Dark Cavity Research Articles

Coupled resonator induced transparency in surface plasmon polariton gap waveguide with two side-coupled cavities

We investigate theoretically the generation process of coupled resonator-induced transparency (CRIT) in surface plasmon polariton gap waveguide system containing two side-coupled cavities, which locate at a symmetric position. The CRIT is original from the destructive interference of the two detuned cavities. In contrast with the existing electromagnetically induced transparency (EIT) schemes, the occurrence of the CRIT is caused by the two radiative cavities in waveguide, instead of interference between a dark cavity and radiative cavity. This behavior mimics the quantum interference between two direct excitation pathways in a three-level V-type atom. The transmission lineshape can be tuned between an EIT-like resonant peak and a Lorentzian-like resonant dip by tailoring the detuning of the two cavities. Moreover, we also find that the transparency peak moves to high frequency with a line shift and its Q factor decreases with the increase of coupling distance between the cavities and waveguide.

Drift of dark cavity solitons in a photonic-crystal fiber resonator

We consider a photonic crystal fiber resonator pumped by a coherent injected beam. We show that temporal cavity solitons exhibit a motion with a constant velocity. This regular drift is induced by a broken reflection symmetry mediated by a third-order dispersion. We focus the analysis on dark temporal cavity solitons. They consist of asymmetric moving dips in a uniform background of the intensity profile. The number of the moving dips and their temporal distribution are determined solely by the initial conditions. We characterize this motion by computing the velocity of the dark temporal cavity soliton. Without fourth-order dispersion, dark cavity solitons do not exist.

Azimuthal Turing Patterns, Bright and Dark Cavity Solitons in Kerr Combs Generated With Whispering-Gallery-Mode Resonators

We investigate the formation of cavity solitons in crystalline whispering-gallery-mode disk resonators that are pumped in different dispersion regimes. In the Fourier domain, these dissipative structures correspond to specific types of mode-locked Kerr optical frequency combs. Depending on the sign of the second-order chromatic dispersion and on the pumping conditions, we show that either bright or dark cavity solitons can emerge, and we show that these two regimes are associated with characteristic spectral signatures that can be discriminated experimentally. We use the Lugiato-Lefever spatiotemporal formalism to investigate the temporal dynamics leading to the formation of these azimuthal solitons, as well as the emergence of Turing patterns. The theoretical results are in excellent agreement with experimental measurements that are obtained using calcium and magnesium fluoride disk resonators pumped near 1550 nm.

Parents take both size and conspicuousness into account when feeding nestlings in dark cavity nests

Parent birds respond to a variety of cues from their offspring when provisioning them with food. Bright flange colours and large body size are two traits of offspring that many parents seem to favour, but little is known about how such traits interact. By experimentally altering the difference in mass between nestmates while concurrently blackening the flanges of either the large or small nestlings in the brood, we tested whether large body size could compensate for dull coloration. In three species of cavity nesters (northern flicker, Colaptes auratus, great tit, Parus major, and pied flycatcher, Ficedula hypoleuca), doubly disadvantaged offspring that were both small and dull performed the worst, whereas large and bright offspring received the most provisioning, consistent with the idea of additive effects. We used regression to show that, for flickers, dull (blackened) nestlings performed as well as bright nestlings when they were 20% larger than their bright nestmates. For passerines, dull nestlings had to be 30–40% larger than bright nestlings to receive equivalent amounts of food from parents. Within-brood differences in mass before manipulation were often greater than this size difference threshold, suggesting that hatching asynchrony has a stronger influence on food allocation than do colour differences among siblings.

SLOW MAGNETOACOUSTIC WAVES OBSERVED ABOVE A QUIET-SUN REGION IN A DARK CAVITY

Waves play a crucial role in diagnosing the plasma properties of various structures in the solar corona and coronal heating. Slow magneto-acoustic (MA) waves are one of the important magnetohydrodynamic waves. In past decades, numerous slow MA waves were detected above the active regions and coronal holes, but rarely found elsewhere. Here, we investigate a `tornado'-like structure consisting of quasi-periodic streaks within a dark cavity at about 40--110 Mm above the quiet-Sun region on 2011 September 25. Our analysis reveals that these streaks are actually slow MA wave trains. The properties of these wave trains, including the phase speed, compression ratio, kinetic energy density, etc., are similar to those of the reported slow MA waves, except that the period of these waves is about 50 s, much shorter than the typical reported values (3--5 minutes).

