APOD: Active Prominences on a Quiet Sun (2018 Aug 20)

[APOD Robot]

Active Prominences on a Quiet Sun

Explanation: Why is the Sun so quiet? As the Sun enters into a period of time known as a Solar Minimum, it is, as expected, showing fewer sunspots and active regions than usual. The quietness is somewhat unsettling, though, as so far this year, most days show no sunspots at all. In contrast, from 2011 - 2015, during Solar Maximum, the Sun displayed spots just about every day. Maxima and minima occur on an 11-year cycle, with the last Solar Minimum being the most quiet in a century. Will this current Solar Minimum go even deeper? Even though the Sun's activity affects the Earth and its surroundings, no one knows for sure what the Sun will do next, and the physics behind the processes remain an active topic of research. The featured image was taken three weeks ago and shows that our Sun is busy even on a quiet day. Prominences of hot plasma, some larger than the Earth, dance continually and are most easily visible over the edge.

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[Boomer12k]

Cool...er....hot....um....Cool....oooohhh....hot....shoot.....COOL LOOKING!!!!!

Back in May or June I got out the 6" and with solar filter looked and saw some Sunspots...It was a small group...did not see any others at that time.

:---[===] *

[heehaw]

It is just astounding! Here we are at solar minimum, no sign of any strong magnetic fields; general magnetic field on the sun is only about double that on Earth, and yet: prominences !! Stuff -- huge masses -- shooting UPWARD, against the strong gravitational attraction downward: which is 28 times stronger than the gravitational attraction downward that is acting on me here in my chair this morning. Great APOD!

[khh]

Suppose the solar minimum does go deeper. What effect will that have on Earth?

[neufer]

Suppose the solar minimum does go deeper.

What effect will that have on Earth?

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Click to play embedded YouTube video.

<<The Maunder Minimum, also known as the "prolonged sunspot minimum", is the name used for the period around 1645 to 1715 during which sunspots became exceedingly rare, as was then noted by solar observers. The term was introduced after John A. Eddy published a landmark 1976 paper in Science. Astronomers before Eddy had also named the period after the solar astronomers Annie Russell Maunder (1868–1947) and her husband, Edward Walter Maunder (1851–1928), who studied how sunspot latitudes changed with time. Because Annie Maunder had not received a university degree, due to restrictions at the time, her contribution was not then publicly recognized.

The Maunder Minimum occurred between 1645 and 1715 when very few sunspots were observed. This was not due to a lack of observations; during the 17th century, Giovanni Domenico Cassini carried out a systematic program of solar observations at the Observatoire de Paris. Johannes Hevelius also performed observations on his own. The sunspot activity was then concentrated in the southern hemisphere of the Sun, except for the last cycle when the sunspots appeared in the northern hemisphere, too.

The Maunder Minimum roughly coincided with the middle part of the Little Ice Age, during which Europe and North America experienced colder than average temperatures. Whether there is a causal relationship, however, is still controversial. Research at the Technical University of Denmark and the Hebrew University of Jerusalem has linked large solar eruptions to changes in the Earth's cloud cover and clouds are known to affect global temperatures. The current best hypothesis for the cause of the Little Ice Age is that it was the result of volcanic action. The onset of the Little Ice Age also occurred well before the beginning of the Maunder minimum, and northern-hemisphere temperatures during the Maunder minimum were not significantly different from the previous 80 years, suggesting a decline in solar activity was not the main causal driver of the Little Ice Age.

In 2011, an article was published in the Nature Geoscience journal that uses a climate model with stratospheric layers and the SORCE data to tie low solar activity to jet stream behavior and mild winters in some places (southern Europe and Canada/Greenland) and colder winters in others (northern Europe and the United States).>>

[CURRAHEE CHRIS]

That is a really pretty picture.

[Chris Peterson]

It is just astounding! Here we are at solar minimum, no sign of any strong magnetic fields; general magnetic field on the sun is only about double that on Earth, and yet: prominences !! Stuff -- huge masses -- shooting UPWARD, against the strong gravitational attraction downward: which is 28 times stronger than the gravitational attraction downward that is acting on me here in my chair this morning. Great APOD!

Gravity isn't considered a weakest of the fundamental interactions for nothing!

[geoffrey.landis]

Amazing picture. I'm struck by the fact that the disk of the sun is brighter on the limb-- this gives a great visualization of the sphericity of the sun, but I would have expected limb darkening. Why is the limb bright?
(http://spiff.rit.edu/classes/phys440/le ... /limb.html)

[geoffrey.landis]

Suppose the solar minimum does go deeper. What effect will that have on Earth?

The correct answer is that climatologists have been looking for a correlation between solar activity and climate for the last 400 years, while many such correlations have been proposed, so far none of them have turned out to be real.
So: the reply is, "nobody knows".

[Chris Peterson]

Amazing picture. I'm struck by the fact that the disk of the sun is brighter on the limb-- this gives a great visualization of the sphericity of the sun, but I would have expected limb darkening. Why is the limb bright?
(http://spiff.rit.edu/classes/phys440/le ... /limb.html)

Alan has developed his own image processing workflow that involves various masking and inverting methods. I think his goal is both aesthetic and directed towards maximizing detail, not a "realistic" image of the Sun, to the extent that's a meaningful concept with scientific imaging.

[neufer]

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Tufts University: Corona Brightness and Electron Density

Variation of coronal surface brightness (left scale) and electron density (right scale) with distance from the Sun’s center, in units of solar radii. The maximum and minimum of the solar magnetic activity cycle are designated by max. and min.. The F corona values (dashed line) are continuous with the zodiacal light. For comparison, the surface brightness for the full Moon and clear sky for day and night and during a total solar eclipse are indicated.

Parker Solar Probe's scheduled approach to the Sun:

Code: Select all

Year  	Date 	Event 	Distance from Sun (solar radii)
----------------------------------------------------
2018 	Nov 5 	Perihelion #1 	35.6
2020 	Jan 29 	Perihelion #4 	27.9
2020 	Sep 27 	Perihelion #6 	20.4
2021 	Aug 9 	Perihelion #9 	15.9
2021 	Nov 21 	Perihelion #10 	13.2
2023 	Sep 27 	Perihelion #17 	11.4
2024 	Dec 24 	Perihelion #22 	9.9 
2025 	Dec 12 	Perihelion #26 	9.9

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Solar Cycle 25 Prediction:

We find that the polar fields indicate that Cycle 25 will be similar in size to (or slightly smaller than) the current small cycle, Cycle 24. Small cycles, like Cycle 24, start late and leave behind long cycles with deep extended minima. Therefor, we expect a similar deep, extended minimum for the Cycle 24/25 minimum in 2020.