Bright Points Research Articles

Rapid Campimetry-A Novel Screening Method for Glaucoma Diagnosis.

One of the most important functions of the retina—the enabling of perception of fast movements—is largely suppressed in standard automated perimetry (SAP) and kinetic perimetry (Goldmann) due to slow motion and low contrast between test points and environment. Rapid campimetry integrates fast motion (=10°/4.7 s at 40 cm patient–monitor distance) and high contrast into the visual field (VF) examination in order to facilitate the detection of absolute scotomas. A bright test point moves on a dark background through the central 10° VF. Depending on the distance to the fixation point, the test point automatically changes diameter (≈0.16° to ≈0.39°). This method was compared to SAP (10-2 program) for six subjects with glaucoma. Rapid campimetry proved to be comparable and possibly better than 10-2 SAP in identifying macular arcuate scotomas. In four subjects, rapid campimetry detected a narrow arcuate absolute scotoma corresponding to the nerve fiber course, which was not identified as such with SAP. Rapid campimetry promises a fast screening method for the detection of absolute scotomas in the central 10° visual field, with a potential for cloud technologies and telemedical applications. Our proof-of-concept study motivates systematic testing of this novel method in a larger cohort.

Effect of AGN on the morphological properties of their host galaxies in the local Universe

ABSTRACT The morphological classification of active galaxies may be affected by the presence of active galactic nuclei (AGNs). In this paper, we provide the most detailed analysis on how different AGN contributions, from 5 per cent to 75 per cent, to the total optical light may affect six commonly used morphological parameters and the final classification of AGN host galaxies at z ∼ 0. We used a local sample of > 2000 visually classified non-active galaxies, to quantify how the contribution of a bright nuclear point source of different intensity could affect morphological parameters such as: asymmetry, Abraham concentration index, Gini, M20 moment of light, smoothness, and Conselice-Bershady concentration index. We found that most of the morphological parameters are affected by AGN contributions above 25 per cent, with late-type galaxies being more affected than early-types. We found that Gini, Abraham concentration index, and asymmetry are the most stable parameters even for AGN contributions above 25 per cent, in comparison to Conselice-Bershady concentration index and M20 moment of light. Smoothness parameter shall be avoided when classifying AGN host galaxies, or at least it shall be used simultaneously in combination with several other parameters.

Characteristics of chromospheric oscillation periods in magnetic bright points

ABSTRACTIn this investigation, oscillation periods in Mg ii k-line intensity, brightness temperature, and Doppler velocity obtained above magnetic bright points (MBPs) are investigated. For this purpose, data from the Interface Region Imaging Spectrometer (IRIS) observing the higher chromosphere and transition region (TR) were analysed, together with imaging and magnetogram data obtained by the Solar Dynamics Observatory(SDO). The MBPs were identified by combining Si iv 1403-Å slit-jaw images with magnetogram information from the Heliospheric and Magnetic Imager (HMI). A time-slice analysis followed by a wavelet inspection were carried out on the Mg ii k (2796-Å and 10 000 K) resonance lines for the detection of the oscillation period. Finally, a power spectrum analysis was performed to characterize the oscillations. It was found that the network points feature a typical intensity, temperature, and velocity oscillation period of about 300 s. The internetwork points have a mean intensity oscillation period of about 180 s, a mean temperature oscillation period of about 202 s, and a mean velocity oscillation period of about 202 s. In addition, one BP that was analysed in detail demonstrates intensity oscillation periods with a value of 500 s, which are obviously not related to the common 3- or 5-min oscillations typically found elsewhere in chromospheric/photospheric structures.

SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation

We report on the presence of numerous tiny bright dots in and around an emerging flux region (an X-ray/coronal bright point) observed with SolO’s EUI/HRIEUV in 174 Å. These dots are roundish and have a diameter of 675 ± 300 km, a lifetime of 50 ± 35 s, and an intensity enhancement of 30% ± 10% above their immediate surroundings. About half of the dots remain isolated during their evolution and move randomly and slowly (<10 km s−1). The other half show extensions, appearing as a small loop or surge/jet, with intensity propagations below 30 km s−1. Many of the bigger and brighter HRIEUV dots are discernible in the SDO/AIA 171 Å channel, have significant emissivity in the temperature range of 1–2 MK, and are often located at polarity inversion lines observed in SDO/HMI LOS magnetograms. Although not as pervasive as in observations, a Bifrost MHD simulation of an emerging flux region does show dots in synthetic Fe ix/x images. These dots in the simulation show distinct Doppler signatures—blueshifts and redshifts coexist, or a redshift of the order of 10 km s−1 is followed by a blueshift of similar or higher magnitude. The synthetic images of O v/vi and Si iv lines, which represent transition region radiation, also show the dots that are observed in Fe ix/x images, often expanded in size, or extended as a loop, and always with stronger Doppler velocities (up to 100 km s−1) than that in Fe ix/x lines. Our observation and simulation results, together with the field geometry of dots in the simulation, suggest that most dots in emerging flux regions form in the lower solar atmosphere (at ≈ 1 Mm) by magnetic reconnection between emerging and preexisting/emerged magnetic field. Some dots might be manifestations of magnetoacoustic shocks through the line formation region of Fe ix/x emission.

Characterization of the polarized synchrotron emission from Planck and WMAP data

The purpose of this work is to characterize the diffuse Galactic polarized synchrotron, which is the dominant CMB foreground emission at low frequency. We present EE, BB, and EB power spectra estimated from polarization frequency maps at 23 and 30 GHz as observed respectively by the WMAP K-band and the Planck lowest frequency channel, for a set of six sky regions covering from 30% to 94% of the sky. We study the synchrotron polarization angular distribution and spectral energy distribution (SED) by means of the so-called pseudo-C ℓ formalism, provided by the NaMaster package, in the multipole interval 30 ≤ ℓ ≤ 300. Best results are obtained cross-correlating Planck and WMAP data. The EE and BB angular power spectra show a steep decay of the spectral amplitude as a function of multipole, approximated by a power law CEE,BB ∝ ℓαEE,BB , with αEE = -2.95 ± 0.04 and αBB = -2.85 ± 0.14. The B/E power asymmetry is proved with a B-to-E ratio, computed as the amplitude ratio at the pivot multipole ℓ = 80, of 0.22 ± 0.02. The EB cross-component is compatible with zero at 1σ, with an upper constraint on the EB/EE ratio of 1.2% at the 2σ level. We show that the EE and BB power-law model with null EB cross-correlation describes reasonably well the diffuse synchrotron polarization emission for the full sky if the bright Galactic center and point sources are masked. The recovered SED shows power-law spectral indices βEE = -3.00 ± 0.10 and βBB = -3.05 ± 0.36 compatible between themselves, in the frequency range 23–30 GHz. Results also seem to indicate that the SED gets steeper from low to high Galactic latitude.

Eruptions from coronal bright points: A spectroscopic view by IRIS of a mini-filament eruption, QSL reconnection, and reconnection-driven outflows

Context. Our study investigates a mini-filament eruption associated with cancelling magnetic fluxes. The eruption originates from a small-scale loop complex commonly known as a coronal bright point (CBP). The event is uniquely recorded in both the imaging and spectroscopic data taken with the Interface Region Imaging Spectrograph (IRIS). Aims. The investigation aims to gain a better understanding of the physical processes driving these ubiquitous small-scale eruptions. Methods. We analysed IRIS spectroscopic and slit-jaw imaging observations as well as images taken in the extreme-ultraviolet channels of the Atmospheric Imaging Assembly (AIA) and line-of-sight magnetic-field data from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory. As the observations can only indicate the possible physical processes at play, we also employed a non-linear force-free field (NLFFF) relaxation approach based on the HMI magnetogram time series. This allowed us to further investigate the evolution of the magnetic-field structures involved in the eruption process. Results. We identified a strong small-scale brightening as a micro-flare in a CBP, recorded in emission from chromospheric to flaring plasmas. The mini-eruption is manifested via the ejection of hot (CBP loops) and cool (mini-filament) plasma recorded in both the imaging and spectroscopic data. The micro-flare is preceded by the appearance of an elongated bright feature in the IRIS slit-jaw 1400 Å images, located above the polarity inversion line. The micro-flare starts with an IRIS pixel size brightening and propagates bi-directionally along the elongated feature. We detected, in both the spectral and imaging IRIS data and AIA data, strong flows along and at the edges of the elongated feature; we believe that these represent reconnection outflows. Both edges of the elongated feature that wrap around the edges of the erupting MF evolve into a J-type shape, creating a sigmoid appearance. A quasi-separatrix layer (QSL) is identified in the vicinity of the polarity inversion line by computing the squashing factor, Q, in different horizontal planes of the NLFFF model. Conclusions. This CBP spectro-imaging study provides further evidence that CBPs represent downscaled active regions and, as such, they may make a significant contribution to the mass and energy balance of the solar atmosphere. They are the sources of all range of typical active-region features, including magnetic reconnection along QSLs, (mini-)filament eruptions, (micro-)flaring, reconnection outflows, etc. The QSL reconnection site has the same spectral appearance as the so-called explosive events identified by strong blue- and red-shifted emission, thus providing an answer to an outstanding question regarding the true nature of this spectral phenomenon.

