Archive for the ‘Solar physics’ Category

A simulation of a cross-section of a thread of solar material, called a filament, hovering in the sun's atmosphere [image credit: NAOJ/Patrick Antolin]

A simulation of a cross-section of a thread of solar material, called a filament, hovering in the sun’s atmosphere
[image credit: NAOJ/Patrick Antolin]


Researchers find this works in ‘the same way that a perfectly-timed repeated push on a swing can make it go higher’, as Phys.org reports:

Modern telescopes and satellites have helped us measure the blazing hot temperatures of the sun from afar. Mostly the temperatures follow a clear pattern: The sun produces energy by fusing hydrogen in its core, so the layers surrounding the core generally get cooler as you move outwards—with one exception.

Two NASA missions have just made a significant step towards understanding why the corona—the outermost, wispy layer of the sun’s atmosphere —is hundreds of times hotter than the lower photosphere, which is the sun’s visible surface [aka the coronal heating problem]

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A bit less of this to look forward to? [image credit: traveldailynews.com]

A bit less of this to look forward to? [image credit: traveldailynews.com]


Some solar theories will be put to the test in the next few decades by the Sun’s ongoing behaviour patterns.

Is Earth slowly heading for a new ice age? Looking at the decreasing number of sunspots, it may seem that we are entering a nearly spotless solar cycle which could result in lower temperatures for decades. “The solar cycle is starting to decline. Now we have less active regions visible on the sun’s disk,” Yaireska M. Collado-Vega, a space weather forecaster at NASA’s Goddard Space Flight Center, told Phys.org.

But does it really mean a colder climate for our planet in the near future? In 1645, the so-called Maunder Minimum period started, when there were almost no sunspots. It lasted for 70 years and coincided with the well-known “Little Ice Age”, when Europe and North America experienced lower-than-average temperatures. However, the theory that decreased solar activity caused the climate change is still controversial as no convincing evidence has been shown to prove this correlation.

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The 'before' version of sunspot numbers [Credit: Wikipedia]

The ‘before’ version of sunspot numbers [Credit: Wikipedia]

This result has been at least half-expected ever since the ‘revision’ of sunspot numbers was announced. The phrase ‘desired outcome’ springs to mind.

The Sunspot Number is a crucial tool used to study the solar dynamo, space weather and climate change, reports Phys.org. It has now been recalibrated and shows a consistent history of solar activity over the past few centuries. The new record has no significant long-term upward trend in solar activity since 1700, as was previously indicated. This suggests that rising global temperatures since the industrial revolution cannot be attributed to increased solar activity.

The analysis, its results and its implications for climate research were made public today at a press briefing at the International Astronomical Union (IAU) XXIX General Assembly, currently taking place in Honolulu, Hawaii, USA.

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What happened to the sunspots?

Posted: July 14, 2015 by oldbrew in Solar physics
Tags:

Giant sunspot group AR1944 in January 2014. [Credit: NASA/SDO]

Giant sunspot group AR1944 in January 2014. [Credit: NASA/SDO]


Communities Digital News explains:

On June 30, 2015 the globally recognized maximum for the current 11-year sunspot cycle was 81.9. On July 1, 2015 that number suddenly leaped all the way up to 116.4!

Stranger still, the current cycle (Cycle 24) fell from being the 7th weakest sunspot maximum since 1749 to being the 4th weakest sunspot maximum. Cycle 24’s sunspot number jumped by 30 percent, yet its ranking dropped by three places. How can that be?

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[Image credit: NASA]

[Image credit: NASA]


Another solar theory rolls off the production line – as ever, time will tell if it lives up to its own billing.

A new model of the Sun’s 11-year heartbeat suggests that solar activity will fall by 60 per cent during the 2030s, dropping to conditions last seen during the Maunder minimum, reports Ice Age Now.

Beginning in about 1645, the Maunder minimum corresponded with the severest portion of the last
“Little Ice Age.”

