Brightness Reduction Research Articles

Imaging the Thermal and Kinematic Sunyaev–Zel’dovich Effect Signals in a Sample of 10 Massive Galaxy Clusters: Constraints on Internal Velocity Structures and Bulk Velocities

Abstract We have imaged the Sunyaev–Zel’dovich (SZ) effect signals at 140 and 270 GHz toward 10 galaxy clusters with Bolocam and AzTEC/ASTE. We also used Planck data to constrain the signal at large angular scales, Herschel–SPIRE images to subtract the brightest galaxies that comprise the cosmic infrared background (CIB), Chandra imaging to map the electron temperature of the intra-cluster medium, and Hubble Space Telescope imaging to derive models of each galaxy cluster’s mass density. The galaxy clusters gravitationally lens the background CIB, which produced an on-average reduction in brightness toward the galaxy clusters’ centers after the brightest galaxies were subtracted. We corrected for this deficit, which was between 5% and 25% of the 270 GHz SZ effect signal within R 2500. Using the SZ effect measurements, along with the X-ray constraint on , we measured each galaxy cluster’s average line of sight (LOS) velocity v z within R 2500, with a median per-cluster uncertainty of ±700 km s−1. We found an ensemble-mean v z of 430 ± 210 km s−1, and an intrinsic cluster-to-cluster scatter of 470 ± 340 km s−1. We also obtained maps of v z over each galaxy cluster’s face with an angular resolution of 70″. All four galaxy clusters previously identified as having a merger oriented along the LOS showed an excess variance in these maps at a significance of ≃2–4σ, indicating an internal v z rms of ≳1000 km s−1. None of the six galaxy clusters previously identified as relaxed or plane-of-sky mergers showed any such excess variance.

Transglutaminase Activity Determines Nuclear Localization of Serotonin Immunoreactivity in the Early Embryos of Invertebrates and Vertebrates.

Serotonin (5-HT) is a key player in many physiological processes in both the adult organism and developing embryo. One of the mechanisms for 5-HT-mediated effects is covalent binding of 5-HT to the target proteins catalyzed by transglutaminases (serotonylation). Despite the implication in a variety of physiological processes, the involvement of serotonylation in embryonic development remains unclear. Here we tested the hypothesis that 5-HT serves as a substrate for transglutaminase-mediated transamidation of the nuclear proteins in the early embryos of both vertebrates and invertebrates. For this, we demonstrated that the level of serotonin immunoreactivity (5-HT-ir) in cell nuclei increases upon the elevation of 5-HT concentration in embryos of sea urchins, mollusks, and teleost fish. Consistently, pharmacological inhibition of transglutaminase activity resulted in the reduction of both brightness and nuclear localization of anti-5-HT staining. We identified specific and bright 5-HT-ir within nuclei attributed to a subset of different cell types: ectodermal and endodermal, macro- and micromeres, and blastoderm. Western blot and dot blot confirmed the presence of 5-HT-ir epitopes in the normal embryos of all the species examined. The experimental elevation of 5-HT level led to the enhancement of 5-HT-ir-related signal on blots in a species-specific manner. The obtained results demonstrate that 5-HT is involved in transglutaminase-dependent monoaminylation of nuclear proteins and suggest nuclear serotonylation as a possible regulatory mechanism during early embryonic development. The results reveal that this pathway is conserved in the development of both vertebrates and invertebrates.

Skew Quadrupole Effect of Laser Plasma Electron Beam Transport

Laser plasma acceleration (LPA) capable of providing femtosecond and GeV electron beams in cm scale distances brings a high interest for different applications, such as free electron laser and future colliders. Nevertheless, LPA high divergence and energy spread require an initial strong focus to mitigate the chromatic effects. The reliability, in particular with the pointing fluctuations, sets a real challenge for the control of the dispersion along the electron beam transport. We examine here how the magnetic defects of the first strong quadrupoles, in particular, the skew terms, can affect the brightness of the transported electron beam, in the case of the COXINEL transport line, designed for manipulating the electron beam properties for a free electron laser application. We also show that the higher the initial beam divergence, the larger the degradation. Experimentally, after having implemented a beam pointing alignment compensation method enabling us to adjust the position and dispersion independently, we demonstrate that the presence of non-negligible skew quadrupolar components induces a transversal spread and tilt of the beam, leading to an emittance growth and brightness reduction. We are able to reproduce the measurements with beam transport simulations using the measured electron beam parameters.

