American Astronomical Society í dag: Þrjá rannsóknir benda til hratt minnkandi sólvirkni á næstunni...

 

Merkilegar fréttir voru að berast í dag frá ráðstefnu Bandaríska Stjarnfræðifélagsins, American Astronomical Society,  sem haldin er í þessari viku í New Mexico State University í Las Cruces, New Mexico.

Lesa má frétt um málið á SPACE.COM.  Sjá hér.     Upphaflega fréttatilkynningin er hér neðst á síðunni og myndir sem henni fylgdu eru hér. Vídeó-frétt John Colemans má sjá hér.

Samkvæmt fréttinni benda niðurstöður þriggja rannsókna til þess að virkni sólar stefni í mjög mikla lægð á næstu árum. Um er að ræða rannsóknir í iðrum sólar, á yfirborðinu og í kórónu hennar.   Um sólina má fræðast hér á Stjörnufræðivefnum.

Fréttin frá ráðstefnunni hefst þannig:

Sun's Fading Spots Signal Big Drop in Solar Activity
http://www.space.com/11960-fading-sunspots-slower-solar-activity-solar-cycle.html

by Denise Chow, SPACE.com Staff Writer

Date: 14 June 2011 Time: 01:01 PM ET

 

 

Some unusual solar readings, including fading sunspots and weakening magnetic activity near the poles, could be indications that our sun is preparing to be less active in the coming years.

The results of three separate studies seem to show that even as the current sunspot cycle swells toward the solar maximum, the sun could be heading into a more-dormant period, with activity during the next 11-year sunspot cycle greatly reduced or even eliminated.

The results of the new studies were announced today (June 14) at the annual meeting of the solar physics division of the American Astronomical Society, which is being held this week at New Mexico State University in Las Cruces.

Ennfremur segir:

"This is highly unusual and unexpected," said Frank Hill, associate director of the National Solar Observatory's Solar Synoptic Network. "But the fact that three completely different views of the sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation."

...

"We expected to see the start of the zonal flow for Cycle 25 by now, but we see no sign of it," Hill said. "This indicates that the start of Cycle 25 may be delayed to 2021 or 2022, or may not happen at all."

...

"If we are right, this could be the last solar maximum we'll see for a few decades," Hill said. "That would affect everything from space exploration to Earth's climate."

 

Þessi frétt barst í dag kl. 17 að íslenskum tíma. Væntanlega á hún eftir að vekja athygli og umræður.

Sjá nánar á Space.com:   

Sun's Fading Spots Signal Big Drop in Solar Activity
http://www.space.com/11960-fading-sunspots-slower-solar-activity-solar-cycle.html

 

 

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Hér er samantekt (abstract) greinanna sem vísað er til í tilkynningunni:

 

P16.10
Large-scale Zonal Flows During the Solar Minimum — Where Is Cycle 25?13
Frank Hill, R. Howe, R. Komm, J. Christensen-Dalsgaard, T. P. Larson, J. Schou, M. J. Thompson

The so-called torsional oscillation is a pattern of migrating zonal flow bands that move from midlatitudes towards the equator and poles as the magnetic cycle progresses. Helioseismology allows us to probe these flows below the solar surface. The prolonged solar minimum following Cycle 23 was accompanied by a delay of 1.5 to 2 years in the migration of bands of faster rotation towards the equator. During the rising phase of Cycle 24, while the lower-level bands match those seen in the rising phase of Cycle 23, the rotation rate at middle and higher latitudes remains slower than it was at the corresponding phase in earlier cycles, perhaps reflecting the weakness of the polar fields. In addition, there is no evidence of the poleward flow associated with Cycle 25. We will present the latest results based on nearly sixteen years of global helioseismic observations from GONG and MDI, with recent results from HMI, and discuss the implications for the development of Cycle 25.

-

P17.21
A Decade of Diminishing Sunspot Vigor
W. C. Livingston, M. Penn, L. Svalgaard
s Convention Center

Sunspots are small dark areas on the solar disk where internal magnetism, 1500 to 3500 Gauss, has been
buoyed to the surface. (Spot life times are the order of one day to a couple of weeks or more. They are thought to be dark because convection inhibits the outward transport of energy there). Their “vigor” can be described by spot area, spot brightness intensity, and magnetic field. From 2001 to 2011 we have measured field strength and brightness at the darkest position in umbrae of 1750 spots using the Zeeman splitting of the Fe 1564.8 nm line. Only one observation per spot per day is carried out during our monthly telescope time of 3-4 days average. Over this interval the temporal mean magnetic field has declined about 500 Gauss and mean spot intensity has risen about 20%. We do not understand the physical mechanism behind these changes or the effect, if any, it will have on the Earth environment.

