Saturday, July 15, 2017

Strong Solar Flare Seen, Although Approaching Sunspot Minimum

animation of SDO observations of a sunspot
A major Sunspot (AR2665) turns toward the Earth on July 13, after the Sun was spotless for two days. A powerful Solar Flare is now headed towards Earth, which will cause an atmospheric geomagnetic storm this weekend.
(Image Sources: NASA Goddard Spaceflight Center / NASA Solar Dynamics Observatory Satellite; Producer: Joy Ng)

By Glenn A. Walsh
Reporting for SpaceWatchtower

After turning towards the Earth in the last few days, large Sunspot AR2665 emitted a large solar flare late on Thursday (July 13). This is despite the fact that the Sun continues getting quieter as it approaches Solar Minimum, the nadir expected around 2019-2020.

This solar blast was observed by ultraviolet telescopes aboard NASA's Solar Dynamics Observatory satellite in Earth orbit. The explosion lasted for more than two hours. It resulted in sustained X-Rays and energetic protons, emitted from the Sun, ionizing the upper layers of Earth's atmosphere. Consequently, there were short-wave radio blackouts over the Pacific Ocean, and particularly in the Arctic region. The explosion also produced a bright coronal mass ejection (CME) that appears headed for Earth.

The National Oceanic and Atmospheric Administration (NOAA), after evaluating late Thursday evening's (July 13, 10:09 p.m. EDT / July 14, 2:09 UTC) solar flare (M2-class) and CME, has issued a geomagnetic storm watch for July 16 and 17. Storms on both days are expected to be a moderately strong Category G2.

Aurora activity is also expected in the far northern and far southern latitudes, at around the same time. Aurora are natural light displays, visible at night mostly in the Arctic and Antarctic regions, caused when charged particles from the solar wind hit the Earth's magnetosphere.

Sunspots are large magnetic storms on the photosphere of the Sun. As the rotation of the Earth helps to mix the atmosphere causing normal weather storms on Earth, the rotation of the Sun (sidereal rotation rate of 24.47 days for one complete rotation) causes the complex magnetic fields to twist and form large storms we call sunspots.

Sunspots appear as dark spots on the Sun because these storms are cooler than the rest of the Sun's photosphere, but by no means are sunspots cold by our standards. The Sun's photosphere is a thin layer of the Sun's upper atmosphere where hot gases rise and give-off light and heat. The temperature of this photosphere is +10,000 degrees Fahrenheit / +5,700 degrees Celsius. The temperature of a sunspot is +6,400 degrees Fahrenheit / +3,500 degrees Celsius.

A geomagnetic storm is a disturbance in the portions of the Earth's upper atmosphere known as the magnetosphere and the ionosphere caused by a magnified solar wind of charged particles from the Sun. During a geomagnetic storm, energy from the Sun provides additional energy to Earth's magnetosphere, enlarging the magnetosphere. This often provides additional drag on satellites and space junk in low Earth orbit, limiting the amount of time the satellite and / or space junk stays in orbit.

A coronal mass ejection or CME is an unusually large ejection of plasma and magnetic field from the solar corona. The solar corona is an aura of plasma that surrounds the Sun and other stars, and extends millions of miles or kilometers into space from the Sun. During a Total Eclipse of the Sun, or Total Solar Eclipse, such as the Great American Solar Eclipse that will occur on August 21, the solar corona can be seen, safely, with the unaided eye—BUT ONLY in the narrow path of totality and during the very short period of the total phase of the eclipse, when the rest of the Sun is completely blocked by the Moon; at all other times it is extremely dangerous to a person's eye-sight to look at the Sun without proper equipment and proper training to do so safely.

This week's major solar activity is in sharp contrast to the waning days of this particular 11-year Sunspot Cycle, when visible sunspots have been few. Before Sunspot AR2665 rotated into view, the portion of the Sun facing the Earth went for two full days with no sunspots.

The period of relative calm on the Sun is known as the Sunspot Minimum or Solar Minimum portion of the 11-year Sunspot Cycle. NASA scientists now expect the Solar Minimum to occur in the time period around 2019-2020. The peak of the Sunspot Cycle seemed to occur in 2014, although recent Sunspot Cycles have not been as active as cycles in the past.

Although sunspots and other solar activity subside during the Solar Minimum, another solar phenomenon can be observed during this time period. Coronal holes often open-up at this time, allowing the Sun's magnetic field to emit streams of solar particles as a fast solar wind.

During Solar Minimum, Galactic cosmic rays, high energy particles from very distant supernova and other high-energy explosions, increasingly reach Earth's upper atmosphere. With a weakened solar magnetic field, there is less natural shielding from such cosmic rays for the Earth's upper atmosphere, which can adversely affect our astronauts in space.

Internet Links to Additional Information ---

Sunspots: Link >>>

Solar Corona: Link >>>

Coronal Mass Ejection (CME): Link >>>

Geomagnetic Storm: Link >>>

Aurora: Link >>>

NASA Solar Dynamics Observatory Satellite:
Link 1 >>>
Link 2 >>>

Solar Eclipse / Eclipse of the Sun: Tips for Safe Viewing:
Link >>>

2017 August 21 -
Public observing session for the Great American Solar Eclipse, co-sponsored by
Friends of the Zeiss and the Mount Lebanon Public Library. The Mount Lebanon Public
Library estimated public attendance at 300. Members of Friends of the Zeiss
participating in this event were Glenn A. Walsh, Lynne S. Walsh, James McKee, and
Josie Dougherty(eighth-grade student who had just attended NASA's Space Camp in
Huntsville, Alabama). 
Link >>> 

Related Blog Posts ---

"'Blank Sun' June 3 & 4 as Sunspot Minimum Expected 2019-2020." 2016 June 14.

Link >>>


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

Link >>>


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

Link >>>


"Huge Sunspot Group Faces Earth w/ X-Class Flares." 2013 Nov. 9.

Link >>>


"Solar Cycle Update: Twin Peaks?" 2013 March 2.

Link >>>


"Colossal Sunspot Growing Fast, Solar Storms Possible." 2013 Feb. 21.

Link >>>


"Sunspot AR1654 Getting Bigger w/ Solar Flare." 2013 Jan. 12.

Link >>>


"Enormous Sunspot Could Lead to Solar Flares." 2012 May 9.

Link >>>

     Safe Public Viewing of the Great American Solar Eclipse
                         Monday, August 21, 2017
     Mt. Lebanon Public Library, South Suburban Pittsburgh
More Info: Link >>>

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2017 July 15.

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Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh:
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  < >
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