Velocity Clouds Research Articles

A debris cloud model for hypervelocity impact of the spherical projectile on reactive material bumper composed of polytetrafluoroethylene and aluminum

In this paper, a debris cloud model is presented for the case of hypervelocity impact of the spherical projectile on the thin PTFE (polytetrafluoroethylene)/Al (aluminum) reactive material bumper at normal incidence. The experiments of projectiles with hypervelocity impact on Whipple shields with PTFE/Al and Al2024 as bumper respectively were carried out by using two-stage light-gas gun, and the movement process of debris cloud was recorded through laser shadow photography system. According to the numerical simulation results and the laser shadow photographs of debris cloud obtained from the experiment of hypervelocity impact, two parts named as internal and external debris cloud are considered in the theoretical model. Several assumptions are made, and the theoretical model of debris cloud is developed by the conservation laws of mass, momentum and energy. Four characteristic velocities of the debris cloud are first calculated, and thus the whole evolution process of the debris cloud is plotted according to those velocities. By comparing the size of the debris cloud shown in the experiment, it can be concluded that the theoretical model agrees well with the experimental results. Moreover, the characteristic velocities of projectile fragments and bumper fragments in the debris cloud are calculated, and the mass areal density and momentum areal density distribution of the debris cloud on the rear wall are also obtained. Additionally, the effects of the detonation reaction of the reactive material bumper on the projectile during the impact are analyzed in contrast with the results on the Al2024 bumper. It is indicated that the detonation reaction of PTFE/Al can reduce the velocity of center of mass of debris cloud and increase the expansion velocity of debris cloud. PTFE/Al bumper can reduce damage caused by debris cloud to rear wall.

Cloud base height estimates from sky imagery and a network of pyranometers

Cloud base height (CBH) is an important parameter for physics-based high resolution solar radiation modeling. In sky imager-based forecasts, a ceilometer or stereographic setup is needed to derive the CBH; otherwise erroneous CBHs lead to incorrect physical cloud velocity and incorrect projection of cloud shadows, causing solar power forecast errors due to incorrect shadow positions and timing of shadowing events. In this paper, two methods to estimate cloud base height from a single sky imager and distributed ground solar irradiance measurements are proposed. The first method (Time Series Correlation, denoted as “TSC”) is based upon the correlation between ground-observed global horizontal irradiance (GHI) time series and a modeled GHI time series generated from a sequence of sky images geo-rectified to a candidate set of CBH. The estimated CBH is taken as the candidate that produces the highest correlation coefficient. The second method (Geometric Cloud Shadow Edge, denoted as “GCSE”) integrates a numerical ramp detection method for ground-observed GHI time series with solar and cloud geometry applied to cloud edges in a sky image. CBH are benchmarked against a collocated ceilometer and stereographically estimated CBH from two sky imagers for 15 min median-filtered CBHs. Over 30 days covering all seasons, the TSC method performs similarly to the GCSE method with nRMSD of 18.9% versus 20.8%. A key limitation of both proposed methods is the requirement of sufficient variation in GHI to enable reliable correlation and ramp detection. The advantage of the two proposed methods is that they can be applied when measurements from only a single sky imager and pyranometers are available.

Exploring the physical properties of the cool circumgalactic medium with a semi-analytic model

We develop a semi-analytic model to explore the physical properties of cool pressure-confined circumgalactic clouds with mass ranging from $10$ to $10^{8} \, \rm M_{\odot}$ in a hot diffuse halo. We consider physical effects that control the motion and mass loss of the clouds, and estimate the lifetime and the observed properties of individual cool gas clouds inferred from the CLOUDY simulation. Our results show that the cool pressure-confined gas clouds have physical properties consistent with absorption line systems with neutral hydrogen column densities $N_{\rm HI}\geq10^{18.5} \rm cm^{-2}$ such as strong metal absorbers, sub-DLAs, and DLAs. The cool circumgalactic clouds are transient due to evaporation and recycling and therefore a constant replenishment is needed to maintain the cool CGM. We further model the ensemble properties of the cool CGM with clouds originated from outflows, inflows, or/and in-situ formation with a range of initial cloud mass function and velocity distribution. We find that only with a certain combination of parameters, an outflow model can broadly reproduce three cool gas properties around star-forming galaxies simultaneously: the spatial distribution, down-the-barrel outflow absorption, and gas velocity dispersion. Both a constant insitu model and gas inflow model can reproduce the observed covering fractions of high $\rm N_{HI}$ gas around passive galaxies but they fail to reproduce sufficient number of low $\rm N_{HI}$ systems. The limitations and the failures of the current models are discussed. Our results illustrate that semi-analytic modeling is a promising tool to understand the physics of the cool CGM which is usually unresolved by state-of-the-art cosmological hydrodynamic simulations.

