Plasmaloopalicious!

The magnetic loop containing hydrogen and nitrogen plasma evolves over 4 micro-seconds. Credit: Bellan & Stenson, 2012

The magnetic loop containing hydrogen and nitrogen plasma evolves over 4 micro-seconds. Credit: Bellan & Stenson, 2012

There’s no better method to understand how something works than to build it yourself. Although computer simulations can help you avoid blowing up a city block when trying to understand the physics behind a supernova, it’s sometimes just nice to physically model space phenomena in the lab.

So, two Caltech researchers have done just that in an attempt to understand a beautifully elegant, yet frightfully violent, solar phenomenon: coronal loops. These loops of magnetism and plasma dominate the lower corona and are particularly visible during periods of intense solar activity (like, now). Although they may look nice and decorative from a distance, these loops are wonderfully dynamic and are often the sites of some of the most energetic eruptions in our Solar System. Coronal loops spawn solar flares and solar flares can really mess with our hi-tech civilization.

A coronal loop as seen by NASA's Transition Region and Coronal Explorer (TRACE). Credit: NASA

A coronal loop as seen by NASA’s Transition Region and Coronal Explorer (TRACE). Credit: NASA

In an attempt to understand the large-scale dynamics of a coronal loop, Paul Bellan, professor of applied physics at Caltech, and graduate student Eve Stenson built a dinky “coronal loop” of their own (pictured top). Inside a vacuum chamber, the duo hooked up an electromagnet (to create the magnetic “loop”) and then injected hydrogen and nitrogen gas into the two “footpoints” of the loop. Then, they zapped the whole thing with a high-voltage current and voila! a plasma loop — a coronal loop analog — was born.

Although coronal loops on the sun can last hours or even days, this lab-made plasma loop lasted a fraction of a second. But by using a high-speed camera and color filters, the researchers were able to observe the rapid expansion of the magnetic loop and watch the plasma race from one footpoint to the other. Interestingly, the two types of plasma flowed in opposite directions, passing through each other.

The simulation was over in a flash, but they were able to deduce some of the physics behind their plasma loop: “One force expands the arch radius and so lengthens the loop while the other continuously injects plasma from both ends into the loop,” Bellan explained. “This latter force injects just the right amount of plasma to keep the density in the loop constant as it lengthens.” It is hoped that experiments like these will ultimately aid the development of space weather models — after all, it would be useful if we could deduce which coronal loops are ripe to erupt while others live out a quiescent existence.

It’s practical experiments like these that excite me. During my PhD research, my research group simulated steady-state coronal loops in the hope of explaining some of the characteristics of these fascinating solar structures. Of particular interest was to understand how magnetohydrodynamic waves interact with the plasma contained within the huge loops of magnetism. But all my research was based on lines of code to simulate our best ideas on the physical mechanisms at work inside these loops. Although modelling space phenomena is a critical component of science, it’s nice to compare results with experiments that aim to create analogs of large-scale phenomena.

The next test for Bellan and Stenson is to create two plasma loops inside their vacuum chamber to see how they interact. It would be awesome to see if they can initiate reconnection between the loops to see how the plasma contained within reacts. That is, after all, the fundamental trigger of explosive events on the Sun.

Read more in my Discovery News article: “Precursors to Solar Eruptions Created in the Lab

Mystery Mars Cloud: An Auroral Umbrella?

The strange cloud-like protursion above Mars' limb (around the 1 o'clock point). Credit: Wayne Jaeschke.

The strange cloud-like protursion above Mars' limb (around the 1 o'clock point). Credit: Wayne Jaeschke.

Last week, amateur astronomer Wayne Jaeschke noticed something peculiar in his observations of Mars — there appeared to be a cloud-like structure hanging above the limb of the planet.

Many theories have been put forward as to what the phenomenon could be — high altitude cloud? Dust storm? An asteroid impact plume?! — but it’s all conjecture until we can get follow-up observations. It is hoped that NASA’s Mars Odyssey satellite might be able to slew around and get a close-up view. However, it appears to be a transient event that is decreasing in size, so follow-up observations may not be possible.

For the moment, it’s looking very likely that it is some kind of short-lived atmospheric feature, and if I had to put money on it, I’d probably edge more toward the mundane — like a high-altitude cloud formation.

But there is one other possibility that immediately came to mind when I saw Jaeschke’s photograph: Could it be the effect of a magnetic umbrella?

