An Explanation For Solar Sigmoids

Hinode X-ray observation of a solar sigmoid (David McKenzie/Montana State University)
Hinode X-ray observation of a solar sigmoid (David McKenzie/Montana State University)

Sigmoids in the solar corona have been studied for many years, but little explanation of their formation or why they are often the seed of powerful solar flares have been forthcoming. Using high-resolution X-ray images from the Japanese-led solar mission Hinode (originally Solar-B), solar physicists have known that these very hot S-shaped structures are composed of many highly stressed magnetic flux tubes filled with energized plasma (also known as ‘fibrils’), but until now, little was known about the formation and flare eruption processes that occur in sigmoids.

Now, a team of solar physicists from the University of St Andrews believe they have found an answer using powerful magnetohydrodynamic (MHD) computer models, aiding our understanding of coronal dynamics and getting us one step closer to forecasting space weather…

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C.A.T. Scans of the Solar Wind

Guest article by Dr. Mario M. Bisi (Research Focus)

A cut in the ecliptic plane through a 3D reconstruction on 08 November 2004 at 0000 UT using white-light data from SMEI. The view is from directly North of the ecliptic; the Sun is at the centre marked by a +, the Earth is on the right marked with a ⊕ along with its orbit as a black near-circular line around the Sun (the Earth orbits anti-clockwise around the Sun from this point of view). The darker the colour, the greater the density of material in the ecliptic.  (©Dr. Mario M. Bisi)
A cut in the ecliptic plane through a 3D reconstruction on 08 November 2004 at 0000 UT using white-light data from SMEI. The view is from directly North of the ecliptic; the Sun is at the centre marked by a +, the Earth is on the right marked with a ⊕ along with its orbit as a black near-circular line around the Sun (the Earth orbits anti-clockwise around the Sun from this point of view). The darker the colour, the greater the density of material in the ecliptic. (©Dr. Mario M. Bisi)

The Computer Assisted Tomography (C.A.T.) technique has been used for many years now and is well known for use on people where certain health conditions need more thorough, detailed, and deeper scans into the human body and the need for three-dimensional (3D) reconstructed imaging. However, similar such scans can also be used on the solar wind to discover the shapes and sizes of structures near Earth and throughout the inner heliosphere in three dimensions. These scans have been carried out for some time, pioneered in the most part by those at the Center for Astrophysics and Space Sciences (CASS), University of California, San Diego (UCSD) in La Jolla, CA, U.S.A. in close-collaboration with the Solar-Terrestrial Environment Laboratory (STELab), Nagoya University, Toyokawa, Japan…
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When the Sun is So Boring, Anything Becomes Interesting

Caption: So boring it doesn't deserve a caption (NASA/SOHO)
Caption: So boring it doesn't deserve a caption (NASA/SOHO)

You know when you have those unremarkable days, those periods of time you experience you know you’ll forget tomorrow? It’s either “just another” day at work, another commute, or a Sunday where you had a beer, fell asleep, only to wake up again to realise it was too late to get up so you stayed in bed till Monday? (And no, I don’t make a habit of that. I’m sure to have at least two beers.) Most days aren’t like that for me, usually I can think of one noteworthy event that sets apart one day from the next, but sometimes it’s as if Stuff Happens™ doesn’t.

It would appear the Sun is having an extended period of time where Stuff Happens™ is at a premium, so you have to make the most of when something really does happen. In this case, the Sun released a crafty CME, thinking we wouldn’t see it…
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Ceres: Life? Pluto: Not So Much

The dwarf planet soap opera continues

The dwarf planet Ceres. Fuzzy (NASA/Hubble)
The dwarf planet Ceres. Fuzzy (NASA/Hubble)

Could the dwarf planet Ceres maintain life? Possibly, says a scientist from a German university. According to new research, this ex-asteroid (who did a deal with the IAU to sell out Pluto, trading in its asteroid status to become a dwarf planet, at the expense of Pluto being demoted from being a planet. Obviously) may have harboured microbial life near geothermal vents in hypothetical liquid oceans (I emphasise hypothetical). Not only that, but Ceres’ chilly microbes could have been kicked into space by meteorites, spreading life throughout the Solar System. Forget Mars (you’re looking too hard), forget Europa (a moon? With life? Pah), the new giver of life could be Ceres, the dwarf planet we know next to nothing about.

Then there’s Pluto. Not much chance of life there either (although it would be fun to speculate, there is methane there after all), but the hard-done-by newly-christened dwarf planet has a rather bizarre atmosphere. Its temperature profile is upside down. Oh, and Pluto has just been reunited with its planetary status… in Illinois only (because a governor really does know more about planets than 400 members of the International Astronomical Union).
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When in the Solar Cycle were You Born?

My birthday, right smack bang in the middle of solar maximum (Space Weather)
My birthday, right smack bang in the middle of solar maximum (Space Weather)

I just came across this rather nifty little tool via fellow Twitterer TaviGreiner, and I really like it. It’s yet another wish-I’d-thought-of-that moments. You input your date of birth, and a sunspot number chart appears, displaying the solar activity on your birthday…
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Our (Painfully) Featureless Sun

The Sun, being boring on Jan. 13th 2009, a whole year after Solar Cycle 24 was supposed to start (solar astrophotography by ©Stephen Sykes)
The Sun, being boring on Jan. 13th 2009, a whole year after Solar Cycle 24 was supposed to start (solar astrophotography by ©Stephen Sykes)

This morning I realised it’s been a whole year since we saw the first reversed polarity sunspot pair on the surface of the Sun. A year ago, Solar Cycle 23 was running out of steam and Cycle 24 was about to take over. Solar physicists the world over were making predictions, some thought Cycle 24 was going to be a “doozy”, others were a little more conservative, saying it might just be an “average” cycle. However, 12 months on, it would appear Cycle 24 is off to a very lazy start. Once again, we have a “blank” Sun, a perfect sphere, looking like a marble, or as my wife observed: a jawbreaker (or as us Brits like to expressively call them, gobstoppers).