Spin dynamics of dark polariton solitons

We study the influence of the spin dynamics of polaritons on the formation and stability properties of cavity polariton solitons in a semiconductor microcavity operating in the strong-coupling regime. A linearly polarized optical pump beam creates both types of polaritons associated with the opposite spin orientations of excitons, which are coupled to the left and right circularly polarized photons. In particular, we show that a linearly polarized dark cavity polariton soliton can undergo a symmetry-breaking instability, giving rise to the spontaneous formation of elliptically polarized solitons nesting on the linearly polarized background. The origin of this symmetry-breaking instability is analyzed analytically. Moreover, we study the interaction dynamics between dark cavity polariton solitons with different polarizations.

Assessment of Differentiation Aspects by the Morphological Classification of Embryoid Bodies Derived from Human Embryonic Stem Cells

In general, the formation of embryoid bodies (EBs) is a commonly known method for initial induction of human embryonic stem cells (hESCs) into their derivatives in vitro. Despite the ability of EBs to mimic developmental processing, the specification and classifications of EBs are not yet well known. Because EBs show various differentiation potentials depending on the size and morphology of the aggregated cells, specification is difficult to attain. Here, we sought to classify the differentiation potentials of EBs by morphologies to enable one to control the differentiation of specific lineages from hESCs with high efficiency. To induce the differentiation of EB formation, we established floating cultures of undifferentiated hESCs in Petri dishes with hESC medium lacking basic fibroblast growth factor. Cells first aggregated into balls; ∼10 days after suspension culture, some different types of EB morphology were present, which we classified as cystic-, bright cavity-, and dark cavity-type EBs. Next, we analyzed the characteristics of each type of EB for its capacity to differentiate into the 3 germ layers via multiplex polymerase chain reaction (PCR), real-time PCR, and immunocytochemistry. Our results indicated that most cells within the cystic EBs were composed of endoderm lineage populations, and both of the cavity EB types were well organized with 3 germ-layer cells. However, the differentiation capacity of the bright cavity EBs was faster than that of the dark cavity EBs. Thus, the bright cavity EBs in this study, which showed equal differentiation tendencies compared with other types of EBs, may serve as the standard for in vitro engineering of EBs. These results indicate that the classification of EB morphologies allows the estimation of the differentiation status of the EBs and may allow the delineation of subsets of conditions necessary for EBs to differentiate into specific cell types.

OBSERVING FLUX ROPE FORMATION DURING THE IMPULSIVE PHASE OF A SOLAR ERUPTION

Magnetic flux rope is believed to be an important structural component of coronal mass ejections (CMEs). While there exist much observational evidence of the flux rope after the eruption, e.g., as seen in remote-sensing coronagraph images or in-situ solar wind data, the direct observation of flux ropes during CME impulsive phase has been rare. In this Letter, we present an unambiguous observation of a flux rope still in the formation phase in the low corona. The CME of interest occurred above the east limb on 2010 November 03 with footpoints partially blocked. The flux rope was seen as a bright blob of hot plasma in AIA 131 \AA\ passband (peak temperature ~11 MK) rising from the core of the source active region, rapidly moving outward and stretching upward the surrounding background magnetic field. The stretched magnetic field seemed to curve-in behind the core, similar to the classical magnetic reconnection scenario in eruptive flares. On the other hand, the flux rope appeared as a dark cavity in AIA 211 \AA\ passpand (2.0 MK) and 171 \AA\ passband (0.6 MK); in these relatively cool temperature bands, a bright rim clearly enclosed the dark cavity. The bright rim likely represents the pile-up of the surrounding coronal plasma compressed by the expanding flux rope. The composite structure seen in AIA multiple temperature bands is very similar to that in the corresponding coronagraph images, which consists of a bright leading edge and a dark cavity, commonly believed to be a flux rope.

Excitation of dark plasmonic cavity modes via nonlinearly induced dipoles: applications tonear-infrared plasmonic sensing

We demonstrate that dark plasmon modes of cavity-shaped plasmonic structures made ofmetallic nanowires can be excited by local dipoles induced via second-harmonicgeneration. The optical properties of these plasmonic cavity modes are thoroughlycharacterized by using a numerical method that provides a complete description of theoptical field at both the fundamental frequency and the second harmonic. Inparticular, we show that the optical properties of these plasmonic cavity modes arestrongly dependent on the geometry of the plasmonic cavity and the materialparameters of its constituents. This enhanced sensitivity of dark plasmonic cavitymodes to the surrounding dielectric environment can find applications in plasmonicsensing. Specifically, this novel approach to sensing reveals that detection limits of10 − 5 refractive index units can readily be achieved by using wavelength-sized plasmonic devices.

