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Auroras are some of Earth’s most spectacular natural phenomena. Travelers come from far and wide to see the incredible Northern Lights and wonder at their beauty. Once thought to be magical in nature, most science fans understand that the lights are formed by the solar wind interacting with our magnetosphere. But did you know they also make sounds?

This isn’t new news – researchers have thought there was a connection for over a decade. In fact, a now Emeritus Professor at the University of Aalto, Unto K. Laine, first recorded what he thought to be auroral sounds back in 2004. They sounded like a series of pops and cracks, but Dr. Laine eventually linked up a series of them to a set of temperature changes recorded by the Finnish Meteorological Institute.

With that data, which was published in a paper in 2016, Dr. Laine was finally able to draw a possible connection that he had been studying. He believed that the sounds were actually caused by electrical discharges across a “temperature inversion layer” of air about 70 meters off the ground. The data lent credence to this idea.

Recording of some of the sounds captured by Dr. Liane.
Credit – Aalto University YouTube Channel / Unto Laine

Those electrical discharges aren’t necessarily visible; however, the pops still happen despite the lack of a visible cause. What’s more – they happen a lot more often than there are visible causes. To Dr. Laine, at least, this means that auroras are much more common than typically thought, even if they aren’t necessarily visible.

Tracking auroras themselves requires geomagnetic readings, and plenty of those matched up with the timing of the auroral sounds Dr. Laine collected in his latest recording near the village of Fiskars, the original home of the multinational company of the same name. Using geomagnetic data alone, Dr. Laine could estimate when the sounds would happen with 90% accuracy. The 60 best sounds he recorded were all directly tied to geomagnetic events.  

Spectacular image of a swirling aurora in the night sky.
Spectacular image of a swirling aurora in the night sky.
Credit – Jason Ahrns

So what does all this data collection actually mean? The simplest explanation is that the popping and cracking sounds recorded by Dr. Laine and numerous others are clearly tied to the same geomagnetic processes that create the visible auroras. However, the precise location and cause of the sounds are still being debated, though a dramatic temperature variant about 70 m off the ground could conceivably create an electrostatic discharge that could be picked up as a click.  

But the most surprising finding, at least according to Dr. Laine, is just how often these sounds occur. The sounds that he describes as akin to “ice cracking or someone walking a dog” are caused by the same geomagnetic forces that create the famous lights and are much more common than the lights themselves. So if you’re ever inspired to see this world-famous natural phenomenon, it might be a good idea to bring along a recording device. Then, if you don’t get a chance to see the lights themselves, you’ll at least be able to hear them.

Learn More:
Aalto University – The aurora borealis can be heard even when they can’t be seen
UT – Mysterious Sounds Made by the Aurora Borealis
UT – The Northern and Southern Lights – What is an Aurora?
UT – An 1874 Citizen Science Project Studying the Aurora Borealis Helped Inspire Time Zones

Lead Image:
Image of some spectacular auroras in Finland.
Credit – Seppo Fagerlund

The post Even if you can’t see Auroras, You Can Sometimes Hear Them. Here’s What They Sound Like appeared first on Universe Today.

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You Can Detect Tsunamis as They Push the Atmosphere Around



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Anyone who’s ever lived along a coastline or been at sea knows the effects of tsunamis. And, they appreciate all the early warning they can get if one’s on the way. Now, NASA’s GNSS Upper Atmospheric Real-time Disaster and Alert Network (GUARDIAN) is using global navigation systems to measure the effect these ocean disturbances have on our atmosphere. The system’s measurements could provide a very effective early warning tool for people to get to higher ground in the path of a tsunami.

Earthquakes and undersea volcanic eruptions often trigger tsunamis. Essentially, those tectonic events displace huge amounts of ocean water. During the resulting tsunami, huge areas of the ocean’s surface rise and fall. As they do, the ocean movement displaces the overlying column of air. That sets off ripples in the atmosphere. Think of it as if the air is responding by creating its own tsunami. It actually does that in response to fast-moving storms and their squall lines. Meteorologists call those reactions “meteotsunamis.” They can push water around into dangerous waves, which then cause flooding and other damage. That’s very similar to tsunamis generated by earthquakes.

What NASA’s Doing to Predict Tsunamis

Weather forecasters can generally predict bad weather leading to meteotsunamis, but that’s not the case for earthquakes and underwater volcanoes and the tsunamis they trigger. So, the NASA project aims to provide advance notice after a temblor or a volcanic eruption.

