APOD: A February without Sunspots (2019 Mar 06)

[APOD Robot]

A February without Sunspots

Explanation: Where have all the sunspots gone? Last month the total number of spots that crossed our Sun was ... zero. Well below of the long term monthly average, the Sun's surface has become as unusually passive this solar minimum just like it did 11 years ago during the last solar minimum. Such passivity is not just a visual spectacle, it correlates with the Sun being slightly dimmer, with holes in the Sun's corona being more stable, and with a reduced intensity in the outflowing solar wind. The reduced wind, in turn, cools and collapses Earth's outer atmosphere (the thermosphere), causing reduced drag on many Earth-orbiting satellites. Pictured in inverted black & white on the left, the Sun's busy surface is shown near solar maximum in 2012, in contrast to the image on the right, which shows the Sun's surface last August, already without spots (for a few days), as solar minimum was setting in. Effects of this unusually static solar minimum are being studied.

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[Boomer12k]

This is not the only cycle we are in....

:---[===] *

[De58te]

If the sunspots last month were zero, then why show a photo from August 2018, instead of last month's? Another question, I heard I believe as a layman that solar flares mostly happen above or near sunspots. Yet in the 2018 photo I can still see a few flares right on the limb of the Sun. Could it be that the sunspots are just on the side facing away from the Earth? Also is it a coincidence that some of the flares particularly the one at about 5 o'clock are in the same location as in 2012? Another one is at about 2 o'clock and another one at about 10:30. Could they be the same flares that have lasted for 6 years?

[Ann]

There was a year in the 1800s that was called "The year without a summer". But that was probably due to volcanoes spewing a lot of soot and smoke into the atmosphere, and it likely had little to do with the activity of the Sun.

Nevertheless... if the Sun is very quiet now, and temperatures on the Earth are still rising, that is not a good sign.

Ann

[Chris Peterson]

Could it be that the sunspots are just on the side facing away from the Earth?

Sure. But the convention for counting sunspots does not consider whether there are any on the opposite side. The count is based on what is observed on the visible face.

Also is it a coincidence that some of the flares particularly the one at about 5 o'clock are in the same location as in 2012? Another one is at about 2 o'clock and another one at about 10:30. Could they be the same flares that have lasted for 6 years?

Keep in mind that the Sun has no stable longitude system. So nothing can be in the "same place" after a few rotations have scrambled things. There is a pattern of what latitude activity occurs at depending on the solar cycle. So yes, what you're seeing is just a coincidence of the time the images were made (and each would look different if they had been taken a day or two earlier or later). The areas of magnetic activity that produce sunspots and flares are short lived. Really big sunspots sometimes last long enough to make it around the back and return to visibility on the front (so hidden for about two weeks). A few historical examples are known of sunspots that persisted for months. But nothing will persist for half a solar cycle.

[Joe25]

Now today's APOD is wonderful ! Terrific ! Totally gorgeous photos !!! And a worthy description/explanation !!! !!! Today's APOD is why we come here !!! Well Done !!! Keep up the Good Work, and don't let the Mainstream 'deep space' 'crackpot theories' take this place over ! Best, Joe25

[geoffrey.landis]

I'm puzzled. Why are the solar prominences bright, instead of dark, if it's inverted?
And why is the sun surrounded by a bright halo in the image on the right, but not on the left?

[Chris Peterson]

I'm puzzled. Why are the solar prominences bright, instead of dark, if it's inverted?
And why is the sun surrounded by a bright halo in the image on the right, but not on the left?

The image is not inverted, just the face of the Sun. Alan's workflow involves masking and selective inversion.

Not sure about the difference in the halos. Maybe his processing method has changed a little over the years, or maybe it's a consequence of bringing up the levels just outside the limb to make more visible the much fainter prominences that we have at solar minimum.

[Fred the Cat]

If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants.

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable.

[Chris Peterson]

If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants. :idea:

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable. 8-)

There is no reason to believe that dark matter is involved in the solar cycle. There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.) While there is much about the solar cycle that is not understood, its basic relationship with the Sun's magnetic field (which largely eliminates any dark matter effect) is well understood.