Further Evidence for the Minifilament-eruption Scenario for Solar Polar Coronal Jets

Abstract We examine a sampling of 23 polar-coronal-hole jets. We first identified the jets in soft X-ray (SXR) images from the X-ray telescope (XRT) on the Hinode spacecraft, over 2014–2016. During this period, frequently the polar holes were small or largely obscured by foreground coronal haze, often making jets difficult to see. We selected 23 jets among those adequately visible during this period, and examined them further using Solar Dynamics Observatory’s (SDO) Atmospheric Imaging Assembly (AIA) 171, 193, 211, and 304 Å images. In SXRs, we track the lateral drift of the jet spire relative to the jet base’s jet bright point (JBP). In 22 of 23 jets, the spire either moves away from (18 cases) or is stationary relative to (4 cases) the JBP. The one exception where the spire moved toward the JBP may be a consequence of line-of-sight projection effects at the limb. From the AIA images, we clearly identify an erupting minifilament in 20 of the 23 jets, while the remainder are consistent with such an eruption having taken place. We also confirm that some jets can trigger the onset of nearby “sympathetic” jets, likely because eruption of the minifilament field of the first jet removes magnetic constraints on the base-field region of the second jet. The propensity for spire drift away from the JBP, the identification of the erupting minifilament in the majority of jets, and the magnetic-field topological changes that lead to sympathetic jets, all support or are consistent with the minifilament-eruption model for jets.

Proton deflectometry with in situ x-ray reference for absolute measurement of electromagnetic fields in high-energy-density plasmas.

We report a technique of proton deflectometry that uses a grid and an in situ reference x-ray grid image for precise measurements of magnetic fields in high-energy-density plasmas. A D3He fusion implosion provides a bright point source of both protons and x-rays, which is split into beamlets by a grid. The protons undergo deflections as they propagate through the plasma region of interest, whereas the x-rays travel along straight lines. The x-ray image, therefore, provides a zero-deflection reference image. The line-integrated magnetic fields are inferred from the shifts of beamlets between the deflected (proton) and reference (x-ray) images. We developed a system for analysis of these data, including automatic algorithms to find beamlet locations and to calculate their deflections from the reference image. The technique is verified in an experiment performed at OMEGA to measure a nonuniform magnetic field in vacuum and then applied to observe the interaction of an expanding plasma plume with the magnetic field.

Synchronization of Small-scale Magnetic Features, Blinkers, and Coronal Bright Points

Abstract We investigate the relationship between different transients such as blinkers detected in images taken at 304 Å, extreme ultraviolet coronal bright points (ECBPs) at 193 Å, X-ray coronal bright points (XCBPs) at 94 Å on the Atmospheric Imaging Assembly, and magnetic features observed by the Helioseismic and Magnetic Imager during 10 yr of solar cycle 24. An automatic identification method is applied to detect transients, and the YAFTA algorithm is used to extract the magnetic features. Using 10 yr of data, we detect in total 7,483,827 blinkers, 2,082,162 ECBPs, and 1,188,839 XCBPs, respectively, with their birth rate of about 1.1 × 10−18 m−2 s−1, 3.8 × 10−19 m−2 s−1, and 1.5 × 10−19 m−2 s−1. We find that about 80% of blinkers are observed at the boundaries of supergranules, and 57% (34%) are associated with ECBPs (XCBPs). We further find that about 61%–80% of transients are associated with the isolated magnetic poles in the quiet Sun and that the normalized maximum intensities of the transients are correlated with the photospheric magnetic flux of poles via a power law. These results conspicuously show that these transients have a magnetic origin and their synchronized behavior provides further clues toward the understanding of the coupling among the different layers of the solar atmosphere. Our study further reveals that the appearance of these transients is strongly anticorrelated with the sunspots’ cycle. This finding can be relevant for a better understanding of solar dynamo and magnetic structures at different scales during the solar cycle.

