Probability Of Catastrophic Geomagnetic Storm Lower Than Estimated

Three mathematicians and a physicist from the Universitat Autònoma de Barcelona (UAB), the Mathematics Research Centre (CRM) and the Barcelona Graduate School of Mathematics (BGSMath) propose a mathematical model which allows making reliable estimations on the probability of geomagnetic storms caused by solar activity.

The researchers, who published the study in the journal Scientific Reports (of the Nature group) in February, calculated the probability in the next decade of a potentially catastrophic event for the Earth’s telecommunications, such as the one which occurred between the end of August and beginning of September 1859, known as the “Carrington Event.” That year, astronomer Richard C. Carrington observed the most powerful geomagnetic storm known up to date. According to this new research, the probability of a similar solar storm occurring in the following decade ranges from 0.46% to 1.88%, far less than the percentage estimated before. “In 2012, the results reported in scientific literature estimated the probability to be around 12%, ten times more than our more pessimistic estimation,” David Moriña, first author of the study and postdoctoral researcher explains. “Our model is more flexible than previous ones and it also includes the model used for the previous estimations as a specific case,” Moriña adds.

The intensity of solar surface perturbations such as flares and coronal mass ejections affecting the Earth’s magnetosphere has been measured since 1957 using the “Dst” index, which centralises the values collected every hour in stations located across the globe. Normally, the value of this parameter ranges from -20 to +20 nT (nanoteslas, one billionth of a tesla unit; a tesla unit can be compared to the magnetic flux density generated by a powerful loudspeaker). It is estimated that the Dst index associated with the Carrington Event had a value of approximately -850 nT.

Geomagnetic storms are responsible for spectacular phenomena such as the aurora borealis observed at the Earth’s highest latitudes, which depending on their intensity can interfere drastically with different aspects of human activity. Examples of severe disruptions occurring in past decades are the interruption of electrical and navigation systems, and satellite communications. “In Carrington’s time, the only infrastructure affected was the global telephone network,” says one of the authors of the study, mathematician Isabel Serra. “Now, a storm of such intensity could have catastrophic effects on our society. According to a 2013 study conducted by the Lloyd’s of London insurance company and Atmospheric and Environmental Research, the duration of these effects could last longer than a year, and costs could rise to 2.5 trillion dollars. These are number that should make us think,” Isabel Serra insists.

“A probability close to 2% which is what we have calculated for a highly intense storm should not be looked over if we take into account the consequences of such an event,” says Professor Pere Puig, one of the authors of the paper. “Governments should have action protocols to react to such disasters, in order to inform and calm the population left without electrical energy and no way to communicate. We cannot forget that there will be very little time of reaction before the unforeseen arrival of this type of storm.”

What Scientists Found After Sifting Through Dust In The Solar System

Just as dust gathers in corners and along bookshelves in our homes, dust piles up in space too. But when the dust settles in the solar system, it’s often in rings. Several dust rings circle the Sun. The rings trace the orbits of planets, whose gravity tugs dust into place around the Sun, as it drifts by on its way to the center of the solar system.

The dust consists of crushed-up remains from the formation of the solar system, some 4.6 billion years ago — rubble from asteroid collisions or crumbs from blazing comets. Dust is dispersed throughout the entire solar system, but it collects at grainy rings overlying the orbits of Earth and Venus, rings that can be seen with telescopes on Earth. By studying this dust — what it’s made of, where it comes from, and how it moves through space — scientists seek clues to understanding the birth of planets and the composition of all that we see in the solar system.

Two recent studies report new discoveries of dust rings in the inner solar system. One study uses NASA data to outline evidence for a dust ring around the Sun at Mercury’s orbit. A second study from NASA identifies the likely source of the dust ring at Venus’ orbit: a group of never-before-detected asteroids co-orbiting with the planet.

“It’s not every day you get to discover something new in the inner solar system,” said Marc Kuchner, an author on the Venus study and astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This is right in our neighborhood.”

Another Ring Around the Sun

Guillermo Stenborg and Russell Howard, both solar scientists at the Naval Research Laboratory in Washington, D.C., did not set out to find a dust ring. “We found it by chance,” Stenborg said, laughing. The scientists summarized their findings in a paper published in The Astrophysical Journal on Nov. 21, 2018.