Despite the lack of a global magnetic field like Earth’s magnetosphere, Mars does have small pockets of magnetism over its surface. When solar wind particles collide with the Earth’s magnetosphere, highly energetic particles are channeled to the poles and impact the high altitude atmosphere — aurorae are the result. On Mars, however, it’s different. Though the planet may not experience the intense “auroral oval” like its terrestrial counterpart, when the conditions are right, solar particles my hit these small pockets of magnetism. The result? Auroral umbrellas.

The physics is fairly straight forward — the discreet magnetic pockets act as bubbles, directing the charged solar particles around them in an umbrella fashion. There is limited observational evidence for these space weather features, but they should be possible.

As the sun is going through a period of unrest, amplifying the ferocity of solar storms, popping off coronal mass ejections (CMEs) and solar flares, could the cloud-like feature seen in Jaeschke’s photograph be a bright auroral umbrella? I’m additionally curious as a magnetic feature like this would be rooted in the planet’s crust and would move with the rotation of the planet. It would also be a transient event — much like an atmospheric phenomenon.

The physics may sound plausible, but it would be interesting to see what amateur astronomers think. Could such a feature appear in Mars observations?

For more information, see Jaeschke’s ExoSky website.

What Do You See When SETI’s Allen Telescope Array Is Aimed At The Sun?

A comparison between an observation of the sun using the ATA's 2.75 GHz band (left) and SOHO's 195A filter. Both are near-simultaneous observations on Oct. 1, 2009 (Saint-Hilaire et al., 2011)

A comparison between an observation of the sun using the ATA's 2.75 GHz band (left) and SOHO's 195A filter. Both are near-simultaneous observations on Oct. 1, 2009 (Saint-Hilaire et al., 2011).

And no, “aliens” isn’t the answer.

The Allen Telescope Array (ATA), located near Hat Creek, California, isn’t only used by the SETI Institute to seek out signals from extraterrestrial civilizations. The 42 6.1-meter antennae form an interferometer that can be used for a variety of astronomical studies — in reality, this is the main focus of the project. SETI studies “piggyback” the active astronomical research, passively collecting data.

Due to the radio interferometer’s wide field of view, one surprising use of the ATA is solar astronomy — at radio frequencies. The ATA can be used to simultaneously observe the whole of the solar disk at a range of frequencies rarely studied. As outlined in a recent arXiv publication, a University of California, Berkeley, team of astronomers headed by Pascal Saint-Hilaire have carried out the first ATA solar study, producing images of the sun in a light we rarely see it in (shown above).

According to the paper, active regions were observed at radio and microwave frequencies, spotting the emissions associated with bremsstrahlung — electromagnetic radiation generated by accelerated charged particles caught in intense magnetic fields, a feature typical inside solar active regions. Also, coronal interactions, or gyroresonance, between solar plasma and plasma waves (propagating along magnetic field lines) was detected.

Combining the ATA’s wide field of view, range of frequencies and high resolution, it looks like the ATA is the only solar radiotelescope on the planet.

For more on this fascinating study, read “Allen Telescope Array Multi-Frequency Observations of the Sun,” Saint-Hilaire et al., 2011. arXiv:1111.4242v1 [astro-ph.SR]

Can Spicules Explain the Mysteries of Coronal Heating?

Solar spicules as imaged by NASA's Solar Dynamics Observatory (NASA)

Solar spicules as imaged by NASA's Solar Dynamics Observatory (NASA)

There’s one recurring question I’ve been asking for nearly a decade: Why is the Sun’s corona (its atmosphere) so hot?

When asking this out loud I inevitably get the sarcastic “um, because the Sun is… hot?” reply. Yes, the Sun is hot, really hot, but solar physicists have spent the last half-century trying to understand why the corona is millions of degrees hotter than the solar surface.

After all, if the air surrounding a light bulb was a couple of magnitudes hotter than the bulb’s surface, you’d want to know why that’s the case, right? At first glance, the solar atmosphere is breaking all kinds of thermodynamic laws.

The Sun is a strange beast and because of its magnetic dominance, energy travels through the solar body in rather unfamiliar ways. And today, a group of solar physicists have put forward a new theory as to where the coronal energy is coming from. But they’ve only been able to do this with help from NASA’s newest and most advanced solar telescope: the Solar Dynamics Observatory, or SDO.

Using the SDO’s high-definition cameras and imagery from the awesome Japanese Hinode solar observatory, features previously invisible to solar astronomers have been resolved. The features in question are known as “spicules.” These small-scale jets inject solar plasma from the solar surface into the lower corona, but until now they’ve been considered too cool to have any appreciable heating effect.

That was until a new type of hot, high-speed spicule was discovered.

