Boas,<br><br>Novas previsões para o Ciclo Solar 24.<br>Original em:<br><a href="http://science.nasa.gov/headlines/y2009/29may_noaaprediction.htm">http://science.nasa.gov/headlines/y2009/29may_noaaprediction.htm</a> <br><br>
Cumprimentos<br><br>Salomão Fresco<br>CT2IRJ<br><br><br><table border="0" cellpadding="0" cellspacing="0" width="600"><tbody><tr><td align="left" width="571"><p><span class="storyTitle"><font size="4"> New Solar Cycle
Prediction </font></span></p>
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<td align="right" width="124"> <span class="storyTitle"> 05.29.2009</span>
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<p><font size="2" face="Verdana, Arial, Helvetica, sans-serif"><strong>May
29, 2009:</strong> An international panel of experts led by
NOAA and sponsored by NASA has released a new prediction for
the next solar cycle. Solar Cycle 24 will peak, they say,
in May 2013 with a below-average number of sunspots. </font></p>
<p><font size="2" face="Verdana, Arial, Helvetica, sans-serif"><a href="http://science.nasa.gov/headlines/y2009/images/noaaprediction/296969main_flare_sxilabeled_HI.jpg"><img src="http://science.nasa.gov/headlines/y2009/images/noaaprediction/flare_sxi2_med.jpg" align="right" border="1" width="270" height="177" hspace="10"></a>"If
our prediction is correct, Solar Cycle 24 will have a peak
sunspot number of 90, the lowest of any cycle since 1928 when
Solar Cycle 16 peaked at 78," says panel chairman Doug
Biesecker of the NOAA Space Weather Prediction Center.</font></p>
<p class="detailImageDesc"><font size="2" face="Verdana, Arial, Helvetica, sans-serif"><strong>Right:</strong>
A solar flare observed in Dec. 2006 by NOAA's GOES-13 satellite.</font></p>
<p><font size="2" face="Verdana, Arial, Helvetica, sans-serif">It
is tempting to describe such a cycle as "weak" or
"mild," but that could give the wrong impression.</font></p>
<p><font size="2" face="Verdana, Arial, Helvetica, sans-serif">"Even
a below-average cycle is capable of producing severe space
weather," points out Biesecker. "The great geomagnetic
storm of 1859, for instance, occurred during a solar cycle
of about the same size we’re predicting for 2013."</font></p>
<p><font size="2" face="Verdana, Arial, Helvetica, sans-serif">The
1859 storm--known as the "Carrington Event" after
astronomer Richard Carrington who witnessed the instigating
solar flare--electrified transmission cables, set fires in
telegraph offices, and produced Northern Lights so bright
that people could read newspapers by their red and green glow.
A recent report by the National Academy of Sciences found
that if a similar storm occurred today, it could cause $1
to 2 trillion in damages to society's high-tech infrastructure
and require four to ten years for complete recovery. For comparison,
Hurricane Katrina caused "only" $80 to 125 billion
in damage. </font></p>
<p align="center"><font size="2" face="Verdana, Arial, Helvetica, sans-serif"><img src="http://science.nasa.gov/headlines/y2009/images/noaaprediction/prediction_strip2.jpg" width="450" height="344"></font></p>
<p class="detailImageDesc"><font size="2" face="Verdana, Arial, Helvetica, sans-serif"><strong>Above:
</strong>This plot of sunspot numbers shows the measured peak
of the last solar cycle in blue and the predicted peak of
the next solar cycle in red. Credit: NOAA/Space Weather Prediction
Center. [<a href="http://www.swpc.noaa.gov/SolarCycle/index.html">more</a>]</font></p>
<p align="left"><font size="2" face="Verdana, Arial, Helvetica, sans-serif">The
latest forecast revises an earlier prediction issued in 2007.
