Our lazy Sun Barbara Sylwester Solar Physics Division Space Research Center, Wrocław
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Transcript of Our lazy Sun Barbara Sylwester Solar Physics Division Space Research Center, Wrocław
Our lazy Sun
Barbara Sylwester
Solar Physics DivisionSpace Research Center, Wrocław
SOHO activity cycle; 171 Å, ~1.3 MK plasma
SOHO UV 1997 & 1999 changing activity
Recurrent behavior of sunspots: 140 years
Sunspots are typically confined to an equatorial belt (-35 degrees south and +35 degrees north latitude). At the beginning of a new cycle,
sunspots tend to form at high latitudes, but as the cycle reaches a maximum the spots form at lower latitudes. This gives rise to the ``butterfly'' pattern first discovered by
Edward Maunder in 1904.
Butterflydiagram
Solar activity - proxies
Rudolf Wolf, inventor of the modern sunspot
number (1848, Zurich observatory).
Red: sunspot number, reconstructed from historical observationsBlue: the beryllium-10 concentration (104 atoms/(gram of ice)) as measured in annually layered ice core (Greenland)
400 years of sunspot observations
1610 Among a huge number of revolutionary discoveries of Galileo Galilei was the first observations of sunspots using telescope. ( "And yet it does move").
1640-1710 the coldest period of Little Ice Age (LIA) the taverns for frozen ramblers have been built at the middle of Baltic Sea ; coincidence with Maunder Minimum
Sporadic observations Regular sunspot number observations (from 1749)
1749Carrington cycles
Sunspot number prediction (March 2006)
6 latest cycles & solar cycles prediction
During the annual Space Weather Workshop held in April 2007 the Solar Cycle 24 Prediction Panel released the prediction for the next solar cycle. They expected that the new cycle will begin in late 2007
or early 2008 – about a year later than earlier predictions. Expected peak sunspot number 140 in October, 2011.
Next Cycle (25) peaking in 2022 could be one of the weakest in centuries.
Predictive Flux-transport Dynamo Model Mausumi
Dikpati team
11 Dec. 2007 Solar Cycle 24 say: Hello !
SOHO UV-wavelength image of the Sun and a map showing positive (white) and negative (black) magnetic polarities. This region fits
both criteria of new cycle: high latitude and magnetically reversed, marking it as a harbinger of a new solar cycle. Good candidate…
But……the first swallow does not make a spring ….
and.…..Solar Cycle 24 official start was later 4 Jan. 2008
The large sunspot region just south of the equator is part of the waning Solar Cycle 23.
Few days later…. SOHO EIT instrument
This image was taken in extreme ultraviolet: 195 Å; ~ 1.6 MK. It
shows the area of the solar surface where the sunspot occured whose appearing marked the start of the new solar cycle (‘Cycle 24’) on 4
January 2008. SOHO also obsered two associated „EIT waves”, blast waves that spread out from the
active regions.
First southern hemisphere spots: 4.05.2008
Solar minimum is upon us !New solar cycle had begun definitely!
EIT/SOHO; 284 Å; ~ 2MK
2008, September - Spotless Sun
Left: A photo of the Sun taken Sept. 27, 2008. The face of the sun is "blank”.Right: The Sun on Sept. 27, 2001. The Sun's face is peppered with sunspots.
The difference is the phase of the 11-year solar cycle.
To find a year with more blank Sun, we have to go back to 1954 (three years
before the launch of Sputnik). 2008 the „blankest year” of the Space
Age
updated: Sept. 27, 2008
29 September 2008; 304 Å
NASA's STEREO (Ahead) spacecraft observed this prominence eruption. It rose up and cascaded to the right over several hours, appearing something like a flag headed into space. The material observed is actually ionized Helium at about 60,000 K. Prominences are relatively cool clouds of
gas controlled by magnetic forces.
New cycle flare activity; Oct. 2008
6 Oct. 2008 A6.4
Signs of life …. Solar minimum behind us?
A new sunspot appeared on 11 Oct. 2008, the third spot seen in many weeks.
New-cycle sunspot group 1007 emerges on Halloween and marches
across the face of the sun over a four-day period in early November 2008.
2 Nov. 2008; B7.2 flare
….boring Sun on 13th Jan. 2009 captured by amateur astronomer
A whole year after Solar Cycle 24 was supposed to start (when the first
reversed polarity sunspot pair appeared on the Sun’s surface) the Sun
is blank (featureless). However we have had flares from „left over” Cycle 23 and a bit of action from Cycle 24 (A, B class flares). 2008 was a
year of overlap with both cycles weakly active at the same time.
KORONAS Photon-TESIS: 20.02.2009
18:34 UT; Outer corona: Fe IX 171 Å; ~1 MK
He II 304; ~80 000 KInner corona: Fe IX 171 Å; ~1 MK
18:27 UT 18:28 UT
27 Feb. 2009; A3.2 flare
28 Feb. 2009 (8 hours period); TESIS
20 March 2009: Where have all activity gone?
http://sohowww.nascom.nasa.gov/data/realtime-images.html
SOHO MDI continuum 304 Å ; T ~ 80 000 K 284 Å ; T ~ 2 MK
Progression of the solar cycle
Data gathered by GOES satellites which monitor solar X-rays (tracking solar flares). Solar flares can also trigger geomagnetic storms which
produce aurora.
The daily effective sunspot numbers over the past year. Two parameters
are plotted: solid line - based on analysis of ionospheric data, and
dotted line based on the observed 10.7 cm solar radio flux.
http://solarcycle24.com/
http://www.nwra-az.com/spawx/ssne-year.html
HINODE XRT Present Sun; 305 Å; ~80 000 K
Why the Sun has gone quiet? Solar dynamo……
something abruptly “switched off” in the inner workings of the solar dynamo ?????the Sun has slowed it’s internal dynamo to a similar level such as was seen during the Dalton Minimum ????The truth is, solar activity never stops, "not even during solar minimum."
dipole field
the rotation rate is 20 ℅ faster at the
equator
the magnetic field lines are wrapped
after many rotations lines
are highly twisted and
bundled
the resulting buoyancy lifts the
bundle to the surface
The Sun is now in the quietest phase of its 11 - year activity cycle. In fact, it has been unusually quiet during 2008 year. Scientists are unsure of the significance
of this unusual calm. The only way to know is to wait and see. Our closest star is continually monitoring with an array of telescopes and satellites. Probably this
time next year we will be inundated with sunspots…fingers crossed.
Conculding ….. the „new millenium solar minimum”?