low frequency radio waves

How Humans Change Space Itself

It’s no surprise that humans influence the surface of our planet, but our reach can go farther than that. Humans affect space, too.

We know storms from the sun can naturally change the space environment around Earth, which can have an impact on satellites and power grids.

Scientists now know that Cold War era nuclear tests in the 1950s caused similar effects.

Particles around Earth are organized into layers known as radiation belts. These 1950s tests created a temporary extra layer of radiation closer to Earth. 

The effects of this could be seen all around the world. Aurora appeared at the equator instead of the poles, utility grids in Hawaii were strained, and in some cases, satellites above test sites were affected. 

Some types of communications signals can also affect Earth’s radiation belts

Very low-frequency waves, or VLFs, are used for radio communications. They are often used to communicate with submarines, because these waves can penetrate deep into the ocean. 

The waves can also travel far into the space environment around Earth. When these waves are in space, they affect how high-energy particles move, creating a barrier against natural radiation.

The outer edge of this radio-wave barrier corresponds almost exactly the inner edge of Earth’s natural radiation belts – meaning it could be human activity that at least partly shapes this natural radiation around Earth.  

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Leading U.S. solar scientists today highlighted research activities that will take place across the country during next month’s rare solar eclipse, advancing our knowledge of the Sun’s complex and mysterious magnetic field and its effect on Earth’s atmosphere.

Experts at the National Science Foundation (NSF), National Aeronautics and Space Administration (NASA), and National Center for Atmospheric Research (NCAR) provided details at this morning’s press conference about the array of technologies and methodologies that will be used to obtain unprecedented views of the Sun on Aug. 21. The experiments, led by specialized researchers, will also draw on observations by amateur skywatchers and students to fill in the picture.

“This total solar eclipse across the United States is a fundamentally unique opportunity in modern times, enabling the entire country to be engaged with modern technology and social media,” said Carrie Black, an associate program director at NSF who oversees solar research. “Images and data from potentially as many as millions of people will be collected and analyzed by scientists for years to come.”

“This is a generational event,” agreed Madhulika Guhathakurta, NASA lead scientist for the 2017 eclipse. “This is going to be the most documented, the most appreciated eclipse ever.”

The scientific experiments will take place along the path of totality, a 70-mile wide ribbon stretching from Oregon to South Carolina where the Moon will completely cover the visible disk of the Sun. Depending on the location, viewers will get to experience the total eclipse for as long as 2 minutes and 40 seconds. It will take about an hour and a half for the eclipse to travel across the sky from the Pacific Coast to the Atlantic.

NASA and other organizations are reminding viewers to take eye safety precautions because it is not safe to look at the Sun during an eclipse except during the brief total phase, when the Moon completely blocks the Sun’s everyday bright face, which will happen only if you are within the path of totality.

For scientists, the celestial event is a rare opportunity to test new instruments and to observe the elusive outer atmosphere of the Sun, or solar corona, which is usually obscured by the bright surface of the Sun. Many scientific questions focus on the corona, including why it is far hotter than the surface and what role it plays in spewing large streams of charged particles, known as coronal mass ejections, that can buffet Earth’s atmosphere and disrupt GPS systems and other sensitive technologies.

Black noted that the Moon will align exactly with the Sun’s surface, which will enable observations of the entire corona, including very low regions that are rarely detectable. Obtaining observations from the ground is particularly important, she explained, because far more data can be transmitted than would be possible from space-based instruments.

“The Moon is about as perfect an occulter as one can get,” she said. “And what makes this an even more valuable opportunity is that everyone has access to it.”

In addition to training ground-based instruments on the Sun, scientists will also deploy aircraft to follow the eclipse, thereby increasing the amount of time they can take observations.

An NCAR research team, for example, will use the NSF/NCAR Gulfstream-V research aircraft to take infrared measurements for about four minutes, helping scientists better understand the solar corona’s magnetism and thermal structure. Scientists with the Southwest Research Institute in Boulder will use visible and infrared telescopes on NASA’s twin WB-57 airplanes in a tag-team approach, enabling them to get a unique look at both the solar corona and Mercury for about eight minutes. The goal is to better understand how energy moves through the corona as well as learning more about the composition and properties of Mercury’s surface.

Scientists will also study Earth’s outer atmosphere during the eclipse. The ionosphere is a remote region of the atmosphere containing particles that are charged by solar radiation. Disturbances in the ionosphere can affect low-frequency radio waves. By blocking energy from the Sun, the eclipse provides scientists with an opportunity to study the ionosphere’s response to a sudden drop in solar radiation.

