Solar minimum – astroengine.com

The Sun Is a Beautifully Blank Billiard Ball for Halloween

For the festive season, our nearest star is keeping its choice of costume simple.

I’m not saying the Sun isn’t being creative, it’s just not putting too much effort into this year’s stellar fancy dress party. I mean, look at it:

The Sun right now, as seen by the Helioseismic and Magnetic Imager (HMI) instrument on NASA’s Solar Dynamics Observatory (SDO) [NASA/SDO]

That flawless orange billiard ball is the photosphere of our Sun. Have you ever seen something so smooth and beautifully unremarkable?

Well, you have now, and its blank gaze is actually the reason why it’s causing a bit of a stir. According to our ever watchful solar sentry, Tony Phillips at SpaceWeather.com, the northern summer of 2019 may go down in history as “the summer without sunspots.”

From June 21st until Sept 22nd, the sun was blank more than 89% of the time. During the entire season only 6 tiny sunspots briefly appeared, often fading so quickly that readers would complain to Spaceweather.com, “you’ve labeled a sunspot that doesn’t exist!” (No, it just disappeared.) Not a single significant solar flare was detected during this period of extreme quiet.
Dr. Tony Phillips

So, what does this mean?

Sunspots are the visual cues for magnetic turmoil within our nearest star. Over cycles of approximately 11 years, the Sun’s internal magnetic field becomes stretched and twisted, driving the ebb and flow of space weather.

Starting with our solar billiard ball here, suffice to say that the solar magnetic field is pretty untwisted and, well, chilled. This is the epitome of “solar minimum” — and, as commented on by Phillips, a deep, potentially record-breaking solar minimum at that. It’s very likely that this is as minimum as solar minimum can be, so we could hazard a guess to say that things are going to start getting interesting very soon.

Differential rotation and the formation of coronal loops as demonstrated by my awesome abilities as a Microsoft Word artist [source: my PhD thesis!]

As our Sun is a massive blob of magnetized plasma, it doesn’t rotate uniformly (like the Earth does), it actually rotates a little faster at its equator than at its poles, a phenomenon known as “differential rotation.” Now, if you imagine the solar magnetic field as straight lines running from pole to pole, you can imagine that, over time, the field will start to wrap around the equator like an elastic band being stretched out of shape and wrapped around the middle. At its most extreme, so much rotational tension will be applied to the magnetic field that it becomes contorted. This contortion creates an upward pressure, forcing vast loops of magnetized plasma, known as coronal loops, to pop through the Sun’s photosphere — a.k.a. the solar “surface” — like annoyingly twisted loops of garden hosepipe (see the diagram above).

As its most extreme, in a few years time, we can expect our boring ol’ billiard ball to look something like this:

The Sun in 2014 (during the previous solar maximum), as seen by the SDO’s HMI [NASA/SDO]

About those blotches: those dark spots are sunspots and they are a direct consequence of the magnetic turmoil that rumbles inside the Sun during solar maximum. Remember those coronal loops I was talking about? Well, these huge, beautiful arcs of plasma cause the hotter outer layers of the Sun to be pushed aside, exposing the comparatively cooler (though still thousands of degrees) plasma under the surface — that’s what creates those dark blotches. And by counting sunspots, you can gauge how magnetically active the Sun is.

By viewing the Sun in different wavelengths, we can view the Sun’s atmosphere at different temperatures and, as the Sun’s atmosphere (the corona) is counter-intuitively hotter the higher above the surface you get, let’s take a look at what solar maximum looks like above these sunspots:

Yikes! The Sun’s corona in October 2014 (during the previous solar maximum), as seen by the SDO’s Atmospheric Imaging Assembly (AIA) instrument. And a damn fine effort just in time for Halloween. [NASA/SDO]

As you can see, there’s a lot of coronal loops erupting through the surface, creating huge regions of activity (called active regions, unsurprisingly). And the above observation was captured on Oct. 8, 2014, when the Sun was, apparently, in a terrifyingly festive Halloween mood! These regions can be hothouses for solar flares and coronal mass ejections; explosive phenomena that can have dramatic space weather effects on Earth.

So that was solar maximum; what does the solar corona look like now, at solar minimum?

*The Sun’s corona right now, as seen by the SDO’s AIA [NASA/SDO]*

Yep, as you guessed, very relaxed. In this state, we can expect very little in the way of explosive space weather events, such as flares and CMEs; there’s simply too little magnetic energy at solar minimum to create many surprises (caveat: even solar minimum can generate flares, they’re just few and far between).

