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TOPIC: Sunspots
Blobrana


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Posts: 131433
Date:
Solar Minimums
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New Insights on How Solar Minimums Affect Earth

Since 1611, humans have recorded the comings and goings of black spots on the sun. The number of these sunspots waxes and wanes over approximately an 11-year cycle -- more sunspots generally mean more activity and eruptions on the sun and vice versa. The number of sunspots can change from cycle to cycle, and 2008 saw the longest and weakest solar minimum since scientists have been monitoring the sun with space-based instruments.
Observations have shown, however, that magnetic effects on Earth due to the sun, effects that cause the aurora to appear, did not go down in synch with the cycle of low magnetism on the sun. Now, a paper in Annales Geophysicae that appeared on May 16, 2011 reports that these effects on Earth did in fact reach a minimum -- indeed they attained their lowest levels of the century -- but some eight months later. The scientists believe that factors in the speed of the solar wind, and the strength and direction of the magnetic fields embedded within it, helped produce this anomalous low.
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Blobrana


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Posts: 131433
Date:
Cycle 24
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Title: Is Cycle 24 the Beginning of a Dalton-Like Minimum?
Authors: M. Lindholm Nielsen, H. Kjeldsen

The unexpected development of cycle 24 emphasizes the need for a better way to model future solar activity. In this article, we analyse the accumulation of spotless days during individual cycles from 1798-2010. The analysis shows that spotless days do not disappear abruptly in the transition towards an active sun. A comparison with past cycles indicates that the ongoing accumulation of spotless days is comparable to that of cycle 5 near the Dalton minimum and to that of cycles 12, 14 and 15. It also suggests that the ongoing cycle has as much as 20 \pm 8 spotless days left, from July 2010, before it reaches the next solar maximum. The last spotless day is predicted to be in December 2012, with an uncertainty of 11 months. This trend may serve as input to the solar dynamo theories.

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Blobrana


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Posts: 131433
Date:
RE: Sunspots
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NASA-Sponsored Research Explains Missing Sunspots

During this deep solar minimum, the sun's magnetic field weakened, allowing cosmic rays to penetrate the solar system in record numbers, making space a more dangerous place to travel. At the same time, the decrease in ultraviolet radiation caused Earth's upper atmosphere to cool and collapse.
As a consequence space debris stopped decaying and started accumulating in Earth orbit due to increased atmospheric drag. These effects demonstrate the importance of understanding the entire solar cycle, during both minimum and maximum.
Observations from NASA's Solar Dynamics Observatory (SDO) will eventually provide measurements that could validate the current model and provide the basis for future solar cycle prediction.
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Blobrana


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Posts: 131433
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Solar Mystery Solved

The Sun has been in the news a lot lately because it's beginning to send out more flares and solar storms. Its recent turmoil is particularly newsworthy because the Sun was very quiet for an unusually long time. Astronomers had a tough time explaining the extended solar minimum. New computer simulations imply that the Sun's long quiet spell resulted from changing flows of hot plasma within it.
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Blobrana


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Posts: 131433
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NASA Reschedules Teleconference To Explain Missing Sunspots

NASA has rescheduled a media teleconference for 2 p.m. EST on Wednesday, March 2, to discuss the first computer model that explains the recent period of decreased solar activity during the sun's 11-year cycle. The recent solar minimum, a period characterised by a lower frequency of sunspots and solar storms, ended in 2008 and was the deepest observed in almost 100 years.
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Blobrana


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Solar experts detect waves in giant magnetic holes the size of the UK

Massive waves in giant magnetic holes on the surface of the Sun have been discovered for the first time by solar scientists from the University of Sheffield and Queen's University Belfast, something that will bring experts a step closer to unlocking the secrets of the Sun.
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Blobrana


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Posts: 131433
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Title: A New Approach in Understanding Growth and Decay of the Sunspots
Authors: K. M. Hiremath, Lovely, M. R

From the previous study (Hiremath 2009b; Hiremath 2010), on the genesis of solar cycle and activity phenomena, it is understood that sunspots are formed at different depths by superposition of Alfven wave perturbations of a strong toroidal field structure in the convective envelope and after attaining a critical strength, due to buoyancy, raise toward the surface along the rotational isocontours that have positive (0.7-0.935 solar radii) and negative (0.935-1.0 solar radii) rotational gradients. Owing to physical conditions in these two rotational gradients, from the equation of magnetic induction, sunspot's area growth and decay problem is solved separately. It is found that rate of growth of sunspot's area during its evolution at different depths is function of steady and fluctuating parts of Lorentzian force of the ambient medium, fluctuations in meridional flow velocity, radial variation of rotational gradient and cot(\vartheta) (where \vartheta is co-latitude). While rate of decay of sunspot's area at different depths during its evolution mainly depends upon magnetic diffusivity, rotational gradient and sin²(\vartheta). Gist of this study is that growth and decay of area of the sunspot mainly depends upon whether sunspot is originated in the region of either positive or negative rotational gradient. For different latitudes and life spans of the sunspots on the surface during their evolutionary history, both the analytically derived theoretical area growth and decay curves match reasonably well with the observed area growth and decay curves.

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Blobrana


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Posts: 131433
Date:
Solar cycle
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Solar cycle may drive Venice's floods

If you want to see Venice while keeping your feet dry, don't go when the sun has lots of spots. Peaks in solar activity cause the city to flood more often, apparently by changing the paths of storms over Europe.
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Blobrana


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Posts: 131433
Date:
RE: Sunspots
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After the most profound lull in solar activity for nearly a century, the Sun is finally coming back to life. But will the solar activity return to previous levels? ESA's venerable solar watchdog SOHO is there, watching and measuring, providing unique information about our nearest star.
It was the perfect Christmas present for solar physicists. In mid-December 2009, the largest group of sunspots to emerge for several years manifested itself on the solar surface. It occurred just as some solar physicists were beginning to wonder if large sunspots would ever return.
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Blobrana


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Posts: 131433
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Lincoln astronomer says big freeze is coming

The worst of the wintry weather may be over, but next winter in Lincolnshire could be equally bad, according to an amateur astronomer.
This time last year Philip Norton, a member of Lincoln Astronomical Society, told the Echo how a lack of sunspot activity was the reason for the bitter conditions.
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Ed ~ It should be noted that this is an El Niño year, and Australia has experienced  one of the warmest periods in recorded history.


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