Re: ARLA/CLUSTER: Mínimo anómalo de manchas solares ou nova Idade do Gelo depois de 2015..?

[Carlos Mourato]

Ja tinha lido isso acerca destes "profetas da desgraça"...Parece que cada
vez que existe alguma coisa fora dos padrões conhecidos, vai logo acabar o
mundo!!173 de CT4RK


2009/9/7 João Gonçalves Costa <joao.a.costa  ctt.pt>

>  <http://www.norcalblogs.com/watts/images/sunspots_earth_size_big.jpg>
>  William Livingston e Matt Penn, investigadores do Observatório Nacional
> Solar – Tucson: EUA - dizem que o nosso Sol, a partir de 2015, poderá perder
> as suas manchas solares, denotando menos actividade, o que poderá levar a
> uma nova pequena idade do gelo - como no Maunder Minimum (Mínimo de
> Maunder), entre 1645 e 1715 quando a actividade de manchas solares
> reduziu-se drasticamente, gerando na Terra uma redução dramática da
> temperatura. No continente europeu e América do Norte registraram-se
> temperaturas baixíssimas, provocando o congelamento de grandes cursos de
> rios que normalmente não passam por essa situação. O nome
> “Maunder” deve-se ao astrónomo inglês E. W. Maunder (1851-1929) do
> Observatório de Greenwich, que o relatou quando estudava os
> registos históricos sobre o Sol
>   *Are sunspots disappearing?*
>
> *Nasa* report that the sun is in the pits of the deepest solar minimum in
> nearly a century. Weeks and sometimes whole months go by without even a
> single tiny sunspot. The quiet has dragged out for more than two years,
> prompting some observers to wonder, *are sunspots disappearing?*
>
> "Personally, I'm betting that sunspots are coming back," says researcher
> Matt Penn of the National Solar Observatory (NSO) in Tucson, Arizona. But,
> he allows, "there is some evidence that they won't."
>
> Penn's colleague Bill Livingston of the NSO has been measuring the magnetic
> fields of sunspots for the past 17 years, and he has found a remarkable
> trend. Sunspot magnetism is on the decline.
>
> While most researchers measure the splitting of spectral lines in the
> visible part of the sun's spectrum, Livingston decided to try an infra-red
> spectral line. Infrared lines are much more sensitive to the Zeeman effect
> and provide more accurate answers. Also, he dedicated himself to measuring a
> large number of sunspots—more than 900 between 1998 and 2005 alone. The
> combination of accuracy and numbers revealed the downturn.
>
> "According to our measurements, sunspots seem to form only if the magnetic
> field is stronger than about 1500 gauss," says Livingston.
>
> "If the current trend continues, we'll hit that threshold in the near
> future, and solar magnetic fields would become too weak to form sunspots."
>
> "This work has caused a sensation in the field of solar physics," comments
> NASA sunspot expert David Hathaway, who is not directly involved in the
> research. "It's controversial stuff."
>
> If sunspots do go away, it wouldn't be the first time.
> In the 17th century, the sun plunged into a 70-year period of spotlessness
> known as the *Maunder Minimum* that still baffles scientists. The sunspot
> drought began in 1645 and lasted until 1715; during that time, some of the
> best astronomers in history (e.g., Cassini) monitored the sun and failed to
> count more than a few dozen sunspots per year, compared to the usual
> thousands.
>
> "Whether [the current downturn] is an omen of long-term sunspot decline,
> analogous to the Maunder Minimum, remains to be seen," Livingston and Penn
> caution in a recent issue of EOS. "Other indications of solar activity
> suggest that sunspots must return in earnest within the next year."
>
> Whatever happens, notes Hathaway, "the sun is behaving in an interesting
> way and I believe we're about to learn something new."
>
> Read the full NASA report at
> http://science.nasa.gov/headlines/y2009/
> 03sep_sunspots.htm?list130845
> Fontes: Blog Ano Zero e Southgate Amateur Radio Club.
>
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>


-- 
Best 73 from: regards from: CT4RK Carlos Mourato - Sines - Portugal

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