APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

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APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by APOD Robot » Sun Jan 26, 2014 5:16 am

Image Sunspot Loops in Ultraviolet

Explanation: It was a quiet day on the Sun. The above image shows, however, that even during off days the Sun's surface is a busy place. Shown in ultraviolet light, the relatively cool dark regions have temperatures of thousands of degrees Celsius. Large sunspot group AR 9169 from the last solar cycle is visible as the bright area near the horizon. The bright glowing gas flowing around the sunspots has a temperature of over one million degrees Celsius. The reason for the high temperatures is unknown but thought to be related to the rapidly changing magnetic field loops that channel solar plasma. Large sunspot group AR 9169 moved across the Sun during 2000 September and decayed in a few weeks.

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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by SoutheastAsia » Sun Jan 26, 2014 6:46 am

Very fascinating. Question: could 'changing magnetic fields' here on Earth contribute to our own increasing temperature cycles? Either indirectly, or directly?

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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by neufer » Sun Jan 26, 2014 2:02 pm

SoutheastAsia wrote:
Question: could 'changing magnetic fields' here on Earth contribute to our own increasing temperature cycles? Either indirectly, or directly?
  • Without readings from the magnetic field to guide their drills the oil industry
    will no longer be able to drill for oil and we will be forced to use tar sands.
http://www.reuters.com/article/2013/11/22/us-space-earth-swarm-idUSBRE9AL0PF20131122 wrote:
<<Scientists say the magnetosphere is weakening and could all but disappear in as little as 500 years as a precursor to flipping upside down. It has happened before - the geological record suggests the magnetic field has reversed every 250,000 years, meaning that, with the last event 800,000 years ago, another would seem to be overdue.

While the effects are hard to predict, the consequences may be enormous. Satellites, essential among others for communications, could be more exposed to solar wind, and the oil industry uses readings from the magnetic field to guide drills.>>
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by BDanielMayfield » Sun Jan 26, 2014 2:14 pm

SoutheastAsia wrote:Very fascinating. Question: could 'changing magnetic fields' here on Earth contribute to our own increasing temperature cycles? Either indirectly, or directly?
Earth’s magnetic field does change slowly because it is driven by slow moving currents of liquid metals in the Earth’s outer core. Normally these changes are very slow, and they result in a very slow drift in the positions of the magnetic poles. I don’t see any way that such small changes in the magnetic field’s position could affect weather.

The Earth’s magnetic field does flip from time to time however, although so rarely that such a reversal has never happened while modern man has been around to notice it. What may happen to the Earth’s surface weather the next time this happens? I’d like to know too.

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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by Chris Peterson » Sun Jan 26, 2014 3:06 pm

SoutheastAsia wrote:Very fascinating. Question: could 'changing magnetic fields' here on Earth contribute to our own increasing temperature cycles? Either indirectly, or directly?
Our current pattern of rapid warming is unrelated to any variation in the Earth's magnetic field.

It has been suggested that variations in the magnetic field allow for changes in the depth charged particles can descend in the atmosphere, which could impact cloud formation. This may have a minor effect on short term climate (decadal, corresponding to the solar cycle), or possibly on some long term, probably non-cyclical climate.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by Psnarf » Sun Jan 26, 2014 4:32 pm