For example, a Boston University research team will use off-the-shelf cell phone technology to construct a single-frequency GPS array of sensors to study the ionospheric effects of the eclipse. This project could lay the foundation for using consumer smartphones to help monitor the outer atmosphere for disturbances, or space weather events, caused by solar storms. Another experiment, run by researchers at the University of Virginia and George Mason University, will use transmitters broadcasting at low frequencies to probe the response of regions of the ionosphere, while a Virginia Tech team will use a network of radio receives and transmitters across the country to observe the ionosphere’s response during the eclipse.

Citizen scientists also are expected to play a major role in taking valuable observations during the eclipse.

“This is a social phenomenon, and we have a significant opportunity to promote this and do all the science that we can,” Guhathakurta said.

The Citizen Continental-America Telescopic Eclipse (CATE) Experiment by the National Solar Observatory and the University of Arizona, for example, will rely on volunteers from universities, high schools, informal education groups, and national labs for an eclipse “relay race.” Participants spaced along the path of totality will use identical telescopes and digital camera systems to capture high-quality images that will result in a dataset capturing the entire, 93-minute eclipse across the country. And a project led by the University of California, Berkeley, will assemble a large number of solar images, obtained by students and amateur observers along the eclipse path to create educational materials as part of the Eclipse Megamovie project.

“As these projects show, the eclipse will place the Sun firmly in the forefront of the national eye,” said Scott McIntosh, director of NCAR’s High Altitude Observatory. “This is a unique opportunity to communicate the fact that our star is complex, beautiful, and mysterious. At the same time, it is more critical than ever to study it, as solar activity can pose significant threats to our technologically driven society.”

Humans Accidentally Created a Protective Bubble Around Earth
The interaction between radio transmissions and high-energy particles in space sometimes forms a shield around the planet, protecting it from dangerous cosmic phenomena.
By Marina Koren

A pair of NASA space probes have detected an artificial bubble around Earth that forms when radio communications from the ground interact with high-energy radiation particles in space, the agency announced this week. The bubble forms a protective barrier around Earth, shielding the planet from potentially dangerous space weather, like solar flares and other ejections from the sun.

Earth already has its own protective bubble, a magnetosphere stretched by powerful solar winds. The artificial bubble that NASA found is an accident, an unintended result of the interplay between human technology and nature. When humans want to communicate with submarines near the surface of the ocean, they use a type of radio communication known as very low frequency waves, or VLF, transmitted from stations on the ground. Some of the waves can stretch all the way out into Earth’s atmosphere and beyond, where they affect the movement of the radiation particles bouncing around in the region. Sometimes, the interaction between VLF and these particles creates a barrier that can be seen by spacecraft orbiting the planet.

This scale that compares the length of different electromagnetic radiation waves to marine creatures and objects might be helpful to people studying or teaching basic physics. 

A high-energy gamma ray’s wavelength is shorter than an atom’s width. A high-frequency, lower energy radio wavelength, meanwhile, can fit three blue whales lined up from snout to fluke. At the longest end of the spectrum sit extremely low frequency radio waves, which can have a wavelength more than 6,000 miles long and are naturally produced by lightning and stars. These can penetrate ocean water and have been used to communicate with submarines.

See a larger version of this graphic here. Courtesy of brookhavenlab, which uses high-energy X-rays to explore materials at the nanoscale.

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NASA mission surfs through waves in space to understand space weather

The space surrounding our planet is full of restless charged particles and roiling electric and magnetic fields, which create waves around Earth. One type of wave, plasmaspheric hiss, is particularly important for removing charged particles from the Van Allen radiation belts, a seething coil of particles encircling Earth, which can interfere with satellites and telecommunications. A new study published in Journal of Geophysical Research using data from NASA’s Van Allen Probes spacecraft has discovered that hiss is more complex than previously understood.

The new study looked at a newly identified population of hiss waves at a lower frequency than usually studied. These low-frequency hiss waves are particularly good at cleaning out high-energy particles – those that can cause damage to satellites – from the radiation belts.

The authors of the study noticed that low-frequency waves are actually a separate and unique population, tending to cluster in different regions around Earth compared to their high-frequency counterparts.

