Areas of Expertise (5)
Civilizations and climate change
Physics and Astronomy
Evolution of Stars and Planets
Science and Religion
Professor Frank's research is in the general area of theoretical astrophysics, and in particular the hydrodynamic and magneto-hydrodynamic evolution of matter ejected from stars. His scientific studies are funded by the National Science Foundation, NASA and the Department of Education.
Current research topic include jets from Young Stellar Objects, bipolar outflows from evolved stars such as Planetary Nebulae and Massive stars. Investigations are carried out though the use of large scale numerical simulations.
Frank is also active member of the department's Plasma Physics program, which is part of the University's interdisciplinary program in High-Energy Density Plasmas. In collaboration with faculty at the University's Laboratory for Laser Energetics (an Inertial Confinement Fusion facility), he is conducting plasma astrophysical research on topics such as magnetic diffusion in interstellar clouds and the evolution of solar magnetic flux tubes.
Professor Frank is also actively involved in science outreach as a popular science writer. He has contributed articles to Discover and Astronomy magazines. He received the science-writing prize from the Solar Physics Division of the American Astronomical Society in 1999.
He received his PhD in Physics (1992) from University of Washington. He held postdoctoral and visiting scientist positions at Leiden University and the University of Minnesota. In 1995, he was awarded a Hubble Fellowship. He joined the University as an Assistant Professor of Physics and Astronomy in 1996. He was promoted to Associate Professor in 2000 and to Professor in 2004. He received a University Bridging Fellowship in 2005.
University of Washington, Seattle: Ph.D., Physics 1992
University of Washington, Seattle: M.S., Physics 1990
University of Colorado, Boulder: B.A., Physics 1984
Selected Media Appearances (40)
Science as a personal journey: from an oasis to the mountains
The Big Think online
From a desert oasis to the Rocky Mountains, being filled with awe makes me a better scientist.
James Webb Space Telescope Launch
Adam Frank, professor of physics and astronomy at the University of Rochester, comments on the launch of the James Webb Space Telescope.
Adam Frank says we've only found about half of the asteroids that pose a danger to Earth, and we don't yet know how to deal with them.
Jeff Bezos Space Launch
Adam Frank says the Jeff Bezos' (and Richard Branson) space launch mark the beginning of human beings becoming a spacefaring species.
Is Earth Smart?
The Atlantic print
Even though Earth might be full of intelligent life, at this point in its cosmic history, it certainly doesn’t seem very smart. Making sense of how a planet’s intelligence might be defined and understood helps shine a little light on humanity’s future on this planet—or lack thereof.
Astrophysicist claims he's skeptical of UFO video leaks
Fox Business tv
University of Rochester Physics and Astronomy Professor Adam Frank joins 'Kennedy' for the latest edition of 'Kennspiracy Theories'
Guest Essay: I'm a Physicist Who Searches for Aliens. UFOs Don't Impress Me
New York Times print
I understand that U.F.O. sightings, which date back at least to 1947, are synonymous in the popular imagination with evidence of extraterrestrials. But scientifically speaking, there is little to warrant that connection. There are excellent reasons to search for extraterrestrial life, but there are equally excellent reasons not to conclude that we have found evidence of it with U.F.O. sightings.
'Helgoland' Offers A New Way To Understand The World, And Our Place In It
As you read these words the world around you seems pretty solid, pretty stable: The device you're using seems to exist on its own, with its own properties of shape and weight and color. So does the chair you're sitting in, the table your coffee cup is resting on and the coffee cup itself.
The impossible cool of cowboy bebop
Big Think online
Cowboy Bebop is a genre-busting Japanese anime series. The stories, music, and science fiction are among the best I've ever experienced.
Op-ed: Biden called for unity in his inaugural address. American science provides it.
NBC News online
With Joe Biden inaugurated as the new president of the United States on Wednesday and as he begins trying to heal the nation, many Americans look with anxiety to the future. We wonder if our institutions, and our very culture, are so broken that they lie beyond repair. While those fears are based in a reality we cannot ignore, there is another reality that should give us reassurance and hope: the triumph of science.