The concentration of carbon dioxide as measured from a mountain observatory in Hawai'i displays a continuously rising function when plotted concentration vs time. The same evidence is stored in seabed core samples showing the current increasing rate since the beginning of the industrial revolution when massive amounts of coal were burned to make steel. That metric is not disputed; temperature increase is. Urbanization of the land surrounding airports where official temperatures are measured is a factor, but that can easily be omitted from more stable temperature sites. The more serious problem IMHO and that of my Ecology professor is the carbon dioxide absorbed by the oceans, increasing its pH, another metric recorded in undisputed ocean floor core samples. The increased acidity already has a negative impact on the sustainability and growth of coral reefs. Hey, Kids!, let's perform an experiment in Science (*yay*); let's keep increasing the acidity of the oceans to see what happens when the bottom of the food chain vanishes. I imagine sushi would get a lot more ridiculously over-priced when the fish populations die off from starvation. This is a situation about which we can do nothing. The primary task of an elected official is to stay in office as long as possible. Since expensive television advertising is such a powerful propaganda tool, what with product recognition affecting consumers who choose one brand of an identical product over another based upon exposure to one brand's increased spending on advertising time, politicians are not about to jump off the gravy train of carbon-based energy corporations. Do you think a ghost town of what was once a thriving coal mining community would vote for the person who cut back production? The oil industry, with its endless supply of readily available cash can guarantee a candidate's re/election by providing the ability to purchase more advertising time than any opponent. *sigh* But I digress.
A million degrees? That's how hot my oven gets during its self-cleaning cycle, when we all go outside to watch the disc in the electricity meter spin faster and faster in the hope that it will reach a critical rate of rotation and shatter, much like the folks on "Mythbusters" did with a cd affixed to a cordless drill.

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The Gleissberg Cycle

Post by neufer » Sun Jan 26, 2014 4:51 pm

http://www.universetoday.com/103803/solar-cycle-24-on-track-to-be-the-weakest-in-100-years/ wrote: Solar Cycle #24: On Track to be the Weakest in 100 Years
by David Dickinson, Universe Today, July 29, 2013

<<Our nearest star has exhibited some schizophrenic behavior thus far for 2013. By all rights, we should be in the throes of a solar maximum, an 11-year peak where the Sun is at its most active and dappled with sunspots.

Thus far though, Solar Cycle #24 has been off to a sputtering start, and researchers that attended the meeting of the American Astronomical Society’s Solar Physics Division earlier this month are divided as to why.“Not only is this the smallest cycle we’ve seen in the space age, it’s the smallest cycle in 100 years,” NASA/Marshall Space Flight Center research scientist David Hathaway said during a recent press teleconference conducted by the Marshall Space Flight Center.

Cycle #23 gave way to a profound minimum that saw a spotless Sol on 260 out of 365 days (71%!) in 2009. Then, #Cycle 24 got off to a late start, about a full year overdue — we should have seen a solar maximum in 2012, and now that’s on track for the late 2013 to early 2014 time frame. For solar observers, both amateur, professional and automated, it seems as if the Sun exhibits a “split-personality” this year, displaying its active Cycle #24-self one week, only to sink back into a blank despondency the next.

This new cycle has also been asymmetrical as well. One hallmark heralding the start of a new cycle is the appearance of sunspots at higher solar latitudes on the disk of the Sun. These move progressively toward the Sun’s equatorial regions as the cycle progresses, and can be mapped out in what’s known as a Spörer’s Law. But the northern hemisphere of the Sun has been much more active since 2006, with the southern hemisphere experiencing a lag in activity. “Usually this asymmetry lasts a year or so, and then the hemispheres synchronize,” said Giuliana de Toma of the High Altitude Observatory.

The Sun is a giant ball of gas, rotating faster (25 days) at the equator than at the poles, which rotate once every 34.5 days. This dissonance sets up a massive amount of torsion, causing the magnetic field lines to stretch and snap, releasing massive amounts of energy. The Sun also changes polarity with every sunspot cycle, another indication that a new cycle is underway. But predictions have run the gamut for Cycle #24. Recently, solar scientists have projected a twin peaked solar maximum for later this year, and thus far, Sol seems to be following this modified trend. Initial predictions by scientists at the start of Cycle #24 was for the sunspot number to have reached 90 by August 2013.