Bubbly flow velocity measurement in multiple scattering regime

We propose a technique to measure the velocity of a bubble cloud based on the coda correlation. The method is founded on successive recordings of multiple scattered waves from a bubble cloud. Our model predicts the dependence between the correlation coefficient of these coda waves and the velocity of the bubble cloud under diffusion approximation. The Acoustic experiments are validated by simultaneous optical measurements in a water tank, with a good agreement between the acoustical and the optical methods (relative difference smaller than 7%). This technique can be transposed to any particle flow velocity problems involving multiple scattering effects in acoustics.

Comparing the properties of GMCs in M33 from simulations and observations

We compare the properties of clouds in simulated M33 galaxies to those observed in the real M33. We apply a friends of friends algorithm and CPROPS to identify clouds, as well as a pixel by pixel analysis. We obtain very good agreement between the number of clouds, and maximum mass of clouds. Both are lower than occurs for a Milky Way-type galaxy and thus are a function of the surface density, size and galactic potential of M33. We reproduce the observed dependence of molecular cloud properties on radius in the simulations, and find this is due to the variation in gas surface density with radius. The cloud spectra also show good agreement between the simulations and observations, but the exact slope and shape of the spectra depends on the algorithm used to find clouds, and the range of cloud masses included when fitting the slope. Properties such as cloud angular momentum, velocity dispersions and virial relation are also in good agreement between the simulations and observations, but do not necessarily distinguish between simulations of M33 and other galaxy simulations. Our results are not strongly dependent on the level of feedback used here (10 and 20%) although they suggest that 15% feedback efficiency may be optimal. Overall our results suggest that the molecular cloud properties are primarily dependent on the gas and mass surface density, and less dependent on the localised physics such as the details of stellar feedback, or the numerical code used.

A model for thermal radiation from the Tunguska airburst

This paper develops a model for simulating the radiative flux reaching the ground originating from a meteor shock-layer and wake. The area of radiant burn measured for the Tunguska event provides a test case for the developed model. This model applies recently developed computational fluid dynamic simulations, which include the impact of ablation and radiation on the shock-layer flowfield, and ray-tracing radiation transport with atmospheric absorption. The impact of the meteor view angle is shown to significantly impact the radiative flux. Looking at the meteor along the flight path (head-on) results in lower radiative heating because it reduces the wake field of view, where the large radiating wake is shown to provide a significant contribution to the radiative flux (when viewed from the side). The impact of ablation on the ground radiative flux is negligible because the ablation products are limited to the optically-thick core of the wake. The resulting simulated radiative flux values are correlated as a function of velocity, altitude, view angle, and meteoroid radius. This correlation is then applied to potential Tunguska entry trajectories to provide a simulated ground heating footprint. Comparing this simulated footprint with the measured radiant burn area provides a metric for assessing unknown Tunguska entry parameters. Using this approach, the initial radius resulting in good agreement with the measured radiant burn footprint was found for a range of maximum debris cloud radii, entry angles, and velocities. The resulting optimal initial radii were between 30 and 45 m for the entire range of cases considered. This provides a valuable constraint on initial radius for complementary Tunguska studies, such as blast-wave simulations that aim to reproduce the tree-fall pattern.

Development of an advection model for solar forecasting based on ground data. Part II: Verification of the forecasting model over a wide geographical area

A new spatiotemporal forecasting model for photovoltaic output power, outlined in the first paper, is validated herein against irradiance measurements. Irradiance measurements were first interpolated onto a grid. By repeating this process over several time steps, cloud motion was visualized, and the velocity of the clouds was estimated. Using these estimations of cloud velocity, the cloud motion for a future time interval was simulated using advection-diffusion equations and the average irradiation over a target region was estimated. The model was applied to a 170 km × 60 km region in northern Kyushu, Japan. Predictions of the transients for average irradiation were in good agreement with ground measurements. Simulation of the distribution of irradiation within the photovoltaic system also agreed well with ground measurements. This approach suggests an additional function for photovoltaic power systems, not only as a power source but also as a sensor for weather forecasting. This application provides a clear incentive to install more photovoltaic power systems.

