opposite is true as shown by this graph from of the Ap Index from 1932.
The Ap Index is back below the floor established by all the previous solar minima. This is important, and there is a correlation between low Ap Index and cooling.
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meemoe_uk
I am not attempting to persuade anyone, but just expressing caution.
For some of my research I looked into the Greenland temperatures during the last 30 years (there is a very reliable instrumental record). As you can see from the link temperature anomaly (normalised at the 1980 value, 10 year moving average) fluctuate widely from east to the west coast and do not appear to very representative of the Northern hemisphere’s temperatures for the same period.
http://www.vukcevic.talktalk.net/GrnlndT.htm
As they say ‘you pays your money and you takes your choice’.
Leif must be busy, so I’ll give a try at answering your somewhat incoherent question.
> … current is generates by the solar wind
> interaction creates a magnetic à la Maxwell …
Magnetic field generated by the solar wind, perhaps? If you already know the plasma current, then the Biot-Savart Law would be sufficient, otherwise, yes, you can compute the magnetic field over a collection of moving point charges using Maxwell’s equations.
> … but what changes the solar wind velocity., please ?
I think that’s a non-sequitur because you’re implying that a change in the current is required to generate the magnetic field. A steady-state current generates a steady B field. A changing current generates an electromagnetic wave.
In any case, the low-speed background solar wind (>= 400k/s) is generated by plasma continuously streaming off the solar equator. Episodes of higher speed wind are triggered by CME’s and coronal holes.
It’s true that big solar flares generate instantaneous magnetic field spikes in the upper atmosphere, due to the enhanced UV/X-ray ionization. But since the solar wind is already ionized, flares don’t have such an instant effect on solar wind unless they’re riding under a plasma filament, which gets pushed out as a CME, which will still take a day or two,three to reach Earth.
> Nearly there.
I hope that gets you to where you were going.
Overlaying the other graph as well, just makes the fit worse.
The correlation is broadly there. At fine resolution its poor, but when your themometers are sedimentary the resolution isn’t expected to be good.
Its good enough for me to see the 5 periods mentioned above in each graph.
“The value for December, 2011 is a case in point. It is plotted as 2, but the real value is estimated [by BGS] to be 4.1”
Big deal. Whether it is 2 or 4.1 those numbers are still in the low range!
meemoe_uk says:
January 6, 2012 at 10:08 am
Its good enough for me to see the 5 periods mentioned above in each graph.
Dealing with true believers is always hard…
John Day says:
January 6, 2012 at 9:58 am
Magnetic field generated by the solar wind, perhaps? If you already know the plasma current, then the Biot-Savart Law would be sufficient, otherwise, yes, you can compute the magnetic field over a collection of moving point charges using Maxwell’s equations.
I think that’s a non-sequitur because you’re implying that a change in the current is required to generate the magnetic field. A steady-state current generates a steady B field. A changing current generates an electromagnetic wave.
you cannot apply those laws directly to a plasma with practically infinite conductivity. What happens is that the magnetic field in the corona reconnects with itself [if the configuration and topology are right] and generates currents that heat the corona and make it expand, basically ‘evaporating’ it away from the sun. Because solar gravity decreases with height, the force [or restriction] that holds the corona near the Sun is gradually relaxed. This causes the expansion speed to become supersonic [much as what happens in a de Laval rocket nozzle, http://en.wikipedia.org/wiki/De_Laval_nozzle ]. Because the conductivity is ‘infinite’, the magnetic field is ‘frozen’ into the plasma and is dragged out into space. So what we see at Earth is an imprint of the solar magnetic field some 4 days earlier [the time it takes the solar wind at 400 km/s to reach the Earth]. The solar atmosphere is a complicated beast where in some places the field pushes around the plasma while in other places it is the other way around. In the end, the plasma wins and drags the field out into space. Nearer the sun the magnetic fields channels the flow of the plasma, and at the surface and below, the plasma pushes around the magnetic field.
who was counting sunspots in 650AD??
Ben D Hillicoss says:
January 6, 2012 at 5:28 pm
who was counting sunspots in 650AD??
Cosmic rays were. Sunspots carry magnetic fields that eventually end up in interplanetary space where they help turn cosmic rays away from the sun, thus changing the number of cosmic rays hitting the Earth where they collide with the air and generate radioactive nuclei that eventually may fall on ice and be embedded in the ice. Drilling cores out of the ice and measuring the radioactivity along the core we can keep track of how the sunspots count changed with time. Also, sunspots can at times be seen with the naked eye, and we have records from China and Korea going back much further than 650AD. So, if you were trying to be facetious, you failed.
@Leif
> … the magnetic field in the corona reconnects with itself
> [if the configuration and topology are right]
> and generates currents that heat the corona and make it expand,
> basically ‘evaporating’ it away from the sun.
