Time Scale Of Interaction Research Articles

Astroparticles from X-Ray Binary Coronae

The recent observation of high-energy neutrinos from the Galactic plane implies an abundant population of hadronic cosmic-ray sources in the Milky Way. We explore the role of the coronae of accreting stellar-mass black holes as such astroparticle emitters. We show that the particle acceleration and interaction timescales in the coronal region are tied to the compactness of the X-ray source. Thus, neutrino emission processes may similarly happen in the cores of active galactic nuclei and black hole X-ray binaries (XRBs), despite their drastically different masses and physical sizes. We apply the model to the well-measured XRB Cygnus X-1 and find that the cascaded gamma rays accompanying the neutrino emission naturally explain the GeV emission that only presents during the source’s hard state, while the state-averaged gamma-ray emission explains the LHAASO observation above 20 TeV. We show that XRB coronae could contribute significantly to the Galactic cosmic-ray and Galactic plane neutrino fluxes. Our model predicts variable high-energy neutrino emission from bright Galactic XRBs that may be observed by IceCube and future neutrino observatories.

Cobaltabis(dicarbollide) Interaction with DNA Resolved at the Atomic Scale.

Boron neutron capture therapy represents a promising avenue for cancer treatment that requires nontoxic drugs with a high boron content efficiently distributed into cancerous cells. The metallacarborane o-cobaltabis(dicarbollide) ([COSAN]-) fulfills these requirements and constitutes an attractive candidate. Nevertheless, the interaction of this promising drug with nucleic acids, the assumed target of the biological damage, is poorly understood since contradictory results are reported in the literature. This work establishes the DNA/[COSAN]- interaction strength, mechanism, and time scale at the atomistic level by using a combination of microsecond-molecular dynamics and hybrid quantum mechanics/molecular mechanics simulations and by quantifying the absolute binding free energy. Results show that the DNA/[COSAN]- interaction is highly dependent on the ionic strength of the medium. A relatively weak DNA major groove binding (ΔGbind= -2.49 kcal/mol) driven mostly by dihydrogen B-H···H-N bonding is observed in the simulations only at a high NaCl concentration, whereas DNA intercalation mode is deemed highly unlikely.

Thermalization and hotspot formation around small primordial black holes

We quantitatively analyze a basic question: what is the stationary solution of the background plasma temperature profile around a black hole (BH)? One may naively expect that the temperature profile continuously decreases from the Hawking temperature at the surface of the BH towards an outer region. We show analytically and numerically that this is not the case because local thermal equilibrium cannot be maintained near the surface of the BH and also because the high-energy particles emitted from Hawking radiation cannot be instantaneously thermalized into the background plasma. The temperature profile has a plateau within a finite distance from the BH, and even the overall amplitude of background temperature at a distance far away from the BH is significantly suppressed compared with the naive expectation. The main reason for these counterintuitive results comes from the fact that the size of the BH is too small that particles of Hawking radiation goes far away within the typical time scale of interactions.

Inverse modeling of time-delayed interactions via the dynamic-entropy formalism.

Although instantaneous interactions are unphysical, a large variety of maximum entropy statistical inference methods match the model-inferred and the empirically measured equal-time correlation functions. Focusing on collective motion of active units, this constraint is reasonable when the interaction timescale is much faster than that of the interacting units, as in starling flocks, yet it fails in a number of counterexamples, as in leukocyte coordination (where signaling proteins diffuse among two cells). Here, we relax this assumption and develop a path integral approach to maximum-entropy framework, which includes delay in signaling. Our method is able to infer the strength of couplings and fields, but also the time required by the couplings to completely transfer information among the units. We demonstrate the validity of our approach providing excellent results on synthetic datasets of non-Markovian trajectories generated by the Heisenberg-Kuramoto and Vicsek models equipped with delayed interactions. As a proof of concept, we also apply the method to experiments on dendritic migration, where matching equal-time correlations results in a significant information loss.