The GUARDIAN system taps into a constant data stream emitted by clusters of global positioning satellites and other wayfinding stations orbiting Earth. They give real-time information about changes in water heights in the ocean and surface measurements of land masses. Those data-rich radio signals get collected by ground stations and sent to NASA Jet Propulsion Laboratory. There, it gets analyzed by the Global Differential network, which constantly improves the real-time positional accuracy of features on the planet.

So, when a tectonic event happens, the system is alerted to look for changes in the air masses over the oceans. Displaced ripples in the air move out in all directions as low-frequency sound and gravity waves. Those vibrations rush to the top of the atmosphere within just a few minutes. There, they crash into the charged particles of the ionosphere. That distorts signals from the GPS satellites, and those distorted signals tell the system that something’s going on down below.

This animation shows how waves of energy from the Tohoku-Oki earthquake and tsunami of March 11, 2011, pierced Earth’s ionosphere in the vicinity of Japan, disturbing the density of electrons. These disturbances were monitored by tracking GPS signals between satellites and ground receivers.
Credits: NASA/JPL-Caltech

Normally navigational systems would correct for the distorted signals because they aren’t useful to their users, according to Léo Martire, who works on the GUARDIAN project. “Instead of correcting for this as an error, we use it as data to find natural hazards,” he said.

Early Warning is the Key

The most active tectonic region on our planet is the area known as the Ring of Fire. It’s basically a large ring of volcanically and tectonically active regions in the Pacific Ocean basin. About 78 percent of tsunamis between 1900 and 2015 occurred there.

Most of us remember the tsunami that hit Japan after a magnitude 9.0 earthquake hit just off the coast in 2011. That event devastated 70 kilometers of coastline, destroyed towns and villages, killed hundreds of people, and shut down the Fukushima nuclear power plant.

Damaged village in Japan in the wake of the tsunami onf 2011. Photo: Katherine Mueller, IFRC
Damaged village in Japan in the wake of the tsunami onf 2011. Photo: Katherine Mueller, IFRC

One of the most damaging tsunamis occurred on the Big Island of Hawai’i on April 1st, 1946. An earthquake off the Aleutian Islands triggered the tsunami that crushed a small village in Alaska and struck California. It also reached out and touched the Hawaiian coast near Hilo. 50-foot waves crashed into the island, taking out buildings, and
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These New Computer Simulations of the Sun are Hypnotic



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It’s almost impossible to over-emphasize the primal, raging, natural power of a star. Our Sun may appear benign in simple observations, but with the advanced scientific instruments at our disposal in modern times, we know differently. In observations outside the narrow band of light our eyes can see, the Sun appears as an enraged, infuriated sphere, occasionally hurling huge jets of plasma into space, some of which slam into Earth.

Jets of plasma slamming into Earth isn’t something to be celebrated (unless you’re in a weird cult); it can cause all kinds of problems.

Some scientists are dedicated to studying the Sun, partly because of the danger it poses. It would be nice to know when the Sun is going to throw a tantrum and if we’ll be in its path. We have multiple spacecraft dedicated to studying the Sun in detail. The Solar Dynamics Observatory (SDO,) the Solar and Heliospheric Observatory (SOHO,) and the Parker Solar Probe are all engaged in solar observations.

The Solar Dynamics Observatory (l), the Solar and Heliospheric Observatory (m) and the Parker Solar Probe (r.) Image Credits: Left: NASA. Middle: By Cgruda - nasa.tif, Public Domain, Right: NASA
The Solar Dynamics Observatory (l), the Solar and Heliospheric Observatory (m) and the Parker Solar Probe (r.) Image Credits: Left: NASA. Middle: By Cgruda – nasa.tif, Public Domain, Right: NASA

The Sun’s mighty magnetic fields play a huge role in the Sun’s outbursts, though scientists are still working out the details. A new study published in Nature Astronomy is helping scientists understand the magnetic fields in more detail. It’s titled “Numerical evidence for a small-scale dynamo approaching solar magnetic Prandtl numbers,” and the first author is Jörn Warnecke, a senior postdoctoral researcher at Max Planck Institute for Solar System Research (MPS.)

The solar dynamo is responsible for the Sun’s magnetic fields. The solar dynamo has two parts: the small-scale dynamo and the large-scale dynamo. The problem is solar researchers have not been able to model them yet, at least not in full detail. Problematically, they can’t confirm that a small-scale dynamo (SSD), which is ubiquitous in astrophysical bodies throughout the Universe, can even be generated by the conditions in the Sun. That’s obviously a big problem because a small-scale dynamo would have a huge influence on the Sun’s behaviour.

