The solar chromosphere and transition region (TR) form an interface between the Sun’s surface and its hot outer atmosphere. There, most of the nonthermal energy that powers the solar atmosphere is transformed into heat, although the detailed mechanism remains elusive. High-resolution (0.33–arc second) observations with NASA’s Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere and TR that are replete with twist or torsional motions on sub–arc second scales, occurring in active regions, quiet Sun regions, and coronal holes alike. We coordinated observations with the Swedish 1-meter Solar Telescope (SST) to quantify these twisting motions and their association with rapid heating to at least TR temperatures. This view of the interface region provides insight into what heats the low solar atmosphere.
Authors: B. De Pontieu, L. Rouppe van der Voort, S. W. McIntosh, T. M. D. Pereira, M. Carlsson, V. Hansteen, H. Skogsrud, J. Lemen, A. Title, P. Boerner, N. Hurlburt, T. D. Tarbell, J. P. Wuelser, E. E. De Luca, L. Golub, S. McKillop, K. Reeves, S. Saar, P. Testa, H. Tian, C. Kankelborg, S. Jaeggli, L. Kleint, J. Martinez-Sykora
The heating of the outer solar atmospheric layers, i.e., the transition region and corona, to high temperatures is a long-standing problem in solar (and stellar) physics. Solutions have been hampered by an incomplete understanding of the magnetically controlled structure of these regions. The high spatial and temporal resolution observations with the Interface Region Imaging Spectrograph (IRIS) at the solar limb reveal a plethora of short, low-lying loops or loop segments at transition-region temperatures that vary rapidly, on the time scales of minutes. We argue that the existence of these loops solves a long-standing observational mystery. At the same time, based on comparison with numerical models, this detection sheds light on a critical piece of the coronal heating puzzle.
Authors: V. Hansteen, B. De Pontieu, M. Carlsson, J. Lemen, A. Title, P. Boerner, N. Hurlburt, T. D. Tarbell, J. P. Wuelser, T. M. D. Pereira, E. E. De Luca, L. Golub, S. McKillop, K. Reeves, S. Saar, P. Testa, H. Tian, C. Kankelborg, S. Jaeggli, L. Kleint, J. Martínez-Sykora
The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it is difficult to determine what is up and down, even in the cool 6000-kelvin photosphere just above the solar surface: This region hosts pockets of hot plasma transiently heated to almost 100,000 kelvin. The energy to heat and accelerate the plasma requires a considerable fraction of the energy from flares, the largest solar disruptions. These IRIS observations not only confirm that the photosphere is more complex than conventionally thought, but also provide insight into the energy conversion in the process of magnetic reconnection.
Authors: H. Peter, H. Tian, W. Curdt, D. Schmit, D. Innes, B. De Pontieu, J. Lemen, A. Title, P. Boerner, N. Hurlburt, T. D. Tarbell, J. P. Wuelser, Juan Martínez-Sykora, L. Kleint, L. Golub, S. McKillop, K. K. Reeves, S. Saar, P. Testa, C. Kankelborg, S. Jaeggli, M. Carlsson, V. Hansteen
The physical processes causing energy exchange between the Sun’s hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High-resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60 seconds) of intensity and velocity on small spatial scales (≲500 kilometers) at the footpoints of hot and dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of nonthermal electrons, which are generated in small impulsive (≲30 seconds) heating events called “coronal nanoflares.” The accelerated electrons deposit a sizable fraction of their energy (≲1025 erg) in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona.
Authors: P. Testa, B. De Pontieu, J. Allred, M. Carlsson, F. Reale, A. Daw, V. Hansteen, J. Martinez-Sykora, W. Liu, E. E. DeLuca, L. Golub, S. McKillop, K. Reeves, S. Saar, H. Tian, J. Lemen, A. Title, P. Boerner, N. Hurlburt, T. D. Tarbell, J. P. Wuelser, L. Kleint, C. Kankelborg, S. Jaeggli
The human sense of fairness is an evolutionary puzzle. To study this, we can look to other species, in which this can be translated empirically into responses to reward distribution. Passive and active protest against receiving less than a partner for the same task is widespread in species that cooperate outside kinship and mating bonds. There is less evidence that nonhuman species seek to equalize outcomes to their own detriment, yet the latter has been documented in our closest relatives, the apes. This reaction probably reflects an attempt to forestall partner dissatisfaction with obtained outcomes and its negative impact on future cooperation. We hypothesize that it is the evolution of this response that allowed the development of a complete sense of fairness in humans, which aims not at equality for its own sake but for the sake of continued cooperation.