They describe evidence of a fine haze of cosmic dust over Mercury’s orbit, forming a ring some 9.3 million miles wide. Mercury — 3,030 miles wide, just big enough for the continental United States to stretch across — wades through this vast dust trail as it circles the Sun.

Ironically, the two scientists stumbled upon the dust ring while searching for evidence of a dust-free region close to the Sun. At some distance from the Sun, according to a decades-old prediction, the star’s mighty heat should vaporize dust, sweeping clean an entire stretch of space. Knowing where this boundary is can tell scientists about the composition of the dust itself, and hint at how planets formed in the young solar system.

So far, no evidence has been found of dust-free space, but that’s partly because it would be difficult to detect from Earth. No matter how scientists look from Earth, all the dust in between us and the Sun gets in the way, tricking them into thinking perhaps space near the Sun is dustier than it really is.

Stenborg and Howard figured they could work around this problem by building a model based on pictures of interplanetary space from NASA’s STEREO satellite — short for Solar and Terrestrial Relations Observatory.

Ultimately, the two wanted to test their new model in preparation for NASA’s Parker Solar Probe, which is currently flying a highly elliptic orbit around the Sun, swinging closer and closer to the star over the next seven years. They wanted to apply their technique to the images Parker will send back to Earth and see how dust near the Sun behaves.

Scientists have never worked with data collected in this unexplored territory, so close to the Sun. Models like Stenborg and Howard’s provide crucial context for understanding Parker Solar Probe’s observations, as well as hinting at what kind of space environment the spacecraft will find itself in — sooty or sparkling clean.

Two kinds of light show up in STEREO images: light from the Sun’s blazing outer atmosphere — called the corona — and light reflected off all the dust floating through space. The sunlight reflected off this dust, which slowly orbits the Sun, is about 100 times brighter than coronal light.

“We’re not really dust people,” said Howard, who is also the lead scientist for the cameras on STEREO and Parker Solar Probe that take pictures of the corona. “The dust close to the Sun just shows up in our observations, and generally, we have thrown it away.” Solar scientists like Howard — who study solar activity for purposes such as forecasting imminent space weather, including giant explosions of solar material that the Sun can sometimes send our way — have spent years developing techniques to remove the effect of this dust. Only after removing light contamination from dust can they clearly see what the corona is doing.

The two scientists built their model as a tool for others to get rid of the pesky dust in STEREO — and eventually Parker Solar Probe — images, but the prediction of dust-free space lingered in the back of their minds. If they could devise a way of separating the two kinds of light and isolate the dust-shine, they could figure out how much dust was really there. Finding that all the light in an image came from the corona alone, for example, could indicate they’d found dust-free space at last.

Mercury’s dust ring was a lucky find, a side discovery Stenborg and Howard made while they were working on their model. When they used their new technique on the STEREO images, they noticed a pattern of enhanced brightness along Mercury’s orbit — more dust, that is — in the light they’d otherwise planned to discard.

“It wasn’t an isolated thing,” Howard said. “All around the Sun, regardless of the spacecraft’s position, we could see the same five percent increase in dust brightness, or density. That said something was there, and it’s something that extends all around the Sun.”

Scientists never considered that a ring might exist along Mercury’s orbit, which is maybe why it’s gone undetected until now, Stenborg said. “People thought that Mercury, unlike Earth or Venus, is too small and too close to the Sun to capture a dust ring,” he said. “They expected that the solar wind and magnetic forces from the Sun would blow any excess dust at Mercury’s orbit away.”

With an unexpected discovery and sensitive new tool under their belt, the researchers are still interested in the dust-free zone. As Parker Solar Probe continues its exploration of the corona, their model can help others reveal any other dust bunnies lurking near the Sun.

Asteroids Hiding in Venus’ Orbit

This isn’t the first time scientists have found a dust ring in the inner solar system. Twenty-five years ago, scientists discovered that Earth orbits the Sun within a giant ring of dust. Others uncovered a similar ring near Venus’ orbit, first using archival data from the German-American Helios space probes in 2007, and then confirming it in 2013, with STEREO data.