Combination of Enhanced Depth Imaging Optical Coherence Tomography and Fundus Images for Glaucoma Screening.

Glaucoma is an eye disease that damages the optic nerve and can lead to irreversible loss of peripheral vision gradually and even blindness without treatment. Thus, diagnosing glaucoma in the early stage is essential for treatment. In this paper, an automatic method for early glaucoma screening is proposed. The proposed method combines structural parameters and textural features extracted from enhanced depth imaging optical coherence tomography (EDI-OCT) images and fundus images. The method first segments anterior the lamina cribrosa surface (ALCS) based on region-aware strategy and residual U-Net and then extracts structural features of the lamina cribrosa, such as lamina cribrosa depth and deformation of lamina cribrosa. In fundus images, scanning lines based on disc center and brightness reduction are used for optic disc segmentation and brightness compensation is utilized for segmenting the optic cup. Afterward, the cup-to-disc ratio (CDR) and textural features are extracted from fundus images. Hybrid features are used for training and classification to screen glaucoma by gcForest in the early stage. The proposed method has given exceptional results with 96.88% accuracy and 91.67% sensitivity.

Beam brightness and its reduction in a 1.2-MV cold field-emission transmission electron microscope

In this paper we discuss probe properties in terms of probe currents, probe sizes, energy spread, virtual source sizes, and brightness in a 1.2-MV cold field-emission (cold FE) transmission electron microscope (TEM) equipped with a magnetic gun lens. The probe size increased gradually in proportion to the (3/8)th power of the probe current, very unusual behavior in cold FE guns but typical behavior in thermionic guns. This is due to the magnetic gun lens, which caused large emission angles for electron beams in the probe before being limited by aberrations at the gun and acceleration tube. The brightness reached the maximum at 1.62 × 1014 A/(m2sr) and then decreased with increasing the emission current. The energy spread of the beam, including the Boersch effect, was 0.32–0.50 eV, comparable to that of conventional cold FE guns without magnetic gun lens. Experimental analysis indicated that neither noises nor aberrations caused the probe size increase under the optimized illumination condition. The virtual source size increased from 11.1 to 24.7 nm with the increase in the emission current. To describe this behavior, we conjecture that this brightness reduction is due to increase in the virtual source size caused by trajectory displacement created by stochastic Coulomb interactions near the emitter.

The formation of ultra-diffuse galaxies in cored dark matter haloes through tidal stripping and heating

We propose that the Ultra-Diffuse Galaxy (UDG) population represents a set of satellite galaxies born in $\sim10^{10}-10^{11}$ M$_\odot$ halos, similar to field dwarfs, which suffer a dramatic reduction in surface brightness due to tidal stripping and heating. This scenario is observationally motivated by the radial alignment of UDGs in Coma as well as the significant dependence of UDG abundance on cluster mass. As a test of this formation scenario, we apply a semi-analytic model describing the change in stellar mass and half-light radius of dwarf satellites, occupying either cored or cuspy halos, to cluster subhalos in the Illustris-dark simulation. Key to this model are results from simulations which indicate that galaxies in cored dark-matter halos expand significantly in response to tidal stripping and heating, whereas galaxies in cuspy halos experience limited size evolution. Our analysis indicates that a population of tidally-stripped dwarf galaxies, residing in cored halos (like those hosting low-surface brightness field dwarfs), is able to reproduce the observed sizes and stellar masses of UDGs in clusters remarkably well.

Investigation of Physico-Chemical Characteristics of Stainless Steel Surface and Their Effect on the Appearance Aspects of the Alloy Surface

Stainless steel alloy SS-304 is widely used in many engineering applications primarily for its excellent corrosion resistance, ease of fabrication and aesthetic appeal. Many kitchen appliances are made from SS-304 alloy because of its durability, ease of cleaning and beautiful finish. However, over the years of continuous usage and cleaning by detergent bar and abrasive clothes the initial brightness and shine of the plates and dishes undergo considerable degradation. In this work, we report the results of a thorough investigation of the physico-chemical characteristics of the surface regions of both new and old SS-304 plates of known history of continuous usage to identify the key physical and chemical factors that are responsible for the loss of shine. Several analytical techniques viz. SEM/EDX, AFM, XPS, XRD, Reflectance FTIR, Profilometry and Reflectance spectrometry in the visible region have been used for experimental investigation of surface structure, morphology, roughness profile, chemical composition and appearance measurements of several steel samples. In addition, glossmeter has been used to measure the gloss of the samples at certain specific angles. It seems that surface roughness is one of the key physical parameters that play an important role in the reduction of brightness and shine. The other parameter is the presence of a thin surface film on the steel surface. In order to analyze the experimental data and to predict the shine and brightness phenomena quantitatively, we have used Fresnel’s theory to compute first the reflectance from each component of SS-304 alloy assuming it to be a smooth surface and then extended it to compute the reflectance of the alloy surface (SS-304). In order to interpret the reflectance from old and used plates, we have further used Beckmann’s theory of light scattering from random rough surface to analyze and predict the appearance aspects of the alloy surface quantitatively. Both the experimental and computed results show good agreement, thus validating the reflectance model used for computing the reflectance from SS-304 alloy surface and the appropriateness of Beckmann’s model of random rough surface.