Op-ed: A new frontier is opening in the search for extraterrestrial life
Washington Post print
On Dec. 18, the world learned that Breakthrough Listen, a privately funded search for extraterrestrial intelligence, had found its first official candidate signal. The signal’s existence lit up the Internet. Was BLC-1, as it’s called, finally our moment of contact? Breakthrough Listen scientists, now hard at work on a paper about their findings, were quick to explain that the answer was probably “no”: Given the wealth of human-made radio signal interference out there, BLC-1 will probably turn out to be of human origin.
The Silurian Hypothesis
The Paris Review online
Modern humans have been around for about 200,000 years, but life has existed on this planet for 3.5 billion. That leaves 3,495,888,000 pre-human years unaccounted for—more than enough time for the rise and fall of not one but several pre-human industrial civilizations. Same screen, different show. Same field, different team. An alien race with alien technology, alien vehicles, alien folklore, and alien fears, beneath the familiar sky. There’d be no evidence of such bygone civilizations, built objects and industry lasting no more than a few hundred thousand years. After a few million, with plate tectonics at work, what is on the surface, including the earth itself, will be at the bottom of the sea and the bottom will have become the mountain peaks. The oldest place on the earth’s surface—a stretch of Israel’s Negev Desert—is just over a million years old, nothing on a geological clock. Called the Silurian Hypothesis, the theory was written in 2018 by Gavin Schmidt, a climate modeler at NASA’s Goddard Institute, and Adam Frank, an astrophysicist at the University of Rochester. Schmidt had been studying distant planets for hints of climate change, “hyperthermals,” the sort of quick temperature rises that might indicate the moment a civilization industrialized...
Galactic Settlement and the Fermi Paradox
A space faring species could easily settle the entire Milky Way given billions of years. Yet the fact is that there is no obvious one in our solar system right now. The supposed inconsistency between these statements is the Fermi Paradox, named for the Nobel Prize-winning physicist who supposedly first formulated it. Jonathan Carroll-Nellenback, at the University of Rochester with Adam Frank, not long ago finished work, with Caleb Scharf and me, on analytic and numerical models for how a realistic settlement front would behave in a real gas of stars, one characteristic of the galactic disk at our distance from the galactic center. The big advances here are a few: Carroll-Nellenback validated an analytic formalism for settlement expansion fronts with numerical models for a realistic gas of stars. He accounted for finite settlement lifetimes, the idea that only a small fraction of stars will be settle-able, and explored the limits of very slow and infrequent settlement ships. He also explored a range of settlement behaviors to see how galactic settlement fronts depend on them. The idea that not all stars are settle-able is important to keep in mind. Adam Frank calls this the Aurora effect, after the Kim Stanley Robinson novel in which a system is “habitable, but not settle-able.”
Why Haven't Aliens Settled Every Star In The Milky Way?
Real Clear Science online
(Video) At the American Astronomical Society's meeting Honolulu I got a chance to talk with Adam Frank about new research he's worked with Caleb Scharf, Jonathan Carroll-Nellenback and Jason Wright about the Fermi Paradox. They calculated how difficult it would be for aliens traveling at 10% the speed of light to settle the entire Milky Way, and it turns out, it's not as simple as you might think.
Alone In A Crowded Milky Way
Scientific American online
On the 15th of January in 1790, nine mutineers from HMS Bounty, 18 people from Tahiti and one baby arrived on Pitcairn Island—one of the most isolated habitable places on the planet. Surrounded by the southern Pacific Ocean and with hundreds of miles of open water between it and the nearest other islands, Pitcairn is the epitome of solitude. Back in 2015 my colleague Adam Frank of the University of Rochester and I were having lunch near Columbia University's campus in New York City. As at Fermi's lunch 65 years earlier, the conversation was about the nature of spacefaring species... In 2018 another of my colleagues, Gavin Schmidt of NASA's Goddard Institute for Space Studies, together with Adam Frank, produced a critical assessment of whether we could even tell if there had been an earlier industrial civilization on our planet.