Expanding the Angle of Incidence Tolerance of Unclonable Anticounterfeiting Labels Based on Microlens Arrays and Luminescent Microparticles

Unclonable anticounterfeiting labels can be based on micrometer‐scale randomness created by stochastic processes like the distribution of luminescent microparticles in a transparent layer. Adding a microlens array to the layer can simplify the hardware needed for authentication in that magnification is no longer required. The bright point‐pattern generated under light‐emitting diode illumination can be captured by a standard digital camera. Shifting the angle of incidence (AOI) relocates the microlens foci changing the bright point‐pattern. This provides unclonability, as several distinct bright point patterns at different AOI can be required for authentication. However, it also imposes technical requirements for the authentication setup in terms of the tolerance with which the AOI must be controlled. Herein, the AOI tolerance, the deviation of angle between reference and test image for which sufficiently similar bright point patterns are recorded that they are considered matching by the authentication algorithm, is investigated. Using microlens arrays with a focal length of 550 μm, the average size of the phosphor particle was varied from 9 ± 1 to 32.5 ± 2 μm, resulting in a relaxation of tolerance from 0.8° to 3.6°. Methods to further increase the AOI tolerance and facilitate the practical implementation of these labels are discussed.

Granular-scale Magnetic Flux Emergence and its Associated Features in an Emerging Active Region

Abstract Using the high-resolution photosphere and chromosphere observations made by the 1 m New Vacuum Solar Telescope, we studied the granular-scale magnetic flux emergence occurring in emerging active region NOAA 12579. Supplementary observations are also provided by the spacecraft Solar Dynamics Observatory. The studied granular-scale flux emergence took place at two different locations. One is completely embedded in the unipolar region of the following sunspots (Case 1), while another is located at the central part in the active region (Case 2). We find that both cases initially emerge from a dark patch like a wide intergranular lane, but showing the different subsequent features. In Case 1, the emerging granule grows in an elongated feature and reaches its maximum size of almost of 5″ × 3″, with an elongated speed of about 2–3 km s−1. An eruption (i.e., surge) with bright footpoints is observed after the emerging granule reaches its maximum scale. There is a time delay of more than 10 minutes between the appearance of the abnormal granule and the Hα surge. Furthermore, its footpoints are clearly rooted at the intergranular lane. We propose that the eruptive surge could be triggered by the reconnection between the emerging magnetic flux and the preexisting ambient field, leading to the localized heating and bidirectional flows. In Case 2, the granular cell emerging is simultaneously associated with bright points with opposite magnetic polarity, showing the separating motion between them and a bunch of newly formed arch filament systems. We infer that the bright points are due to the strong-field magnetic concentration in the dark intergranular lanes rather than the instantaneous Ellerman bombs.

Autofocus Methods for Moving Target Imaging in Synthetic Aperture Radar

To use moving target signatures in synthetic aperture radar (SAR) for classification and identification, it is desirable to obtain a well-focused image from the blurred moving target signature. While a substantial amount of research has been done on solving the constant chirp rate defocusing of a moving target, this often leaves significant blurring in the moving target signature of a real target. This work aims at improving previous work on autofocus, specifically considering higher order motion terms, including those due to range walk and small rotations. Additionally, we aim to reduce the reliance on bright well-separated point scatterers. We apply SAR autofocus methods normally used for full imagery to moving targets: minimum entropy and phased gradient autofocus, and include recent innovations that allow these methods to handle range walk. Finally, we add a novel range-varying autofocus stage. We use SAR imagery of a truthed moving pickup truck collected with the MIT Airborne Radar Testbed (ARTB) to compare autofocus algorithms.

Observational evidence for two-component distributions describing solar magnetic bright points