So does that magnetic process manifest itself in those plasma loops that are rendered so clearly in EUV at 171A? http://sdo.gsfc.nasa.gov/assets/img/latest/latest_1024_0171.jpg
> …The solar atmosphere is a complicated beast …
Yes, but actually I was addressing the solar wind closer to the Earth. Could those plasma currents be modelled using the classical physics formulae? I guess I don’t quite understand how the magnetic field could be ‘frozen’ into the plasma 93 million miles from the Sun.
BBC, February 13, 1998
The Sun is more active than it has ever been in the last 300 years
Climate changes such as global warming may be due to changes in the sun rather than to the release of greenhouse gases on Earth.
Climatologists and astronomers speaking at the American Association for the Advancement of Science meeting in Philadelphia say the present warming may be unusual – but a mini ice age could soon follow.
=========
BBC, 6 July 2004
Sunspots reaching 1,000-year high
A new analysis shows that the Sun is more active now than it has been at anytime in the previous 1,000 years.
Scientists based at the Institute for Astronomy in Zurich used ice cores from Greenland to construct a picture of our star’s activity in the past. They say that over the last century the number of sunspots rose at the same time that the Earth’s climate became steadily warmer.
============
BBC, April 21, 2009
‘Quiet Sun’ baffling astronomers
“If the Sun’s dimming were to have a cooling effect, we’d have seen it by now.” – Mike Lockwood
============
BBC 5 July 2011
UK faces more harsh winters in solar activity dip
[…] Last year, Professor Lockwood and colleagues published a paper that identified a link between fewer sunspots and atmospheric conditions that “blocked” warm westerly winds reaching Europe during winter months, opening the way for cold easterlies from the Arctic and Russia to sweep across the region.
Professor Lockwood, while acknowledging that there were a range of possible meteorological factors that could influence blocking events, said the latest study moved things forward by showing that there was “improvement in the predictive skill” when solar activity was taken into account.
=========
An improvement in predictive skill is more important than understanding mechanism. You can have a predictive tool without understanding how it works.
I always love a good Solar thread. I’m still, after all these years, still trying to understand why it ISN’T the Sun!!! to blame for the agreed warming and the general state of affairs down here. . I believe the onesss is on the one trying to show that it is the Sun but never realized how thin the connection is. .
THat one of the world’s foremost authorities on all things solar, blogs here in the first place is amazing, but that he believes, correctly by the looks of it, that the Sun has nowt to do with it is even more amazing. The whole solar thing is just……flipping fascinating!!! SO, thanks to all. And Cheers to Tallbloke. We’re thinking of you. Did you get your computers back?? Call them and bug them about it. You need them…..etc.
John Day says:
January 6, 2012 at 5:55 pm
So does that magnetic process manifest itself in those plasma loops that are rendered so clearly in EUV at 171A?
The loops are in the region where the magnetic field overpowers the plasma, which is then forced to move along the field and trace out those beautiful loops. When loops of different directions [of the magnetic field] touch, the fields can connect to form a different loop, in the process inducing electrical currents that heat [both by ordinary Joule heating and by accelerating particles to high speed that heat on impact with other material] the plasma [and you have a solar flare].
…The solar atmosphere is a complicated beast …
Yes, but actually I was addressing the solar wind closer to the Earth. Could those plasma currents be modelled using the classical physics formulae? I guess I don’t quite understand how the magnetic field could be ‘frozen’ into the plasma 93 million miles from the Sun.
The solar wind is also just a part of the solar atmosphere extending more than 100 astronomical units away from the Sun. The classical physics formula have to be modified to their MHD-versions to work: http://en.wikipedia.org/wiki/Magnetohydrodynamics
The trick to understand the frozen in condition is as follows: moving a conductor in a magnetic field [or vice versa] induces an electric field. Lenz’s law [ http://en.wikipedia.org/wiki/Lenz%27s_law ] works such that an induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux, meaning that the flux cannot change, is thus ‘frozen in’.
Khwarizmi says:
January 6, 2012 at 7:04 pm
The Sun is more active than it has ever been in the last 300 years…
A new analysis shows that the Sun is more active now than it has been at anytime in the previous 1,000 years.
I don’t think so.
An improvement in predictive skill is more important than understanding mechanism. You can have a predictive tool without understanding how it works.
True enough, but that is VERY hard to accomplish. In most cases it will fail eventually if you don’t know how it works.
Johnnythelowery says:
January 6, 2012 at 7:26 pm
That one of the world’s foremost authorities on all things solar, blogs here in the first place is amazing, but that he believes, correctly by the looks of it, that the Sun has nowt to do with it is even more amazing. The whole solar thing is just……flipping fascinating!!!
It is, indeed. And the Sun does have a lot to do with SPACE weather and its technological consequences.
“The reason for the low activity is that the solar wind speed is low [365 km/s]. This often happens near solar maximum.”