Some researchers predict that the following sunspot Cycle #25 may even be absent all together. “If this trend continues, there will be almost no spots in Cycle 25,” Noted Matthew Penn of the National Solar Observatory, hinting that we may be on the edge of another Maunder Minimum. The Maunder Minimum was a period from 1645 to 1715 where almost no sunspots were seen. This span of time corresponded to a medieval period known as the Little Ice Age. During this era, the Thames River in London froze, making Christmas “Frost Fairs” possible on the ice covered river. Several villages in the Swiss Alps were also consumed by encroaching glaciers, and the Viking colony established in Greenland perished. The name for the period comes from Edward Maunder, who first noted the minimum in papers published in the 1890s. The term came into modern vogue after John Eddy published a paper on the subject in the journal of Science in 1976. Keep in mind, the data from the period covered by the Maunder Minimum is far from complete— Galileo had only started sketching sunspots via projection only a few decades prior to the start of the Maunder Minimum. But tellingly, there was a span of time in the early 18th century when many researchers supposed that sunspots were a myth! They were really THAT infrequent…>>
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by BDanielMayfield » Wed Jan 29, 2014 5:00 am

Something I meant to ask about the way this solar image was presented is, why show it as red when it's an ultraviolet photo :?:
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by geckzilla » Wed Jan 29, 2014 5:11 am

UV is invisible. Red is just as applicable as purple or green or black and white. I'm feeling a little weird about violet because in order for us to see it you have to mix red with blue. I want to say that blue rather than violet would be the closest color approximation to UV light, but it sounds wrong.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by Nitpicker » Wed Jan 29, 2014 5:33 am

The RGB colour model is triangular and has no beginning or end. When you use this model to mix red and blue in various ratios, you can get colours that appear similar to the colours at each end of the visible spectrum of light.

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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by Chris Peterson » Wed Jan 29, 2014 5:45 am

geckzilla wrote:UV is invisible. Red is just as applicable as purple or green or black and white. I'm feeling a little weird about violet because in order for us to see it you have to mix red with blue. I want to say that blue rather than violet would be the closest color approximation to UV light, but it sounds wrong.
Spectrally, blue on your monitor is much closer to UV than purple (which isn't the same as violet, which represents a more spectrally pure color, and which monitors can't display). But our eyes aren't spectrometers. Simulating a spectrally pure color on a monitor usually requires odd mixes.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by geckzilla » Wed Jan 29, 2014 5:53 am

Yeah, that's right, I PM'ed you about that at some point. As you can see, it continues to confound me. I have spent virtually all of my time in the monitor RGB world. Alice gave me these cool little plastic rainbow makers and I've found myself gazing at the patterns on the walls on sunny days. It's easy to forget the limitations of my computer screen.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by Nitpicker » Wed Jan 29, 2014 6:48 am

This is probably akin to preaching to the FSM, but this page made a lot of sense to me, regarding spectral to RGB conversion:
http://mintaka.sdsu.edu/GF/explain/opti ... ering.html

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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by geckzilla » Wed Jan 29, 2014 7:03 am

Nitpicker wrote:This is probably akin to preaching to the FSM, but this page made a lot of sense to me, regarding spectral to RGB conversion:
http://mintaka.sdsu.edu/GF/explain/opti ... ering.html
Andrew T. Young wrote:Learn something about color science; and then learn something about the technical side of color printing; and, when you've finally learned how to print spectra on paper so they look good, please come back and let me know. I'd like to be able to do it myself.
Amusing of him to issue a challenge like this after all that.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by BDanielMayfield » Wed Jan 29, 2014 2:44 pm

BDanielMayfield wrote:Something I meant to ask about the way this solar image was presented is, why show it as red when it's an ultraviolet photo :?:
geckzilla wrote:UV is invisible. Red is just as applicable as purple or green or black and white. I'm feeling a little weird about violet because in order for us to see it you have to mix red with blue. I want to say that blue rather than violet would be the closest color approximation to UV light, but it sounds wrong.
So I guess the short answer would be, it’s hard for our monitors to reproduce violet? Still red seems like an odd choice for an ultraviolet image. I knew that ultraviolet is invisible, so to make it visible the image must be shifted or mapped into a color that we can see, but why choose red? Blue or purple would have seemed like more logical choices, but I know that this is just a subjective opinion.