“It’s a little jet, then it takes off,” solar physicist Scott McIntosh, of the National Center for Atmospheric Research’s High Altitude Observatory, told Discovery News’ Larry O’Hanlon. “What we basically find is that the connection is the heated blobs of plasma. It’s kind of a missing link that we’ve been looking for since the 1960s.”

These Type II spicules blast hot multi-million degree Kelvin plasma at speeds of 100 to 150 kilometers per second (62 to 93 miles per second) into the corona and then dissipate. What’s more, these aren’t isolated events, they’ve been observed all over the Sun. “This phenomenon is truly ubiquitous and populates the solar wind,” said McIntosh.

While this research provides more clarity on coronal dynamics, McIntosh is keen to point out that Type II spicules probably don’t tell the whole coronal heating story.

NASA’s coronal physics heavyweight James Klimchuk agrees. “It is very nice work, but it is absolutely not the final story on the origin of hot coronal plasma,” he said.

“Based on some simple calculations I have done, spicules account for only a small fraction of the hot plasma.”

Klimchuk favors coronal heating through magnetic stresses in the lower atmosphere generating small reconnection events. Right at the base of the corona, loops of magnetic flux channeling multi-million degree plasma high above the Sun’s chromosphere become stressed and eventually snap. These reconnection processes produce sub-resolution nanoflare events — akin to small explosions releasing energy into the solar plasma, heating it up.

Another heating mechanism — a mechanism I studied during my solar research days (.pdf) — is that of wave heating, when magnetohydrodynamic waves (I studied high-frequency Alfven waves, or ion cyclotron waves) interact with the lower corona, heating it up.

But which heating mechanism injects the most energy into the corona? For now, although there’s plenty of theorized processes (including these new transient Type II spicules), we don’t really know. We can only observe the solar corona from afar, so getting a true grasp on coronal dynamics is very hard. We really need a probe to dive deep into the solar atmosphere and take a measurement in-situ. Although the planned Solar Probe Plus will provide some answers, it may still be some time before we know why the corona is so hot.

But it is most likely that it’s not one coronal heating mechanism, but a combination of the above and, perhaps, a mechanism we haven’t uncovered yet.

For more on this fascinating research, check out Larry O’Hanlon’s Discovery News article “New Clue May Solve Solar Mystery.”

Compex Magnetic Eruption Witnessed by Solar Observatories

Solar Dynamics Observatory view of the solar disk shortly after eruption (NASA).

This morning, at 08:55 UT, NASA’s Solar Dynamics Observatory (SDO) detected a C3-class flare erupt inside a sunspot cluster. 100,000 kilometers away, deep within the solar atmosphere (the corona), an extended magnetic field filled with cool plasma forming a dark ribbon across the face of the sun (a feature known as a “filament”) erupted at the exact same time.

It seems very likely that both events were connected after a powerful shock wave produced by the flare destabilized the filament, causing the eruption.

A second solar observatory, the Solar and Heliospheric Observatory (SOHO), then spotted a huge coronal mass ejection (CME) blast into space, straight in the direction of Earth. Solar physicists have calculated that this magnetic bubble filled with energetic particles should hit Earth on August 3, so look out for some intense aurorae, a solar storm is on its way…

For more on this impressive solar eruption, read my Discovery News article, “Incoming! The Sun Unleashes CME at Earth

The UK’s Brain Drain (been there, done that)

Professor-Stephen-Hawking-001

Back in 2006, I remember sitting in my local UK Job Centre finding out how I could claim for unemployment benefits.

I can see it now, the moment I explained to my liaison officer that I had been looking for work but received little interest. She looked at me and said, candidly, “Have you thought about not mentioning you have a PhD? It might help.” She smiled.

What? I now need to hide my qualifications if I want to get a job? Isn’t that a little counter-intuitive? Actually, as it turned out, she was right. Many of the jobs I had applied for didn’t require a postdoc to do them; why would a company hire me when they can hire a younger postgrad with lower salary expectations?

Up until that moment, I was still hopeful that I might be able to land an academic position; possibly back in my coronal physics roots, but funding was tight, and I hadn’t done enough networking during my PhD to find a position (I had been too busy scoping out the parties and free booze at the conference dinners).

So there I was, with all the qualifications in the world with no career prospects and a liaison officer who deemed it necessary to advise me to forget the last four years of my academic career. It was a low point in my life, especially as only a few months earlier I had been enjoying one of the highest points in my life: graduating as a doctor in Solar Physics.

Fortunately for me, I had another option. My girlfriend (now lovely wife) was living in the US, and although searching for a job in the UK was a priority for us (we were planning on living in the UK at the time), I knew I could try my luck in the US as well. So after a few months of searching, I cancelled my Job Centre subscription and moved to the other side of the Atlantic.