Three-dimensional fluid simulations of the Cs plasma release in the ionosphere

Releasing plasma cloud is an efficient way to manage ionosphere properties. In this paper, we establish a three-dimensional fluid model to simulate the spatiotemporal evolution of released Cs plasma. Four types of particles are taken into account: released neutral Cs, ambient O, Cs+ and electron, among which the Cs+ and electron move according to the classical ambipolar diffusion. Meanwhile, photoionization induced by solar radiation and recombination of Cs+/electron are included in model as two chemical reactions. Based on this model, we investigate the influence of three factors: initial velocity of neutral Cs cloud, photoionization rate and altitude. The initial velocity can change the whole distribution of plasma cloud. When there is no velocity or velocity along the background magnetic field, the plasma cloud shows an ellipsoid shape and moves with neutral cloud. If the velocity is perpendicular to the magnetic field line, the cloud will be stretched in the same direction and does not move. We investigate the influence of photoionization rate under different initial velocities, and find that with the photoionization rate increasing, more and more particles remain in the initial release position. Moreover, the altitude affects the density of ambient O and temperature result in the diffusion coefficient and drifting velocity reducing and then the size of bulk plasma inclines to be reduced at lower altitude.

ALMA Detections of the Youngest Protostars in Ophiuchus

Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.1 mm dust continuum and CO 2–1 emission toward six dense cores within the Ophiuchus molecular cloud. We detect compact, subarcsecond continuum structures toward three targets, two of which (Oph A N6 and SM1) are located in the Ophiuchus A ridge. Two targets, SM1 and GSS 30, contain two compact sources within the ALMA primary beam. We argue that several of the compact structures are small (R ≲ 80 au) accretion disks around young protostars, based on their resolved, elongated structures, coincident radio and X-ray detections, or bipolar outflow detections. While CO line wings extend to ±10–20 km s−1 for the more evolved sources GSS 30 IRS3 and IRS1, CO emission toward other sources, where detected, only extends a few km s−1 from the cloud v LSR. The dust spectral index toward the compact objects suggests either that the disks are optically thick at 1.1 mm or that significant grain growth has already occurred. We identify, for the first time, a single compact continuum source (R ∼ 100 au) toward N6 embedded within a larger continuum structure. SM1N is extended in the continuum but is highly centrally concentrated, with a density profile that follows a r −1.3 power law within 200 au and additional structure suggested by the uv-data. Both N6 and SM1N show no clear bipolar outflows with velocities greater than a few km s−1 from the cloud velocity. These sources are candidates to be the youngest protostars or first hydrostatic cores in the Ophiuchus molecular cloud.

Solar Radiation Forecast Using Cloud Velocity for Photovoltaic Systems

Today, solar energy is used in a many different ways. One of the most popular technological developments for this purpose is photovoltaic conversion to electricity. However, power fluctuations due to the variability of solar energy are one of the challenges faced by the implementation of photovoltaic systems. To overcome this problem, forecasting solar radiation data several minutes in advance is needed. In this research, a methodology to forecast solar radiation using cloud velocity and cloud moving angle is proposed. Generally, a red-to-blue ratio (RBR) color model and correlation analysis are used for obtaining the cloud velocity and moving angle. Artificial neural network (ANN) forecast models with different input combinations are established. This methodology requires lower computational time since it only uses part of the pixels in the sky image. Based on R-squared analysis, it can be concluded that the ANN model with inputs of cloud velocity and moving angle and average solar radiation showed the highest accuracy among other combinations of inputs. The R-squared value was 0.59 with only a relatively small sample size of 42. The proposed model showed a highest improvement of 75.79% when compared to the ANN model based on historical solar radiation data only.