Connections: Rochester and Western New York's favorite books of 2019, part 1
We continue an annual Connections tradition by talking to community leaders about their favorite books of the year. We also get insight into how they think, what they read, and why. Our guests: Adam Frank, author and professor of astrophysics at the University of Rochester (“The Crowded Hour: Theodore Roosevelt, the Rough Riders, and the Dawn of the American Century” by Clay Risen)
Sci-Fi Movies Of The Decade (Sort Of)
NPR (Short Wave) radio
Astrophysicist Adam Frank is a big fan of science and movies. He's even been a science adviser to Marvel's "Doctor Strange." So we asked Adam to give us his sci-fi films of the decade - movies that tell us about striking the right balance between science and storytelling.
'A Marvelous Life' Holds Stan Lee High As The Man Who Made Superheroes Matter
In 2018, Marvel Studios released Black Panther. The film grossed 1.3 billion dollars and was nominated for 7 Oscars including Best Picture (a first time for a superhero film). Beyond the money and awards, the release of Black Panther was a global event. The story of a super-powered African king, leader of the most technologically advanced nation on Earth, allowed the film to address racism and the history of colonial oppression in entirely new and unexpected ways. If anyone was still raising questions about comics mattering for culture, Black Panther meant the definitive end of the argument. Marvel comics and their characters were culture.
(OP-ED) What 'Ad Astra' and Brad Pitt get wrong about space travel, science and life in the cosmos
NBC News THINK online
Over the next few centuries, if we can make it through climate change intact, human beings are going to be building homes wherever they can in the vast frontier of the solar system. That means we urgently need feature films that take the settlement of the solar system seriously, as it’s only through science fiction that we get to explore the shapes of our possible futures. Given that imperative, as an astrophysicist, a passionate advocate for space exploration and a scientist who has consulted on numerous movie scripts (including Marvel’s “Doctor Strange”), I was excited to watch “Ad Astra,” the new Brad Pitt space thriller. The film was promoted with the promise of scientific realism in depicting a solar system well on its way to being settled by humanity.
(OP-ED) Reframing climate change as a story of human evolutionary success
Washington Post online
So it’s official. According to the National Oceanic and Atmospheric Administration, this summer was the hottest recorded in the Northern Hemisphere. But is anyone really surprised anymore? We’re five decades into warnings about the climate catastrophe rushing toward us, but the politics of climate change has never looked less promising. The overwhelming scientific evidence that global warming is occurring has reached everyone it can. Among those who accept that evidence, some are galvanized to protest and demand change — as the recent “climate strikes” demonstrated — and others retreat into fatalism. At the same time, climate change denialists cling to their views, even as, in the face of each new deadly heat wave, flood or firestorm, their position sinks ever deeper into absurdity. Yet denial still retains a hold on a large proportion of the U.S. voting population.
(OP-ED) What if we reframed climate change as a story of human evolutionary success?
Star Tribune online
So, it’s official. According to the National Oceanic and Atmospheric Administration, this summer was the hottest ever recorded in the Northern Hemisphere. But is anyone really surprised anymore? We’re five decades into warnings about the climate catastrophe rushing toward us, but the politics of climate change have never looked less promising.
Reframing climate change as a symptom of evolutionary success
Scientists say climate change is an urgent problem that needs drastic action, but not everyone buys it. And so, astrophysics professor Adam Frank suggests that we should reframe the debate in a more positive light. Rather than place blame, he believes we should talk about climate change as a story of humanity’s evolutionary success.
(OP-ED) In 'Something Deeply Hidden,' Sean Carroll Argues There Are Infinite Copies Of You
Everyone knows we live in a partisan age. It's hard to find any issue these days that people aren't ready to square off on, with sharp, snarky barbs. While no one will be surprised to find these kinds of arguments playing out about immigration or the importance of NATO, finding it among staid physicists — and about the nature of physical reality — might not be so expected. But all too often over the last 100 years, this has been the case, as scientists have disagreed sharply over the meaning of their greatest and most potent theory known as quantum mechanics.