-

P18.04
Whither goes Cycle 24? A View from the Fe XIV Corona
Richard C. Altrock

Solar Cycle 24 had a historically prolonged and weak start. Observations of the Fe XIV corona from the Sacramento Peak site of the National Solar Observatory showed an abnormal pattern of emission compared to observations of Cycles 21, 22, and 23 from the same instrument. The previous three cycles had a strong, rapid “Rush to the Poles” in Fe XIV. Cycle 24 displays a delayed, weak, intermittent, and slow “Rush” that is mainly apparent in the northern hemisphere. If this Rush persists at its current rate, evidence from previous cycles indicates that solar maximum will occur in approximately early 2013. At lower latitudes, solar maximum previously occurred when the greatest number of Fe XIV emission regions* first reached approximately 20° latitude. Currently, the value of this parameter at 20° is approximately 0.15. Previous behavior of this parameter indicates that solar maximum should occur in approximately two years, or 2013. Thus, both techniques yield an expected time of solar maximum in early 2013.
*annual average number of Fe XIV emission features per day greater than 0.19

 

 

 

 

 

 

Sólin í dag. Sjá dagsetningu og tíma á myndinni.

(UT = Universal Time sem er sama og íslenskur staðartími).

Fjölda beintengdra mynda og ferla má sjá hér á Solar Reference Page.

 

 

Fréttin í dag hefur vakið athygli og er víða. Sjá til dæmis:   Hér. Hér. Hér. Hér.

 

 

 

 

National Geographic:

Sun Headed Into Hibernation, Solar Studies Predict

Sunspots may disappear altogether in next cycle.

 

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Sjá upphaflegu fréttatilkynningurna hér:
http://www.boulder.swri.edu/~deforest/SPD-sunspot-release/SPD_solar_cycle_release.txt

** Please note the strict embargo until Tuesday, 14 June 2011, at 11 a.m.
MDT (17:00 UTC), coincident with presentation at the annual meeting of the
AAS Solar Physics Division in Las Cruces, NM. {RTF} **

EMBARGOED until:
June 14, 2011
1 p.m. EDT / 10 a.m. PDT

Contacts:
Dave Dooling
NSO Education and Public Outreach
[phone] (office); [phone] (cell)
[e-mail]

Craig DeForest
AAS/SPD Press Officer
[phone] (cell)
[e-mail]

Text & Images (after the embargo expires):
http://www.boulder.swri.edu/~deforest/SPD-sunspot-release
(Media teleconference information at bottom of this release.)

WHAT’S DOWN WITH THE SUN?
MAJOR DROP IN SOLAR ACTIVITY PREDICTED

A missing jet stream, fading spots, and slower activity near the poles say
that our Sun is heading for a rest period even as it is acting up for the
first time in years, according to scientists at the National Solar
Observatory (NSO) and the Air Force Research Laboratory (AFRL).

As the current sunspot cycle, Cycle 24, begins to ramp up toward maximum,
independent studies of the solar interior, visible surface, and the corona
indicate that the next 11-year solar sunspot cycle, Cycle 25, will be
greatly reduced or may not happen at all.

The results were announced at the annual meeting of the Solar Physics
Division of the American Astronomical Society, which is being held this week
at New Mexico State University in Las Cruces:
http://astronomy.nmsu.edu/SPD2011/

“This is highly unusual and unexpected,” Dr. Frank Hill, associate director
of the NSO’s Solar Synoptic Network, said of the results. “But the fact that
three completely different views of the Sun point in the same direction is a
powerful indicator that the sunspot cycle may be going into hibernation.”

Spot numbers and other solar activity rise and fall about every 11 years,
which is half of the Sun’s 22-year magnetic interval since the Sun’s
magnetic poles reverse with each cycle. An immediate question is whether
this slowdown presages a second Maunder Minimum, a 70-year period with
virtually no sunspots during 1645-1715.