On the indeterministic nature of star formation on the cloud scale

Molecular clouds are turbulent structures whose star formation efficiency (SFE) is strongly affected by internal stellar feedback processes. In this paper we determine how sensitive the SFE of molecular clouds is to randomised inputs in the star formation feedback loop, and to what extent relationships between emergent cloud properties and the SFE can be recovered. We introduce the yule suite of 26 radiative magnetohydrodynamic (RMHD) simulations of a 10,000 solar mass cloud similar to those in the solar neighbourhood. We use the same initial global properties in every simulation but vary the initial mass function (IMF) sampling and initial cloud velocity structure. The final SFE lies between 6 and 23 percent when either of these parameters are changed. We use Bayesian mixed-effects models to uncover trends in the SFE. The number of photons emitted early in the cluster's life and the length of the cloud provide are the strongest predictors of the SFE. The HII regions evolve following an analytic model of expansion into a roughly isothermal density field. The more efficient feedback is at evaporating the cloud, the less the star cluster is dispersed. We argue that this is because if the gas is evaporated slowly, the stars are dragged outwards towards surviving gas clumps due to the gravitational attraction between the stars and gas. While star formation and feedback efficiencies are dependent on nonlinear processes, statistical models describing cloud-scale processes can be constructed.

ALMA Observations of Molecular Absorption in the Gravitational Lens PMN 0134−0931 at z = 0.7645

Abstract We report the detection of molecular absorption lines at z = 0.7645 toward the radio-loud quasi-stellar object (QSO) PMN 0134−0931. The CO J = 2–1 and HCO+ J = 2–1 lines are seen in absorption along two different lines of sight to lensed images of the background QSO. The lines of sight are separated by ∼0.″7, corresponding to 5 kpc in the lens plane. PMN 0134−0931 represents one out of only five known molecular absorption line systems at cosmologically significant distances. Moreover, it is also one of three such systems where the absorption occurs in a galaxy acting as a gravitational lens. The absorption lines through the two lines of sight are shifted by 215 ± 8 km s−1, possibly representing rotational motion in one of the lensing galaxies. The absorption profiles are wide, ∼200 km s−1, suggesting that the absorption occurs in a highly inclined disk galaxy with a flat rotation curve and a cloud–cloud velocity dispersion ∼30 km s−1. Gravitational lens models require two equal mass galaxies to account for the observed configuration of lensed images. The presence of two galaxies in close proximity means that they might be interacting and potentially merging and the kinematics of the molecular gas may not reflect ordered rotational motion. Compared with other high-redshift molecular absorption systems, the column densities of both CO and HCO+ are normal for diffuse molecular gas toward one of the lensed images, but significantly higher toward the other. Also, the abundance ratio is 2 − 3 times higher than in typical diffuse molecular gas. It is plausible that the second line of sight probes denser molecular gas than what is normally the case for absorption.

Is Dark Matter Needed in Galaxies?

We present arguments indicating that galaxies and their clusters should be considered as open developing systems. Galaxies interact with the intergalactic medium and are not in a virial equilibrium (which is determined by the gravity and rotation). In this case, the conventional interpretation of the rotation curves of galaxy outer regions outside the visible stellar disk (i.e. the presence of high mass dark matter haloes) may be erroneous. If there is an accretion of the intergalactic medium in these regions, then the orbital velocities of neutral hydrogen clouds are determined not only by the gravitation of the mass inside their orbits. Galaxy clusters accrete the material (intergalactic gas and galaxies) from filaments of the large-scale structure, at the intersections of which they are located. Only their central regions can approach the virial equilibrium. Therefore, the high velocities of galaxies and the high temperatures of the intergalactic gas in a cluster do not necessarily indicate the presence of a large mass of dark matter in the cluster.