GEOMETRIC TRIANGULATION OF IMAGING OBSERVATIONS TO TRACK CORONAL MASS EJECTIONS CONTINUOUSLY OUT TO 1 AU

We describe a geometric triangulation technique, based on time–elongation maps constructed from imaging observations, to track coronal mass ejections (CMEs) continuously in the heliosphere and predict their impact on the Earth. Taking advantage of stereoscopic imaging observations from the Solar Terrestrial Relations Observatory, this technique can determine the propagation direction and radial distance of CMEs from their birth in the corona all the way to 1 AU. The efficacy of the method is demonstrated by its application to the 2008 December 12 CME, which manifests as a magnetic cloud (MC) from in situ measurements at the Earth. The predicted arrival time and radial velocity at the Earth are well confirmed by the in situ observations around the MC. Our method reveals non-radial motions and velocity changes of the CME over large distances in the heliosphere. It also associates the flux-rope structure measured in situ with the dark cavity of the CME in imaging observations. Implementation of the technique, which is expected to be a routine possibility in the future, may indicate a substantial advance in CME studies as well as space weather forecasting.

Expression and evolutionary divergence of the non-conventional olfactory receptor in four species of fig wasp associated with one species of fig

BackgroundThe interactions of fig wasps and their host figs provide a model for investigating co-evolution. Fig wasps have specialized morphological characters and lifestyles thought to be adaptations to living in the fig's syconium. Although these aspects of natural history are well documented, the genetic mechanism(s) underlying these changes remain(s) unknown. Fig wasp olfaction is the key to host-specificity. The Or83b gene class, an unusual member of olfactory receptor family, plays a critical role in enabling the function of conventional olfactory receptors. Four Or83b orthologous genes from one pollinator (PFW) (Ceratosolen solmsi) and three non-pollinator fig wasps (NPFWs) (Apocrypta bakeri, Philotrypesis pilosa and Philotrypesis sp.) associated with one species of fig (Ficus hispida) can be used to better understand the molecular mechanism underlying the fig wasp's adaptation to its host. We made a comparison of spatial tissue-specific expression patterns and substitution rates of one orthologous gene in these fig wasps and sought evidence for selection pressures.ResultsA newly identified Or83b orthologous gene was named Or2. Expressions of Or2 were restricted to the heads of all wingless male fig wasps, which usually live in the dark cavity of a fig throughout their life cycle. However, expressions were widely detected in the antennae, legs and abdomens of all female fig wasps that fly from one fig to another for oviposition, and secondarily pollination. Weak expression was also observed in the thorax of PFWs. Compared with NPFWs, the Or2 gene in C. solmsi had an elevated rate of substitutions and lower codon usage. Analyses using Tajima's D, Fu and Li's D* and F* tests indicated a non-neutral pattern of nucleotide variation in all fig wasps. Unlike in NPFWs, this non-neutral pattern was also observed for synonymous sites of Or2 within PFWs.ConclusionThe sex- and species-specific expression patterns of Or2 genes detected beyond the known primary olfactory tissues indicates the location of cryptic olfactory inputs. The specialized ecological niche of these wasps explains the unique habits and adaptive evolution of Or2 genes. The Or2 gene in C. solmsi is evolving very rapidly. Negative deviation from the neutral model of evolution reflects possible selection pressures acting on Or2 sequences of fig wasp, particularly on PFWs who are more host-specific to figs.

Could cavity solitons exist in bidirectional ring lasers?

We show numerically that bright and dark cavity solitons can be obtained in bidirectional class A ring lasers only if the phase invariance of the electromagnetic field is broken. The phase invariance symmetry is responsible for the existence of phase waves, which generate long-range interactions destroying the property of independence among otherwise localized structures. We improved the usual model describing such types of lasers, and we prove that it leads to genuine cavity solitons.