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Via Benny Peiser at the GWPF
Image courtesy of CartoonbyJosh.com

Image courtesy of CartoonsbyJosh.com

Britain could be on the verge of a mini Ice Age as the Sun enters a cooler phase, the Met Office warned yesterday. The last big chill was felt hundreds of years ago when Frost Fairs were held on the frozen River Thames. However the Met Office said the new freeze will not be enough to cancel out the effects of global warming. Met Office’s Hadley Centre, which looks at long term forecasts, said there was a 15-20 per cent chance that we could match the temperatures last seen in 1645-1715 – sometimes called the Little Ice Age – when the River Thames froze over. –Colin Fernandez, Daily Mail, 24 June 2015
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Image

Variation in sunspot properties between 1999 and 2014

R. Rezaei1, C. Beck, A. Lagg, J. M. Borrero, W. Schmidt and M. Collados

A&A Volume 578, June 2015 Article Number A43
DOI http://dx.doi.org/10.1051/0004-6361/201425557
Published online 01 June 2015
Open access with registration

Abstract

Aims. We study the variation in the magnetic field strength, area, and continuum intensity of umbrae in solar cycles 23 and 24.

Conclusions. The umbral brightness decreases in the rising stage of a solar cycle, but increases from maximum toward the end of the cycle. Our results do not indicate a drastic change of the solar cycle toward a grand minimum in the near future.

Specifically disagrees with Livingson et.al. concluding the weak trending lower is too minor for there to be much change on the horizon.

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Level and length of cyclic solar activity during the Maunder minimum as deduced from the active-day statistics
J. M. Vaquero, G. A. Kovaltsov, I. G. Usoskin, V. M. S. Carrasco and M. C. Gallego
A&A, 577 (2015) A71
Published online: 06 May 2015
DOI: http://dx.doi.org/10.1051/0004-6361/201525962
(open access with registration)

Image

 

ABSTRACT
Aims. The Maunder minimum (MM) of greatly reduced solar activity took place in 1645–1715, but the exact level of sunspot activity is uncertain because it is based, to a large extent, on historical generic statements of the absence of spots on the Sun. Using a conservative approach, we aim to assess the level and length of solar cycle during the MM on the basis of direct historical records by astronomers of that time.

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This paper published 10th March tries to identify major episodic solar activity by using both 14C and 10BeImage

(note to reader, above x-axis has advancing time running right to left)

Grand solar minima and maxima deduced from 10Be and 14C: magnetic dynamo configuration and polarity reversal
F. Inceoglu, R. Simoniello, M. F. Knudsen, C. Karoff, J. Olsen, S. Turck-Chiéze, B. H. Jacobsen
A&A 577 A20 (2015)
DOI: 10.1051/0004-6361/201424212

Abstract

Aims. This study aims to improve our understanding of the occurrence and origin of grand solar maxima and minima.
Methods. We first investigate the statistics of peaks and dips simultaneously occurring in the solar modulation potentials reconstructed using the Greenland Ice Core Project (GRIP) 10 Be and IntCal13 14 C records for the overlapping time period spanning between ~1650 AD to 6600 BC.

Image

I’ve included this on the front page because I think the bimodality of solar data is an important matter where this work adds weight to the effect being real.

http://www.aanda.org/articles/aa/abs/2015/04/aa21064-13/aa21064-13.html
Open access with registration

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A solar 'prominence' [credit: NASA]

A solar ‘prominence’ [credit: NASA]


Not being an expert in such matters I turn to NASA for a brief explanation of terms:

‘The primary source of energy to the Earth is radiant energy from the Sun. This radiant energy is measured and reported as the solar irradiance. When all of the radiation is measured it is called the Total Solar Irradiance (TSI); when measured as a function of wavelength it is the spectral irradiance.’
NASA – Solar Irradiance

The abstract of a new paper suggests there’s a need to take a lot more notice of ‘SSI’ compared to ‘TSI’.
Note in particular its last sentence
:
‘Therefore, it appears that SSI rather than TSI is a good indicator of the chromospheric activity, and its cycle length dependent variation would be more relevant to the possible role of the Sun in the cyclic variation of the Earth’s atmosphere.’