While the Sun may look boring, the effects of space weather are anything but. During these times of solar minimum, the extended solar magnetic field (called the heliosphere), a magnetic bubble that reaches beyond the orbits of all the planets, contracts and weakens, allowing more cosmic rays from energetic events from the rest of the cosmos to reach Earth. Cosmic rays are ionizing particles that can boost the radiation exposure of astronauts and frequent fliers. Also, the solar wind can become a more persistent presence; streams of energized particles that are continuously streaming from the lower corona, so we still get our aurorae at high latitudes.

Recognition that the Sun is now in a deep minimum means the solar vacation is nearing an end. Astronomers have reported that of the handful of sunspots have made an appearance over the last few months with a flip in magnetic polarity, which can mean only one thing: Solar Cycle 25 is coming and the next solar maximum is only four years away.

Solar Cycle Prediction: “None of Our Models Were Totally Correct”

nov4flare

Predicting space weather is not for the faint-hearted. Although the Sun appears to have a predictable and regular cycle of activity, the details are a lot more complex. So complex in fact, that the world’s greatest research institutions have to use the most powerful supercomputers on the planet to simulate the most basic of solar dynamics. Once we have a handle on how the Sun’s interior is driven, we can start making predictions about how the solar surface may look and act in the future. Space weather prediction requires a sophisticated understanding of the Sun, but even the best models are flawed.

Today, another solar cycle prediction has been released by the guys that brought us the “$2 trillion-worth of global damage if a solar storm hits us” valuation earlier this month. According to NOAA scientists sponsored by NASA, Solar Cycle 24 will peak in May 2013 with a below-average number of sunspots.

“If our prediction is correct, Solar Cycle 24 will have a peak sunspot number of 90, the lowest of any cycle since 1928 when Solar Cycle 16 peaked at 78,” says Doug Biesecker of the NOAA Space Weather Prediction Center.

Although this may be considered to be a “weak” solar maximum, the Sun still has the potential to generate some impressive flares and coronal mass ejections (CMEs). Although I doubt we’ll see the record-breaking flares we saw in 2003 (pictured top), we might be hit by some impressive solar storms and auroral activity will certainly increase in Polar Regions. But just because the Sun will be more active, it doesn’t mean we will be struck by any big CMEs; space is a big place, we’d be (un)lucky to be staring directly down the solar flare barrel.

So, we have a new prediction and the solar models have been modified accordingly, but it is hard to understand why such tight constraints are being put on the time of solar maximum peak (one month in 2013) and the number of sunspots expected (90, or thereabouts). Yes, sunspot activity is increasing, but we are still seeing high-latitude sunspots from the previous cycle (Solar Cycle 23) pop up every now and again. This is normal, an overlap in cycles do occur, yet it surprises me that any definitive figures are being placed on a solar maximum that may or may not peak four years from now.

Ah, I see, it's obvious Solar Cycle 24 will look like that... is it really? (NOAA/NASA) — Tenuous link: Are you really happy with that prediction? (NOAA/NASA)

We are able to look at the history of sunspot number and we can see the cycles wax and wane, and we can pick out a cycle that most resembles the one we are going through now, but that doesn’t mean that particular cycle will happen this time around. Statistically-speaking, there’s a higher chance of a similar-looking cycle from the past happening in this 24th cycle, but predictions based on this premise are iffy to say the least.

Also, solar models are far from being complete, and many aspects of the physics behind the Sun’s internal dynamics are a mystery. The Sun really is acting strange, which is fascinating for solar physicists.

“It turns out that none of our models were totally correct,” says Dean Pesnell of the Goddard Space Flight Center, NASA’s lead representative on the panel. “The sun is behaving in an unexpected and very interesting way.”

Personally, I think we should concentrate less on predicting when or how the next solar maximum presents itself. Solar models are not going to suddenly predict the nature of the solar cycle any more than we can predict terrestrial weather systems more than a few days in advance.

Using the atmospheric weather analogy, we know the seasons cycle as the year goes on, but there is no way we can say with any degree of certainty when the hottest day of the year is going to be, or which week will yield the most rain.

The same goes for our Sun. It is vastly complex and chaotic, a system we are only just beginning to understand. We need more observatories and more solar missions with advanced optics and spectrometers (and therefore a huge injection of funding, something solar physicists have always struggled without). Even then, I strongly doubt we’ll be able to predict exactly when the peak of the solar cycle is going to occur.

That said, space weather prediction is a very important science, but long-term forecasts don’t seem to be working, why keep on releasing new forecasts when the old one was based on the same physics anyway? Predicting an inactive, active or mediocre solar maximum only seems to cause alarm (although it is a great means to keep solar physics in the headlines, which is no bad thing in my books).

I suppose if you make enough predictions, eventually one will be correct in four years time. Perhaps there will be a peak of 90 sunspots by May 2013, who knows?