Field validation and benchmarking of a cloud shadow speed sensor

With ramp rate regulations for photovoltaic plants being discussed in many countries, the speed of clouds has gained significant importance lately. Besides, measuring cloud velocities and directions is of interest for validations of numerical weather predictions and solar nowcasting systems. Recently, the Cloud Shadow Speed Sensor (CSS) was developed and validated in San Diego for low cumulus clouds. In this publication, the CSS is studied under different weather and cloud conditions in the desert of Tabernas in southern Spain. Furthermore, a novel shadow camera based low-cost, low-maintenance approach to determine cloud shadow motion vectors is presented and used as a reference to benchmark the CSS. In comparison, the absolute velocities derived from the CSS and the shadow camera on 59 days for ±5 min temporal medians show deviations of RMSD 2.1 m/s (28.0%), MAD 1.2 m/s (15.7%) and a bias of −0.2 m/s (2.8%). Deviations of the cloud shadow direction are RMSD 47.9° (26.6%), MAD 25.3° (14.0%) and bias 3.7° (2.0%). An adaption of the CSS software yields 91% more measurements on 59 days in comparison to the previously used algorithms at the expense of reduced accuracies, both for the measured velocities and for the measured directions.The CSS and the novel shadow camera based reference system enable long-time, low-maintenance ground measurements of cloud shadow speeds, which were previously not available. The distinct advantages and limitations of the two systems are discussed. In addition to the comparisons between the shadow camera system and the CSS on 59 days, the detection rates of the CSS are classified and measured on 223 days by analyzing CSS radiometer signals. Depending on the shading strength and shading durations, detection rates vary between 3.7% and 21.6%. Furthermore, the basic assumption as well as possible correction approaches of the linear cloud edge – curve fitting method are studied.The CSS was found to be a robust tool with great potential. However, optically thin clouds with diffuse edges pose a challenge and the detection rate leaves room for improvements. The newly developed shadow camera system provides more measurements which scatter less but needs certain geographical requirements. The shadow camera is found to be a feasible validation tool for cloud (shadow) motion vectors.

Physical properties and scaling relations of molecular clouds: the effect of stellar feedback

Using hydrodynamical simulations of entire galactic discs similar to the Milky Way, reaching 4.6pc resolution, we study the origins of observed physical properties of giant molecular clouds (GMCs). We find that efficient stellar feedback is a necessary ingredient in order to develop a realistic interstellar medium (ISM), leading to molecular cloud masses, sizes, velocity dispersions and virial parameters in excellent agreement with Milky Way observations. GMC scaling relations observed in the Milky Way, such as the mass-size ($M$--$R$), velocity dispersion-size ($\sigma$--$R$), and the $\sigma$--$R\Sigma$ relations, are reproduced in a feedback driven ISM when observed in projection, with $M\propto R^{2.3}$ and $\sigma\propto R^{0.56}$. When analysed in 3D, GMC scaling relations steepen significantly, indicating potential limitations of our understanding of molecular cloud 3D structure from observations. Furthermore, we demonstrate how a GMC population's underlying distribution of virial parameters can strongly influence the scatter in derived scaling relations. Finally, we show that GMCs with nearly identical global properties exist in different evolutionary stages, where a majority of clouds being either gravitationally bound or expanding, but with a significant fraction being compressed by external ISM pressure, at all times.

A New Look at the Molecular Gas in M42 and M43: Possible Evidence for Cloud–Cloud Collision that Triggered Formation of the OB Stars in the Orion Nebula Cluster

Abstract The Orion Nebula Cluster toward the H ii region M42 is the most outstanding young cluster at the smallest distance (410 pc) among the rich high-mass stellar clusters. By newly analyzing the archival molecular data of the 12CO(J = 1–0) emission at 21″ resolution, we identified at least three pairs of complementary distributions between two velocity components at 8 and 13 km s−1. We present a hypothesis that the two clouds collided with each other and triggered formation of the high-mass stars, mainly toward two regions including the nearly 10 O stars in M42 and the B star, NU Ori, in M43. The timescale of the collision is estimated to be ∼0.1 Myr by a ratio of the cloud size and velocity corrected for projection, which is consistent with the age of the youngest cluster members less than 0.1 Myr. The majority of the low-mass cluster members were formed prior to the collision in the last Myr. We discuss the implications of the present hypothesis and the scenario of high-mass star formation by comparing with the other eight cases of triggered O-star formation via cloud–cloud collision.

Quantifying the effect of aerosol on vertical velocity and effective terminal velocity in warm convective clouds

Abstract. Better representation of cloud–aerosol interactions is crucial for an improved understanding of natural and anthropogenic effects on climate. Recent studies have shown that the overall aerosol effect on warm convective clouds is non-monotonic. Here, we reduce the system's dimensions to its center of gravity (COG), enabling distillation and simplification of the overall trend and its temporal evolution. Within the COG framework, we show that the aerosol effects are nicely reflected by the interplay of the system's characteristic vertical velocities, namely the updraft (w) and the effective terminal velocity (η). The system's vertical velocities can be regarded as a sensitive measure for the evolution of the overall trends with time. Using a bin-microphysics cloud-scale model, we analyze and follow the trends of the aerosol effect on the magnitude and timing of w and η, and therefore the overall vertical COG velocity. Large eddy simulation (LES) model runs are used to upscale the analyzed trends to the cloud-field scale and study how the aerosol effects on the temporal evolution of the field's thermodynamic properties are reflected by the interplay between the two velocities. Our results suggest that aerosol effects on air vertical motion and droplet mobility imply an effect on the way in which water is distributed along the atmospheric column. Moreover, the interplay between w and η predicts the overall trend of the field's thermodynamic instability. These factors have an important effect on the local energy balance.