Since then, scientists determined the dust ring in Earth’s orbit comes largely from the asteroid belt, the vast, doughnut-shaped region between Mars and Jupiter where most of the solar system’s asteroids live. These rocky asteroids constantly crash against each other, sloughing dust that drifts deeper into the Sun’s gravity, unless Earth’s gravity pulls the dust aside, into our planet’s orbit.

At first, it seemed likely that Venus’ dust ring formed like Earth’s, from dust produced elsewhere in the solar system. But when Goddard astrophysicist Petr Pokorny modeled dust spiraling toward the Sun from the asteroid belt, his simulations produced a ring that matched observations of Earth’s ring — but not Venus’.

This discrepancy made him wonder if not the asteroid belt, where else does the dust in Venus’ orbit come from? After a series of simulations, Pokorny and his research partner Marc Kuchner hypothesized it comes from a group of never-before-detected asteroids that orbit the Sun alongside Venus. They published their work in The Astrophysical Journal Letters on March 12, 2019.

“I think the most exciting thing about this result is it suggests a new population of asteroids that probably holds clues to how the solar system formed,” Kuchner said. If Pokorny and Kuchner can observe them, this family of asteroids could shed light on Earth and Venus’ early histories. Viewed with the right tools, the asteroids could also unlock clues to the chemical diversity of the solar system.

Because it’s dispersed over a larger orbit, Venus’ dust ring is much larger than the newly detected ring at Mercury’s. About 16 million miles from top to bottom and 6 million miles wide, the ring is littered with dust whose largest grains are roughly the size of those in coarse sandpaper. It’s about 10 percent denser with dust than surrounding space. Still, it’s diffuse — pack all the dust in the ring together, and all you’d get is an asteroid two miles across.

Using a dozen different modeling tools to simulate how dust moves around the solar system, Pokorny modeled all the dust sources he could think of, looking for a simulated Venus ring that matched the observations. The list of all the sources he tried sounds like a roll call of all the rocky objects in the solar system: Main Belt asteroids, Oort Cloud comets, Halley-type comets, Jupiter-family comets, recent collisions in the asteroid belt.

“But none of them worked,” Kuchner said. “So, we started making up our own sources of dust.”

Perhaps, the two scientists thought, the dust came from asteroids much closer to Venus than the asteroid belt. There could be a group of asteroids co-orbiting the Sun with Venus — meaning they share Venus’ orbit, but stay far away from the planet, often on the other side of the Sun. Pokorny and Kuchner reasoned a group of asteroids in Venus’ orbit could have gone undetected until now because it’s difficult to point earthbound telescopes in that direction, so close to the Sun, without light interference from the Sun.

Co-orbiting asteroids are an example of what’s called a resonance, an orbital pattern that locks different orbits together, depending on how their gravitational influences meet. Pokorny and Kuchner modeled many potential resonances: asteroids that circle the Sun twice for every three of Venus’ orbits, for example, or nine times for Venus’ ten, and one for one. Of all the possibilities, one group alone produced a realistic simulation of the Venus dust ring: a pack of asteroids that occupies Venus’s orbit, matching Venus’ trips around the Sun one for one.

But the scientists couldn’t just call it a day after finding a hypothetical solution that worked. “We thought we’d discovered this population of asteroids, but then had to prove it and show it works,” Pokorny said. “We got excited, but then you realize, ‘Oh, there’s so much work to do.'”

They needed to show that the very existence of the asteroids makes sense in the solar system. It would be unlikely, they realized, that asteroids in these special, circular orbits near Venus arrived there from somewhere else like the asteroid belt. Their hypothesis would make more sense if the asteroids had been there since the very beginning of the solar system.

The scientists built another model, this time starting with a throng of 10,000 asteroids neighboring Venus. They let the simulation fast forward through 4.5 billion years of solar system history, incorporating all the gravitational effects from each of the planets. When the model reached present-day, about 800 of their test asteroids survived the test of time.

Pokorny considers this an optimistic survival rate. It indicates that asteroids could have formed near Venus’ orbit in the chaos of the early solar system, and some could remain there today, feeding the dust ring nearby.

The next step is actually pinning down and observing the elusive asteroids. “If there’s something there, we should be able to find it,” Pokorny said. Their existence could be verified with space-based telescopes like Hubble, or perhaps interplanetary space-imagers similar to STEREO’s. Then, the scientists will have more questions to answer: How many of them are there, and how big are they? Are they continuously shedding dust, or was there just one break-up event?