Context.High-resolution observations of the solar photosphere reveal the presence of fine structures, in particular the so-called Magnetic Bright Points (MBPs), which are small-scale features associated with strong magnetic field regions of the order of kilogauss (kG). It is especially relevant to study these magnetic elements, which are extensively detected in all moments during the solar cycle, in order to establish their contribution to the behavior of the solar atmosphere, and ultimately a plausible role within the coronal heating problem.Aims.Characterisation of size and velocity distributions of MBPs in the solar photosphere in two different datasets of quiet Sun images acquired with high-resolution solar instruments i.e. Solar Optical Telescope SOT/Hinode and the High-resolution Fast Imager HiFI/GREGOR, in theG-band (4308 Å).Methods.In order to detect the MBPs, an automatic segmentation and identification algorithm is used. Next, the identified features were tracked to measure their proper motions. Finally, a statistical analysis of hundreds of MBPs is carried out, generating histograms for areas, diameters and horizontal velocities.Results.This work establishes that areas and diameters of MBPs display log-normal distributions that are well-fitted by two different components, whereas the velocity vector components follow Gaussians and the vector magnitude a Rayleigh distribution revealing again for all vector elements a two component composition.Conclusions.The results can be interpreted as due to the presence of two different populations of MBPs in the solar photosphere one likely related to stronger network magnetic flux elements and the other one to weaker intranetwork flux elemens. In particular this work concludes on the effect of the different spatial resolution of GREGOR and Hinode telescopes, affecting detections and average values.

Probing Upflowing Regions in the Quiet Sun and Coronal Holes

Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which constantly emit material to feed the wind. In this article we analyse 14 upflow regions in the solar corona to find potential sources for plasma flow. The upflow regions are derived from spectroscopic data from the EUV Imaging Spectrometer (EIS) on board Hinode determining their Doppler velocity and defining regions which have blueshifts stronger than -6~mbox{km},mbox{s}^{-1}. To identify the sources of these blueshift data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), and the X-ray Telescope (XRT), on board Hinode, are used. The analysis reveals that only 5 out of 14 upflows are associated with frequent transients, like obvious jets or bright points. In contrast to that, seven events are associated with small-scale features, which show a large variety of dynamics. Some resemble small bright points, while others show an eruptive nature, all of which are faint and only live for a few minutes; we cannot rule out that several of these sources may be fainter and, hence, less obvious jets. Since the complex structure of the solar wind is known, this suggests that new sources have to be considered or better methods used to analyse the known sources. This work shows that small and frequent features, which were previously neglected, can cause strong upflows in the solar corona. These results emphasise the importance of the first observations from the Extreme-Ultraviolet Imager (EUI) on board Solar Orbiter, which revealed complex small-scale coronal structures.

Gravitational caustics in an atom laser

Typically discussed in the context of optics, caustics are envelopes of classical trajectories (rays) where the density of states diverges, resulting in pronounced observable features such as bright points, curves, and extended networks of patterns. Here, we generate caustics in the matter waves of an atom laser, providing a striking experimental example of catastrophe theory applied to atom optics in an accelerated (gravitational) reference frame. We showcase caustics formed by individual attractive and repulsive potentials, and present an example of a network generated by multiple potentials. Exploiting internal atomic states, we demonstrate fluid-flow tracing as another tool of this flexible experimental platform. The effective gravity experienced by the atoms can be tuned with magnetic gradients, forming caustics analogous to those produced by gravitational lensing. From a more applied point of view, atom optics affords perspectives for metrology, atom interferometry, and nanofabrication. Caustics in this context may lead to quantum innovations as they are an inherently robust way of manipulating matter waves.

Possible Signature of Sausage Waves in Photospheric Bright Points

Sausage waves have been frequently reported in solar magnetic structures such as sunspots, pores, and coronal loops. However, they have not been unambiguously identified in photospheric bright points (BPs). Using high-resolution TiO image sequences obtained with the Goode Solar Telescope at the Big Bear Solar Observatory, we analyzed four isolated BPs. It was found that their area and average intensity oscillate for several cycles in an in-phase fashion. The oscillation periods range from 100 to 200 seconds. We interpreted the phase relation as a signature of sausage waves, particularly slow waves, after discussing sausage-wave theory and the opacity effect.