Can our self-conscious minds save us from our selfish selves?
The pace of change to our ecosystem has become fast and furious. Global temperatures and sea levels are rising. Weather patterns are in flux. Forests are burning. Deserts are expanding. Species are becoming extinct at unprecedented rates. Many alarmed observers have called for efforts to reverse, or at least slow, changes brought on by our choices. According to the astrophysicist Adam Frank, the Earth will surely persist in some form, but it is likely that some of the life forms present today will not make it. History tells us that large organisms with energy-demanding lifestyles are especially vulnerable to environmental reconfigurations. Never, in the history of life, has any species asked more of the environment than we have.
The end of the world: a history of how a silent cosmos led humans to fear the worst
Such fears are ramping up. Last year, the astrophysicist Adam Frank implored an audience at Google that we see climate change – and the newly baptised geological age of the Anthropocene – against this cosmological backdrop. The Anthropocene refers to the effects of humanity’s energy-intensive activities upon Earth. Could it be that we do not see evidence of space-faring galactic civilisations because, due to resource exhaustion and subsequent climate collapse, none of them ever get that far? If so, why should we be any different?
An Imagined Future Speaks In 'Talking To Robots'
In the decade or so since Siri and her compatriots first appeared, we've all gotten pretty used to having conversations with computers in various forms. While your Alexa doesn't look much like a Cylon (the scary metal kind or hotty flesh kind) now, it seems like it's just a matter of time of time before we'll be talking with all kinds of robots — including those that look just like us. Time, robots and conversations are at the heart of David Ewing Duncan's new book Talking to Robots: Tales from Our Human-Robot Futures. And if you want to see what that future might look like, Duncan's book is a fun place to start.
Astronomers Get Serious About Alien Technosignatures
The hunt for optical technological signatures of extraterrestrial civilizations has finally gone mainstream. For nearly six decades, a small, but gung-ho group of scientists have been looking for radio and optical signals from space aliens. Now, the Search for Extraterrestrial Intelligence (SETI) has been adopted by a more mainstream group of researchers eager to look for optical technosignatures of otherworldly civilizations. At the recent AbSciCon 2019 conference on astrobiology in Bellevue, Wash., the topic was very well represented in a series of oral presentations. In his AbSciCon presentation abstract, Adam Frank, a University of Rochester astrophysicist and author of “Light of the Stars: Alien Worlds and the Fate of the Earth,” divides terrestrial planetary atmospheres into five classes. These classes begin with no atmosphere on up through Class 4 and Class 5 atmospheres which have thick biospheres where life really changes how the "planetary systems” (atmosphere, hydrosphere (oceans, rivers), cryosphere (ice, glaciers), geosphere (surface rocks) function, he told me. Then finally, he says, a Class 5 planetary atmosphere is one in which a technological civilization has adapted itself to work with the biosphere to create a sustainable whole. “This is where we need to get to last a long time,” said Frank. “Earth now is in-between Class 4 and 5. We don't know if we make it to Class 5.” (Related story reported by The New York Times Spanish Edition)
The Blind Spot
Australian Broadcasting Corporation Radio National radio
What is scientific truth? A small group of scientists and philosophers are saying that science can't reveal everything; that there can be no 'God's eye view of the universe' that's independent of human biases. This idea isn't brand new—in some sense, it goes back to Kant—but it's interesting to see today's physicists promoting what at first glance might seem like an anti-science (or at least anti-realist) view of the world. Guests Adam Frank Professor of Astrophysics, University of Rochester NY
Marcelo Gleiser Wins Templeton Prize For Quest To Confront 'Mystery Of Who We Are'
Like much of the known universe — not to mention all that rests beyond it — Marcelo Gleiser eludes straightforward classification. He is a theoretical physicist, a cosmologist, an Ivy League professor, an ultramarathon runner, an author, a blogger and book reviewer for NPR, a starry-eyed seeker of truth and a gimlet-eyed realist about just how much (or how little) of it he'll find in his lifetime. Now, on his 60th birthday, he can add a new title to that long list of labels that so valiantly attempt to describe him: Templeton Prize winner. "You have to understand science in a more cultural and less technical context in order to really, truly get its value," Gleiser tells NPR. He says it was partly this mission that drove him, along with astrophysicist Adam Frank, to co-found NPR's 13.7: Cosmos and Culture blog in 2009. Before the blog's retirement last year, Gleiser estimates that he wrote more than 400 posts — which, despite their varied subject matter, often had a single idea undergirding them.
