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Electromagnetic ion cyclotron (EMIC) waves and fast magnetosonic (MS) waves were previously reported to be simultaneously generated by ring current protons (10s keV) within the magnetic dip. In this work, we present a distinct physical scenario of concurrent high‐frequency EMIC (HFEMIC) and MS waves within a magnetic dip where low‐energy (10s–100s eV) and hot (10s keV) protons facilitate the local growth of HFEMIC and MS waves, respectively. Moreover, the low‐energy protons exhibit remarkable perpendicular flux enhancements, which are well modulated by MS waves as evidenced by their significant correlation coefficient (∼0.78). Consequently, the concurrent two wave modes should arise from the complicated coupling between HFEMIC and MS waves, marking a departure from previous studies. Our observations demonstrate that the magnetic dip can provide favorable conditions for such intricate coupling processes, offering novel insights into its impact on magnetospheric dynamics. Plain Language Summary: The magnetic dip denotes a local minimum of magnetic field strength. Such a magnetic structure can modulate ion distributions, thereby playing significant roles in wave generation and evolution within the magnetic dip. In this work, we report a special case of concurrent high‐frequency electromagnetic ion cyclotron (HFEMIC) waves and fast magnetosonic (MS) waves observed within a magnetic dip. The dip structure and the ion distributions therein favor the local growth of HFEMIC and MS waves. Additionally, the fluxes of low‐energy (10s–100s eV) protons are modulated by MS waves as evidenced by their significant correlation coefficient. Hence this case suggests a quite different scenario of wave generation and energy transfer within the magnetic dip, which will be of importance to understanding the dynamics of magnetic dips. Key Points: High‐frequency electromagnetic ion cyclotron waves and low‐harmonic magnetosonic waves are simultaneously observed inside a magnetic dipThe magnetic dip structure and ion distributions therein favor the local growth for those two kinds of wavesThe low‐energy (10s–100s eV) proton fluxes should be well modulated by fast magnetosonic waves as evidenced by their significant correlation [ABSTRACT FROM AUTHOR]

In recent years, it has been found that magnetic dip caused by diamagnetic motion of injected plasma can provide an appropriate environment for excitation of electromagnetic ion cyclotron (EMIC) waves. These findings have been widely reported in the Earth's magnetic environment. However, it has rarely been reported in Jupiter's magnetic environment. This paper reports the characteristics of EMIC waves observed by Juno in the magnetic dip of Jupiter. Multiple‐band EMIC waves are observed in frequency range from 10−3 Hz to several Hz. The theoretical analysis shows that in this event both He+ band and O+ band EMIC waves can be constrained in the magnetic dip, which is consistent with the wave emissions observed inside the magnetic dip. Our result provides the first evidence that EMIC wave can be ducted inside a magnetic dip in Jupiter's magnetosphere. Plain Language Summary: The relationship between magnetic structures and electromagnetic waves in the Earth's magnetosphere has been widely reported. Recent studies have theoretically displayed the effects of the magnetic dip on the EMIC wave propagation in Earth's magnetic field. In this paper, we use the event observed by Juno in the magnetic environment of Jupiter to analyze the effect of the magnetic dip on the propagation of EMIC waves. As a result, the observed EMIC waves can be ducted inside the magnetic dip of Jupiter's magnetosphere. Since these ducted waves would influence the dynamics of energetic protons through longtime scattering effects, the magnetic dip is expected to play an important role in the dynamics of Jupiter's magnetosphere. Key Points: Electromagnetic ion cyclotron (EMIC) waves are observed during the magnetic dip by JunoTheoretical analysis about the effects of magnetic dips on the EMIC wave propagation in Jupiter's magnetosphere is performedBoth He+ and O+ band EMIC waves can be ducted inside the magnetic dip in Jupiter's magnetosphere [ABSTRACT FROM AUTHOR]

