Solar storm – 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.

Did a Solar Storm Detonate Dozens of Vietnam War Mines?

Some 25 underwater mines mysteriously exploded in the summer of 1972. A newly declassified report points its finger at a surprising culprit: the sun.

Something very strange happened on Aug. 4, 1972 in the waters near Vietnam. Dozens of undersea mines detonated for seemingly no reason. The matter was classified, as was a report trying to get to the bottom of what happened. Initial hypotheses focused on a malfunctioning self-destruct feature meant to prevent lost mines from posing an underwater hazard for decades after hostilities were over, but there was no corroborating evidence. Soviet subs might have accounted for one or two, but not systematic detonations across the whole minefield, not to mention their defensive countermeasures.

But one of the suggestions seemed to very neatly explain the observed phenomenon. The mines were magnetic, meaning that they reacted to the natural magnetism of metals in ships’ hulls and the changes in the strengths of their magnetic fields as those ships approached. It was an old, reliable technology and it would’ve taken a massive magnetic event to have set them off. And wouldn’t you know it, some of the most intense solar activity on record happened in that exact time frame, causing numerous power surges and telegraph outages across North America.

On the day Navy aircraft saw the mines go off, the sun erupted in what’s known as an X-class flare, a burst of energy more than 10,000 times more powerful than the high end of typical solar emissions. With the path to Earth cleared by supercharged solar winds, the resulting coronal mass ejection hit Earth in just 14.6 hours instead of the typical three days and caused massive magnetic and electrical disruptions in the atmosphere, quite possibly powerful enough to set off detectors on the underwater mines off the coast of Hon La Port as the plasma slammed into our planet.

So, case closed? Not exactly. We measure the intensity of the disruption in the Earth’s magnetic field caused by solar storms in negative nTs, or nano-Teslas. By itself, a nano-Tesla isn’t much. Your run of the mill fridge magnet is a million times stronger, although it’s only spread over tens of square centimeters, instead of millions of square kilometers like the fraction of a coronal mass ejection that hits Earth and lingers in the upper layers of the atmosphere. In 2003, a massive flare hit us with a magnetic disruption measuring almost -400 nT without melting anything down, although it did cause problems with air traffic.

By comparison, the ejection in 1972 measured a third of that at just -125 nT. Was it really strong enough to set off underwater mines? We’ll probably never know for sure, but it’s still entirely possible. Over the decades, we’ve learned much more about solar storms and what they can do, developed better shielding and early warning systems, more sophisticated equipment, and unwittingly created a shield of radio emissions to reroute charged particles from Earth. It’s quite plausible that older, less insulated technology was more sensitive to major solar storms and the trigger mechanisms for those mines were just one example.

[This article originally appeared on World of Weird Things]

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

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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!