There is little evidence that solar cycles, including extreme minimums or maximums, play a very large role in Earth's climate. Indeed, there is some evidence that they do not.

[BDanielMayfield]

Could it be that the sunspots are just on the side facing away from the Earth?

Sure. But the convention for counting sunspots does not consider whether there are any on the opposite side. The count is based on what is observed on the visible face.

Consider also the Sun's rotation:

The Sun rotates faster at its equator than at its poles. This differential rotation is caused by convective motion due to heat transport and the Coriolis force due to the Sun's rotation. In a frame of reference defined by the stars, the rotational period is approximately 25.6 days at the equator and 33.5 days at the poles. Viewed from Earth as it orbits the Sun, the apparent rotational period of the Sun at its equator is about 28 days.

So last month as the sun turned we got to see both sides during a 28 day month.

[Chris Peterson]

Could it be that the sunspots are just on the side facing away from the Earth?

Sure. But the convention for counting sunspots does not consider whether there are any on the opposite side. The count is based on what is observed on the visible face.

Consider also the Sun's rotation:

The Sun rotates faster at its equator than at its poles. This differential rotation is caused by convective motion due to heat transport and the Coriolis force due to the Sun's rotation. In a frame of reference defined by the stars, the rotational period is approximately 25.6 days at the equator and 33.5 days at the poles. Viewed from Earth as it orbits the Sun, the apparent rotational period of the Sun at its equator is about 28 days.

So last month as the sun turned we got to see both sides during a 28 day month.

Yes, but that doesn't mean that the Sun didn't have any sunspots during that 28 day month. It's quite common for sunspots to last only a few days. It's even possible (although very unlikely) that the Sun had sunspots every single day of February!

[BDanielMayfield]

Yes, but that doesn't mean that the Sun didn't have any sunspots during that 28 day month. It's quite common for sunspots to last only a few days. It's even possible (although very unlikely) that the Sun had sunspots every single day of February!

Yikes. We've been trying to stamp out the "Dark side of the Moon" saying. Now you've raised the specter of the Dark Side of the Sun!

[Chris Peterson]

Yes, but that doesn't mean that the Sun didn't have any sunspots during that 28 day month. It's quite common for sunspots to last only a few days. It's even possible (although very unlikely) that the Sun had sunspots every single day of February!

Yikes. We've been trying to stamp out the "Dark side of the Moon" saying. Now you've raised the specter of the Dark Side of the Sun! :lol2:

There was a time period when the two STEREO spacecraft could see the entire Sun at the same time (including the Dark Side). I don't think we have anything in place right now that can do that, though.

[BDanielMayfield]

If the sunspots last month were zero, then why show a photo from August 2018, instead of last month's?

Good catch, and good question.

My guesses, one spotless Sun photo is as good as another, and/or they didn't think anyone would notice.

[RJN]

If the sunspots last month were zero, then why show a photo from August 2018, instead of last month's?

Good catch, and good question.

My guesses, one spotless Sun photo is as good as another, and/or they didn't think anyone would notice.

Good question. Typically, APOD will run images that are submitted rather than compose its own. It would have been nice if the photographer submitted an image that included a spotless Sun from February, but he did not. No one did. So we went with the best and most educational image that we had.

- RJN

[Fred the Cat]

If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants.

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable.

There is no reason to believe that dark matter is involved in the solar cycle. There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.) While there is much about the solar cycle that is not understood, its basic relationship with the Sun's magnetic field (which largely eliminates any dark matter effect) is well understood.

There is little evidence that solar cycles, including extreme minimums or maximums, play a very large role in Earth's climate. Indeed, there is some evidence that they do not.

The simplest answer usually turns out correct so by reading I ''a'muse" my head out loud. As always, I appreciate your thoughts on these topics. I didn't realize there was such a hullabaloo.

But aren't deeper ( Milankovitch Cycles) sun-related cycles reflected in Earth's geology by climate change?