Dust Rings Around Other Stars

The dust rings that Mercury and Venus shepherd are just a planet or two away, but scientists have spotted many other dust rings in distant star systems. Vast dust rings can be easier to spot than exoplanets, and could be used to infer the existence of otherwise hidden planets, and even their orbital properties.

But interpreting extrasolar dust rings isn’t straightforward. “In order to model and accurately read the dust rings around other stars, we first have to understand the physics of the dust in our own backyard,” Kuchner said. By studying neighboring dust rings at Mercury, Venus and Earth, where dust traces out the enduring effects of gravity in the solar system, scientists can develop techniques for reading between the dust rings both near and far.

Researchers Uncover Additional Evidence For Massive Solar Storms

Our planet is constantly being bombarded by cosmic particles. However, at times the stream of particles is particularly strong when a solar storm sweeps past. Solar storms are made up of high-energy particles unleashed from the sun by explosions on the star’s surface.

For the past 70 years, researchers have studied these solar storms by direct instrumental observations, which has led to an understanding of how they can pose a risk to the electrical grid, various communication systems, satellites and air traffic. Two examples of severe solar storms in modern times that caused extensive power cuts took place in Quebec, Canada (1989) and Malmö, Sweden (2003).

Now, an increasing amount of research indicates that solar storms can be even more powerful than measurements have shown so far via direct observations.

The researchers behind the new, international study led by researchers from Lund University have used drilled samples of ice, or ice cores, to find clues about previous solar storms. The cores come from Greenland and contain ice formed over the past about 100,000 years. The material contains evidence of a very powerful solar storm that occurred in 660 BCE.

“If that solar storm had occurred today, it could have had severe effects on our high-tech society,” says Raimund Muscheler, professor of geology at Lund University.

The new study means that a third known case of a massive solar storm dating back in time has been discovered via indirect observations in nature’s own archive. Raimund Muscheler also took part in research that confirmed the existence of two other massive solar storms, using both ice cores and the annual growth rings of old trees. These storms took place in 775 and 994 CE.

Raimund Muscheler points out that, even though these massive solar storms are rare, the new discovery shows that they are a naturally recurring effect of solar activity.

“That’s why we must increase society’s protection again solar storms,” he says.

Today’s risk assessment is largely based on direct observations made over the past 70 years, but Raimund Muscheler suggests that there is a need for a reassessment in view of the three massive solar storms that have now been discovered. He argues that there is a need for greater awareness of the possibility of very strong solar storms and the vulnerability of our society.

“Our research suggests that the risks are currently underestimated. We need to be better prepared,” concludes Raimund Muscheler.

LAMP Instrument Sheds Light On Lunar Water Movement

Using the Southwest Research Institute-led Lyman Alpha Mapping Project (LAMP) aboard NASA’s Lunar Reconnaissance Orbiter (LRO), scientists have observed water molecules moving around the dayside of the Moon. A paper published in Geophysical Research Letters describes how LAMP measurements of the sparse layer of molecules temporarily stuck to the surface helped characterize lunar hydration changes over the course of a day.

Up until the last decade or so, scientists thought the Moon was arid, with any water existing mainly as pockets of ice in permanently shaded craters near the poles. More recently, scientists have identified surface water in sparse populations of molecules bound to the lunar soil, or regolith. The amount and locations vary based on the time of day. This water is more common at higher latitudes and tends to hop around as the surface heats up.

“This is an important new result about lunar water, a hot topic as our nation’s space program returns to a focus on lunar exploration,” said SwRI’s Dr. Kurt Retherford, the principal investigator of the LRO LAMP instrument. “We recently converted the LAMP’s light collection mode to measure reflected signals on the lunar dayside with more precision, allowing us to track more accurately where the water is and how much is present.”

Water molecules remain tightly bound to the regolith until surface temperatures peak near lunar noon. Then, molecules thermally desorb and can bounce to a nearby location that is cold enough for the molecule to stick or populate the Moon’s extremely tenuous atmosphere, or “exosphere,” until temperatures drop and the molecules return to the surface. SwRI’s Dr. Michael Poston, now a research scientist on the LAMP team, had previously conducted extensive experiments with water and lunar samples collected by the Apollo missions. This research revealed the amount of energy needed to remove water molecules from lunar materials, helping scientists understand how water is bound to surface materials.