NASA Hosts Conference All About Looking For Signs Of Civilization Beyond Earth
NPR "All Things Considered" radio
NPR's Mary Louise Kelly speaks with astrophysicist Adam Frank, who is attending a NASA conference in Houston that's exploring how to discover intelligent life beyond earth.
“Where are They Hiding?” –NASA’s Former Chief Scientist Says Alien Life Could Be ‘Nowhere and No-When & Two Other Theories’
The Daily Galaxy
Humanity may be as few as 10 years away from discovering evidence of extraterrestrial life. Once we do, it will only deepen the mystery of where alien intelligence might be hiding. In the seventh episode of Crazy/Genius, the new podcast from The Atlantic on tech, science, and culture, puts the question to several experts, including Ellen Stofan, the former chief scientist of NASA and current director of the Smithsonian National Air and Space Museum; Adam Frank, a writer and astrophysicist at the University of Rochester; Anders Sandberg, a scientist and futurist at the University of Oxford; and Tim Urban, the science essayist at Wait But Why...
Earth Will Survive. We May Not
New York Times print
In 1968, the astronaut William Anders looked out from his moon-circling Apollo 8 capsule and saw the mottled blue Earth emerging over the gray lunar horizon. It was the first time anyone had seen an Earthrise, and the picture he snapped became iconic. In it, our world appears lonely and fragile set against the blackness of space. Fifty years later, Mr. Anders’s picture remains a visual shorthand for the pressing need to save the planet from our worst behavior. But what if we’ve misunderstood the real meaning of that image? What does it even mean to “save” the Earth?
How Do Aliens Solve Climate Change? Scientists recently modeled a range of interactions between energy-intensive civilizations and their planets. The results were sobering.
The Atlantic online
The universe does many things. It makes galaxies, comets, black holes, neutron stars, and a whole mess more. We’ve lately discovered that it makes a great deal of planets, but it’s not clear whether it regularly makes energy-hungry civilizations, nor is it clear whether such civilizations inevitably drive their planets into climate change. There’s lots of hope riding on our talk about building a sustainable civilization on Earth. But how do we know that’s even possible? Does anyone across the cosmos ever make it?
Did another advanced species exist on Earth before humans?
NBC News online
Our Milky Way galaxy contains tens of billions of potentially habitable planets, but we have no idea whether we’re alone. For now Earth is the only world known to harbor life, and among all the living things on our planet we assume Homo sapiens is the only species ever to have developed advanced technology.
Could Intelligent Life Have Existed on Earth Millions of Years Before Humans?
The Washington Post online
Reptilian menaces called Silurians evolved on Earth before humankind — at least in the “Doctor Who” rendition of the universe. But, science fiction aside, how would we know if some advanced civilization existed on our home planet millions of years before brainy humans showed up? This is a serious question, and serious scientists are speculating about what traces these potential predecessors might have left behind. And they're calling this possibility the Silurian hypothesis. “Now, I don't believe an industrial civilization existed on Earth before our own — I don't think there was a dinosaur civilization or a giant tree sloth civilization,” said Adam Frank, an astrophysicist at the University of Rochester and a co-author of a new study on the topic. “But the question of what one would look like if it did [exist] is important. How do you know there hasn't been one? The whole point of science is to ask a question and see where it leads. That's the essence of what makes science so exciting.”