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This failed work is presented as a cautionary tale but nevertheless there might be good parts.

Earlier oldbrew published an article on a theory by Nelson on forecasting the armada of radio propagation conditions. There were not many comments, possibly from the lack of solid further material.
Image

From this paper, we can see why the technique fell at the hurdle. Nevertheless looking at what people were thinking and doing is important.

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A resent post by Roger and comments thereon led to my  realising there are misunderstandings on the intepretation of the polar field relationships.

Wilcox Observatory[1] measure and publish a time series of the solar polar magnetic field, a difficult measurement. Started 31st May 1976, data point every 10 days.

Image

Figure 1, straight plot of f10.7 radio noise[3] as a proxy for solar activity and mean solar polar magnetic field[1].

Firstly here are some clarification notes.

The polar field is not the interplanetary field[6] indirectly associated with terrestrial cosmic ray flux. This field at earth roughly follows the F10.7 / sunspot shape, is very noisy.

Neither is it the Livingstone & Penn[2] finding about the change in sunspot magnetic field possibly reducing with time.

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Back in 2011. Tim Channon used his cycles analysis software to predict the evolution of the solar polar fields. The basis of the curve he produced is the motion of the gas giant planets, Jupiter, Saturn, Uranus and Neptune. As they orbit the Sun, they force the Sun to move relative to the centre of mass of the entire solar system. We see this motion when astronomers look out into the near cosmos and observe other stars ‘wobbling’. By measuring the wobble with respect to time, they are able to deduce the mass and distance of planets orbiting those stars, even though they are too small and dim to see directly.

Tim found that our Sun’s wobble due to the gas giant planets matched the observational data of the evolution of the Solar polar magnetic fields mentioned in the post put up by Stuart ‘Oldbrew‘ yesterday.

Here’s the plot Tim put up in 2011

Evolution of combined solar polar fields (red) vs motion of Sun relative to barycentre caused by planetary motion

At the time, it looked like the data was going to diverge from the prediction, but read on below the break to see the outcome.

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The Sun from NASA's SDO spacecraft

The Sun from NASA’s SDO spacecraft


According to new research entitled: “The crucial role of surface magnetic fields for the solar dynamo”, a prediction method for solar cycles, first proposed decades ago, has been validated:
‘As the dipole field [of the Sun] is the source of the toroidal field of the next cycle, its strength should be a measure of the activity of the next cycle.’

Phys.org reports:
Sunspots, bursts of radiation and violent eruptions are signs that our sun is permanently active. Researchers have long known that this activity varies in a cycle of around eleven years’ duration. Even if many questions are still unresolved, one thing is certain: magnetic fields which emerge on the surface of our sun from within its depths are the cause of the manifold activities.

Robert Cameron and Manfred Schüssler from the Max Planck Institute for Solar System Research in Göttingen have now proved that it is possible to deduce what the internal mechanism is simply by observing the magnetic processes on the surface. This even allows predictions to be made about the strength of a forthcoming activity cycle.

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Back in 1987, Robert M Wilson of NASA’s Space Science Laboratory in Huntsville published this paper in the Journal of Geophysical Research. It’s important to our solar-planetary theory because it shows that the Sun is bi-modal in terms of its solar cycle lengths. They cluster around  periods of a little over ten and a little under twelve years. These periods correlate to the periods of Jupiter-Earth-Venus syzygy cycles and Jupiter’s orbital period respectively. Leif Svalgaard vehemently denied this correlation when I pointed it out to him a few years ago.

rob-wilson-bimodal-sun

The same correlation was noted by independent researcher Timo Niroma in 1989, who conducted his own survey and analysis of solar cycle lengths. He produced this simple ascii-art graphic to present his results.

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Solar cycle 4b, support from 10BE proxy

Posted: February 28, 2015 by tchannon in Solar physics

One of the unsolved solar mysteries is the peculiar behaviour around year 1800. The data we have is poor leading to ambiguity on whether a solar sunspot cycle is missing from the record.

Image

Figures from paper. For a legible copy you will need to register and download the PDF.