But don’t get me wrong, I’m not seeing red over the use of red, I love red. It’s always been my favorite color. It’s just that the choice of red here reminds me of a common misconception; that red is hot and violet is cool. Part of the description info was about how hot this region of the Sun is, so since people think red is hotter, use red?

And while I’m on a color rant, I only used purple in “ultraviolet” because the Font colour palette doesn’t contain violet. Which must be because “it’s hard for our monitors to reproduce violet?” I seem to be repeating myself. Like a color wheel.

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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by geckzilla » Wed Jan 29, 2014 3:19 pm

Hard... or impossible. Red was likely used because even though it's ultraviolet light, the Sun is still a fiery ball and in absence of other nearby images to need a color distinction, the fire palette still looks aesthetically pleasing, makes sense when applied to the sun, and it's a lot easier to see than pure blue. Details get lost in the blackest areas with blue. Anyway, the combination of aesthetically pleasing and making sense to a lay person is a winning combination.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by Chris Peterson » Wed Jan 29, 2014 3:23 pm

BDanielMayfield wrote:So I guess the short answer would be, it’s hard for our monitors to reproduce violet?
No, our monitors simulate violet fairly well. That comment was simply pointing out the subtle difference between violet, which is a term that technically refers to the the short end of the visible spectrum, and purple, which is a color (created on monitors by mixing red and blue).
Still red seems like an odd choice for an ultraviolet image. I knew that ultraviolet is invisible, so to make it visible the image must be shifted or mapped into a color that we can see, but why choose red? Blue or purple would have seemed like more logical choices, but I know that this is just a subjective opinion.
The choice of palette is well considered. The image itself has a single intensity layer (sometimes called monochromatic, although it technically isn't). So the most natural display choice is grayscale. And that works pretty well:
sun_grey.jpg
But our eyes are limited in the number of intensity levels we can distinguish between black and white. It isn't many- less than the 256 that most monitors can display (and the number in the image data may be much more than that). So we can cheat by taking advantage of the fact that we see hue as well as intensity. The different intensity levels can be mapped to some sort of color map. And the choice of color is far from arbitrary. Our eyes are much better at distinguishing between subtle changes of color at the long end of the spectrum than at the short. So many of the most popular and useful pseudocolor maps utilize reds and oranges for the midtones:
heatscale.jpg
This palette is often called heat, and is one of the best for maximizing the range of intensities our eyes can see. There are certainly pseudocolor palettes based on blue, but they aren't as good for seeing detail in single channel images with a wide continuous range of intensities. So while the choice of palette has aesthetic ramifications, it isn't necessarily an aesthetic choice, but a well considered scientific one.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by geckzilla » Wed Jan 29, 2014 3:53 pm

What's the best one for maximizing the range of intensities? Is it green? I don't think it's a coincidence that heat is often used for Sun imagery, especially when doling out images to the public.
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by BDanielMayfield » Wed Jan 29, 2014 3:58 pm

Thanks again Chris for another completely logical and very clear answer.

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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by Chris Peterson » Wed Jan 29, 2014 4:19 pm

geckzilla wrote:What's the best one for maximizing the range of intensities? Is it green? I don't think it's a coincidence that heat is often used for Sun imagery, especially when doling out images to the public.
I think the heat scale is close to optimal for images with very smooth intensity transitions. There are scales that use more colors, and which let us see more intensities, but we don't perceive them as smooth, and they are more likely to confuse an inexperienced eye.
sun_bscale.jpg
(If you're interested in these things, I recommend DS9, a free utility that lets you quickly play around with FITS files. It's not a file editor, but rather a tool for creating different visualizations. It only works with FITS format, but there are lots of free utilities that can convert JPEG or TIFF to FITS.)
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Re: APOD: Sunspot Loops in Ultraviolet (2014 Jan 26)

Post by geckzilla » Wed Jan 29, 2014 4:38 pm

DS9 is free so I'm all over that.

Just for the record, when I said "aesthetic" I did mean that it is good for viewing all of the intensities. I'd like to think my sense of aesthetics is strongly influenced by science and not pure whim but that's not necessarily obvious to anyone but myself.
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