[alanfgag]

I'm puzzled. Why are the solar prominences bright, instead of dark, if it's inverted?
And why is the sun surrounded by a bright halo in the image on the right, but not on the left?

The image is not inverted, just the face of the Sun. Alan's workflow involves masking and selective inversion.

Not sure about the difference in the halos. Maybe his processing method has changed a little over the years, or maybe it's a consequence of bringing up the levels just outside the limb to make more visible the much fainter prominences that we have at solar minimum.

Thanks for the explanation, Chris. For the sky background, the tonality in the original data is black. The solar filter allows only a very small percentage of the sun's energy to pass so the sky background is not illuminated at all. In processing the images, I have used a gradient to add back some sky light (and in the original images, color). The techniques I have used for this have varied over the years. Below you can see the two original images that were used to make this comparison of an active and a quiet sun.

2018 http://www.avertedimagination.com/img_p ... lues2.html

2012 http://www.avertedimagination.com/img_p ... y_sun.html

[MarkBour]

Below you can see the two original images that were used to make this comparison of an active and a quiet sun ...

Thanks for posting those! The originals are very nice!

For those who wanted a more current image, pertaining to the "spotless February" story, here is a link:
https://sdo.gsfc.nasa.gov/gallery/potw/item/952
Now that pic is very plain.

[Chris Peterson]

If dark matter is involved in solar cycles mapping it, via its effects, would seem to be the best plan to elucidate a scheme that may explain how it will impact Earth and all its inhabitants. :idea:

Whatever the mechanism, detected by geology or sunspots, solar cycles point to something remarkable. 8-)

There is no reason to believe that dark matter is involved in the solar cycle. There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.) While there is much about the solar cycle that is not understood, its basic relationship with the Sun's magnetic field (which largely eliminates any dark matter effect) is well understood.

There is little evidence that solar cycles, including extreme minimums or maximums, play a very large role in Earth's climate. Indeed, there is some evidence that they do not.

But aren't deeper ( Milankovitch Cycles) sun-related cycles reflected in Earth's geology by climate change?

But these cycles are the product of ordinary orbital dynamics in a multiple body system. Dark matter is not needed to explain them.

[orin stepanek]

Cool period on the sun!

[geoffrey.landis]

... There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.)

Dark matter accumulates inside a gravity well (since it has mass), and the amount by which it is concentrated in the gravity well depends on the mass and temperature (according to the law of Jeans' escape). So, yes, dark matter would be somewhat concentrated inside the sun. Different models predict different temperatures-- cold dark matter, warm dark matter, and hot dark matter are all models still in contention.

However, the density of dark matter is so low, and its interaction with ordinary matter so extraordinarily low, it's unlikely to have any significant effect (it only plays a role in galactic rotation because even a very low density of matter adds up over volumes of space measured in trillions of cubic parsecs).

[Chris Peterson]

... There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.)

Dark matter accumulates inside a gravity well (since it has mass), and the amount by which it is concentrated in the gravity well depends on the mass and temperature (according to the law of Jeans' escape). So, yes, dark matter would be somewhat concentrated inside the sun. Different models predict different temperatures-- cold dark matter, warm dark matter, and hot dark matter are all models still in contention.

However, the density of dark matter is so low, and its interaction with ordinary matter so extraordinarily low, it's unlikely to have any significant effect (it only plays a role in galactic rotation because even a very low density of matter adds up over volumes of space measured in trillions of cubic parsecs).

In the absence of interaction with other matter, it is unclear why dark matter would concentrate in an gravity well. It might orbit around a gravity well, but would not necessarily concentrate. To do that, it would required some mechanism for transferring momentum. With ordinary matter that's mostly via electromagnetic interactions. Of course, we don't know how dark matter interacts with itself (other than straightforward gravitational interaction), so that's a big unknown in terms of hydrodynamic equivalents in dark matter.

[Droffarc]

Just what are sunpots please (see index) . I know about sunspots

[geoffrey.landis]

True. But over the five billion years that the sun has been around, even a very very slight self interaction would equilibrate the concentration.