Accounting for the Variability of Earthquake Rates within Low-Seismicity Regions: Application to the 2022 Aotearoa New Zealand National Seismic Hazard Model

ABSTRACT The distribution of earthquakes in time and space is seldom stationary, which could hinder a robust statistical analysis, particularly in low-seismicity regions with limited data. This work investigates the performance of stationary Poisson and spatially precise forecasts, such as smoothed seismicity models (SSMs), in terms of the available training data. Catalog bootstrap experiments are conducted to: (1) identify the number of training data necessary for SSMs to perform spatially better than the least-informative Uniform Rate Zone (URZ) models; and (2) describe the rate temporal variability accounting for the overdispersion and nonstationarity of seismicity. Formally, the strict-stationarity assumption used in traditional forecasts is relaxed into local and incremental stationarity (i.e., a catalog is only stationary in the vicinity of a given time point t) along with self-similar behavior described by a power law. The results reveal rate dispersion up to 10 times higher than predicted by Poisson models and highlight the impact of nonstationarity in assuming a constant mean rate within training-forecast intervals. The temporal rate variability is translated into a reduction of spatial precision by means of URZ models. First, counting processes are devised to capture rate distributions, considering the rate as a random variable. Second, we devise a data-driven method based on geodetic strain rate to spatially delimit the precision of URZs, assuming that strain/stress rate is related to the timescales of earthquake interactions. Finally, rate distributions are inferred from the available data within each URZ. We provide forecasts for the New Zealand National Seismic Hazard Model update, which can exhibit rates up to ten times higher in low-seismicity regions compared with SSMs. This study highlights the need to consider nonstationarity in seismicity models and underscores the importance of appropriate statistical descriptions of rate variability in probabilistic seismic hazard analysis.

Effects of the third body (O and N) on the recombination of molecular nitrogen using quasi-classical trajectory methods

The investigation of the recombination reactions poses significant challenges due to the complexities involved in three-body collisions including simultaneous interaction of three bodies and multiple time scales. This work aims to investigate the complex dynamics involved in the recombination of atomic nitrogen to form molecular nitrogen using the quasi-classical trajectory method for the N3 and the N2O systems. The recombination pathways considered include a single-step direct reaction and a two-step mechanism that involves the formation of an intermediate with a finite lifetime which is stabilized through a subsequent collision with a third body. The latter is further classified as Lindemann or Chaperon mechanism based on the role played by the third body. The model uses a time-lag parameter to allow for a consistent treatment of all the reaction pathways. It is observed that the recombination probability is greatest for collisions involving low translational energies and low time lags. Recombination rate coefficients are evaluated using a novel rate coefficient expression developed for three-body collisions. Low temperature recombination rate coefficients, which can be computationally prohibitive to evaluate using traditional detailed balance methods, can be evaluated at a low computational cost. The recombination pathways are determined algorithmically by identifying the various interaction time scales. The direct mechanism is found to have a larger recombination probability, but a lower rate coefficient. The effect of the third body (oxygen and nitrogen atoms) on the recombination dynamics is explored in detail. It is observed that the recombination in excess of O atom leads to a larger population of the low internal energy states, as opposed to recombination in the excess of N atoms. The dominance of the Chaperon mechanism is seen in both systems.

From Discovery to the First Month of the Type II Supernova 2023ixf: High and Variable Mass Loss in the Final Year before Explosion

We present the discovery of the Type II supernova SN 2023ixf in M101 and follow-up photometric and spectroscopic observations, respectively, in the first month and week of its evolution. Our discovery was made within a day of estimated first light, and the following light curve is characterized by a rapid rise (≈5 days) to a luminous peak (M V ≈ − 18.2 mag) and plateau (M V ≈ − 17.6 mag) extending to 30 days with a fast decline rate of ≈0.03 mag day−1. During the rising phase, U − V color shows blueward evolution, followed by redward evolution in the plateau phase. Prominent flash features of hydrogen, helium, carbon, and nitrogen dominate the spectra up to ≈5 days after first light, with a transition to a higher ionization state in the first ≈2 days. Both the U−V color and flash ionization states suggest a rise in the temperature, indicative of a delayed shock breakout inside dense circumstellar material (CSM). From the timescales of CSM interaction, we estimate its compact radial extent of ∼(3–7) × 1014 cm. We then construct numerical light-curve models based on both continuous and eruptive mass-loss scenarios shortly before explosion. For the continuous mass-loss scenario, we infer a range of mass-loss history with 0.1–1.0 M ⊙ yr−1 in the final 2−1 yr before explosion, with a potentially decreasing mass loss of 0.01–0.1 M ⊙ yr−1 in ∼0.7–0.4 yr toward the explosion. For the eruptive mass-loss scenario, we favor eruptions releasing 0.3–1 M ⊙ of the envelope at about a year before explosion, which result in CSM with mass and extent similar to the continuous scenario. We discuss the implications of the available multiwavelength constraints obtained thus far on the progenitor candidate and SN 2023ixf to our variable CSM models.