I had just become a part of the UK’s “brain drain” statistic. I had qualifications, but I was in a weird grey area where companies thought I was over-qualified and funds were in short supply for me to return to academic research.

A lot has happened since those uncertain postdoc times, and although I tried (and failed) to pick up my academic career in solar physics in the US (it turns out that even the sunny state of California suffers from a lack of solar physics funding), the job climate was different. Suddenly, having a PhD was a good thing and the world was my oyster again.

To cut a long story short, I’m happily married, we own five rabbits (don’t ask), we live just north or Los Angeles and I have a dream job with Discovery Channel, as a space producer for Discovery News.

Although I’d like to think that if I was currently living in the UK, I might have landed an equivalent career, I somehow doubt I would be as happy as I am right now with how my academic qualifications helped me get to where I am today.

Why am I bringing this up now? Having just read about Stephen Hawking stepping down as Lucasian professor of Mathematics at Cambridge University and the Guardian’s report about the risk of losing British thinkers overseas, I wonder if employment opportunities have improved since 2006. What’s most worrying is that there appears to be this emphasis on making money as quickly as possible, rather than pursuing academic subjects. However, in my experience, having a PhD doesn’t mean you can even land a job in industry, you might be over-qualified.

Giving up on that tradition of deep intellectual discovery in favour of immediate economic benefit is a huge mistake. You lose the gem of creative, insightful, long-term thinking. That is what Britain has done so spectacularly in the past, and to give that up is a tragedy.” –Neil Turok

A special thanks to Brian Cox, who tweeted the inspiration to this post.

Deconstructing Doomsday

Alex Young in front of the cameras in the post-Apocalyptic setting of a Brooklyn building site.

Alex Young in front of the cameras in the post-Apocalyptic setting of a Brooklyn building site.

The funny thing about being involved in a doomsday documentary is trying to find a suitable balance between entertainment and science. This is the conclusion I reached after the interview I did for KPI productions in New York for the upcoming 2012 documentary on the Discovery Channel last week (just in case you were wondering why Astroengine.com was being a little quiet these last few days).

Apparently, the Apocalypse will be very dusty.

Apparently, the Apocalypse will be very dusty.

Naturally, the production team was angling for what it might be like to be hit by a “killer” solar flare, what kinds of terror and destruction a brown dwarf could do to Earth and what would happen if our planet’s magnetic poles decided to do a 180°. It’s always fun to speculate after all. However, I wasn’t there to promote half-baked theories of 2012 doom, I was there to bring some reality to the nonsensical doomsday claims. But with real science comes some unexpected concerns for the safety of our planet — not in 2012, but sometime in the future.

An added bonus to my NYC trip was meeting the awesome Alex Young, a solar physicist from NASA’s Goddard Space Flight Center. Alex was asked to New York for the same reasons I was, but he has a current and comprehensive understanding of solar dynamics (whereas my solar physics research is so 2006). He actually works with SOHO data, a mission I have massive respect for.

Alex Young and myself... very excited about doomsday.

Alex Young and myself... very excited about doomsday.

My interview was carried out on Wednesday morning, and Alex’s was in the afternoon. The KPI guys were great, a joy to be involved in such a professional project. The documentary producer, Jonathan, asked me the questions in a great location, a huge Brooklyn building that was undergoing renovation. Very dusty with a post-apocalyptic twist. If I was going to shoot a movie about the end of the world, this building would be it.

The KPI documentary will certainly be very different from the Penn & Teller: Bullshit! episode I was involved with, but it was just as much fun, if not more so (it was like a day-long science fest).

Of particular note was Alex’s sobering words about the woeful lack of funds in solar physics (i.e. Earth-damaging solar flares and CMEs). I hope his closing statement about NOAA space weather prediction funding makes the final cut; it was nothing less than chilling.

Jon and Sarah from KPI on the set.

Jon and Sarah from KPI on the set.

Although we both hammered home the point that the fabled Earth-killing solar flare wont happen in 2012 (let’s face it, our Sun is still going through an epic depression, why should solar maximum be anything spectacular?), it is probably the one theory that holds the most scientific merit. In fact, as both Alex and I agreed, for a civilization that depends on sensitive technology in space and on the ground, we really need to prepare for and understand solar storms far better than we do at present.

I won’t go into any more details, but the documentary will be on the Discovery Channel in November, so I’ll give plenty of warning to fire up those DVRs.

Thank you Sarah, Jonathan and the rest of the crew from KPI for making the New York visit so memorable…