Was There a Civilization On Earth Before Humans? A look at the available evidence
The Atlantic online
When it comes to direct evidence of an industrial civilization—things like cities, factories, and roads—the geologic record doesn’t go back past what’s called the Quaternary period 2.6 million years ago. For example, the oldest large-scale stretch of ancient surface lies in the Negev Desert. It’s “just” 1.8 million years old—older surfaces are mostly visible in cross section via something like a cliff face or rock cuts. Go back much farther than the Quaternary and everything has been turned over and crushed to dust. And, if we’re going back this far, we’re not talking about human civilizations anymore. Homo sapiens didn’t make their appearance on the planet until just 300,000 years or so ago. That means the question shifts to other species, which is why Gavin called the idea the Silurian hypothesis, after an old Dr. Who episode with intelligent reptiles.
I Want to Believe: What would religious leaders do if aliens showed up?
When asked how he’d explain Buddhism to an alien, University of Rochester astrophysicist Adam Frank offered a succinct response: “I would say that Buddhism is just this. It’s a religion that focuses on exactly what’s happening: nothing more.” Believers and nonbelievers alike would do well to go with the Buddhists on this one and regularly take measure of a universe that’s at once perplexing and comprehensible. Something’s happening—in the skies, in our souls, or both, or neither, depending on whom you ask—and everyone’s this deserves a fair hearing.
Climate change for aliens
Scientists have yet to discover life, or evidence of civilizations, on these or other planets. But in the search for extra-terrestrial intelligence, they often categorize hypothetical worlds according to the amount of energy their inhabitants could potentially harness.
SCOTUS ruling on carbon emissions
Adam Frank says the SCOTUS ruling is not only a blow to the environment and public health, it tells the world that the US is not interested in in the competition to build the next energy infrastructure.
Images from James Webb Space Telescope
Adam Frank, professor of astrophysics at the University of Rochester, discusses the first images from the James Webb Space Telescope.
Selected Articles (5)
The Anthropocene Generalized: Evolution of Exo-Civilizations and Their Planetary FeedbackAstrobiology
2018 We present a framework for studying generic behaviors possible in the interaction between a resource-harvesting technological civilization (an exo-civilization) and the planetary environment in which it evolves. Using methods from dynamical systems theory, we introduce and analyze a suite of simple equations modeling a population which consumes resources for the purpose of running a technological civilization and the feedback those resources drive on the state of the host planet. The feedbacks can drive the planet away from the initial state the civilization originated in and into domains that are detrimental to its sustainability. Our models conceptualize the problem primarily in terms of feedbacks from the resource use onto the coupled planetary systems. In addition, we also model the population growth advantages gained via the harvesting of these resources. We present three models of increasing complexity: (1) Civilization-planetary interaction with a single resource; (2) Civilization-planetary interaction with two resources each of which has a different level of planetary system feedback; (3) Civilization-planetary interaction with two resources and nonlinear planetary feedback (i.e., runaways). All three models show distinct classes of exo-civilization trajectories. We find smooth entries into long-term, “sustainable” steady states. We also find population booms followed by various levels of “die-off.” Finally, we also observe rapid “collapse” trajectories for which the population approaches n = 0. Our results are part of a program for developing an “Astrobiology of the Anthropocene” in which questions of sustainability, centered on the coupled Earth-system, can be seen in their proper astronomical/planetary context. We conclude by discussing the implications of our results for both the coupled Earth system and for the consideration of exo-civilizations across cosmic history.
The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record?Earth and Planetary Astrophysics