Spin-exchange carrier multiplication in manganese-doped colloidal quantum dots.

Carrier multiplication is a process whereby a kinetic energy of a carrier relaxes via generation of additional electron-hole pairs (excitons). This effect has been extensively studied in the context of advanced photoconversion as it could boost the yield of generated excitons. Carrier multiplication is driven by carrier-carrier interactions that lead to excitation of a valence-band electron to the conduction band. Normally, the rate of phonon-assisted relaxation exceeds that of Coulombic collisions, which limits the carrier multiplication yield. Here we show that this limitation can be overcome by exploiting not 'direct' but 'spin-exchange' Coulomb interactions in manganese-doped core/shell PbSe/CdSe quantum dots. In these structures, carrier multiplication occurs via two spin-exchange steps. First, an exciton generated in the CdSe shell is rapidly transferred to a Mn dopant. Then, the excited Mn ion undergoes spin-flip relaxation via a spin-conserving pathway, which creates two excitons in the PbSe core. Due to the extremely fast, subpicosecond timescales of spin-exchange interactions, the Mn-doped quantum dots exhibit an up-to-threefold enhancement of the multiexciton yield versus the undoped samples, which points towards the considerable potential of spin-exchange carrier multiplication in advanced photoconversion.

Effective Chiral Magnetic Effect from Neutrino Radiation.

We develop an approach to chiral kinetic theories for electrons close to equilibrium and neutrinos away from equilibrium based on a systematic power counting scheme for different timescales of electromagnetic and weak interactions. Under this framework, we derive electric and energy currents along magnetic fields induced by neutrino radiation in general nonequilibrium states. This may be regarded as an effective chiral magnetic effect (CME), which is present without a chiral chemical potential, unlike the conventional CME. We also consider the so-called gain region of core-collapse supernovae as an example and find that the effective CME enhanced by persistent neutrino emission in time is sufficiently large to lead to the inverse cascade of magnetic and fluid kinetic energies and observed magnitudes of pulsar kicks. Our framework may also be applicable to other dense-matter systems involving nonequilibrium neutrinos.

Wave Detection and Tracking Within a Rotating Detonation Engine Through Object Detection

As the operational time window of experimental rotating detonation engines (RDEs) is expanded and the technology matures toward integration within gas turbines, monitoring techniques must evolve to offer computationally efficient and highly time-resolved diagnostics. A computer vision object detection methodology that seeks to reduce data processing time and calculate wave velocity within drastically reduced time intervals as compared to traditional high-frame-rate RDE images analysis techniques is proposed. The adapted you-only-look-once object detection network is trained to detect individual detonation waves within single down-axis RDE images. The wave location and rotational direction detected within a frame are tracked through a series of high-speed images to calculate the frame-to-frame wave velocity with the time-step resolution of across a series of frames. The analysis of the annotation box size and image linearization effects is presented, demonstrating the lowest frame-to-frame velocity total uncertainty of and the highest classification speed of 9.5 frames per second using linearized images. Linearized images “unwrap” the RDE annulus pixel region to a reduced image size. This new method offers great reductions in data processing times and unsteady detonation behavior insight at intervals more comparable to the timescales of detonation wave interactions via the application of machine learning to experimental RDE data.

Interaction between dry and hot extremes at a global scale using a cascade modeling framework

Climate change amplifies dry and hot extremes, yet the mechanism, extent, scope, and temporal scale of causal linkages between dry and hot extremes remain underexplored. Here using the concept of system dynamics, we investigate cross-scale interactions within dry-to-hot and hot-to-dry extreme event networks and quantify the magnitude, temporal-scale, and physical drivers of cascading effects (CEs) of drying-on-heating and vice-versa, across the globe. We find that locations exhibiting exceptionally strong CE (hotspots) for dry-to-hot and hot-to-dry extremes generally coincide. However, the CEs differ strongly in their timescale of interaction, hydroclimatic drivers, and sensitivity to changes in the soil-plant-atmosphere continuum and background aridity. The CE of drying-on-heating in the hotspot locations reaches its peak immediately driven by the compounding influence of vapor pressure deficit, potential evapotranspiration, and precipitation. In contrast, the CE of heating-on-drying peaks gradually dominated by concurrent changes in potential evapotranspiration, precipitation, and net-radiation with the effect of vapor pressure deficit being strongly controlled by ecosystem isohydricity and background aridity. Our results help improve our understanding of the causal linkages and the predictability of compound extremes and related impacts.