“Lunar hydration is tricky to measure from orbit, due to the complex way that light reflects off of the lunar surface,” Poston said. “Previous research reported quantities of hopping water molecules that were too large to explain with known physical processes. I’m excited about these latest results because the amount of water interpreted here is consistent with what lab measurements indicate is possible. More work is needed to fully account for the complexities of the lunar surface, but the present results show that work is definitely worth doing!”

Scientists have hypothesized that hydrogen ions in the solar wind may be the source of most of the Moon’s surface water. With that in mind, when the Moon passes behind the Earth and is shielded from the solar wind, the “water spigot” should essentially turn off. However, the water observed by LAMP does not decrease when the Moon is shielded by the Earth and the region influenced by its magnetic field, suggesting water builds up over time, rather than “raining” down directly from the solar wind.

“These results aid in understanding the lunar water cycle and will ultimately help us learn about accessibility of water that can be used by humans in future missions to the Moon,” said Amanda Hendrix, a senior scientist at the Planetary Science Institute and lead author of the paper. “A source of water on the Moon could help make future crewed missions more sustainable and affordable. Lunar water can potentially be used by humans to make fuel or to use for radiation shielding or thermal management; if these materials do not need to be launched from Earth, that makes these future missions more affordable.”

The funding for this research came from NASA Goddard Space Flight Center’s LRO program office, including an LRO LAMP subcontract between SwRI and PSI, and the team received additional support from a NASA Solar System Exploration Research Virtual Institute (SSERVI) cooperative agreement.

What Does The Milky Way Weigh? Hubble And Gaia Investigate

We can’t put the whole Milky Way on a scale, but astronomers have been able to come up with one of the most accurate measurements yet of our galaxy’s mass, using NASA’s Hubble Space Telescope and the European Space Agency’s Gaia satellite.

The Milky Way weighs in at about 1.5 trillion solar masses (one solar mass is the mass of our Sun), according to the latest measurements. Only a few percent of this is contributed by the approximately 200 billion stars in the Milky Way and includes a 4-million-solar-mass supermassive black hole at the center. Most of the rest of the mass is locked up in dark matter, an invisible and mysterious substance that acts like scaffolding throughout the universe and keeps the stars in their galaxies.

Earlier research dating back several decades used a variety of observational techniques that provided estimates for our galaxy’s mass ranging between 500 billion to 3 trillion solar masses. The improved measurement is near the middle of this range.

“We want to know the mass of the Milky Way more accurately so that we can put it into a cosmological context and compare it to simulations of galaxies in the evolving universe,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “Not knowing the precise mass of the Milky Way presents a problem for a lot of cosmological questions.”

The new mass estimate puts our galaxy on the beefier side, compared to other galaxies in the universe. The lightest galaxies are around a billion solar masses, while the heaviest are 30 trillion, or 30,000 times more massive. The Milky Way’s mass of 1.5 trillion solar masses is fairly normal for a galaxy of its brightness.

Astronomers used Hubble and Gaia to measure the three-dimensional movement of globular star clusters — isolated spherical islands each containing hundreds of thousands of stars each that orbit the center of our galaxy.

Although we cannot see it, dark matter is the dominant form of matter in the universe, and it can be weighed through its influence on visible objects like the globular clusters. The more massive a galaxy, the faster its globular clusters move under the pull of gravity. Most previous measurements have been along the line of sight to globular clusters, so astronomers know the speed at which a globular cluster is approaching or receding from Earth. However, Hubble and Gaia record the sideways motion of the globular clusters, from which a more reliable speed (and therefore gravitational acceleration) can be calculated.

The Hubble and Gaia observations are complementary. Gaia was exclusively designed to create a precise three-dimensional map of astronomical objects throughout the Milky Way and track their motions. It made exacting all-sky measurements that include many globular clusters. Hubble has a smaller field of view, but it can measure fainter stars and therefore reach more distant clusters. The new study augmented Gaia measurements for 34 globular clusters out to 65,000 light-years, with Hubble measurements of 12 clusters out to 130,000 light-years that were obtained from images taken over a 10-year period.