2018 If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event.
The formation and evolution of wind-capture discs in binary systemsMonthly Notices of the Royal Astronomical Society
M. Huarte-Espinosa, J. Carroll-Nellenback, J. Nordhaus, A. Frank, E. G. Blackman
2013 We study the formation, evolution and physical properties of accretion discs formed via wind capture in binary systems. Using the adaptive mesh refinement (AMR) code AstroBEAR, we have carried out high-resolution 3D simulations that follow a stellar mass secondary in the corotating frame as it orbits a wind producing asymptotic giant branch (AGB) primary. We first derive a resolution criteria, based on considerations of Bondi–Hoyle flows, that must be met in order to properly resolve the formation of accretion discs around the secondary. We then compare simulations of binaries with three different orbital radii (Ro = 10, 15, 20 au). Discs are formed in all three cases, however, the size of the disc and, most importantly, its accretion rate decreases with orbital radii. In addition, the shape of the orbital motions of material within the disc becomes increasingly elliptical with increasing binary separation. The flow is mildly unsteady with ‘fluttering’ around the bow shock observed. The discs are generally well aligned with the orbital plane after a few binary orbits. We do not observe the presence of any large-scale, violent instabilities (such as the flip-flop mode). For the first time, moreover, it is observed that the wind component that is accreted towards the secondary has a vortex tube-like structure, rather than a column-like one as it was previously thought. In the context of AGB binary systems that might be precursors to pre-planetary nebula (PPN) and planetary nebula (PN), we find that the wind accretion rates at the chosen orbital separations are generally too small to produce the most powerful outflows observed in these systems if the companions are main-sequence stars but marginally capable if the companions are white dwarfs. It is likely that many of the more powerful PPN and PN involve closer binaries than the ones considered here. The results also demonstrate principles of broad relevance to all wind-capture binary systems.
Efficient parallelization for AMR MHD multiphysics calculations; implementation in AstroBEARJournal of Computational Physics
Carroll-Nellenback, J.J., Shroyer, B., Frank, A., Ding, C.
2013 Current adaptive mesh refinement (AMR) simulations require algorithms that are highly parallelized and manage memory efficiently. As compute engines grow larger, AMR simulations will require algorithms that achieve new levels of efficient parallelization and memory management. We have attempted to employ new techniques to achieve both of these goals. Patch or grid based AMR often employs ghost cells to decouple the hyperbolic advances of each grid on a given refinement level. This decoupling allows each grid to be advanced independently. In AstroBEAR we utilize this independence by threading the grid advances on each level with preference going to the finer level grids. This allows for global load balancing instead of level by level load balancing and allows for greater parallelization across both physical space and AMR level. Threading of level advances can also improve performance by interleaving communication with computation, especially in deep simulations with many levels of refinement. While we see improvements of up to 30% on deep simulations run on a few cores, the speedup is typically more modest (5–20%) for larger scale simulations. To improve memory management we have employed a distributed tree algorithm that requires processors to only store and communicate local sections of the AMR tree structure with neighboring processors. Using this distributed approach we are able to get reasonable scaling efficiency (>80%) out to 12288 cores and up to 8 levels of AMR – independent of the use of threading.
On the Structure and Stability of Magnetic Tower JetsThe Astrophysical Journal
Huarte-Espinosa, M., Frank, A., Blackman, E. G., Ciardi, A., Hartigan, P., Lebedev, S. V., Chittenden, J. P.
2012 Modern theoretical models of astrophysical jets combine accretion, rotation, and magnetic fields to launch and collimate supersonic flows from a central source. Near the source, magnetic field strengths must be large enough to collimate the jet requiring that the Poynting flux exceeds the kinetic energy flux. The extent to which the Poynting flux dominates kinetic energy flux at large distances from the engine distinguishes two classes of models. In magneto-centrifugal launch models, magnetic fields dominate only at scales lesssim 100 engine radii, after which the jets become hydrodynamically dominated (HD). By contrast, in Poynting flux dominated (PFD) magnetic tower models, the field dominates even out to much larger scales. To compare the large distance propagation differences of these two paradigms, we perform three-dimensional ideal magnetohydrodynamic adaptive mesh refinement simulations of both HD and PFD stellar jets formed via the same energy flux. We also compare how thermal energy losses and rotation of the jet base affects the stability in these jets. For the conditions described, we show that PFD and HD exhibit observationally distinguishable features: PFD jets are lighter, slower, and less stable than HD jets. Unlike HD jets, PFD jets develop current-driven instabilities that are exacerbated as cooling and rotation increase, resulting in jets that are clumpier than those in the HD limit. Our PFD jet simulations also resemble the magnetic towers that have been recently created in laboratory astrophysical jet experiments.