Using Global Simulations to Relate the Three‐Part Structure of Coronal Mass Ejections to In Situ Signatures

White-light observations of coronal mass ejections (CMEs) often show the classic three-part structure consisting of (1) a bright front; (2) a dark cavity; and (3) a bright, compact core. It has proven difficult to unambiguously associate these features with in situ measurements of interplanetary CMEs (ICMEs), in all but a few cases. In this study we use a global MHD model to simulate the eruption and evolution of a CME out to 0.25 AU, allowing us to continuously track these features from the Sun and through the solar wind. Our results support the generally held view that the interplanetary flux rope corresponds to the dark cavity. We find that the bright front merges with solar wind material swept up by the ICME. Thus, the sheath material found ahead of fast ejecta is in fact composed from both ambient solar wind material, as well the bright front. We also note that, in this simulation, the bright front is formed from the overlying streamer configuration from within which the CME erupted and is not itself coronal material swept up during the early phase of the eruption. The conclusions reached in this study are undoubtedly sensitive to the initial configuration and mechanism used to initiate the CME, and thus care should be taken when using them to interpret specific observations. On the other hand, they provide a unique, unbroken connection between remote solar and interplanetary observations. Ultimately, detailed comparisons between observations and simulation results may be able to constrain or even rule out some mechanisms of CME initiation.

Prominence height shows the proximity of an ejection

The onset of a coronal mass ejection (CME) is not preceded by any specific form of activity that could be recognized several days before the event. The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fills the whole volume of the dark cavity stretched in the corona along the photospheric polarity inversion line. Cold dense prominence matter accumulates in the lower parts of helical flux tubes, which serve as magnetic traps in the gravitation field. So, prominences and filaments are the best tracers of the flux ropes in the corona long before the beginning of eruption. A twisted flux rope is held by the tension of field lines of photospheric sources until parameters of the system reach critical values and catastrophe happens. The flux rope height above the photosphere is one of these parameters and it is revealed by the height of the filament. We had analyzed some 80 of filaments and found that eruptive prominences were near the limit of stability a few days before eruptions. We believe that a comparison of the real heights of prominences with the calculated critical heights could be helpful for revealing the filaments that are prone to erupt.

Kink‐induced Catastrophe in a Coronal Eruption

We investigate the kinking motion and its role in the eruption of a filament/cavity system that occurred on 2002 October 31. The evolution of the eruptive filament consists of four distinct phases. After an initial slow upward acceleration, the filament experiences a quasi-static phase exhibiting kinking motions of the filament axis. The kinking phase is followed by a sudden jump, coincident with the onset of the unkinking of the filament. The loss of equilibrium initiates a gradual relaxation phase at the end of which the filament reattains a similar unkinked configuration as its initial state. The filament/cavity structure, evident in the white-light observations, interacts with a large-scale coronal helmet streamer to the north, and material is observed to eject outward, aligned with a preexisting, low-density, dark channel that originally separated the northern helmet streamer from the southern streamer, where the dark cavity resides. The bulk of the filament, however, remains confined in the lower corona throughout the eruption along the channel. This suggests a partial eruption of the filament/cavity structure. The observations presented here manifest a catastrophic loss of equilibrium in response to the evolution of kinking motions in the filament activation.

Rotating cavity solitons in semiconductor microresonators

We predict the existence of a ring-like localized solutions in wide aperture passive semiconductor quantum well microresonators. These dark ring cavity solitons exist for positive cavity detuning in a frequency range where nonlinear dispersive effects prevail against absorptive ones. As a rule, destabilization of these ring solitons leads to the formation of radial asymmetric rotating solitons in externally driven optical cavities.

Two new species of linebellies (Genus Pseudoscopelus) with a revised key of species (Perciformes: Chiasmodontidae)

The swallowerfishes previously identified as Pseudoscopelus altipinnis and P. cf. altipinnis (Prokofiev, Kukuev, 2005) are described as a complex of two new, closely-related, allopatric species having antitropical distribution. P. astronesthidens—superspecies is most closely related to P. altipinnis due to its dark orobranchial cavity and the details of its photophore arrangement, but is unique within the genus in the disconnection between the mxf and apf series of photophores and in the details of jaws dentition. P. astronesthidens sp. n. (North Atlantic) differs from P. australis sp. n. (Southern Hemisphere) mainly in the long upper jaw and pectoral fins and in the presence of the ppf series of photophores. P. altipinnis Parr, 1933 is considered as a senior synonym of P. microps Fowler, 1934. A revised key for identification of the linebellies of the genus Pseudoscopelus is given.