Authors: Sarah F. Brosnan, Frans B. M. de Waal
As the interface between the Sun’s photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~105 kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind.
Authors: H. Tian, E. E. DeLuca, S. R. Cranmer, B. De Pontieu, H. Peter, J. Martínez-Sykora, L. Golub, S. McKillop, K. K. Reeves, M. P. Miralles, P. McCauley, S. Saar, P. Testa, M. Weber, N. Murphy, J. Lemen, A. Title, P. Boerner, N. Hurlburt, T. D. Tarbell, J. P. Wuelser, L. Kleint, C. Kankelborg, S. Jaeggli, M. Carlsson, V. Hansteen, S. W. McIntosh
Two categories of evolutionary challenges result from escalating human impacts on the planet. The first arises from cancers, pathogens, and pests that evolve too quickly and the second, from the inability of many valued species to adapt quickly enough. Applied evolutionary biology provides a suite of strategies to address these global challenges that threaten human health, food security, and biodiversity. This Review highlights both progress and gaps in genetic, developmental, and environmental manipulations across the life sciences that either target the rate and direction of evolution or reduce the mismatch between organisms and human-altered environments. Increased development and application of these underused tools will be vital in meeting current and future targets for sustainable development.
Authors: Scott P. Carroll, Peter Søgaard Jørgensen, Michael T. Kinnison, Carl T. Bergstrom, R. Ford Denison, Peter Gluckman, Thomas B. Smith, Sharon Y. Strauss, Bruce E. Tabashnik
The 25th anniversary of the magnitude (M) 6.9 Loma Prieta earthquake that struck the San Francisco Bay Area on 17 October 1989 is a fitting time to examine what progress has been made in increasing community resilience to minimize seismic risk. The regions affected by the 2010 M 7.0 earthquake that struck Port-au-Prince, Haiti, and the M 8.8 event near Concepción, Chile, a few weeks later illustrate the extremes in earthquake resilience. In the zone of most intense shaking, 1 of every 10 Haitians was killed, compared to 1 of every 2500 Chileans, reflecting huge differences in construction quality and community resilience. The Loma Prieta event left 63 people dead, largely the result of the collapse of a bridge, an overpass, and homes built on unconsolidated fill. But beyond the loss of life, the Bay Area was affected by more than $10 billion in disruption of economic activity and damaged infrastructure. One challenge in implementing community resilience is to use science and engineering to find solutions that not only save lives but also get communities back to business as quickly as possible after a seismic event.
Author: Mary Lou Zoback
Tornadoes clustering in greater numbers | What's inside Saturn's tiniest moon? | Detoxing drug overdoses with nanoparticles | Ensuring a one-way flow of lymph | A thorny defense keeps grazers at bay | Complex light and matter interactions | Smart monkeys can outwit a computer | Ions knock each other across the membrane | Finding the targets of T cells gone bad | Exploiting evolution for humanity's sake | Learning requires the brain to change | The evolutionary benefits of behaving fairly | Stellar outflows replicated in miniature | Achieving gain despite increasing loss | A very quick look at phenylalanine | Getting to the root of a root problem | Insight into a retinal degeneration disease | Cytoskeleton protects from stress and aging
Charting the course of antibiotic failure | Protein sorting sets digit number | Unraveling ringwoodite hydration in mantle | Meat-eater lived in extinction's wake | A costly reluctance to speak out | How many lakes are there on Earth? | Taking the temperature of virulence | Finding ways to reach the right endpoint
Mice need myelinating cells in the brain to master an unpredictable motor task. [Also see Perspective by Long and Corfas]
Authors: Ian A. McKenzie, David Ohayon, Huiliang Li, Joana Paes de Faria, Ben Emery, Koujiro Tohyama, William D. Richardson
The precise difference between rotational and orbital periods suggests an unexpected interior for one of Saturn’s moons.