The stunning image above was shot by skilled astrophotographer Stephen Sykes, over at AstroSlacker.com, demonstrating what superb views of the Sun can be captured by amateur astronomers. When I (eventually) get my telescope, and/or a new camera, the Sun will be my first astronomical object to observe, but I doubt I’ll get as good a view as this.

So, another day, another featureless Sun. That’s not to say it’s been a totally boring year; we’ve had flares from “left over” active regions from Cycle 23 and we’ve had a bit of action from Cycle 24 (the most recent set of spots–Sunspot 1010–have just rotated out of view), and I’m pretty sure this time next year we’ll be inundated with sunspots… fingers crossed (I can’t wait to see some coronal loop arcades again). For now, good night our lazy Sun, I look forward to seeing more action in the coming months…

Solar Views from SOHO (Wallpapers)

304A SOHO/EIT image of the solar disk (NASA/ESA)
304A SOHO/EIT image of the solar disk (NASA/ESA)

Back in 2006, I was feeling a bit nostalgic about my four years of research at the University of Wales, Aberystwyth Solar Group, so I decided to try to find some high resolution prints of the Sun. After a lot of effort, I didn’t find any prints I could buy or download, but I did find some high resolution images from the Solar and Heliospheric Observatory (SOHO) image archive. Although some were a bit noisy, I was able to clean them up with Photoshop and did some layer tweaking/saturation/balance to draw out the fine detail of the chromospheric network–as seen above in the 304A Extreme ultraviolet Imaging Telescope filter–plus a distinct prominence (in the bottom left-hand of the image).

Not stopping there, I decided to give the same treatment to high resolution 171A and 195A images. They came out very well and I kept rotating them as my wallpaper for months. Having just read Phil’s post on today’s perihelion (the time of year when the Earth is at its closest to the Sun during its orbit), I came across a comment asking whether anyone had any wallpapers of the same 304A EIT image. Well, here it is! Plus two more!

If anyone wants to find out how the images were edited, feel free to ask and I’ll let you know. Truth be known, there’s thousands of space images held by NASA, ESA etc. open to the public domain that rarely get the “airtime” they deserve. So it’s about time I dust off these three-year old edits and share the magnetohydrodynamic love.

I miss active regions, I wish the Sun would amp it up a bit so we can see all those lovely flares, CMEs, filaments and coronal loops… ahhhh… coronal loops

Cycle 24 Sunspot Observed… At Last!

Thar she blows! Solar Cycle 24 sunspots make their first appearence since January (SOHO MDI image showing Cycle 24 polarity)
Thar she blows! Solar Cycle 24 sunspots make their first appearence since January (SOHO MDI image showing Cycle 24 polarity)

This day has been a long time coming. Ever since the beginning of Solar Cycle 24 back on January 4th 2008, solar physicists have been eagerly awaiting the fireworks to begin… alas, the Sun decided to take a break and stay blank for nine months, keeping any Cycle 24 sunspot activity hidden. That’s not to say there have been no sunspots. Due to a strange quirk in solar activity, the previous cycle took some time to wind down and continued to send groups of spots to the surface, occasionally unleashing some surprise flares and coronal mass ejections (CMEs).

However, it has now been confirmed that the sunspot group seen today by the Solar and Heliospheric Observatory (SOHO) and international amateur astronomers do in fact belong to Cycle 24.

Phew, I was beginning to feel a little chilly
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Breaking News: We Have Sunspots, First for Over a Month

New sunspots observed on Aug. 21st (© Pavol Rapavy)
New sunspots observed on Aug. 21st (© Pavol Rapavy)

Just as we were getting concerned that the Sun may be facing an extended solar minimum, amateur astronomers, in the last few hours, have observed a new sunspot pair appearing around the Sun’s south-eastern limb. They are young, emergent spots, gradually getting larger. It will be interesting to see how they evolve. The observation above was taken by Pavol Rapavy in Rimavska Sobota, Slovakia, and now we have detailed images of the region by a British astronomer too (sounds like the Sun might be making an appearance for the UK summer at last!)…
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Could Past Sunspot Variations Lead to the Current “Blank Sun”?

The Sun as seen on Aug. 6th 2008. Still no sunspots. It's like watching paint dry... (SOHO/MDI)
The Sun as seen on Aug. 6th 2008. Still no sunspots. It's like watching paint dry... (SOHO/MDI)

Wow, what an unremarkable few months the Sun is having. Yes it is going through its solar minimum and yes that means it’s going to be fairly quiet, but the total (and I mean total) lack of sunspots is beginning to get a little boring. Sometimes the Sun does this, it does something unpredicted, like generating historic X-ray flares after solar maximum (like in 2003) or being unseasonably quiet (like now). This is the big issue with solar physics; although we can study our nearest star in great depth, we still do not appreciate what drives the inner workings of the Sun. We don’t fully understand why its atmosphere (corona) is so hot, let alone the nature of the 11-year solar cycle.

So, when asked “what are your views on the current lack of sunspots?”, I have to remain vague and point out that any form of solar forecasting is not possible at this stage, and more work needs to be done when working out the nature of sunspot activity. But now, with the help of a fellow blogger, a paper has been brought to my attention that actually predicted there will be no sunspots by 2015. What makes this enthralling is that this dual-author paper was written in 2006… back when the Sun was winding down from a pretty ferocious Solar Cycle 23. Could their prediction be coming true?
Continue reading “Could Past Sunspot Variations Lead to the Current “Blank Sun”?”