Multi-Wavelength Observations of CMEs and Associated Phenomena

This chapter reviews how our knowledge of CMEs and CME-associated phenomena has been improved, since the launch of the SOHO mission, thanks to multi-wavelength analysis. The combination of data obtained from space-based experiments and ground based instruments allows us to follow the space-time development of an event from the bottom of the corona to large distances in the interplanetary medium. Since CMEs originate in the low solar corona, understanding the physical processes that generate them is strongly dependant on coordinated multi-wavelength observations. CMEs display a large diversity in morphology and kinematic properties, but there is presently no statistical evidence that those properties may serve to group them into different classes. When a CME takes place, the coronal magnetic field undergoes restructuring. Much of the current research is focused on understanding how the corona sustains the stresses that allow the magnetic energy to build up and how, later on, this magnetic energy is released during eruptive flares and CMEs. Multi-wavelength observations have confirmed that reconnection plays a key role during the development of CMEs. Frequently, CMEs display a rather simple shape, exhibiting a well known three-part structure (bright leading edge, dark cavity and bright knot). These types of events have led to the proposal of the ‘`standard model’' of the development of a CME, a model which predicts the formation of current sheets. A few recent coronal observations provide some evidence for such sheets. Other more complex events correspond to multiple eruptions taking place on a time scale much shorter than the cadence of coronagraph instruments. They are often associated with large-scale dimming and coronal waves. The exact nature of these waves and the physical link between these different manifestations are not yet elucidated. We also discuss what kind of shocks are produced during a flare or a CME. Several questions remain unanswered. What is the nature of the shocks in the corona (blast-wave or piston-driven?) How they are related to Moreton waves seen in Hα? How they are related to interplanetary shocks? The last section discusses the origin of energetic electrons detected in the corona and in the interplanetary medium. “Complex type III-like events,”which are detected at hectometric wavelengths, high in the corona, and are associated with CMEs, appear to originate from electrons that have been accelerated lower in the corona and not at the bow shock of CMEs. Similarly, impulsive energetic electrons observed in the interplanetary medium are not the exclusive result of electron acceleration at the bow shocks of CMEs; rather they have a coronal origin.

The Calm before the Storm: The Link between Quiescent Cavities and Coronal Mass Ejections

Determining the state of the corona prior to CMEs is crucial to understanding and ultimately predicting solar eruptions. A common and compelling feature of CMEs is their three-part morphology, as seen in white-light observations of a bright expanding loop, followed by a relatively dark cavity, and finally a bright core associated with an erupting prominence/filament. This morphology is an important constraint on CME models. It is also quite common for a three-part structure of loop, cavity, and prominence core to exist quiescently in the corona, and this is equivalently an important constraint on models of CME-precursor magnetic structure. These quiescent structures exist in the low corona, primarily below approximately 1.6R� , and so are currently observable in white light duringsolar eclipses, or else by the Mauna Loa Solar Observatory Mk4 coronameter. We present the first comprehensive, quantitative analysis of white-light quiescent cavities as observed by the Mk4 coronameter. We find that such cavities are ubiquitous, as they are the coronal limb counterparts to filament channels observed on the solar disk. We consider examples that range from extremely long-lived, longitudinally extended polar-crown-filament-related cavities to smallercavitiesassociated withfilamentsnearorwithinactiveregions.Theformerareoftenvisiblefordaysandeven weeks at a time and can be identified as long-lived cavities that survive for months. We quantify cavity morphology and intensity contrast properties and consider correlations between these properties. We find multiple cases in which quiescentcavitiesdirectlyeruptintoCMEsandconsiderhowmorphologicalandintensitycontrastpropertiesofthese cases differ from the general population of cavities. Finally, we discuss the implications that these observations may have for the state of the corona just prior to a CME, and more generally for the nature of coronal MHD equilibria.

Observable Properties of the Breakout Model for Coronal Mass Ejections

We compare the model for coronal mass ejections (CMEs) with observed general properties of CMEs by analyzing in detail recent high-resolution MHD simulations of a complete breakout CME. The model produces an eruption with a three-part plasma density structure that shows a bright circular rim outlining a dark central cavity in synthetic coronagraphic images of total brightness. The model also yields height-time profiles similar to most three-part CMEs, but the eruption speed by 2.5 R☉ is of order the Alfven speed, indicative of a fast CME. We show that the evolution of the posteruptive flare loop and chromospheric ribbons determined from the model are in agreement with observations of long-duration flares, and we propose an explanation for the long-standing observation that flares have an impulsive and gradual phase. A helical magnetic flux rope is generated during eruption and is consistent with a large class of interplanetary CME observations. The magnetic fields in this flux rope are well approximated by the Lundquist solution when the ejecta are at 15 R☉ and beyond. Furthermore, the interior density structure of the magnetic flux rope appears to have some of the basic features of an average magnetic cloud profile at 1 AU. Future simulation improvements and more stringent observational tests are discussed.