Bright Blobs Research Articles

Infrared Bilateral Polarity Ship Detection in Complex Maritime Scenarios.

In complex maritime scenarios where the grayscale polarity of ships is unknown, existing infrared ship detection methods may struggle to accurately detect ships among significant interference. To address this issue, this paper first proposes an infrared image smoothing method composed of Grayscale Morphological Reconstruction (GMR) and a Relative Total Variation (RTV). Additionally, a detection method considering the grayscale uniformity of ships and integrating shape and spatiotemporal features is established for detecting bright and dark ships in complex maritime scenarios. Initially, the input infrared images undergo opening (closing)-based GMR to preserve dark (bright) blobs with the opposite suppressed, followed by smoothing the image with the relative total variation model to reduce clutter and enhance the contrast of the ship. Subsequently, Maximally Stable Extremal Regions (MSER) are extracted from the smoothed image as candidate targets, and the results from the bright and dark channels are merged. Shape features are then utilized to eliminate clutter interference, yielding single-frame detection results. Finally, leveraging the stability of ships and the fluctuation of clutter, true targets are preserved through a multi-frame matching strategy. Experimental results demonstrate that the proposed method outperforms ITDBE, MRMF, and TFMSER in seven image sequences, achieving accurate and effective detection of both bright and dark polarity ship targets.

On the physical mechanism causing strongly enhanced radar backscatter in C-Band SAR images of convective rain over the ocean

ABSTRACT Radar signatures of rain over the ocean have a complex structure since they receive contributions from surface scattering and volume scattering and attenuation by hydrometeors in the atmosphere. These contributions overlap and are often difficult to detangle. While most of the mechanisms contributing to radar signatures of rain over the ocean are well understood, there is one remaining issue that has been discussed controversially in the literature for a long time. It is the question what scattering mechanism causes the areas of strongly enhanced radar backscatter, also called ‘bright blobs’ or ‘bright patches’, which are frequently observed on spaceborne C-band SAR images acquired over tropical and subtropical oceans in the presence of convective rain. Recently, papers have been published in which it is hypothesized that they are caused by radar backscattering at hydrometeors in the melting layer (ML). Although many observational facts seem to support this hypothesis, there exists one strong argument against this hypothesis: It is the observation that the position of the ML radar signatures (bright blob) in the SAR image is not shifted in anti-range from the position, where the rain column hits the sea surface. This absence of a shift is observed when 1) comparing Sentinel-1 SAR images on which rain cells are visible with quasi-concurrently acquired weather radar images and 2) when inter-comparing of SAR images of rain cells acquired concurrently at different frequencies and polarizations. Based on these observations, we discard the hypothesis that the bright blobs are due to volume scattering at hydrometeors in the ML and hypothesize instead that they are due to scattering at splash products at the sea surface. This hypothesis is supported by radar backscattering measurements carried out in the laboratory and from a shore-based platform, which show that, at C-and X-band, strong rain can give rise to strong radar returns also at cross-polarization.

Ram-pressure stripped radio tail and two ULXs in the spiral galaxy HCG 97b

ABSTRACT We report LOFAR and Very Large Array (VLA) detections of extended radio emission in the spiral galaxy HCG 97b, hosted by an X-ray bright galaxy group. The extended radio emission detected at 144 MHz, 1.4 GHz, and 4.86 GHz is elongated along the optical disc and has a tail that extends 27 kpc in projection towards the centre of the group at GHz frequencies or 60 kpc at 144 MHz. Chandra X-ray data show two off-nuclear ultra-luminous X-ray sources (ULXs), with the farther one being a plausible candidate for an accreting intermediate-mass black hole (IMBH). The asymmetry observed in both CO emission morphology and kinematics indicates that HCG 97b is undergoing ram-pressure stripping, with the leading side at the south-eastern edge of the disc. Moreover, the VLA 4.86 GHz image reveals two bright radio blobs near one ULX, aligning with the disc and tail, respectively. The spectral indices in the disc and tail are comparable and flat (α > −1), suggesting the presence of recent outflows potentially linked to ULX feedback. This hypothesis gains support from estimates showing that the bulk velocity of the relativistic electrons needed for transport from the disc to the tail is approximately ${\sim}1300\, \rm km~s^{-1}$. This velocity is much higher than those observed in ram-pressure stripped galaxies ($100{-}600\, \rm km~s^{-1}$), implying an alternative mechanism aiding the stripping process. Therefore, we conclude that HCG 97b is subject to ram pressure, with the formation of its stripped radio tail likely influenced by the putative IMBH activities.