Pc1 geomagnetic pulsations within the frequency range of 0.2–5 Hz, the ground signatures of electromagnetic ion cyclotron (EMIC) waves, are usually observed to progress westward. A plausible explanation is that their westward‐excursion speed is defined by the drift velocity of the source particles in the geomagnetic dipole field. In this study, this relationship is examined through conjugate observations from ground‐based and spaceborne instruments. The ground‐based observations, including Pc1 pulsations and auroral emissions, consistently demonstrate a westward‐excursion speed of ∼4–5 MLT per hour, which agrees with the time delay between EMIC wave observations at two equatorial spacecraft. Observations of the wave source particles, however, indicate an inconsistency between the slow westward excursion speed and the high energy of the wave source protons. This apparent inconsistency is reconciled by the trapping motion of energetic particles within magnetic dips, which is supported by the simultaneous flux enhancements of protons across a broad energy range between ∼50 and ∼100 keV. These results improve our understanding of the westward excursion of Pc1 pulsations, and also underscore the need for caution when directly linking their westward‐excursion speed to the energies of the source particles. Plain Language Summary: Ground‐based magnetometers often observe geomagnetic field oscillations at various frequencies, among which are Pc1 pulsations within the frequency range of 0.2–5 Hz. It is commonly believed that these pulsations correspond to electromagnetic ion cyclotron (EMIC) waves in Earth's magnetosphere, which are excited by anisotropic distributions of energetic ions. The Pc1/EMIC waves are usually observed to progress westward, and the excursion speed is thought to be determined by the drift velocity of source ions in the geomagnetic dipole field. This relationship is examined in this study based on multi‐point observations of ground‐based magnetic pulsations, auroral emissions, EMIC waves near the equatorial magnetosphere, and energetic particles in space. Ground‐based magnetometers show the westward excursion of Pc1 pulsations at a speed of ∼4–5 magnetic local time per hour, consistent with proton auroral emissions and equatorial spacecraft observations. However, this speed does not match the drift speed of observed source protons in the geomagnetic dipole field. We suggest that this apparent inconsistency can be reconciled after considering the revision of particles' drift motion in the presence of concomitant, localized field depressions in the magnetosphere. This explanation, supported by spacecraft observations, sheds new light on the intricate interactions between geomagnetic disturbances and the behavior of energetic particles. Key Points: We observe the westward excursion of ground Pc1 pulsations at ∼4–5 MLT/hr, consistent with auroral and multi‐spacecraft observationsThe excursion speed appears to be lower than the drift speed of the anisotropic source protons in the unperturbed geomagnetic fieldThe apparent inconsistency can be reconciled after considering the trapped motion of particles in localized magnetic dips [ABSTRACT FROM AUTHOR]

Abstract In recent years, it has been found that magnetic dip caused by diamagnetic motion of injected plasma can provide an appropriate environment for excitation of electromagnetic ion cyclotron (EMIC) waves. These findings have been widely reported in the Earth's magnetic environment. However, it has rarely been reported in Jupiter's magnetic environment. This paper reports the characteristics of EMIC waves observed by Juno in the magnetic dip of Jupiter. Multiple‐band EMIC waves are observed in frequency range from 10−3 Hz to several Hz. The theoretical analysis shows that in this event both He+ band and O+ band EMIC waves can be constrained in the magnetic dip, which is consistent with the wave emissions observed inside the magnetic dip. Our result provides the first evidence that EMIC wave can be ducted inside a magnetic dip in Jupiter's magnetosphere.

Recent studies have found that magnetic dips resulting from the diamagnetic motion of injected plasmas can provide a favorable environment for electromagnetic ion cyclotron (EMIC) wave excitation. However, another critical question how magnetic dips affect the propagation of EMIC waves remains uncovered. In this paper, with plasma environment as well as wave properties observed in a typical event, theoretical analysis about this topic has been provided. Our results show that in this event both H+ band and He+ band EMIC waves can be constrained in the magnetic dip, which is consistent with the wave emissions observed inside the magnetic dip. The energetic protons have also been found to fall around the saturated states, suggesting a stable balance built among EMIC waves, energetic protons, and magnetic structures. Our results provide one new insight into the EMIC wave propagation inside a magnetic dip and their important roles in the dynamics of magnetic dips. Plain Language Summary: Magnetic structures and electromagnetic waves are two of the most common phenomena in space plasmas. One key scientific topic is to study the relation between them. Recent studies have found that plasma waves can be excited inside magnetic structures. Specifically, electromagnetic ion cyclotron (EMIC) waves have been reported to be excited in a large‐scale magnetic dip resulting from the diamagnetic drift of energetic protons. Here, we focus on the effect of the magnetic dip on the propagation of EMIC waves. If EMIC waves can be ducted inside the magnetic dip, they will be involved into the total balance of the magnetic structure since these waves would influence the dynamics of energetic protons through long‐time scattering effects. Thus, our result will be of importance to understanding the dynamics of magnetic dips. Key Points: Theoretical analysis about the effects of magnetic dips on electromagnetic ion cyclotron (EMIC) wave propagations has been givenOur theoretical result shows that both H+ and He+ band EMIC waves can be ducted inside the magnetic dipEnergetic protons inside the magnetic dip are verified near the saturated states, suggesting a stable force balance in the magnetic dip [ABSTRACT FROM AUTHOR]