The physics of Lyman α escape from high-redshift galaxies

Lyman-alpha (Ly{\alpha}) photons from ionizing sources and cooling radiation undergo a complex resonant scattering process that generates unique spectral signatures in high-redshift galaxies. We present a detailed Ly{\alpha} radiative transfer study of a cosmological zoom-in simulation from the Feedback In Realistic Environments (FIRE) project. We focus on the time, spatial, and angular properties of the Ly{\alpha} emission over a redshift range of z = 5-7, after escaping the galaxy and being transmitted through the intergalactic medium (IGM). Over this epoch, our target galaxy has an average stellar mass of $M_{\rm star} \approx 5 \times 10^8 {\rm M}_\odot$. We find that many of the interesting features of the Ly{\alpha} line can be understood in terms of the galaxy's star formation history. The time variability, spatial morphology, and anisotropy of Ly{\alpha} properties are consistent with current observations. For example, the rest frame equivalent width has a ${\rm EW}_{{\rm Ly}\alpha,0} > 20 {\rm \AA}$ duty cycle of 62% with a non-negligible number of sightlines with $> 100 {\rm \AA}$, associated with outflowing regions of a starburst with greater coincident UV continuum absorption, as these conditions generate redder, narrower (or single peaked) line profiles. The lowest equivalent widths correspond to cosmological filaments, which have little impact on UV continuum photons but efficiently trap Ly{\alpha} and produce bluer, broader lines with less transmission through the IGM. We also show that in dense self-shielding, low-metallicity filaments and satellites Ly{\alpha} radiation pressure can be dynamically important. Finally, despite a significant reduction in surface brightness with increasing redshift, Ly{\alpha} detections and spectroscopy of high-$z$ galaxies with the upcoming James Webb Space Telescope is feasible.

Adaptation to Brightness Perception in Patients Implanted With a Small Aperture

PurposeSmall apertures are successfully used to extend depth of focus in presbyopic patients implemented either as corneal inlays or intraocular lenses. The use of small apertures reduces retinal illuminance. In this study, we quantify the relative perceived brightness in the 2 eyes of patients implanted monocularly with a small-aperture inlay.DesignProspective case series.MethodsWe used a binocular adaptive optics vision simulator to determine the relative perceived brightness. Four patients implanted monocularly with the KAMRA corneal inlay (1.6 mm) and a group of control subjects participated in the study. The projected pupil on the eye implanted with the inlay alternated in diameter between 0 and 2.5 mm (effective 1.6 mm) to eliminate potential for light to project around the periphery of the inlay while the corresponding fellow eye projected pupil alternated between 0 and 3.0 mm or 0 and 4.0 mm at a frequency of 1 Hz. Alternation on both eyes was synchronized so that only 1 eye at a time had a nonblocked pupil. At equal transmittance, a flickering was perceived. Patients' task consisted of modifying the transmittance of the pupil corresponding to the fellow eye until the perceived flickering, owing to the different perceived brightness, was minimized. This equalizing transmittance (ET) value indicates the relative perceived brightness.ResultsIn the KAMRA's patients, ET was found to be greater than expected considering the difference in pupil sizes and the Stiles-Crawford effect, showing an enhanced a greater brightness perception in the eye with the small aperture in comparison with the fellow eye. Compared with the control subjects, this difference was on average bigger by a factor of ×1.42.ConclusionsPatients implanted with the small-aperture corneal inlay exhibited an enhanced brightness perception with the eye implanted, in comparison with their untreated fellow eye. The amount of this increase is much larger than what could be expected owing to the Stiles-Crawford effect and was probably attributable to a neural adaptation process. This phenomenon could explain a reported equalization of brightness between eyes in patients with unilateral inlays and implies that the expected reduction of brightness may have a less significant impact on these patients, as expected.