Evolution of dynamic fibrils from the cooler chromosphere to the hotter corona

Dynamic fibrils (DFs) are commonly observed chromospheric features in solar active regions. Recent observations from the Extreme Ultraviolet Imager (EUI) aboard the Solar Orbiter have revealed unambiguous signatures of DFs at the coronal base in extreme ultraviolet (EUV) emission. However, it remains unclear if the DFs detected in the EUV are linked to their chromospheric counterparts. Simultaneous detection of DFs from chromospheric to coronal temperatures could provide important information on their thermal structuring and evolution through the solar atmosphere. In this paper, we address this question by using coordinated EUV observations from the Atmospheric Imaging Assembly (AIA), Interface Region Imaging Spectrograph (IRIS), and EUI to establish a one-to-one correspondence between chromospheric and transition region DFs (observed by IRIS) with their coronal counterparts (observed by EUI and AIA). Our analysis confirms a close correspondence between DFs observed at different atmospheric layers and reveals that DFs can reach temperatures of about 1.5 million Kelvin, typical of the coronal base in active regions. Furthermore, the intensity evolution of these DFs, as measured by tracking them over time, reveals a shock-driven scenario in which plasma piles up near the tips of these DFs and, subsequently, these tips appear as bright blobs in coronal images. These findings provide information on the thermal structuring of DFs and their evolution and impact through the solar atmosphere.

Tracing Hot Spot Motion in Sagittarius A* Using the Next-Generation Event Horizon Telescope (ngEHT)

We propose the tracing of the motion of a shearing hot spot near the Sgr A* source through a dynamical image reconstruction algorithm, StarWarps. Such a hot spot may form as the exhaust of magnetic reconnection in a current sheet near the black hole horizon. A hot spot that is ejected from the current sheet into an orbit in the accretion disk may shear and diffuse due to instabilities at its boundary during its orbit, resulting in a distinct signature. We subdivide the motion into two different phases: the first phase refers to the appearance of the hot spot modeled as a bright blob, followed by a subsequent shearing phase. We employ different observational array configurations, including EHT (2017, 2022) and the next-generation Event Horizon Telescope (ngEHTp1, ngEHT) arrays, with several new sites added, and make dynamical image reconstructions for each of them. Subsequently, we infer the hot spot angular image location in the first phase, followed by the axes ratio and the ellipse area in the second phase. We focus on the direct observability of the orbiting hot spot in the sub-mm wavelength. Our analysis demonstrates that for this particular simulation, the newly added dishes are better able to trace the first phase as well as part of the second phase before the flux is reduced substantially, compared to the EHT arrays. The algorithm used in this work can be easily extended to other types of dynamics, as well as different shearing timescales. More simulations are required to prove whether the current set of newly proposed sites are sufficient to resolve any motions near variable sources, such as Sgr A*.

Simulating Jellyfish Galaxies: A Case Study for a Gas-rich Dwarf Galaxy

Abstract We investigate the formation of jellyfish galaxies using radiation-hydrodynamic simulations of gas-rich dwarf galaxies with a multiphase interstellar medium (ISM). We find that the ram-pressure-stripped (RPS) ISM is the dominant source of molecular clumps in the near wake within 10 kpc from the galactic plane, while in situ formation is the major channel for dense gas in the distant tail of the gas-rich galaxy. Only 20% of the molecular clumps in the near wake originate from the intracluster medium (ICM); however, the fraction reaches 50% in the clumps located at 80 kpc from the galactic center since the cooling time of the RPS gas tends to be short owing to the ISM–ICM mixing (≲10 Myr). The tail region exhibits a star formation rate of 0.001–0.01 M ⊙ yr−1, and most of the tail stars are born in the stripped wake within 10 kpc from the galactic plane. These stars induce bright Hα blobs in the tail, while Hα tails fainter than 6 × 1038 erg s−1 kpc−2 are mostly formed via collisional radiation and heating due to mixing. We also find that the stripped tails have intermediate X-ray-to-Hα surface brightness ratios (1.5 ≲ F X/F Hα ≲ 20), compared to the ISM (≲1.5) or pure ICM (≫20). Our results suggest that jellyfish features emerge when the ISM from gas-rich galaxies is stripped by strong ram pressure, mixes with the ICM, and enhances the cooling in the tail.