When the Gaia and Hubble measurements are combined as anchor points, like pins on a map, astronomers can estimate the distribution of the Milky Way’s mass out to nearly 1 million light-years from Earth.

“We know from cosmological simulations what the distribution of mass in the galaxies should look like, so we can calculate how accurate this extrapolation is for the Milky Way,” said Laura Watkins of the European Southern Observatory in Garching, Germany, lead author of the combined Hubble and Gaia study, to be published in The Astrophysical Journal. These calculations based on the precise measurements of globular cluster motion from Gaia and Hubble enabled the researchers to pin down the mass of the entire Milky Way.

The earliest homesteaders of the Milky Way, globular clusters contain the oldest known stars, dating back to a few hundred million years after the big bang, the event that created the universe. They formed prior to the construction of the Milky Way’s spiral disk, where our Sun and solar system reside.

“Because of their great distances, globular star clusters are some of the best tracers astronomers have to measure the mass of the vast envelope of dark matter surrounding our galaxy far beyond the spiral disk of stars,” said Tony Sohn of STScI, who led the Hubble measurements.

The international team of astronomers in this study are Laura Watkins (European Southern Observatory, Garching, Germany), Roeland van der Marel (Space Telescope Science Institute, and Johns Hopkins University Center for Astrophysical Sciences, Baltimore, Maryland), Sangmo Tony Sohn (Space Telescope Science Institute, Baltimore, Maryland), and N. Wyn Evans (University of Cambridge, Cambridge, United Kingdom).

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

New Surprises From Jupiter And Saturn

The latest data sent back by the Juno and Cassini spacecraft from giant gas planets Jupiter and Saturn have challenged a lot of current theories about how planets in our solar system form and behave.

The detailed magnetic and gravity data have been “invaluable but also confounding,” said David Stevenson from Caltech, who will present an update of both missions this week at the 2019 American Physical Society March Meeting in Boston.

“Although there are puzzles yet to be explained, this is already clarifying some of our ideas about how planets form, how they make magnetic fields and how the winds blow,” Stevenson said.

Cassini orbited Saturn for 13 years before its dramatic final dive into the planet’s interior in 2017, while Juno has been orbiting Jupiter for two and a half years.

Juno’s success as a mission to Jupiter is a tribute to innovative design. Its instruments are powered by solar energy alone and protected so as to withstand the fierce radiation environment.

Stevenson says the inclusion of a microwave sensor on Juno was a good decision.

“Using microwaves to figure out the deep atmosphere was the right, but unconventional, choice,” he said. The microwave data have surprised the scientists, in particular by showing that the atmosphere is evenly mixed, something conventional theories did not predict.

“Any explanation for this has to be unorthodox,” Stevenson said.

Researchers are exploring weather events concentrating significant amounts of ice, liquids and gas in different parts of the atmosphere as possible explanations, but the matter is far from sealed.

Other instruments on board Juno, gravity and magnetic sensors, have also sent back perplexing data. The magnetic field has spots (regions of anomalously high or low magnetic field) and also a striking difference between the northern and southern hemispheres.

“It’s unlike anything we have seen before,” Stevenson said.

The gravity data have confirmed that in the midst of Jupiter, which is at least 90 percent hydrogen and helium by mass, there are heavier elements amounting to more than 10 times the mass of Earth. However, they are not concentrated in a core but are mixed in with the hydrogen above, most of which is in the form of a metallic liquid.

The data has provided rich information about the outer parts of both Jupiter and Saturn. The abundance of heavier elements in these regions is still uncertain, but the outer layers play a larger-than-expected role in the generation of the two planets’ magnetic fields. Experiments mimicking the gas planets’ pressures and temperatures are now needed to help the scientists understand the processes that are going on.

For Stevenson, who has studied gas giants for 40 years, the puzzles are the hallmark of a good mission.

“A successful mission is one that surprises us. Science would be boring if it merely confirmed what we previously thought,” he said.

UPDATE : Searches To Resume After Tornado Kills 23 In Alabama

BEAUREGARD, Ala. –  Rescuers prepared Monday to tear through the rubble of mobile homes and houses in search of survivors of a powerful tornado that rampaged through southeast Alabama and killed at least 23 people.