It is typically at the lowest on the rising side of the cycle in the first couple of years after minimum:
http://users.telenet.be/j.janssens/SC24web/AreaAp.png
@Phil says:
January 5, 2012 at 11:58 am
“Net decrease in AP relative to the Earth’s energy budget index leads to La Nina, upward spikes in the AP index lead to El Nino, 6.5 years down the road due to the thermal inertia of the ocean body.”
That is the wrong way round and there is little lag. A falling trend in the solar wind speed brings on El Nino conditions, and a rising trend in the solar wind speed brings on La Nina conditions.
Leif Svalgaard says:
January 5, 2012 at 6:01 pm
“look at the deepest minimum of all the past 2000 years around 650AD”
Exactly what I was looking at, and all I can find is cold events in the 7th Century…
http://www.geo.arizona.edu/palynology/geos462/holobib.html
http://syrcom.cua.edu/Hugoye/Vol3No2/HV3N2Morony.html
http://booty.org.uk/booty.weather/climate/500_750.htm
Phil says:
January 5, 2012 at 7:13 pm
“There is no proof that this is the direct causative mechanism, but ENSO/variation in the global temp and the AP index correlate very well especially in the 2009-10 El Nino.”
It correlates particularly well with falling solar wind speeds, as does the 1997/98 Ell Nino:
http://omniweb.gsfc.nasa.gov/tmp/images/ret_30887.gif
(no lag involved)
Ulric Lyons says:
January 7, 2012 at 11:17 am
“The reason for the low activity is that the solar wind speed is low [365 km/s]. This often happens near solar maximum.”
It is typically at the lowest on the rising side of the cycle in the first couple of years after minimum:
http://users.telenet.be/j.janssens/SC24web/AreaAp.png
There are two local minima, one just after minimum and one at maximum: http://www.leif.org/research/Climatological%20Solar%Wind.png the density is lowest at solar maximum, leading to a minimum in solar wind pressure right at solar minimum.
There are two local minima, one just after minimum and one at maximum: http://www.leif.org/research/Climatological%20Solar%20Wind.png the density is lowest at solar maximum, leading to a minimum in solar wind pressure right at solar minimum: http://www.leif.org/research/Space-Climate-n-B-V-Flow.png
@Leif Svalgaard says:
January 7, 2012 at 2:57 pm
“There are two local minima, one just after minimum and one at maximum:”
Yes I am aware of the one at maximum, as you may remember from my comments about more frequent colder winters around cycle maximum`s. Though I must say they vary considerably, and clearly the Ap index is consistently lower at the one just after minimum:
http://users.telenet.be/j.janssens/SC24web/AreaAp.png
Leif Svalgaard says:
January 7, 2012 at 2:57 pm
Fingers a bit stiff today:
There are two local minima in solar wind speed, one just after minimum and one at maximum: http://www.leif.org/research/Climatological%20Solar%20Wind.png the density is lowest at solar maximum, leading to a minimum in solar wind pressure right at solar maximum http://www.leif.org/research/Space-Climate-n-B-V-Flow.png
Ulric Lyons says:
January 7, 2012 at 4:01 pm
Though I must say they vary considerably, and clearly the Ap index is consistently lower at the one just after minimum
Basically because the solar wind magnetic field is lowest then. At solar max, the magnetic field B is at a maximum, so Ap tends to be less low. To good approximation Ap = 1/3 * B * Vo^2 where B is in nanoTesla near Earth and Vo is wind speed in units of 100 km/s.
@Leif Svalgaard says:
January 7, 2012 at 4:03 pm
“the density is lowest at solar maximum, leading to a minimum in solar wind pressure right at solar maximum”
So there is a low in flow pressure around maximum yes:
http://omniweb.gsfc.nasa.gov/tmp/images/ret_20809.gif
but the Ap index is still typically at its lowest just after cycle minimum`s:
http://users.telenet.be/j.janssens/SC24web/AreaAp.png
@Leif Svalgaard says:
January 7, 2012 at 4:07 pm
Ulric Lyons says:
January 7, 2012 at 4:01 pm
Though I must say they vary considerably, and clearly the Ap index is consistently lower at the one just after minimum
>Basically because the solar wind magnetic field is lowest then.
No I am saying that the local Ap minima at maximum varies considerably from cycle to cycle
http://users.telenet.be/j.janssens/SC24web/AreaAp.png
Ulric Lyons says:
January 7, 2012 at 4:32 pm
No I am saying that the local Ap minima at maximum varies considerably from cycle to cycle
That is why it takes 13 cycles to see the systematic variation. Ap varies then because the magnetic field B varies [with the sunspot number]. All this is well understood in physical terms.
Basically we must breed in times off the apocalypse this solves everything i mean we all cant die its just like roaches…………………………..