Electron Density Changes and Ultrafast Carrier Dynamics of the Antiferromagnetic Semiconductor MnPS3 through Magnetic Phase Transition.

Studying ultrafast dynamics provides us with a way to modify materials from the timescale of particle interaction, and the related research on antiferromagnetic semiconductors is still inadequate. Based on the electron density reconstruction, we achieve the visualization of magnetic interactions of bulk antiferromagnetic MnPS3 in the ground state, reveal the role of two atomic site occupations of S atoms in different magnetic phase transitions, and provide the theoretical and experimental support for modifying magnetic properties by selectively replacing the S atom. The ultrafast carrier dynamics can provide information from the excited state to the ground state. Based on time-resolved transmittance measurements, ultrafast carrier dynamics of MnPS3 are reported. The phonon-assisted gap transition driven by the electronic structure is characterized. The coupling relationship among electrons, spin, and phonons is established. Furthermore, the spin orientations within different phases are confirmed.

OpenQASM 3: A Broader and Deeper Quantum Assembly Language

Quantum assembly languages are machine-independent languages that traditionally describe quantum computation in the circuit model. Open quantum assembly language (OpenQASM 2) was proposed as an imperative programming language for quantum circuits based on earlier QASM dialects. In principle, any quantum computation could be described using OpenQASM 2, but there is a need to describe a broader set of circuits beyond the language of qubits and gates. By examining interactive use cases, we recognize two different timescales of quantum-classical interactions: real-time classical computations that must be performed within the coherence times of the qubits, and near-time computations with less stringent timing. Since the near-time domain is adequately described by existing programming frameworks, we choose in OpenQASM 3 to focus on the real-time domain, which must be more tightly coupled to the execution of quantum operations. We add support for arbitrary control flow as well as calling external classical functions. In addition, we recognize the need to describe circuits at multiple levels of specificity, and therefore we extend the language to include timing, pulse control, and gate modifiers. These new language features create a multi-level intermediate representation for circuit development and optimization, as well as control sequence implementation for calibration, characterization, and error mitigation.

Resonance capture and long-term evolution of planets in binary star systems

Aims. The growing population of planets discovered in orbit around one stellar component of a binary star raises the question of the influence of the binary companion on the formation process of planetary systems. The aim of this work is to study the impact of a binary companion on the evolution of two-planet systems during both the Type-II migration phase and their long-term evolution after the dissipation of the protoplanetary disk. Methods. We used the symplectic integrator SyMBA, modified to include a wide binary companion. We also included the Type-II migration of giant planets during the protoplanetary disk phase with suitable eccentricity and inclination damping as well as the gravitational potential acting on the planets due to the disk and the nodal precession of the disk induced by the binary companion. We considered various inclinations, eccentricities, and separations of the binary companion. Results. Disk migration allows for the formation of planet pairs in mean-motion resonances despite the presence of the binary companion. When the binary separation is wide (1000 au), the timescale of the perturbations that it raises on the planets is longer than the disk’s lifetime and resonant pairs are routinely formed in the 2:1, 5:2, and 3:1 commensurabilities. Provided the planet-planet interaction timescale is smaller than the timescale of binary perturbations, these systems can remain in resonance long after the disk has dissipated. When the binary separation is smaller (250 au), only planets in the 2:1 resonance tend to remain in a resonant state and more chaotic evolutions are observed, as well as more ejections. After those ejections, the remaining planet can become eccentric due to the perturbations from the binary companion in addition, for strongly inclined binary companions, captures in the von Ziepel-Lidov-Kozai resonance can occur. Whereas in systems with two planets, this mechanism is quenched by planet-planet interactions. Our simulations reveal that the interplay between planet-disk, planet-planet, and planet-binary interactions can lead to the formation of resonant pairs of planets which remain stable over timescales much longer than the disk’s lifetime.

