Tuesday, June 14, 2016

'Blank Sun' June 3 & 4 as Sunspot Minimum Expected 2019-2020

Photograph of a "blank Sun," with no sunspots on the side of the Sun facing the Earth, from June 4.
(Image Sources: NASA's Solar Dynamics Observatory, SpaceWeather.com)

By Glenn A. Walsh
Reporting for SpaceWatchtower

Solar Cycle 24, one of the weakest sunspot cycles on-record, is nearing its minimum, with the first two days with no visible sunspots since 2014 (which was the last year to have one day with a “blank Sun” since 2011). Although two sunspots were visible today (June 14), no sunspots were visible on the side of the Sun visible from the Earth on June 3 and 4.

Sunspots are areas of intense magnetic activity on the photosphere, or visible surface, of the Sun. These areas appear dark, often black (central umbra) surrounded by a gray area (penumbra), because sunspots are much cooler than the rest of the Sun. Temperatures of sunspots measure between +4,892° and +7,592° Fahrenheit / +2,700° and +4,200° Celsius, while the rest of the Sun's visible surface has a temperature of about +9,932° Fahrenheit / +5,500° Celsius.

Sunspots were first observed by the famous Italian Astronomer Galileo Galilei in the early seventeenth century. By 1755, an eleven-year sunspot cycle was recognized and has been extensively observed ever since. With the first numbered sunspot cycle, Solar Cycle 1, beginning in 1755, we are now observing Solar Cycle 24.

Although a “blank Sun” for two days this month does not mean we have reached the absolute low point in the current sunspot cycle, it does mean we can expect the lowest point of the cycle in the coming few years. At this point in time, they predict that the low point in the cycle may come sometime in 2019 or 2020.

Our current sunspot cycle, Solar Cycle 24, has been observed as the weakest sunspot cycle in more than a century. This cycle has had the fewest sunspots since Solar Cycle 14 peaked in February of 1906.

After more than seven years in Solar Cycle 24, scientists have now determined that the peak of the cycle (month with the most sunspots visible) came in April of 2014. This peak slightly surpassed an earlier peak in March of 2012. Often sunspot cycles have two peaks, however this is the first time that scientists recorded the second peak as greater than the first peak. The previous solar minimum phase, which was quite weak, occurred from 2007 to 2009.

As we approach the solar minimum for this cycle, we must note that a smaller number of sunspots does not, necessarily, mean the Earth will experience inactivity. During a solar minimum, the solar magnetic field weakens and the solar wind decreases. This allows galactic cosmic rays to penetrate further into the Solar System and get closer to the Earth. This is a much more dangerous time for astronauts in Earth orbit or beyond, as cosmic rays can damage human DNA.

Further, with fewer sunspots, the Sun's extreme ultraviolet radiation (EUV) declines. This causes the Earth's upper atmosphere to cool and contract. Now, this does reduce aerodynamic drag on satellites in orbit, which reduces the need for satellites, including the International Space Station, to use extra fuel to prevent a premature deorbiting. However, it also means space junk will stay in orbit longer, providing an additional danger to astronauts.

With this new century bringing significantly weaker sunspot cycles, this has brought to the Earth lower-than-normal space-weather / geomagnetic storms. However, while major solar storms are predicted to occur less often in such weak cycles, some major storms can still occur. Indeed, it was during a weak solar cycle (Solar Cycle 10 of 1855 to 1867), in 1859, when Earth experienced the famous “Carrington Event.” During this Solar Storm of 1859, Earth's magnetosphere was hit by a solar coronal mass ejection. In addition to inducing one of the strongest geomagnetic storms on-record, telegraph systems all over the Earth failed, telegraph operators received electric shocks, some telegraph systems sparked causing small fires, and bright aurorae were observed closer to the equator than ever previously recorded.

And, there is some evidence that stronger solar flares and geomagnetic storms are more likely to occur while a solar cycle is waning. So such solar activity could still be possible over the next couple of years.