“You want to know the state of the Van Allen radiation belts so you know how long satellites will last, and part of that is understanding the state of the waves,” said David Malaspina, lead author and researcher at the Laboratory for Atmospheric and Space Physics in Boulder, Colorado. “We found the low frequency hiss interacts more effectively with higher energy electrons and can knock those electrons out of the belts more efficiently.

In order to protect satellites, NASA wants to better understand this region of near-Earth space. The space environment surrounding Earth is filled with plasma – clouds of charged particles – whose movement is determined not only by gravity, but also by electromagnetics. Constantly changing electric and magnetic fields rolling through space interact with the particles, creating waves in the plasma (like hiss), which are integral to sculpting the near-Earth space environment.

To understand the ever-changing near-Earth particle ecosystem and make better space weather predictions, scientists create models of the plasma waves. Incorporating this new information will make for better simulations. Homayon Aryan, researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said, “Most current wave models do not include this low frequency population of hiss waves. This is definitely an improvement and will allow us to understand the region better and compare theoretical predictions with observations more effectively.”

Hiss is aptly named: its typical frequencies are right in the middle of the audible range, and it sounds like static noise when picked up by radio receivers. No one knows with certainty how low-frequency hiss waves originate, but current theories suggest that they form when charged particles are injected into the region of cold near-Earth plasma known as the plasmasphere.

NASA’s Van Allen Probes spacecraft study hiss and other plasma waves as part of their work to understand the complex interactions of particles and electromagnetic fields in near-Earth space.

What’s Killing People in Day 5? (spoilers through Episode 5)

I don’t think it was the TV signal. Partially because that would leave the finale to be mostly denouement (and there needs to be something else), but mostly because the TV signal explanation doesn’t really line up with the observed effects.

Here’s what I have inferred so far:

1. People are dying once they reach slow-wave sleep, in which brain activity is predominated by delta waves, which are brain-wide oscillations that range in frequency from .1 to 4 Hz. This is the stage of sleep you reach shortly after you doze off, and you generally pass through a cycle of going into and then back out of this stage before you begin dreaming (REM).

This conclusion is supported by the fact that people beginning to doze off don’t die (they can be awakened just fine), people experiencing microsleeps or waking dreams don’t die (see Jake in just about every episode), and people who are thrown directly into REM (dreaming) sleep don’t die. It’s also supported by the fact that birds and mammals have died (both experience slow-wave sleep) but sharks (which do not experience slow-wave sleep) have not.

It may also be supported by the fact that Lex mentioned brains needing to reach a certain “frequency” in order to be killed by the phenomenon, because that suggests that a certain pattern of brain oscillations is what’s being interfered with.

2. There is a safe (or relatively safe) zone near the antipodes of the general area of Texas. The man at the broadcast station in Dallas mentioned that there were rumors of “safe sleep zones” in places like Malaysia and Australia. These landmasses are about as close as one can get to being on the opposite side of the world from Texas (the actual antipodes of which lie in the Indian Ocean). It appears that whatever is being transmitted from Texas and killing people is weakened enough by going all the way around or through the Earth that it has a lower chance of killing people in these areas.

3. People don’t appear to have been saved by bad TV reception. I’d expect that in some apocalyptic scenario, there’d be at least a fraction of government personnel and homespun crackpots who’d have fallout-hardened bunkers to hide in. And yet, we haven’t heard from any people who napped safely behind six feet of concrete. We also haven’t seen any locals who were protected from a majority of the signal by terrain features that block TV reception, like the various mountain ranges and “uplifts” dotted across Texas.

So, what I expect here is that it’s not the TV signal that was killing people. If it were, then people would be surviving in places with bad TV reception (even if it’s being bounced to every TV tower in the world, there are always spots) and not just at the antipodes of Texas. Furthermore, I think it’s unlikely that a signal in the MHz frequency range (as TV signals are) would interfere with a brain phenomenon on the order of single-digit Hz.

I do think it’s suspicious that the warning broadcast began around the time the phenomenon did, but I think that could be explained by the fact that someone out there, whom we haven’t met yet, knew this phenomenon was about to occur and called Jen Brown’s character to wake her up. That alone makes me suspect that whatever happened here was the result of a secret project, potentially one with unintended side effects—like killing people.

This also means that Ellis’s group is under the mistaken impression that it’s safe to go to sleep, which is bad. I’ll get back to that later, though.

I hear a hypothetical person asking, “But what do you think has been killing people then, if not the TV broadcast?”

I’m glad you asked, hypothetical person. My idea is below the cut for length.

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