Perceived brightness with small apertures

To quantify the relative perceived brightness when viewing through a small aperture as that used by presbyopic patients with small-aperture corneal inlays or intraocular lenses with an embedded aperture. Laboratorio de Óptica, Universidad de Murcia, Murcia, Spain. Prospective case series. The relative perceived brightness when 2 apertures (3.0mm and 1.6mm diameters) were presented monocularly to the participant was determined. With equal transmittances in both apertures, a flickering effect caused by the different retinal illuminance for each condition is perceived. The participant's task was to modify the transmittance of the 3.0mm pupil until the flickering was minimized. This transmittance value indicates the relative perceived brightness reduction. The measurements were performed under 3 average luminance levels. The perceived relative luminance measured ranged between 38.5% and 46.9%. This represents an increase in brightness perception with a small aperture of 1.24 and 1.51, respectively, compared with what would be expected. This trend was consistent for all the participants in the study. The perceived brightness with a small aperture was less pronounced than what would be predicted by the reduction in retinal illuminance. Under real visual conditions, this effect could be even more significant because binocular effects and temporal adaptation might further increase the perceived brightness with the small aperture.

Light pollution modelling, and measurements at Malvern hills AONB, of county conversion to blue rich LEDs.

The introduction of blue rich colour, Correlated-Colour-Temperature (CCT) 6000 K road lighting could increase skyglow significantly compared with CCT 3000 K types, if the blue content reaches the sky.Highways England have a policy for lighting specification on motorways advised by the author's work. This is a categorised environmental impact point system of summed brightness as a function of angle from vertically down to the cut off angle; but with no CCT limitation.Modelling was done for Malvern-Hills Area-of-Outstanding-Natural-Beauty (MHAONB), for the nighttime environmental impact of the LED replacement of Low-Pressure-Sodium throughout Herefordshire. The study was extended to include High-Pressure-Sodium and to LEDs at several CCTs, for the same Photopic ground illuminance.Dark-Sky-Survey geographic location results for the MHAONB (2012) are described. Near-Zenith sky brightness photometry became continuous from 2016 at 2 minute intervals in all weathers, not just clear nights, with a networked calibrated Unihedron Lensed Sky Quality Meter (LSQM). Samples were also taken of all-sky camera images, corrected for vignetting and near-Zenith calibrated with the LSQM, to study weather effects, Milky Way contribution, and Herefordshire lighting conversion to blue-rich LEDs (2013–15), compared with the less converted Severn valley direction.Time-plots and histogram analysis showed a small reduction in brightness (2012–2018), 0.1 mag.arcsec−2. Most variation is from increased sampling of distant cloud cover effects. Mist or low cloud on the horizon obscures light sources beyond reducing local skyglow, while high cloud reflects, increasing clear sky brightness. The Milky Way is critically 20% above background. Darkest periods near Zenith reach 21.1 mag.arcsec−2, to 21.2 after rain or surrounding low-cloud or poor-visibility. Clear-sky brightness decreases into early hours (∼0.03 mag.arcsec−2/h); dimming effects were not seen.The Zenith brightness is still set by distant cities, while towards the horizon, commercial and private uncontrolled non-directional LED lighting is increasing, negating the improvements in road lighting.

Working Conditions on the Afterglow Characteristics of Rare-earth Luminous Fibers

To test and clarify the stability of afterglow performance of luminescent fibers can accelerate the step of the commercialized application on luminescent textiles. This work investigated the possible effects of a number of working conditions on the afterglow characteristics of luminous fibers. The fibers in our studies did not show any significant change in their afterglow brightness and duration after storage for 12 months under conditions of constant temperature and humidity, after 5 hours of light exposure, or soaking in water for 4 hours. The insignificant decay appears to follow the same mechanism. Thermal perturbation seemed to cause some changes to the initial brightness and decay time with the best performance being observed at about 80°C. Moreover, contact with acid or base for 5 minutes only resulted in slight reduction of the afterglow brightness. Our studies thus indicate a high degree of stability of the afterglow performance of the luminous fibers used.