Authors: R. Tajeddine, N. Rambaux, V. Lainey, S. Charnoz, A. Richard, A. Rivoldini, B. Noyelles
A scaled-down plasma experiment shows that axial magnetic fields in young stars can shape their bipolar jet outflows.
Authors: B. Albertazzi, A. Ciardi, M. Nakatsutsumi, T. Vinci, J. Béard, R. Bonito, J. Billette, M. Borghesi, Z. Burkley, S. N. Chen, T. E. Cowan, T. Herrmannsdörfer, D. P. Higginson, F. Kroll, S. A. Pikuz, K. Naughton, L. Romagnani, C. Riconda, G. Revet, R. Riquier, H.-P. Schlenvoigt, I. Yu. Skobelev, A.Ya. Faenov, A. Soloviev, M. Huarte-Espinosa, A. Frank, O. Portugall, H. Pépin, J. Fuchs
Introducing loss into a coupled optical system can result in an enhancement of the optical properties. [Also see Perspective by Schwefel]
Authors: B. Peng, Ş. K. Özdemir, S. Rotter, H. Yilmaz, M. Liertzer, F. Monifi, C. M. Bender, F. Nori, L. Yang
Optics may provide insight into the complex many-body interactions of a two-dimensional electron gas.
Authors: Stephan Smolka, Wolf Wuester, Florian Haupt, Stefan Faelt, Werner Wegscheider, Ataç Imamoglu
Electronic dynamics in a complex polyatomic molecule are tracked faster than the time scale for vibrational motion.
Authors: F. Calegari, D. Ayuso, A. Trabattoni, L. Belshaw, S. De Camillis, S. Anumula, F. Frassetto, L. Poletto, A. Palacios, P. Decleva, J. B. Greenwood, F. Martín, M. Nisoli
Nitrogen-starved rootlets send small peptides to the shoot to initiate compensatory uptake in other rootlets. [Also see Perspective by Bisseling and Scheres]
Authors: Ryo Tabata, Kumiko Sumida, Tomoaki Yoshii, Kentaro Ohyama, Hidefumi Shinohara, Yoshikatsu Matsubayashi
Changes to thorny plant defenses and high predator risk for impala determine density and distribution of savanna trees.
Authors: Adam T. Ford, Jacob R. Goheen, Tobias O. Otieno, Laura Bidner, Lynne A. Isbell, Todd M. Palmer, David Ward, Rosie Woodroffe, Robert M. Pringle
Simulation shows that ions crossing a potassium channel are in direct contact with one another and repel each other through. [Also see Perspective by Hummer]
Authors: David A. Köpfer, Chen Song, Tim Gruene, George M. Sheldrick, Ulrich Zachariae, Bert L. de Groot
A bacterial homolog structure gives insights into ion permeation, gating, and mutations that cause retinal degeneration.
Authors: Tingting Yang, Qun Liu, Brian Kloss, Renato Bruni, Ravi C. Kalathur, Youzhong Guo, Edda Kloppmann, Burkhard Rost, Henry M. Colecraft, Wayne A. Hendrickson
A transcription factor may promote longevity by stabilizing the actin cytoskeleton in nematodes.
Authors: Nathan A. Baird, Peter M. Douglas, Milos S. Simic, Ana R. Grant, James J. Moresco, Suzanne C. Wolff, John R. Yates, Gerard Manning, Andrew Dillin
In a mouse model of rheumatoid arthritis, autoimmune T cells recognize a protein from the ribosome.
Authors: Yoshinaga Ito, Motomu Hashimoto, Keiji Hirota, Naganari Ohkura, Hiromasa Morikawa, Hiroyoshi Nishikawa, Atsushi Tanaka, Moritoshi Furu, Hiromu Ito, Takao Fujii, Takashi Nomura, Sayuri Yamazaki, Akimichi Morita, Dario A. A. Vignali, John W. Kappler, Shuichi Matsuda, Tsuneyo Mimori, Noriko Sakaguchi, Shimon Sakaguchi