Hill is the lead author on one of three papers on these results being
presented this week. Using data from the Global Oscillation Network Group
(GONG) of six observing stations around the world, the team translates
surface pulsations caused by sound reverberating through the Sun into models
of the internal structure. One of their discoveries is an east-west zonal
wind flow inside the Sun, called the torsional oscillation, which starts at
mid-latitudes and migrates towards the equator. The latitude of this wind
stream matches the new spot formation in each cycle, and successfully
predicted the late onset of the current Cycle 24.

“We expected to see the start of the zonal flow for Cycle 25 by now,” Hill
explained, “but we see no sign of it. This indicates that the start of Cycle
25 may be delayed to 2021 or 2022, or may not happen at all.”

In the second paper, Matt Penn and William Livingston see a long-term
weakening trend in the strength of sunspots, and predict that by Cycle 25
magnetic fields erupting on the Sun will be so weak that few if any sunspots
will be formed. Spots are formed when intense magnetic flux tubes erupt from
the interior and keep cooled gas from circulating back to the interior. For
typical sunspots this magnetism has a strength of 2,500 to 3,500 gauss
(Earth’s magnetic field is less than 1 gauss at the surface); the field must
reach at least 1,500 gauss to form a dark spot.

Using more than 13 years of sunspot data collected at the McMath-Pierce
Telescope at Kitt Peak in Arizona, Penn and Livingston observed that the
average field strength declined about 50 gauss per year during Cycle 23 and
now in Cycle 24. They also observed that spot temperatures have risen
exactly as expected for such changes in the magnetic field. If the trend
continues, the field strength will drop below the 1,500 gauss threshold and
spots will largely disappear as the magnetic field is no longer strong
enough to overcome convective forces on the solar surface.

Moving outward, Richard Altrock, manager of the Air Force’s coronal research
program at NSO’s Sunspot, NM, facilities has observed a slowing of the “rush
to the poles,” the rapid poleward march of magnetic activity observed in the
Sun’s faint corona. Altrock used four decades of observations with NSO’s
40-cm (16-inch) coronagraphic telescope at Sunspot.

“A key thing to understand is that those wonderful, delicate coronal
features are actually powerful, robust magnetic structures rooted in the
interior of the Sun,” Altrock explained. “Changes we see in the corona
reflect changes deep inside the Sun.”

Altrock used a photometer to map iron heated to 2 million degrees C (3.6
million F). Stripped of half of its electrons, it is easily concentrated by
magnetism rising from the Sun. In a well-known pattern, new solar activity
emerges first at about 70 degrees latitude at the start of a cycle, then
towards the equator as the cycle ages. At the same time, the new magnetic
fields push remnants of the older cycle as far as 85 degrees poleward.

“In cycles 21 through 23, solar maximum occurred when this rush appeared at
an average latitude of 76 degrees,” Altrock said. “Cycle 24 started out late
and slow and may not be strong enough to create a rush to the poles,
indicating we’ll see a very weak solar maximum in 2013, if at all. If the
rush to the poles fails to complete, this creates a tremendous dilemma for
the theorists, as it would mean that Cycle 23’s magnetic field will not
completely disappear from the polar regions (the rush to the poles
accomplishes this feat). No one knows what the Sun will do in that case.”

All three of these lines of research to point to the familiar sunspot cycle
shutting down for a while.

“If we are right,” Hill concluded, “this could be the last solar maximum
we’ll see for a few decades. That would affect everything from space
exploration to Earth’s climate.”

                          # # #

Media teleconference information: This release is the subject of a media
teleconference at the current meeting of the American Astronomical Society’s
Solar Physics Division (AAS/SPD). The telecon will be held at 11 a.m. MDT
(17:00 UTC) on Tuesday, 14 June. Bona fide journalists are invited to attend
the teleconference and should send an e-mail to the AAS/SPD press officer,
Craig DeForest, at [e-mail], with the subject heading “SPD:
SOLAR MEDIA TELECON”, before 16:00 UTC. You will receive dial-in information
before the telecon.

These results have been presented at the current meeting of the AAS/SPD.
Citations:

16.10: “Large-Scale Zonal Flows During the Solar Minimum -- Where Is Cycle
25?” by Frank Hill, R. Howe, R. Komm, J. Christensen-Dalsgaard, T.P. Larson,
J. Schou & M. J. Thompson.

17.21: “A Decade of Diminishing Sunspot Vigor” by W. C. Livingston, M. Penn
& L. Svalgard.

18.04: “Whither Goes Cycle 24? A View from the Fe XIV Corona” by R. C.
Altrock.

 

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21:30