The lost sunspot cycle: New support from 10Be measurements
C. Karoff, F. Inceoglu, M. F. Knudsen, J. Olsen, A. Fogtmann-Schulz
A&A 575 A77 (2015)
DOI: http://dx.doi.org/10.1051/0004-6361/201424927
(early preview with registration)

ABSTRACT

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Solar cycle 24 enigma: TSI on the rise again

Posted: February 25, 2015 by tallbloke in Solar physics
Tags: ,

The latest results from the TIM/SORCE TSI instrument show that solar cycle 24 hit a peak on Feb 6th at around 1362.3W/m^2. Does anyone think it’ll go any higher?

tim_level3_tsi_24hour_3month_640x480

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In Astronomy & Astrophysics this week is an article of interest to some Talkshop readers. The authors are looking at the little understood variation is solar rotation in the context of peculiar change in recent years. Article has been amended with a new figure kindly provided by  L. Zhang showing more detail.

Figure caption: Yearly values of the N-S asymmetry (N-S)/(N+S) of the solar rotation at latitude 17 deg in 1978-2013 for X-ray flares (blue open circles) and for sunspots (red open circles). The blue (red) filled circles denote 11 year running mean values for flares (sunspots).

Figure caption: Yearly values of the N-S asymmetry (N-S)/(N+S) of the solar rotation at latitude 17 deg in 1978-2013 for X-ray flares (blue open circles) and for sunspots (red open circles).
The blue (red) filled circles denote 11 year running mean values for flares (sunspots).

Letter to the Editor

Solar surface rotation: N-S asymmetry and recent speed-up
L. Zhang, K. Mursula and I. Usoskin
A&A 575 L2 (2015)
DOI: http://dx.doi.org/10.1051/0004-6361/201425169
(open access)

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As regular readers know, I’m interested in small devices for generating trickle charging solutions for batteries out in the cloudy mountains where the sun rarely shines. We’ve looked at potentially useful stirling engine designs before, but I just found this interesting video on Youtube which differs fundamentally from the stirling design, while retaining some of its thermodynamic features.

 

This type of very simple engine is known by various names such as laminar flow, thermo-acoustic, thermal lag etc, but no-on seems to have a fully developed thermodynamic theory of exactly how it works. Unlike classic stirling engines, there is no ‘displacer’ to shunt the working gas from the hot to the cold end in order to drive a cycle of expansion/contraction which then sucks and pushes a power piston which drives a flywheel (or a linear electric motor). It’s more reminiscent in a way of a pulse-jet engine, but with a closed cycle, rather than an open system generating thrust directly from the explosive expansion of combustible gases.

But besides thinking about the way this engine operates as a collection of glass and aluminium parts heated at one end, it put me in mind of the way the Sun ‘pulses’ every eleven years or so. So this is today’s brainstormer. If objects can be set into oscillation by the application of heat (and let’s not forget thermodynamic theory here, whereby atoms and molecules ‘vibrate’ more vigorously as heat is applied to them), then what if the heavy dense metallic hydrogen core of the Sun is set into oscillation by the heat generated in the fusion process? It wouldn’t oscillate so easily in the X-Y plane, because the Sun is rotating, but it is freer to move in the Z axis.
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Solar contiguous activity cycle 23/24

Posted: December 20, 2014 by tchannon in Astrophysics, Solar physics

At first sight this Brazilan paper in Astronomy & Astrophysics is relatively uninteresting if you are familar with sunspot activity, appears to be another general look using waveletts.

Two features strike me as worthy of highlighting

  • a double burst of activity during cycle 23, not obvious from sunspot data alone
  • continuing activity right through the 23/24 transition

Image

Extract from paper Fig. 5, my highlight of strong X activity post the cycle 23 sunspot peak.

Wavelet analysis of CME, X-ray flare, and sunspot series

M. R. G. Guedes, E. S. Pereira and J. R. Cecatto

A&A 573 A64 (2015)

DOI: http://dx.doi.org/10.1051/0004-6361/201323080

(access with registration, large PDF 17.7MB)

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