“Space weather is thought by many scientists, lay people, and policy makers as something that is driven only by the Sun and its outputs,” said Dan Baker director of the University of Colorado’s Laboratory for Atmospheric and Space Physics, via email to Seeker. “What we wanted to show is that humans have in the past — and may into the future — cause important effects that can also be rightly considered to be space weather.”
The paper written by Baker and several colleagues, titled “Anthropogenic Space Weather” and published in the journal Space Science Reviews, outlines how human activity has affected the region around our planet — the near-Earth space where satellites and astronauts on the International Space Station reside. Some human activities have created changes in the magnetosphere and the radiation belts that surround Earth. Some effects have been short-term, while others may have created permanent environmental alterations.
Baker said that the goal of this research was to map out “the broader view that will help all of us deal with — and prepare for — space weather in its many forms.”
Scientists have been studying the effects of the sun on Earth’s atmosphere ever since geomagnetic disturbances started causing telegraph outages in the 19th century. But recently declassified data on high-altitude nuclear explosion tests in the 1950s and 60s details the research that was being done at the time in order to understand the effects this human activity was having on the space environment.
The nuclear tests were carried out by the United States and the Soviet Union. From 1958 to 1962 explosives were detonated at heights from 16 to 250 miles above the planet’s surface. The effects were similar to natural effects from the sun, as the explosions created an expanding gas of electrically charged particles that created a geomagnetic disturbance, sometimes distorting Earth’s magnetic field lines and inducing an electric field on the surface. This sometimes caused power and communications outages, while other nuclear tests produced artificial auroras that could be seen around the world.
Other human impacts on the space environment include chemical release experiments and high-frequency wave heating of the ionosphere.
“The tests were a human-generated and extreme example of some of the space weather effects frequently caused by the sun,” said Phil Erickson, assistant director at MIT’s Haystack Observatory, Westford, Massachusetts, and co-author on the paper. “If we understand what happened in the somewhat controlled and extreme event that was caused by one of these man-made events, we can more easily understand the natural variation in the near-space environment.”
Another, unexpected impact of the high-altitude nuclear tests came from the electromagnetic pulse (EMP) produced by the blasts, which can have devastating effects over a large geographic area. The burst of electromagnetic radiation created by nuclear explosions and the resulting rapidly changing electric and magnetic fields can produce damaging current and voltage surges in electrical grids and electronics.
Given mankind’s current reliance on electronics, the researchers wrote that “the EMP generated by a high altitude nuclear explosion is one of a small number of threats that can hold our society at risk of catastrophic consequences,” since the EMP signal will cover the wide geographic region.
“This broad band, high amplitude EMP, when coupled into sensitive electronics,” the paper says, “has the capability to produce widespread and long lasting disruption and damage to the critical infrastructures that underpin the fabric of U.S. society.”
But one type of human activity seems to have had the unintended consequence of actually helping protect Earth from harmful radiation.
VLF signals are transmitted from ground stations at huge powers to communicate with submarines deep in the ocean. While these waves are intended for communications below the surface, they also extend out beyond our atmosphere, shrouding Earth in a VLF bubble. This bubble can be seen by spacecraft high above Earth’s surface, such as NASA’s Van Allen Probes, which study electrons and ions in the near-Earth environment.
The probes have detected that the outward extent of the VLF bubble corresponds almost exactly to the inner edge of the Van Allen radiation belts. Baker called this inner edge an “impenetrable barrier,” and speculates that if there were no human VLF transmissions, the boundary would likely stretch closer to Earth. In fact, the researchers compared the modern extent of the radiation belts with satellite data from the 1960s, when VLF transmissions were more limited, and found that the bubble had expanded.
The scientists suggested that VLF transmissions may serve as a way to remove excess radiation from the near-Earth environment. Plans are already underway to test VLF transmissions in the upper atmosphere to see if they could remove excess charged particles from intense, naturally induced space weather.
The researchers did stress that despite these human impacts, space weather is dominated by natural phenomena from the sun. Our local star sends out millions of high-energy particles, called the solar wind, which races out across the solar system before reaching Earth. Our planet’s magnetosphere provides a protective magnetic field that surrounds us, deflecting most of the charged particles.
During stronger solar storm events such as solar flares and coronal mass ejections some particles can make their way into near-Earth space and can impact our satellites by damaging onboard electronics and disrupting communications or GPS signals. These particles, along with electromagnetic energy that accompanies them, can also cause auroras, while changes in the magnetic field can induce currents that damage power grids.
These natural events from the sun pose a risk mainly to the advanced technology we’ve developed. Even in the largest events, no “killer” solar storm that would strip away Earth’s atmosphere is possible. The relatively thick atmosphere and the planet’s magnetosphere can stop the harmful radiation.
But even if the VLF radio emissions could help protect Earth, the consensus is that it is best not to interfere with natural phenomena, as any human-caused changes to this region could ultimately have disastrous effects. Even the further expansion of this protective VLF bubble could have consequences in the future.
Read more at Discovery News