The excitation of electrostatic and/or electromagnetic waves in the plasma universe is often associated with anisotropic velocity distributions of charged particles. In Earth's inner magnetosphere, this anisotropy can gradually develop as particles injected from the magnetotail drift around the Earth at different speeds depending on their energy and pitch angle. Here, we show that the perpendicular‐moving and bouncing ions can be separated more abruptly near the injection front. These pitch‐angle filters are localized magnetic dip structures formed by the diamagnetic behavior of the injected particles, which can trap perpendicular‐moving ions and allow bouncing ions to overtake. The resulting ion anisotropy facilitates the rapid generation of electromagnetic ion cyclotron (EMIC) waves, which in turn can largely reshape the Van Allen radiation belts. This scenario is examined by case and statistical observations, together with numerical simulations that reproduce most of the observational signatures, to support the causal relationship between magnetic dips, anisotropic ion distributions, and localized excitation of EMIC waves. Our study highlights the important roles of magnetic dips in the inner magnetospheric dynamics, as pitch‐angle filters of the injected ions and traveling hotspots of EMIC wave activities. Plain Language Summary: In Earth's Van Allen radiation belts, energetic particles are magnetically trapped to form a hazardous environment for spacecraft and astronauts. These particles can stay trapped for years before they are scattered toward the atmosphere by resonant interactions with plasma waves. Among these waves, the electromagnetic ion cyclotron (EMIC) waves are particularly important in the removal of energetic ions and relativistic electrons. The EMIC wave excitation is often associated with strong ion anisotropy, which gradually develops as particles injected from the magnetotail drift around the Earth at different speeds depending on their energy and pitch angle. Here, we propose a new scenario of localized EMIC wave excitation, in which the injected perpendicular‐moving and bouncing ions are abruptly separated by their associated diamagnetic dips, to develop strong ion anisotropy inside the dip structure and generate EMIC waves. This scenario is validated via case and statistical observations, together with numerical simulations that reproduce most of the observational signatures, which reveals the importance of the magnetic dips as traveling hotspots of EMIC wave activities. These insights indicate the localized and dynamical removal of energetic particles and provide key revision to the prevailing radiation belt models. Key Points: We perform case and statistical study on the association between magnetic dips, anisotropic proton distributions and EMIC wavesMagnetic dips serve as reversed pitch‐angle filters to trap the perpendicular‐moving protons and allow the bouncing protons to overtakeThe pitch‐angle filter leads to a higher ion anisotropy therein, which favors the localized excitation of electromagnetic ion cyclotron wave [ABSTRACT FROM AUTHOR]

Kinetic-scale magnetic holes (KSMHs) are structures characterized by a significant magnetic depression with a length scale on the order of the proton gyroradius. These structures have been investigated in recent studies in near-Earth space, and found to be closely related to energy conversion and particle acceleration, wave-particle interactions, magnetic reconnection, and turbulence at the kinetic-scale. However, there are still several major issues of the KSMHs that need further study — including (a) the source of these structures (locally generated in near-Earth space, or carried by the solar wind), (b) the environmental conditions leading to their generation, and (c) their spatio-temporal characteristics. In this study, KSMHs in near-Earth space are investigated statistically using data from the Magnetospheric Multiscale mission. Approximately 200,000 events were observed from September 2015 to March 2020. Occurrence rates of such structures in the solar wind, magnetosheath, and magnetotail were obtained. We find that KSMHs occur in the magnetosheath at rates far above their occurrence in the solar wind. This indicates that most of the structures are generated locally in the magnetosheath, rather than advected with the solar wind. Moreover, KSMHs occur in the downstream region of the quasi-parallel shock at rates significantly higher than in the downstream region of the quasi-perpendicular shock, indicating a relationship with the turbulent plasma environment. Close to the magnetopause, we find that the depths of KSMHs decrease as their temporal-scale increases. We also find that the spatial-scales of the KSMHs near the subsolar magnetosheath are smaller than those in the flanks. Furthermore, their global distribution shows a significant dawn-dusk asymmetry (duskside dominating) in the magnetotail.