First observations from the SPICE EUV spectrometer on Solar Orbiter

Aims. We present first science observations taken during the commissioning activities of the Spectral Imaging of the Coronal Environment (SPICE) instrument on the ESA/NASA Solar Orbiter mission. SPICE is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths. In this paper we illustrate the possible types of observations to give prospective users a better understanding of the science capabilities of SPICE. Methods. We have reviewed the data obtained by SPICE between April and June 2020 and selected representative results obtained with different slits and a range of exposure times between 5 s and 180 s. Standard instrumental corrections have been applied to the raw data. Results. The paper discusses the first observations of the Sun on different targets and presents an example of the full spectra from the quiet Sun, identifying over 40 spectral lines from neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur, magnesium, and iron. These lines cover the temperature range between 20 000 K and 1 million K (10 MK in flares), providing slices of the Sun’s atmosphere in narrow temperature intervals. We provide a list of count rates for the 23 brightest spectral lines. We show examples of raster images of the quiet Sun in several strong transition region lines, where we have found unusually bright, compact structures in the quiet Sun network, with extreme intensities up to 25 times greater than the average intensity across the image. The lifetimes of these structures can exceed 2.5 hours. We identify them as a transition region signature of coronal bright points and compare their areas and intensity enhancements. We also show the first above-limb measurements with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and far off limb measurements in the equatorial plane in Mg IX, Ne VIII, and O VI lines. We discuss the potential to use abundance diagnostics methods to study the variability of the elemental composition that can be compared with in situ measurements to help confirm the magnetic connection between the spacecraft location and the Sun’s surface, and locate the sources of the solar wind. Conclusions. The SPICE instrument successfully performs measurements of EUV spectra and raster images that will make vital contributions to the scientific success of the Solar Orbiter mission.

Reflection and Evolution of Torsional Alfvén Pulses in Zero-beta Flux Tubes

Abstract We model the behavior of a torsional Alfvén pulse, assumed to propagate through the chromosphere. Building on our existing model, we utilize the zero-beta approximation appropriate for plasma in an intense magnetic flux tube, e.g., a magnetic bright point. The model is adapted to investigate the connection between these features and chromospheric spicules. A pulse is introduced at the lower, photospheric boundary of the tube as a magnetic shear perturbation, and the resulting propagating Alfvén waves are reflected from an upper boundary, representing the change in density found at the transition region. The induced upward mass flux is followed by the reversal of the flux that may be identified with the rising and falling behavior of certain lower solar atmospheric jets. The ratio of the transmitted and reflected mass flux is estimated and compared with the relative total mass of spicules and the solar wind. An example is used to study the properties of the pulse. We also find that the interaction between the initial and reflected waves may create a localized flow that persists independently from the pulse itself.

Spatio-temporal bands of coronal bright points and their relation to solar torsional oscillations

ABSTRACT Using automatic processing of daily fits files from SOHO_EIT, we studied the temporal evolution of the latitudinal distribution of bright coronal points from 1995 to 2020. The study revealed homogeneous and inhomogeneous components of the latitudinal distribution. The homogeneous component has cyclical variations with a significant phase shift compared to the number of sunspots. The residual inhomogeneous component manifests itself as migration of the centre of increased density from high to low latitudes. The bands of the residual density of coronal bright points (CBP) reflect solar torsional oscillations. It should be associated with the strengthening of the local alpha-omega dynamo. However, the cyclical nature of the number of CBP is explained by the diffusion of large-scale magnetic fluxes.

Fault Detection in PV Tracking Systems Using an Image Processing Algorithm Based on PCA

Photovoltaic power plants nowadays play an important role in the context of energy generation based on renewable sources. With the purpose of obtaining maximum efficiency, the PV modules of these power plants are installed in trackers. However, the mobile structure of the trackers is subject to faults, which can compromise the desired perpendicular position between the PV modules and the brightest point in the sky. So, the diagnosis of a fault in the trackers is fundamental to ensure the maximum energy production. Approaches based on sensors and statistical methods have been researched but they are expensive and time consuming. To overcome these problems, a new method is proposed for the fault diagnosis in the trackers of the PV systems based on a machine learning approach. In this type of approach the developed method can be classified into two major categories: supervised and unsupervised. In accordance with this, to implement the desired fault diagnosis, an unsupervised method based on a new image processing algorithm to determine the PV slopes is proposed. The fault detection is obtained comparing the slopes of several modules. This algorithm is based on a new image processing approach in which principal component analysis (PCA) is used. Instead of using the PCA to reduce the data dimension, as is usual, it is proposed to use it to determine the slope of an object. The use of the proposed approach presents several benefits, namely, avoiding the use of a wide range of data and specific sensors, fast detection and reliability even with incomplete images due to reflections and other problems. Based on this algorithm, a deviation index is also proposed that will be used to discriminate the panel(s) under fault. Several test cases are used to test and validate the proposed approach. From the obtained results, it is possible to verify that the PCA can successfully be adapted and used in image processing algorithms to determine the slope of the PV modules and so effectively detect a fault in the tracker, even when there are incomplete parts of an object in the image.