Properties and rotation of molecular clouds in M 33

The sample of 566 molecular clouds identified in the CO(2–1) IRAM survey covering the disk of M 33 is explored in detail. The clouds were found using CPROPS and were subsequently catalogued in terms of their star-forming properties as non-star-forming (A), with embedded star formation (B), or with exposed star formation (C, e.g., presence of Hα emission). We find that the size-linewidth relation among the M 33 clouds is quite weak but, when comparing with clouds in other nearby galaxies, the linewidth scales with average metallicity. The linewidth and particularly the line brightness decrease with galactocentric distance. The large number of clouds makes it possible to calculate well-sampled cloud mass spectra and mass spectra of subsamples. As noted earlier, but considerably better defined here, the mass spectrum steepens (i.e., higher fraction of small clouds) with galactocentric distance. A new finding is that the mass spectrum of A clouds is much steeper than that of the star-forming clouds. Further dividing the sample, this difference is strong at both large and small galactocentric distances and the A vs. C difference is a stronger effect than the inner vs. outer disk difference in mass spectra. Velocity gradients are identified in the clouds using standard techniques. The gradients are weak and are dominated by prograde rotation; the effect is stronger for the high signal-to-noise clouds. A discussion of the uncertainties is presented. The angular momenta are low but compatible with at least some simulations. Finally, the cloud velocity gradients are compared with the gradient of disk rotation. The cloud and galactic gradients are similar; the cloud rotation periods are much longer than cloud lifetimes and comparable to the galactic rotation period. The rotational kinetic energy is 1–2% of the gravitational potential energy and the cloud edge velocity is well below the escape velocity, such that cloud-scale rotation probably has little influence on the evolution of molecular clouds.

Study on flow field characteristics in a reverse rotation cyclone with PIV

This study adopted particle image velocimetry (PIV) to understand flow-field movements in the conventional cyclone and reverse-rotation cyclone (RC). Tracer particles were prepared by preparing a 5-wt% sugar solution at normal temperature and pressure for velocity measurement, cloud and distribution velocity maps were generated at various flow rates using three cross-sections. Compared with conventional cyclone, the PIV testing results indicate that the tangential and radial velocities of RC increased at higher flow rates and decreased at lower heights, suggesting adequate radially symmetric distributions despite variations in heights and flow rates. The radial velocity exhibited adequate diagonally symmetric distribution, implying that the indicating excellent symmetry and regularity in the velocity distribution of the flow-field images of the separator, a sign of stable flow fields in the separator. Finally, the comparison showed a similar distribution and variation patterns, which was collected through PIV testing and computational fluid dynamics (CFD) simulation.

High-energy radiation from collisions of high-velocity clouds and the Galactic disc

High-velocity clouds (HVCs) are interstellar clouds of atomic hydrogen that do not partake of the Galactic rotation and have velocities of a several hundred kilometers per second. A considerable number of these clouds are falling down towards the Galactic disk. HVCs form large and massive complexes, so their collisions with the disk must release a great amount of energy into the interstellar medium. The cloud-disk interaction produces two shocks, one propagates through the cloud and the other through the disk; the properties of these shocks depend mainly on the cloud velocity and the disk-cloud density ratio. In this work we study the conditions necessary for these shocks to accelerate particles by diffusive shock acceleration and the produced non-thermal radiation. We analyze particle acceleration in both the cloud and disk shocks. Solving a time-dependent 2-D transport equation for both relativistic electrons and protons we obtain particle distributions and non-thermal spectral energy distributions. In a shocked cloud significant synchrotron radio emission is produced along with soft gamma rays. In the case of acceleration in the shocked disk, the non-thermal radiation is stronger; the gamma rays, of leptonic origin, might be detectable with current instruments. A large number of protons are injected into the Galactic interstellar medium, and locally exceed the cosmic-ray background. We conclude that under adequate conditions the contribution from HVC-disk collisions to the galactic population of relativistic particles and the associated extended non-thermal radiation might be important.