The Van Allen Probe B satellite simultaneously observed electromagnetic ion cyclotron (EMIC) and fast magnetosonic (MS) waves in a magnetic dip on April 29, 2017. During the magnetic dip, we found the coexistence of flux enhancements of ring current protons (∼11.2–∼51.7 keV) and flux reductions of relativistic electrons (∼1 MeV), which are identified as typical signatures of a magnetic dip in the inner magnetosphere. Based on linear theoretical calculations and observational analysis, the observed ring current protons show an anisotropic temperature distribution and partial shell distribution for different energies during the magnetic dip to provide free energies for the generation of EMIC and MS waves, respectively. Our findings indicate that the complex unstable distribution in the velocity phase space of ring current protons during the magnetic dip can trigger the simultaneous generation of EMIC and MS waves in the inner magnetosphere. Plain Language Summary: Magnetic dip in the inner magnetosphere has local complex distribution of waves and particles and has become a research focus of the inner magnetosphere. Electromagnetic ion cyclotron (EMIC) waves have also been observed during the magnetic dip. However, up to now, the simultaneous observations of EMIC and magnetosonic (MS) waves have been seldom reported during the magnetic dip in the inner magnetosphere. If so, it is unresolved whether the free energies for driving EMIC and MS waves are attributed to different energy ions or the same proton ring. For the first time, in this letter, EMIC and MS waves are observed simultaneously by the Van Allen Probe B in the magnetic dip. To understand the excitation of the observed EMIC and MS waves, after examining the distribution of ring current protons during the magnetic dip and calculating the growth rate based on linear theory, we found that unstable protons during the magnetic dip could provide free energy for the generation of EMIC and MS waves. Our results show that the complex distribution in the velocity phase space of ring current protons during the magnetic dip has the potential to simultaneously trigger EMIC and MS waves. Key Points: Electromagnetic ion cyclotron (EMIC) and fast magnetosonic (MS) waves are simultaneously observed during the magnetic dipThe excitations of EMIC and MS waves are attributed to the complex unstable distribution of ring current protons during the magnetic dipThis manuscript is helpful to understand the evolution of injected energetic ions during the magnetic dip [ABSTRACT FROM AUTHOR]

Localized magnetic field depressions in the inner magnetosphere, known as magnetic dips, are produced by the diamagnetic motion of energetic ions injected via substorm activities. The magnetic dips, if deep enough, can produce a local minimum in the radial profile of the field strength to trap the injected protons. Therefore, the trapped protons would drift at the same speed as the dip propagation, which leads to the simultaneous enhancements of proton fluxes in multiple energy channels at the leading edge of the dip structure. On the trailing side, the reduction of proton fluxes shows dispersive features, which can be attributed to the energy‐dependent drift motion of the injected protons in the absence of the local field minimum. This scenario is examined based on comparisons between multi‐spacecraft observations and test‐particle simulations, and their good agreement validates the scenario to shed new light on the dynamics of the inner magnetosphere‐magnetotail coupled system. Plain Language Summary: During magnetospheric substorms, energetic ions are injected from the magnetotail toward the inner magnetosphere, and the diamagnetic motion of these ions produces longitudinally localized field depressions named magnetic dips. Recent studies with multi‐spacecraft observations have revealed the westward propagation of the magnetic dips, which are believed to originate from the westward drift of the injected ions in the geomagnetic field. One may expect from the wide energy range of the injected ions and the energy‐dependence of their drift motion that these ions would be gradually dispersed in the longitude to cause the expansion and shallowing of the dip structure. These expectations, however, are not consistent with the observations of sustained magnetic dips associated with simultaneous ion flux enhancements at multiple energy channels. To reconcile this inconsistency, we propose the ion trapping process for magnetic dips with sufficient depths, which explains the simultaneous flux enhancements observed on the leading edge of the dip structure. On the trailing side, the ions cannot be trapped due to the weaker field depressions, which explains the observations of dispersive ion flux reduction given a discontinued and/or localized process of substorm injection. This scenario is supported by the good agreement between test‐particle simulations and multi‐spacecraft observations. Key Points: We analyze the behavior of energetic protons associated with magnetic dip structures based on observations and test‐particle simulationsMagnetic dips with strong field depressions can trap energetic protons inside and have them drift at the same speed as the dip propagationObserved dispersionless increases and dispersive reductions of proton fluxes on dip leading and trailing sides are reproduced by simulations [ABSTRACT FROM AUTHOR]