Emergent decoherence induced by quantum chaos in a many-body system: A Loschmidt echo observation through NMR

In the long quest to identify and compensate the sources of decoherence in many-body systems far from the ground state, the varied family of Loschmidt echoes (LEs) became an invaluable tool in several experimental techniques. A LE involves a time-reversal procedure to assess the effect of perturbations in a quantum excitation dynamics. However, when addressing macroscopic systems one is repeatedly confronted with limitations that seem insurmountable. This led to the formulation of the central hypothesis of irreversibility stating that the timescale of decoherence, ${T}_{3}$, is proportional to the timescale of the many-body interactions we reversed, ${T}_{2}$. We test this by implementing two experimental schemes based on Floquet Hamiltonians where the effective strength of the dipolar spin-spin coupling, i.e., $1/{T}_{2}$, is reduced by a variable scale factor $k$. This extends the perturbation timescale, ${T}_{\mathrm{\ensuremath{\Sigma}}}$, in relation to ${T}_{2}$. Strikingly, we observe the superposition of the normalized Loschmidt echoes for the bigger values of $k$. This manifests the dominance of the intrinsic dynamics over the perturbation factors, even when the Loschmidt echo is devised to reverse that intrinsic dynamics. Thus, in the limit where the reversible interactions dominate over perturbations, the LE decays within a timescale, ${T}_{3}\ensuremath{\approx}{T}_{2}/R$ with $R=(0.15\ifmmode\pm\else\textpm\fi{}0.01)$, confirming the emergence of a perturbation independent regime. These results support the central hypothesis of irreversibility.

Signals of low grade organic matter alteration in the Upper Permian Kupferschiefer (Spremberg area, Eastern Germany) – A by-product of copper mineralization?

Organic matter (OM) is known to be an important reductant in many sediment-hosted base metal deposits. However, the precise nature of the interactions between OM and hydrothermal fluids is still debated, as is just how such interconnected reactions develop over geological timescales. We investigated the Kupferschiefer mineralization in two drill cores from the Spremberg-Graustein field in Eastern Germany focusing on the inventory of organonitrogen, -sulfur and -oxygen (NSO) compounds, which are most affected by organic–inorganic interactions with mineral surfaces, metals and aqueous fluids. Rather homogeneous deposition of type II marine organic matter, prevailing photic zone euxinia and an early oil window thermal maturity were documented using conventional hydrocarbon analysis. Furthermore, a slight level of hydrothermal alteration was detected in the lower part of drill core 121 h/72, in proximity to the epigenetic hematitic alteration zone known as ‘Rote Fäule’. A minor loss of extractable organic matter and especially long-chain n-alkanes was accompanied by significant enrichment in oxygenated compounds and increased molecular oxygen content detected by ultra-high resolution mass spectrometry (FT–ICR–MS). A strong enrichment of deuterium observed in the n-alkanes (up to −36‰) and isoprenoids (up to −20‰) indicates that hydrogen exchange with an evaporitic fluid occurred in the Spremberg Kupferschiefer over geological timescales at maximum temperatures not exceeding 110 °C. We therefore conclude that FT–ICR–MS, combined with determination of stable hydrogen isotope compositions, can provide valuable information about interaction time scales and the origin of mineralizing hydrothermal fluids.

Timescales of delay propagation in airport networks

Flight delays persist and spread in airport networks due to high interconnectivity in the air transportation infrastructure. How quickly delay propagates between two airports is determined by factors such as the number of flights between airports, the duration of the flight, presence of disruptions, and schedule buffers. Accurate estimation of the time for delay propagation can improve system predictability and reliability. However, noisy airport delay data, along with a lack of visibility into airline scheduling and disruption management strategies, result in a challenging estimation problem for such propagation timescales. We present an algorithm to estimate statistically significant time lags between airport delays from noisy, aggregate operational data. The algorithm uses sliding correlation windows to extract the airport pairs with stable delay lags. We apply our method to identify different timescales of interactions for US airport delays in 2017. Our analysis yields two main results: (1) The most stable lags between airport delays involve the Northeast airports; (2) The stable lags between two airports are negatively correlated to the scheduled flight times between the same two airports. These results regarding delay propagation speeds have potential implications for delay prediction models and airline schedule design.

Gap carving by a migrating planet embedded in a massive debris disc

ABSTRACT When considering gaps in debris discs, a typical approach is to invoke clearing by an unseen planet within the gap, and derive the planet mass using Wisdom overlap or Hill radius arguments. However, this approach can be invalid if the disc is massive, because clearing would also cause planet migration. This could result in a calculated planet mass that is incompatible with the inferred disc mass, because the predicted planet would in reality be too small to carve the gap without significant migration. We investigate the gap that a single embedded planet would carve in a massive debris disc. We show that a degeneracy is introduced, whereby an observed gap could be carved by two different planets: either a high-mass, barely migrating planet, or a smaller planet that clears debris as it migrates. We find that, depending on disc mass, there is a minimum possible gap width that an embedded planet could carve (because smaller planets, rather than carving a smaller gap, would actually migrate through the disc and clear a wider region). We provide simple formulae for the planet-to-debris disc mass ratio at which planet migration becomes important, the gap width that an embedded planet would carve in a massive debris disc, and the interaction time-scale. We also apply our results to various systems, and in particular show that the disc of HD 107146 can be reasonably well-reproduced with a migrating, embedded planet. Finally, we discuss the importance of planet–debris disc interactions as a tool for constraining debris disc masses.