Coronal Rain in Randomly Heated Arcades

Abstract Adopting the MPI-AMRVAC code, we present a 2.5-dimensional magnetohydrodynamic simulation, which includes thermal conduction and radiative cooling, to investigate the formation and evolution of the coronal rain phenomenon. We perform the simulation in initially linear force-free magnetic fields that host chromospheric, transition-region, and coronal plasma, with turbulent heating localized on their footpoints. Due to thermal instability, condensations start to occur at the loop top, and rebound shocks are generated by the siphon inflows. Condensations fragment into smaller blobs moving downwards, and as they hit the lower atmosphere, concurrent upflows are triggered. Larger clumps show us clear coronal rain showers as dark structures in synthetic EUV hot channels and as bright blobs with cool cores in the 304 Å channel, well resembling real observations. Following coronal rain dynamics for more than 10 hr, we carry out a statistical study of all coronal rain blobs to quantify their widths, lengths, areas, velocity distributions, and other properties. The coronal rain shows us continuous heating–condensation cycles, as well as cycles in EUV emissions. Compared to the previous studies adopting steady heating, the rain happens faster and in more erratic cycles. Although most blobs are falling downward, upward-moving blobs exist at basically every moment. We also track the movement of individual blobs to study their dynamics and the forces driving their movements. The blobs have a prominence-corona transition-region-like structure surrounding them, and their movements are dominated by the pressure evolution in the very dynamic loop system.

Dynamical Evolution of an Active-region Filament Driven by Magnetic Reconnection

Abstract Studying solar filament dynamical evolutions is an important approach to reveal the driving mechanism of solar eruptions, which seriously impact on the Sun–Earth system and could cause disastrous space weather. To better understand the evolution process of solar filaments, here we investigate an active-region filament by employing observations from the New Vacuum Solar Telescope (NVST), Solar Dynamics Observatory, and Interface Region Imaging Spectrograph. The high-resolution NVST Hα images show that the northern footpoint of the filament gradually moved northward. Near the northern footpoint, there is an arch filament system (AFS). Between adjacent footpoints of the filament and the AFS, transient brightening, underlying magnetic cancellation, and bidirectional flows were detected, which jointly imply that it could be the magnetic reconnection between the filament and the AFS that changes the connection of filament threads and drives its footpoint to move northward. In addition, during the footpoint evolution, the filament with highly twisted structure underwent several untwisting motions. Meanwhile, transient brightenings were also observed and appeared as bright knots around several positions where filament threads might braid with each other. And some bright blobs were also detected to propagate outward from the brightening region. These observations suggest that magnetic reconnection might be responsible for the untwisting motion. This work exposes us to a dynamical scenario of the filament evolution driven by magnetic reconnection, which will promote our understanding of the formation and eruption of the filaments.

Formation of Solar Quiescent Coronal Loops through Magnetic Reconnection in an Emerging Active Region

Abstract Coronal loops are the building blocks of solar active regions. However, their formation mechanism remains poorly understood. Here we present direct observational evidence for the formation of coronal loops through magnetic reconnection as new magnetic fluxes emerge into the solar atmosphere. Extreme-ultraviolet observations by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) clearly show the newly formed loops following magnetic reconnection within a plasma sheet. Formation of the loops is also seen in the Hα line-core images taken by the New Vacuum Solar Telescope. Observations from the Helioseismic and Magnetic Imager on board SDO show that a positive-polarity flux concentration moves toward a negative-polarity one with a speed of ∼0.4 km s−1 before the formation of coronal loops. During the loop formation process, we found signatures of flux cancellation and subsequent enhancement of the transverse field between the two polarities. The three-dimensional magnetic field structure reconstructed through a magnetohydrostatic model shows field lines consistent with the loops in AIA images. Numerous bright blobs with an average width of 1.37 Mm appear intermittently in the plasma sheet and move upward with a projected velocity of ∼114 km s−1. The temperature, emission measure, and density of these blobs are about 3 MK, 2.0 × 1028 cm−5, and 1.2 × 1010 cm−3, respectively. A power spectral analysis of these blobs indicates that the observed reconnection is likely not dominated by a turbulent process. We have also identified flows with a velocity of 20–50 km s−1 toward the footpoints of the newly formed coronal loops.