Nano-machining, surface analysis and emittance measurements of a copper photocathode at SPARC_LAB

R&D activity on Cu photocathodes is under development at the SPARC_LAB test facility to fully characterize each stage of the photocathode “life” and to have a complete overview of the photoemission properties in high brightness photo-injectors. The nano(n)-machining process presented here consists in diamond milling, and blowing with dry nitrogen. This procedure reduces the roughness of the cathode surface and prevents surface contamination introduced by other techniques, such as polishing with diamond paste or the machining with oil. Both high roughness and surface contamination cause an increase of intrinsic emittance and consequently a reduction of the overall electron beam brightness. To quantify these effects, we have characterized the photocathode surface in terms of roughness measurement, and morphology and chemical composition analysis by means of Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Atomic Force Microscopy (AFM) techniques. The effects of n-machining on the electron beam quality have been also investigated through emittance measurements before and after the surface processing technique. Finally, we present preliminary emittance studies of yttrium thin film on Cu photocathodes.

Atta (whole wheat flour) with multi-wholegrains: flour characterization, nutritional profiling and evaluation of chapati making quality.

Non-wheat grains, complementing the nutritional profile of wheat were utilized for the development of atta with multi-whole grains. Based on the dimensions, selected grains were segregated and the grinding techniques were applied for the production of multi whole grains flour. Multi whole grains flour was replaced with whole wheat flour to obtain five different formulations and further compared with control atta. With the increase in incorporation of the multi whole grain flours reduction in brightness (L*) from 79.73 to 78.47 and redness (a*) from 2.47 to 12.12 while the increase in yellowness (b*) was observed (12.10-12.70). Protein content increased from 13.44 to 14.83% while dietary fibre content was also found to be increased in all the formulations compared to control atta. Ash content, an indicator of mineral content showed an increasing trend with the increase in the level of non-wheat grains. Shear force required for tearing the chapatis at 0h was observed to be in the range of 15.6 and 10.1N and moisture content between 32.6 and 30.4%. Mineral analysis carried out for the 10% replacement showed an increase in the level of the estimated minerals. An overall eating quality of the chapatis was found to be acceptable up to 10% replacement compared to control atta chapati.

Brightness reduction in parafoveal stimuli in the simultaneous presence of light inside the natural blind spot

Brightness reduction in parafoveal stimuli in the simultaneous presence of light inside the natural blind spot

Variations in energy, flux, and brightness of pulsating aurora measured at high time resolution

Abstract. High-resolution multispectral optical and incoherent scatter radar data are used to study the variability of pulsating aurora. Two events have been analysed, and the data combined with electron transport and ion chemistry modelling provide estimates of the energy and energy flux during both the ON and OFF periods of the pulsations. Both the energy and energy flux are found to be reduced during each OFF period compared with the ON period, and the estimates indicate that it is the number flux of foremost higher-energy electrons that is reduced. The energies are found never to drop below a few kilo-electronvolts during the OFF periods for these events. The high-resolution optical data show the occurrence of dips in brightness below the diffuse background level immediately after the ON period has ended. Each dip lasts for about a second, with a reduction in brightness of up to 70 % before the intensity increases to a steady background level again. A different kind of variation is also detected in the OFF period emissions during the second event, where a slower decrease in the background diffuse emission is seen with its brightness minimum just before the ON period, for a series of pulsations. Since the dips in the emission level during OFF are dependent on the switching between ON and OFF, this could indicate a common mechanism for the precipitation during the ON and OFF phases. A statistical analysis of brightness rise, fall, and ON times for the pulsations is also performed. It is found that the pulsations are often asymmetric, with either a slower increase of brightness or a slower fall.

DOXORUBICIN-INDUSED DISTURBANCES OF CARDIOMYOCYTE CONTRACTILE ACTIVITY.

The aim of our study was to find out the mechanisms of cardiomyocyte contractile activity disturbances under the influence of anthracycline antibiotics and curcumin correction capabilities, to clarify the role of the mitochondrial membrane potential changes in cardiomyocyte contractile activity. It was investigated disturbances of contractile activity of the rat neonatal cardiomyocytes under the influence of anthracycline antibiotics (doxorubicin), and the possibility of correcting these violations using antioxidant curcumin. In addition, there was researched the role of mitochondrial membrane potential changes in reducing contractile activity of the cardiomyocytes. We established that doxorubicin causes significant changes in all reduction parameters compared to control: increased frequency of spontaneous contractions, violation of rhythm, lower amplitude and the shortening %, increase in the maximum speed of contraction and relaxation without changes in duration of these processes. Compatible incubation with doxorubicin and curcumin caused a consid- erable decrease of the incidence of spontaneous emission (3 times), restored their rhythm, increasing the amplitude of 2 times and the shortening % (8,15 ± 0,37), rising the maximum speed reduction to 1,8 times and the relaxation speed of 16 %, with no significant change in duration of these processes compared to monoincubation with doxorubicin. In the fluorescence study of neonatal cardiomyocytes mitochondrial potential was detected a significant reduction in mitochondria color brightness under the influence of doxorubicin - in 1,7 times compared to control. A compatible incubation of cells with curcumin and doxorubicin resulted in an elevation of mitochondria fluorescence (2,2 times compared to using of doxorubicin only).