On the Feasibility of Rovibrational Laser Cooling of Radioactive RaF+ and RaH+ Cations

Polar radioactive molecules have been suggested to be exceptionally sensitive systems in the search for signatures of symmetry-violating effects in their structure. Radium monofluoride (RaF) possesses an especially attractive electronic structure for such searches, as the diagonality of its Franck-Condon matrix enables the implementation of direct laser cooling for precision experiments. To maximize the sensitivity of experiments with short-lived RaF isotopologues, the molecular beam needs to be cooled to the rovibrational ground state. Due to the high kinetic energies and internal temperature of extracted beams at radioactive ion beam (RIB) facilities, in-flight rovibrational cooling would be restricted by a limited interaction timescale. Instead, cooling techniques implemented on ions trapped within a radiofrequency quadrupole cooler-buncher can be highly efficient due to the much longer interaction times (up to seconds). In this work, the feasibility of rovibrationally cooling trapped RaF+ and RaH+ cations with repeated laser excitation is investigated. Due to the highly diagonal nature between the ionic ground state and states in the neutral system, any reduction of the internal temperature of the molecular ions would largely persist through charge-exchange without requiring the use of cryogenic buffer gas cooling. Quasirelativistic X2C and scalar-relativistic ECP calculations were performed to calculate the transition energies to excited electronic states and to study the nature of chemical bonding for both RaF+ and RaH+. The results indicate that optical manipulation of the rovibrational distribution of trapped RaF+ and RaH+ is unfeasible due to the high electronic transition energies, which lie beyond the capabilities of modern laser technology. However, more detailed calculations of the structure of RaH+ might reveal possible laser-cooling pathways.

Timescales of Local and Cross-Area Interactions during Neuroprosthetic Learning.

How does the brain integrate signals with different timescales to drive purposeful actions? Brain-machine interfaces (BMIs) offer a powerful tool to causally test how distributed neural networks achieve specific neural patterns. During neuroprosthetic learning, actuator movements are causally linked to primary motor cortex (M1) neurons, i.e., "direct" neurons that project to the decoder and whose firing is required to successfully perform the task. However, it is unknown how such direct M1 neurons interact with both "indirect" local (in M1 but not part of the decoder) and across area neural populations (e.g., in premotor cortex/M2), all of which are embedded in complex biological recurrent networks. Here, we trained male rats to perform a M1-BMI task and simultaneously recorded the activity of indirect neurons in both M2 and M1. We found that both M2 and M1 indirect neuron populations could be used to predict the activity of the direct neurons (i.e., "BMI-potent activity"). Interestingly, compared with M1 indirect activity, M2 neural activity was correlated with BMI-potent activity across a longer set of time lags, and the timescale of population activity patterns evolved more slowly. M2 units also predicted the activity of both M1 direct and indirect neural populations, suggesting that M2 population dynamics provide a continuous modulatory influence on M1 activity as a whole, rather than a moment-by-moment influence solely on neurons most relevant to a task. Together, our results indicate that longer timescale M2 activity provides modulatory influence over extended time lags on shorter-timescale control signals in M1.SIGNIFICANCE STATEMENT A central question in the study of motor control is whether primary motor cortex (M1) and premotor cortex (M2) interact through task-specific subpopulations of neurons, or whether tasks engage broader correlated networks. Brain-machine interfaces (BMIs) are powerful tools to study cross-area interactions. Here, we performed simultaneous recordings of M1 and M2 in a BMI task using a subpopulation of M1 neurons (direct neurons). We found that activity outside of direct neurons in M1 and M2 was predictive of M1-BMI task activity, and that M2 activity evolved at slower timescales than M1. These findings suggest that M2 provides a continuous modulatory influence on M1 as a whole, supporting a model of interactions through broad correlated networks rather than task-specific neural subpopulations.