Say Goodbye to Sunspots?
by Phil Berardelli on 14 September 2010, 2:41 PM
Scientists studying sunspots for the past 2 decades have concluded that the magnetic field that triggers their formation has been steadily declining. If the current trend continues, by 2016 the sun's face may become spotless and remain that way for decades—a phenomenon that in the 17th century coincided with a prolonged period of cooling on Earth.
Sunspots appear when upwellings of the sun's magnetic field trap ionized plasma—or electrically charged, superheated gas—on the surface. Normally, the gas would release its heat and sink back below the surface, but the magnetic field inhibits this process. From Earth, the relatively cool surface gas looks like a dark blemish on the sun.
Source: KSJTracker
Astronomers have been observing and counting sunspots since Galileo began the practice in the early 17th century. From those studies, scientists have long known that the sun goes through an 11-year cycle, in which the number of sunspots spikes during a period called the solar maximum and drops—sometimes to zero—during a time of inactivity called the solar minimum.
The last solar minimum should have ended last year, but something peculiar has been happening. Although solar minimums normally last about 16 months, the current one has stretched over 26 months—the longest in a century. One reason, according to a paper submitted to the International Astronomical Union Symposium No. 273, an online colloquium, is that the magnetic field strength of sunspots appears to be waning.
...
Read more here/Leia mais aqui: Science
+++++
Artigo do Arxiv mencionado na Science:
Long-term Evolution of Sunspot Magnetic Fields
Matthew Penn, William Livingston
(Submitted on 3 Sep 2010)
Independent of the normal solar cycle, a decrease in the sunspot magnetic field strength has been observed using the Zeeman-split 1564.8nm Fe I spectral line at the NSO Kitt Peak McMath-Pierce telescope. Corresponding changes in sunspot brightness and the strength of molecular absorption lines were also seen. This trend was seen to continue in observations of the first sunspots of the new solar Cycle 24, and extrapolating a linear fit to this trend would lead to only half the number of spots in Cycle 24 compared to Cycle 23, and imply virtually no sunspots in Cycle 25.
We examined synoptic observations from the NSO Kitt Peak Vacuum Telescope and initially (with 4000 spots) found a change in sunspot brightness which roughly agreed with the infrared observations. A more detailed examination (with 13,000 spots) of both spot brightness and line-of-sight magnetic flux reveals that the relationship of the sunspot magnetic fields with spot brightness and size remain constant during the solar cycle. There are only small temporal variations in the spot brightness, size, and line-of-sight flux seen in this larger sample. Because of the apparent disagreement between the two data sets, we discuss how the infrared spectral line provides a uniquely direct measurement of the magnetic fields in sunspots.
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1009.0784v1 [astro-ph.SR]
Submission historyFrom: Matthew Penn [view email]
[v1] Fri, 3 Sep 2010 23:03:17 GMT (34kb)
+++++
NOTA CAUSTICANTE DESTE BLOGGER:
Os afirmacionistas do aquecimento global ser antropogenicamente provocado vão enfiar a viola no saco, pois se estas manchas solares desaparecerem o que virá é um ESFRIAMENTO GLOBAL com ações unicamente naturais, caras-pálidas!!!
Fui, nem sei por que, pensando que em ciência nada como um dia atrás do outro...
+++++