The trail of destruction was at least half a mile wide and overwhelmed rural Lee County’s coroners’ office, forcing it to call in help from the state.

“The devastation is incredible,” Lee County Sheriff Jay Jones said.

Drones flying overheard equipped with heat-seeking devices had scanned the area for survivors, but the dangerous conditions halted the search late Sunday, Sheriff Jones said. Rescuers planned to resume the search at daylight Monday.

The Sunday tornado, which had winds that appeared to be around 160 mph (257 kph) or greater, was part of a powerful storm system that also slashed its way across parts of Georgia, South Carolina and Florida.

Levi Baker, who lives near the hard-hit area in Alabama, took a chain saw to help clear a path for ambulances and other first-responder vehicles. He said he saw bodies of dead people and dead animals.

He said some houses were demolished and trees were uprooted or snapped in half. One house was swept off its foundation and was sitting in the middle of the road.

“It was just destruction,” Baker said. “There were mobile homes gone. Frames on the other side of the road.”

Jones said the twister traveled straight down a county road in the rural community of Beauregard reducing homes to slabs.

Scott Fillmer was at home when the storm hit in Lee County.

“I looked out the window and it was nothing but black, but you could hear that freight train noise,” Fillmer said.

The National Weather Service confirmed late Sunday a tornado with at least an F3 rating caused the destruction in Alabama. Although the statement did not give exact wind estimates, F3 storms typically are gauged at wind speeds of between 158-206 mph (254-331 kph).

After nightfall Sunday, the rain had stopped and pieces of metal debris and tree branches littered roadways in Beauregard. Two sheriff’s vehicles blocked reporters and others from reaching the worst-hit area. Power appeared to be out in many places.

In a tweet late Sunday, President Donald Trump said: “To the great people of Alabama and surrounding areas: Please be careful and safe. Tornadoes and storms were truly violent and more could be coming. To the families and friends of the victims, and to the injured, God bless you all!”

Rita Smith, spokeswoman for the Lee County Emergency Management Agency, said about 150 first responders had quickly jumped in to help search the debris after the storm struck in Beauregard. At least one trained canine could be seen with search crews as numerous ambulances and emergency vehicles, lights flashing, converged on the area.

At the R&D Grocery on Monday morning in Beauregard, residents were constantly asking each other if they were okay.

“I’m still thanking God I’m among the living,” said John Jones, who has lived in Beauregard for most of his life.

No deaths had been reported Sunday evening from storm-damaged Alabama counties other than Lee County, said Gregory Robinson, spokesman for the Alabama Emergency Management Agency. But he said crews were still surveying damage in several counties in the southwestern part of the state.

Numerous tornado warnings were posted across parts of Alabama, Georgia, Florida and South Carolina on Sunday afternoon as the storm system raced across the region. Weather officials said they confirmed other tornadoes around the region by radar alone and would send teams out Monday to assess those and other storms.

In rural Talbotton, Georgia, about 80 miles (130 kilometers) south of Atlanta, a handful of people were injured by either powerful straight-line winds or a tornado that destroyed several mobile homes and damaged other buildings, said Leigh Ann Erenheim, director of the Talbot County Emergency Management Agency.

News footage showed smashed buildings with rooftops blown away, cars overturned and debris everywhere. Trees all around had been snapped bare of branches.

“The last check I had was between six and eight injuries,” Erenheim said in a phone interview. “From what I understand it was minor injuries, though one fellow did say his leg might be broken.”

She said searches of damaged homes and structures had turned up no serious injuries or deaths there.

Henry Wilson of the Peach County Emergency Management Agency near Macon in central Georgia said a barn had been destroyed and trees and power poles had been snapped, leaving many in the area without power.

Authorities in southwest Georgia were searching door-to-door in darkened neighborhoods after a possible tornado touched down in the rural city of Cairo, about 33 miles (53 kilometers) north of Tallahassee, Florida, on Sunday evening. There were no immediate reports of serious injuries.

Authorities said a tornado was confirmed by radar in the Florida Panhandle late Sunday afternoon. A portion of Interstate 10 on the Panhandle was blocked in one direction for a time in Walton County in the aftermath, said Don Harrigan, a meteorologist for the National Weather Service in Tallahassee.