Prolonged weak solar cycles can have a cooling effect on average Earth temperatures. What scientists and historians now refer to as the “Little Ice Age” occurred during the low solar activity of the “Maunder Minimum,” which occurred from 1645 to 1715, and the “Dalton Minimum,” which ran from 1790 to 1830,

Viewing of sunspot activity on the Sun by the general public was often available, on sunny days in the Astronomical Observatory of Pittsburgh's original Buhl Planetarium and Institute of Popular Science. A large image of the Sun would be projected onto a nearby projection screen from Buhl's historic 10-inch Siderostat-type Refractor Telescope. This rather unique telescope, which also was used to view the Moon, planets, and stars in both the daytime and nighttime skies, will be 75 years old on November 19.

Links to Additional Information ---

More details with graphs:
Link >>> http://www.vencoreweather.com/blog/2016/6/4/300-pm-the-sun-has-gone-completely-blank

Daily Space-Weather Forecasts and Information, including information on sunspots:
Link >>> http://spaceweather.com/

More on sunspots: Link >>> https://en.wikipedia.org/wiki/Sunspot

More on the Carrington Event of 1859: Link >>> https://en.wikipedia.org/wiki/Solar_storm_of_1859

More on Galileo: Link >>> https://en.wikipedia.org/wiki/Galileo_Galilei

More on Buhl Planetarium's historic 10-inch Siderostat-type Refractor Telescope:
Link >>> http://spacewatchtower.blogspot.com/2016/01/astronomical-calendar-2016-january.html

Related Blog Posts ---

"Largest Sunspot in 24 Years Returns for 2nd Month." 2014 Nov. 23.

Link >>> http://spacewatchtower.blogspot.com/2014/11/largest-sunspot-in-24-years-returns-for.html


"Sunspot Count Max Finally Arrives, But 'Mini-Max.'" 2014 June 10.

Link >>> http://spacewatchtower.blogspot.com/2014/06/sunspot-count-max-finally-arrives-but.html

Sources: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss, Meteorologist Paul Dorian of Vencore, Inc.
             2016 June 14.

                                                               Historic 10-inch Siderostat-type Refractor Telescope at Pittsburgh's original Buhl Planetarium and Institute of Popular Science.
        2016: 75th Year of Pittsburgh's Buhl Planetarium Observatory
     Link >>> http://spacewatchtower.blogspot.com/2016/01/astronomical-calendar-2016-january.html

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Glenn A. Walsh, Project Director,
Friends of the Zeiss < http://buhlplanetarium.tripod.com/fotz/ >
Electronic Mail - < gawalsh@planetarium.cc >
SpaceWatchtower Blog: < http://spacewatchtower.blogspot.com/ >
Also see: South Hills Backyard Astronomers Blog: < http://shbastronomers.blogspot.com/ >
Barnestormin: Writing, Essays, Pgh. News, & More: < http://www.barnestormin.blogspot.com/ >
About the SpaceWatchtower Editor / Author: < http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/ >
http://buhlplanetarium.tripod.com/#news >
Twitter: < https://twitter.com/spacewatchtower >
Facebook: < http://www.facebook.com/pages/SpaceWatchtower/238017839577841?sk=wall >
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh:
  < http://www.planetarium.cc >
* Adler Planetarium, Chicago:
  < http://adlerplanetarium.tripod.com >
* Astronomer, Educator, Optician John A. Brashear:
  < http://johnbrashear.tripod.com >
* Andrew Carnegie & Carnegie Libraries:
  < http://www.andrewcarnegie.cc >
* Civil War Museum of Andrew Carnegie Free Library:
  < http://garespypost.tripod.com >
Duquesne Incline cable-car railway, Pittsburgh:
  < http://inclinedplane.tripod.com >
* Public Transit:
  < http://andrewcarnegie2.tripod.com/transit >

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