The magnetosheath is inherently complex and rich, exhibiting various kinds of structures and perturbations. It is important to understand how these structures propagate and evolve and how they relate to the perturbations. Here we investigate a kind of magnetosheath structure known as a magnetic dip (MD). As far as we are aware, there have been no previous studies concerning the evolution (contracting or expanding) of these types of structures, and their propagation properties cannot be unambiguously determined. In this study, using Magnetospheric MultiScale (MMS) high‐temporal resolution data and multispacecraft analysis methods, we obtain the propagation and dynamic features of a set of MDs. Four different types of MDs are identified: "frozen‐in," "expanding," "contracting," and "stable‐propagating." Significantly, a stable‐propagation event is observed with a sunward propagation component. This indicates that the source of the structure in this case is closely associated with the magnetopause, which provides strong support to the contention in earlier research. We further reveal the mechanism leading to the MD contraction or expansion. The motion of the MDs boundary is found closely related with the dynamic pressure. The scale of the contracting and expanding events are typically ~5–20 ρi (ion gyroradius), significantly smaller than that of frozen‐in events (~40 ρi). The observations could relate large‐scale (more than several tens of ρi) and kinetic‐scale (less than ρi) MDs, by revealing an evolution that spans these different scales, and help us better understand the variation and dynamics of magnetosheath structures and plasmas. Key Points: Four different propagation properties of magnetosheath magnetic dips are identified by using several multispacecraft analysis methodsPressure imbalance plays an important role in the evolution (contracting and expanding) of sub‐MHD scale magnetic dipsA sunward propagating magnetic dip indicates that the structure source is closely associated with the magnetopause [ABSTRACT FROM AUTHOR]

The magnetic dips can create the electron butterfly pitch angle distribution (PAD) in the inner magnetosphere. However, its universality is still unconfirmed. We statistically investigate the global distribution of the occurrence rate of the magnetic dip‐related butterfly PAD for 466 keV and 2.1 MeV electrons using the measurements of the twin Van Allen Probes spanning from September 2012 to November 2018. The statistical results show that the magnetic dip‐related butterfly PADs are mainly confined to duskside to midnight within 4.5 < L < 6, and the peak occurrence rate (30% for 466 KeV and 70% for 2.1 MeV) occurs at the duskside equator around L = 5. The parametric study results suggest that the butterfly PADs preferably occur for high energy electrons with a negative initial radial flux gradient and a nearly isotropic initial PAD, which is consistent with the statistic results. This work confirms the vital importance of the magnetic dips on the evolution of the electron PADs. Plain Language Summary: A previous case study has shown that small localized depression of the background magnetic field can lead to the formation of butterfly pitch angle distribution (PAD) of the energetic electrons in the outer radiation belt. We present a statistical study to investigate the occurrence rate of the electron butterfly PAD with magnetic field depression at different locations in the near‐Earth space. The statistical result shows that the magnetic field depression‐related electron butterfly PAD preferably takes place at duskside equator with altitude ~4 Earth radius at which the occurrence rate reaches 30% for low energy electrons (~400 keV) and 70% for high energy electrons (~2 MeV). We also apply a parametric study to understand in detail how the electron butterfly PAD is created by magnetic field depression and the result suggests that the butterfly PAD preferably occurs for high energy electrons with a negative initial radial flux gradient and a nearly isotropic initial PAD, which is consistent with Van Allen Probe observations. The results of this paper have confirmed the generality of the magnetic field depression‐related electron butterfly PAD in the inner magnetosphere and improved the understating of the influence of magnetic field variation on electron PAD in the space environment. Key Points: The occurrence rate of bz dip‐related electron butterfly PADs peaks (30% for 466 keV and 70% for 2.1 MeV) at duskside equator around L = 5Bz dip events are common at night side and duskside within L = 4–6 and the depth of bz dips peaks (~10%) around L = 5 at MLT = 18Butterfly PADs preferably occur for electron with large negative radial flux gradient and isotropic initial PAD in large bz dip at high L [ABSTRACT FROM AUTHOR]