ELLIPSOID ZONE MAPPING AND OUTER RETINAL CHARACTERIZATION AFTER INTRAVITREAL OCRIPLASMIN.

To assess outer retinal architectural alterations after intravitreal ocriplasmin with a novel automated ellipsoid zone (EZ) mapping algorithm. A single-center, retrospective, consecutive case series of image analysis was performed. Quantitative assessment of EZ status imaged with spectral-domain optical coherence tomography was performed before and after single intravitreal injection of 0.125 mg of ocriplasmin (Jetrea, Thrombogenics). A novel EZ mapping algorithm was used to assess the EZ retinal pigment epithelium (RPE) central area, EZ-RPE macular volume, and en face EZ integrity based on the percentage of sampling areas with 20 μm or greater EZ-RPE thickness. Longitudinal assessment of these changes with custom optical coherence tomography reading software was completed. Clinical characteristics and outcomes were compared with these retinal changes. Nineteen eyes were included in this study. The retinal volume between EZ and RPE was significantly reduced at 1 week after ocriplasmin (P = 0.0036). Seven of 19 patients (36.8%) complained of color abnormalities or brightness reduction after injection. All of these seven patients had increased subretinal fluid after ocriplasmin and EZ attenuation. The EZ-RPE volume was reduced at 1 week (P = 0.0036), 1 month (P = 0.015) after ocriplasmin, and restored by 3 months. The area with EZ-RPE thickness below 20 μm was increased at 1 week (P = 0.046) after ocriplasmin and recovered with time. Mapping of EZ is feasible to assess EZ-RPE volume and overall EZ integrity with en face thickness mapping. Alterations in EZ occur in a significant proportion of eyes after ocriplasmin therapy. The EZ-RPE volume and the EZ-RPE central foveal area typically recover to baseline by 3 months. This effect appears to be panretinal and associated with subjective symptoms.

IV-th Great Visible Brightness Minimum of R CrB. II. Spectral Observations

Low and high resolution spectral observations during the main stages of a uniquely long and deep minimum in the visible brightness of R CrB during 2007-2015 are reported. As it developed, the spectrum manifested typical tendencies in the variation of line and molecular emission, with replacement of an absorption spectrum by an emission spectrum. The significant, sustained attenuation of the star’s emission aided the detection of rarely observed forbidden emission lines. In particular, the [OII] λλ 3726 – 3729 lines appeared for more than 1500 days during a brightness reduction by 6 ÷9m . The velosity at which the shielding dust was removed to the circumstellar surroundings was reduced by roughly a factor of 1.5 compared to the previously known values. This was interpreted in terms of the formation of a multilayer circumstellar dust shell with an inner radius equal to 1.5 ÷ 3 times the star’s radius. Several possible reasons are proposed for unique Great brightness minima of R CrB with duration and attenuation similar to the minimum of 2007-2015.

Influence of the crustal magnetic field on the Mars aurora electron flux and UV brightness

Observations with the SPICAM instrument on board Mars Express have shown the occasional presence of localized ultraviolet nightside emissions associated with enhanced energetic electron fluxes. These features generally occur in regions with significant radial crustal magnetic field. We use a Monte-Carlo electron transport model to investigate the role of the magnetic field on the downward and upward electron fluxes, the brightness and the emitted power of auroral emissions. Simulations based on an ASPERA-3 measured auroral electron precipitation indicate that magnetic mirroring leads to an intensification of the energy flux carried by upward moving electrons– from about 20% in the absence of crustal magnetic field up to 33–78% when magnetic field is included depending on magnetic field topology. Conservation of the particle flux in a flux tube implies that the presence of the B-field does not appreciably modify the emission rate profiles for an initially isotropic pitch angle distribution. However, we find that crustal magnetic field results in increase of the upward electron flux, and, consequently, in reduction of the total auroral brightness for given energy flux of precipitating electrons.