If you’re blindfolded, spun around and armed with an infinite supply of darts, you’ll eventually hit the board. Hell, you’ll probably even hit the bullseye…

Source: NASA, special thanks to Jamie Rich for bringing this subject to my attention!

A Wide Angle View of Our Nearest Star

A comparison of solar minimum and solar maximum in EUV wavelengths (SOHO/NASA)

In case you were wondering why Astroengine has been a little quiet of late, this is why. I’ve been working with my Discovery Space colleagues to produce a “Wide Angle” all about the current solar minimum, space weather and the influence of the Sun on our planet.

It’s been fun to do, but it’s also been a steep learning curve to get up to speed with my new duties as producer for Discovery. Currently getting through a tonne of training, but I’ll get there. When organized, Astroengine will be back to full capacity, pumping out the best space news and opinion.

But for now, have an explore of Discovery Space and enjoy the current Wide Angle: Solar Minimum.

Hubble and Atlantis Transit the Sun (Photo)

The Hubble Space Telescope and Shuttle Atlantis pass in front of the blank Sun. Can't see their silhouettes? Click on the image for the large version and look in the bottom-left-hand corner. That's no sunspot pair... (©Thierry Legault)

Thierry Legault is one highly skilled astrophotographer. The transit of the Hubble Space Telescope and Space Shuttle Atlantis took only 0.8 seconds to clear the disk of the Sun, so Legault rapidly took four pictures per second, starting his series of pictures two seconds before the pair were predicted to pass in front of the Sun.

STS-125 Atlantis and Hubble Solar Transit. The image was captured from Florida at 12:17pm EST on May 13th as the Shuttle approached the orbiting telescope at 600km from Earth (©Thierry Legault)

In the image above, the 35 meter-long Atlantis is easily identifiable, but the tiny speck of the 13 meter-long Hubble isn’t so easy to define, but the result is superb. According to Legault’s website, this is the only picture of the STS-125 and the observatory, orbiting at an altitude of 600 km.

Back in July 2008, Astroengine reported on the transit of the International Space Station across the disk of the Sun. Fortunately, in both cases, the Sun’s face was blank, and no sunspots are prominent enough to ruin the view.

Stunning!

Sources: NASA on Flickr, Astrosurf

The Sun Has An Anti-Climax

The solar disk on May 11th: Is it? Are they? Not quite (SOHO)

Some recent solar articles are freaking out, proclaiming that the Sun is waiting to unleash it’s fury on the Earth (re: Warning: Sunspot cycle beginning to rise) or that it’s lowering its energy output, possibly kickstarting Maunder Minimum 2.0 (re: New Forecast Calls for Calmer Sun).

So which one is it? Is the Sun just biding its time, waiting for the perfect moment to fire a salvo of flares at us? Or will it remain quiet, well into Solar Cycle 24, impacting our planet like the Maunder Minimum did during the Little Ice Age from the 16th-19th century?

It’s funny actually, both the above articles are based on the same research, and yet two very different conclusions were drawn from the text.

On the one hand, the Sun is acting rather strange; it’s undergoing a sustained solar minimum, the longest period of low sunspot population for the best part of a century. On the other hand, when the Sun does get active, steadily growing to a peak in activity for the 2012-2013 predicted solar maximum, the resulting flares and coronal mass ejections (CMEs) could inflict $2 trillion in damages on global infrastructure (according to a recent study), leaving us to mop up the mess for a decade. It’s these two extremes that are causing such a stir, generating the attention-grabbing headlines.

However, I seriously doubt that we are facing another Little Ice Age and I am highly skeptical of the predictions that the 11 years of Cycle 24 are going to be overly violent. To be honest, we just don’t know. Considering we live so close to the Sun, we actually know very little about it; to even begin trying to predict what it’s going to do next remains problematic.

That said, once the Sun starts producing lost of sunspots, this means magnetic activity is on the rise and solar activity is increasing, so when I see sunspots rotate into view, I can’t help but be a little excited. Today, it happened, two active regions appeared on the disk of the Sun. Could this be the real start to the solar cycle?

Today’s image is a magnetic map of the sun. Two active regions are circled. Their polarity identifies them as members of new Solar Cycle 24, but they lack the dark cores required of true sunspots. So, in spite of these lively magnetic imprints, we must still say “the sun is blank–no sunspots.” —SpaceWeather.com

No sunspots, another blank disk day and therefore low magnetic activity still.

How dull.

When the Sun is So Boring, Anything Becomes Interesting

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…
Continue reading “When the Sun is So Boring, Anything Becomes Interesting”

Breaking News: We Have Sunspots, First for Over a Month

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!)…
Continue reading “Breaking News: We Have Sunspots, First for Over a Month”