Localized injections of hot anisotropic plasma sheet particles into the inner magnetosphere can significantly deform the quiet time dipole‐like magnetic field and thus disturb electron and ion's drift paths and scattering rates. Although many details of magnetic field deformation can be inferred from empirical models, roles of different characteristics of injected plasma on the structure of such deformation require further investigation. In this study, we use the 2‐D axisymmetric equilibrium model to calculate self‐consistent magnetic field in force balance with a Gaussian thermal pressure distribution characterized by four input parameters: the ratio between plasma pressure and magnetic pressure (β) at the pressure peak β0, the radial location of the pressure peak L0, the width of the half peak pressure σ0, and the equatorial pressure anisotropy Ae. Using the modeled magnetic field, we find that the magnetic field perturbation increases with increasing β0 and decreasing σ0 while the magnetic curvature perturbation increases with increasing Ae, β0, and σ0 and decreasing L0. For energetic particles the change of magnetic gradient drift motion is much greater than that of curvature drift motion. The magnetic dip structure formation requires a critical β value that increases with increasing σ0 and decreasing L0. Despite the unavailability of observations in the existing literatures to check the condition of magnetic dip formation, such condition will be checked against observations as a future study. Finally, we also use 3‐D ring current‐atmosphere interactions model with self‐consistent magnetic field model to illustrate the effect of azimuthal pressure distribution, which is relevant to asymmetric ring current. Key Points: Self‐consistent magnetic field is obtained under a Gaussian distribution of thermal pressureThe dependence of the magnetic dip depth on thermal pressure distribution is shownThe change in the magnetic field topology by thermal pressure can lead to additional gradient drift [ABSTRACT FROM AUTHOR]

We present Van Allen Probe observations of electromagnetic ion cyclotron (EMIC) waves triggered solely due to individual substorm‐injected ions in the absence of storms or compressions of the magnetosphere during 9 August 2015. The time at which the injected ions are observed directly corresponds to the onset of EMIC waves at the location of Van Allen Probe A (L = 5.5 and 18:06 magnetic local time). The injection was also seen at geosynchronous orbit by the Geostationary Operational Environmental Satellite and Los Alamos National Laboratory spacecraft, and the westward(eastward) drift of ions(electrons) was monitored by Los Alamos National Laboratory spacecraft at different local times. The azimuthal location of the injection was determined by tracing the injection signatures backward in time to their origin assuming a dipolar magnetic field of Earth. The center of this injection location was determined to be close to ∼20:00 magnetic local time. Geostationary Operational Environmental Satellite and ground magnetometer responses confirm substorm onset at approximately the same local time. The observed EMIC wave onsets at Van Allen Probe were also associated with a magnetic field decrease. The arrival of anisotropic ions along with the decrease in the magnetic field favors the growth of the EMIC wave instability based on linear theory analysis. Key Points: Substorm ion injections can trigger EMIC waves; a decrease in the magnetic field magnitude is associated with the arrival of injected ionsInjection signatures are observed at GOES, Van Allen Probe A, and LANL spacecraft; energy and pitch angle dispersion are observed by Van Allen ProbeDrift paths of injected ions/electrons from various LANL spacecraft are traced back to find their injection location at  20:00 MLT [ABSTRACT FROM AUTHOR]

We present a multiple-satellite observation of the magnetic dip event during the substorm on 10 October 2013. The observation illustrates the temporal and spatial evolution of the magnetic dip and gives a compelling evidence that ring current ions induce the magnetic dip by enhanced plasma beta. The dip moves with the energetic ions in a comparable drift velocity and affects the dynamics of relativistic electrons in the radiation belt. In addition, the magnetic dip provides a favorable condition for the electromagnetic ion cyclotron (EMIC) wave generation based on the linear theory analysis. The calculated proton diffusion coefficients show that the observed EMIC wave can lead to the pitch angle scattering losses of the ring current ions, which in turn partially relax the magnetic dip in the observations. This study enriches our understanding of magnetic dip evolution and demonstrates the important role of the magnetic dip for the coupling of radiation belt and ring current. [ABSTRACT FROM AUTHOR]