“A powerful SSD may potentially have a large impact on the dynamical processes in the Sun,” the authors write in their paper. “Hence, it is of great importance to clarify whether or not an SSD can exist in the Sun.”

What’s a small-scale dynamo?

A small-scale dynamo amplifies magnetic fields on scales smaller than the driving scale of turbulence in diverse astrophysical media, according to this study. You can quickly go down a rabbit hole trying to understand this in detail. But in fairly simple terms, an SSD requires much stronger turbulence than a large-scale dynamo.

It all comes down to what’s called a Prandtl number (PrN,) and what the Sun’s Prandtl number tells us about its properties. The Sun’s PrN tells us how quickly its magnetic field variations and its velocity even out. The Sun has a low PrN, and for a long time, scientists who study the Sun thought that the low number prevented the development of an SSD.

But this research shows otherwise. It’s based on massive computer simulations on petascale supercomputers in Finland and Germany.

This figure from the study is a visualization of flow and SSD solution. The flow speed is on the left, and the magnetic field strength is on the right. This simulation run featured a very low Prandt number. Did you miss our previous article…

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If You’re Going to Visit Venus, Why Not Include an Asteroid Flyby Too?



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A recent study submitted to Acta Astronautica examines the prospect of designing a Venus mission flight plan that would involve visiting a nearby asteroid after performing a gravity assist maneuver at Venus but prior to final contact with the planet. The study was conducted by Vladislav Zubko, who is a researcher and PhD Candidate at the Space Research Institute of the Russian Academy of Science (RAS) and has experience studying potential flight plans to various planetary bodies throughout the solar system.

“The motivation behind this study was to enhance the efficiency and success rate of Venus missions by including an asteroid flyby in the flight scheme,” Zubko tells Universe Today. “As widely acknowledged, Venus’s particular atmospheric conditions make a mission to the planet a challenging prospect, with designing a spacecraft and achieving a landing being notably difficult tasks. Additionally, Venus’ slow rotation, taking 243 Earth days, restricts potential landing sites on its surface.”

For the study, Zubko examined the potential for conducting flybys of 117 asteroid candidates with diameters greater than 1 km (0.62 miles) using the Solar System Dynamics catalog from NASA JPL, referring it his plan as an Earth-Venus-Asteroid-Venus flight plan that could potentially occur using launch dates between 2029 and 2050. Using a variety of calculations, Zubko found 53 mission scenarios with 35 asteroid targets between 2029 and 2050 where a spacecraft could encounter an asteroid while en route to Venus.

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Graph from the study displaying the number of mission scenarios per year between 2029 and 2050. (Credit: Zubko (2023), Figure 4)

Zubko tells Universe Today he believes the “most promising” asteroids for scientific exploration for these mission scenarios are 3554 Amun due to its a M-class (also called M-type) classification, 3753 Cruithne since it exhibits a 1:1 orbital resonance ratio with the Earth, and 5731 Zeus since it’s the largest asteroid examined in the study at 5.23 km (3.25 miles) in diameter. M-class asteroids like 3554 Amun are intriguing targets for scientific exploration—and potential resources for Earth—since they are comprised largely of metal phases (i.e., iron-nickel) and are believed to be the source of iron meteorites that have been found on Earth and Mars. For 3753 Cruithne, a 1:1 orbital resonance with Earth means it completes one orbit around the Sun for every one orbit of Earth. Essentially, their orbital periods are exactly the same, otherwise known as a co-orbital object.

Zubko also mentions asteroids 2002 FB3 and 2002 SY50 as potential targets due to their closest approaches to Earth at less than 0.05 astronomical units (AU), or approximately 7.5 million km (4.6 million miles). Along with identifying asteroid candidates for flybys, Zubko also analyzed a potential flyby of the 2P/Eucke comet and potential landing sites on Venus once the spacecraft finally arrives there.

“We believe that conducting an asteroid flyby while en route to Venus is of great importance as it can significantly enhance the scientific value of a mission to Venus, especially in terms of landing on its
surface,” Zubko tells Universe Today. “In addition, an impulse-free flyby of an asteroid can help minimize the mission’s costs by combining the exploration of both Venus and the asteroid. The study of asteroids is a high priority for science in general due to their relevance in understanding the history of our Solar System as well as the planetary defense mechanisms (if studying hazardous asteroids).”

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Image of Venus captured by NASA’s Mariner 10 spacecraft in February 1974 as it left the
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