At that time, a sharply divided panel believed solar minimum
would come in March 2008 followed by either a strong solar
maximum in 2011 or a weak solar maximum in 2012. Competing
models gave different answers, and researchers were eager
for the sun to reveal which was correct.</font></p>
<p align="left"><font size="2" face="Verdana, Arial, Helvetica, sans-serif">"It
turns out that none of our models were totally correct,"
says Dean Pesnell of the Goddard Space Flight Center, NASA's
lead representative on the panel. "The sun is behaving
in an unexpected and very interesting way."</font></p>
<p><font size="2" face="Verdana, Arial, Helvetica, sans-serif">Researchers
have known about the solar cycle since the mid-1800s. Graphs
of sunspot numbers resemble a roller coaster, going up and
down with an approximately 11-year period. At first glance,
it looks like a regular pattern, but predicting the peaks
and valleys has proven troublesome. Cycles vary in length
from about 9 to 14 years. Some peaks are high, others low.
The valleys are usually brief, lasting only a couple of years,
but sometimes they stretch out much longer. In the 17th century
the sun plunged into a 70-year period of spotlessness known
as the Maunder Minimum that still baffles scientists.</font></p>
<p align="center"><font size="2" face="Verdana, Arial, Helvetica, sans-serif"><a href="http://science.nasa.gov/headlines/y2009/images/noaaprediction/maunderminimum.jpg"><img src="http://science.nasa.gov/headlines/y2009/images/noaaprediction/maunderminimum_strip2.gif" border="0" width="450" height="188"></a></font></p>
<p class="detailImageDesc"><font size="2" face="Verdana, Arial, Helvetica, sans-serif"><strong>Above:</strong>
Yearly-averaged sunspot numbers from 1610 to 2008. Researchers
believe upcoming Solar Cycle 24 will be similar to the cycle
that peaked in 1928, marked by a red arrow. Credit: NASA/MSFC
</font></p>
<p align="left"><font size="2" face="Verdana, Arial, Helvetica, sans-serif">Right
now, the solar cycle is in a valley--the deepest of the past
century. In 2008 and 2009, the sun set Space Age records for
low sunspot counts, weak solar wind, and low solar irradiance.
The sun has gone more than two years without a significant
solar flare.</font></p>
<p align="left"><font size="2" face="Verdana, Arial, Helvetica, sans-serif">"In
our professional careers, we've never seen anything quite
like it," says Pesnell. "Solar minimum has lasted
far beyond the date we predicted in 2007."</font></p>
<p><font size="2" face="Verdana, Arial, Helvetica, sans-serif">In
recent months, however, the sun has begun to show timorous
signs of life. Small sunspots and "proto-sunspots"
are popping up with increasing frequency. Enormous currents
of plasma on the sun’s surface ("zonal flows") are
gaining strength and slowly drifting toward the sun’s equator.
Radio astronomers have detected a tiny but significant uptick
in solar radio emissions. All these things are precursors
of an awakening Solar Cycle 24 and form the basis for the
panel's new, almost unanimous forecast.</font></p>
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</tbody></table><font size="2" face="Verdana, Arial, Helvetica, sans-serif">According
to the forecast, the sun should remain generally calm for
at least another year. From a research point of view, that's
good news because solar minimum has proven to be more interesting
than anyone imagined. Low solar activity has a profound effect
on Earth’s atmosphere, allowing it to cool and contract. Space
junk accumulates in Earth orbit because there is less aerodynamic
drag. The becalmed solar wind whips up fewer magnetic storms
around Earth's poles. Cosmic rays that are normally pushed
back by solar wind instead intrude on the near-Earth environment.
There are other side-effects, too, that can be studied only
so long as the sun remains quiet.</font>
<p align="left"><font size="2" face="Verdana, Arial, Helvetica, sans-serif">Meanwhile,
the sun pays little heed to human committees. There could
be more surprises, panelists acknowledge, and more revisions
to the forecast.</font></p>
<p align="left"><font size="2" face="Verdana, Arial, Helvetica, sans-serif">"Go
ahead and mark your calendar for May 2013," says Pesnell.
"But use a pencil." </font></p></td></tr></tbody></table><br>