An observationally constrained model of strong magnetic reconnection in the solar chromosphere

Context.The evolution of the photospheric magnetic field plays a key role in the energy transport into the chromosphere and the corona. In active regions, newly emerging magnetic flux interacts with the pre-existent magnetic field, which can lead to reconnection events that convert magnetic energy into thermal energy.Aims.We aim to study the heating caused by a strong reconnection event that was triggered by magnetic flux cancelation.Methods.We use imaging and spectropolarimetric data in the Fe I6301& 6302 Å, Ca II8542 Å, and Ca IIK spectral lines obtained with the CRISP and CHROMIS instruments at the Swedish 1-m Solar Telescope. These data were inverted with the STiC code by performing multi-atom, multi-line, non-local thermodynamic equilibrium inversions. These inversions yielded a three-dimensional model of the reconnection event and surrounding atmosphere, including temperature, velocity, microturbulence, magnetic field, and radiative loss rate.Results.The model atmosphere shows the emergence of magnetic loops with a size of several arcseconds into a pre-existing predominantly unipolar field. Where the reconnection region is expected to be, we see an increase in the chromospheric temperature of roughly 2000 K as well as bidirectional flows of the order of 10 km s−1emanating from there. We see bright blobs of roughly 0.2 arcsec in diameter in the Ca IIK, moving at a plane-of-the-sky velocity of the order of 100 km s−1and a blueshift of 100 km s−1, which we interpret as ejected plasmoids from the same region. This scenario is consistent with theoretical reconnection models, and therefore provides evidence of a reconnection event taking place. The chromospheric radiative losses at the reconnection site are as high as 160 kW m−2, providing a quantitative constraint on theoretical models that aim to simulate reconnection caused by flux emergence in the chromosphere.

Small-scale Bright Blobs Ejected from a Sunspot Light Bridge

Abstract Light bridges (LBs) are bright lanes that divide an umbra into multiple parts in some sunspots. Persistent oscillatory bright fronts at a temperature of ∼105 K are commonly observed above LBs in the 1400/1330 Å passbands of the Interface Region Imaging Spectrograph (IRIS). Based on IRIS observations, we report small-scale bright blobs ejected from the oscillating bright front above a light bridge. Some of these blobs reveal a clear acceleration, whereas the others do not. The average speed of these blobs projected onto the plane of sky is 71.7 ± 14.7 km s−1, with an initial acceleration of 1.9 ± 1.3 km s−2. These blobs normally reach a projected distance of 3–7 Mm from their origin sites. They have an average projected area of 0.57 ± 0.37 Mm2. The blobs were also detected in multiple extreme-ultraviolet passbands of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, but not in the Hα images taken by the New Vacuum Solar Telescope. The typical temperature and electron density of these blobs are around K and cm−3, respectively. The estimated kinetic and thermal energies are on the order of erg and erg, respectively. These small-scale blobs appear to show three different types of formation processes. They are possibly triggered by induced reconnection or release of enhanced magnetic tension due to interaction of adjacent shocks, local magnetic reconnection between emerging magnetic bipoles on the light bridge and surrounding unipolar umbral fields, and plasma acceleration or instability caused by upward shocks, respectively.

Shock–Cloud Interaction in the Southwestern Rim of RX J1713.7–3946 Evidenced by Chandra X-Ray Observations

Abstract We report on results of Chandra X-ray observations of the southwestern part of the supernova remnant (SNR) RX J1713.7−3946. We measure proper motions of two X-ray bright blobs, named Blobs A and B, in regions presumably corresponding to the forward shock of the SNR. The measured velocities are 3800 ± 100 km s−1 and 2300 ± 200 km s−1 for Blobs A and B, respectively. Since a dense molecular clump is located close to Blob B, its slower velocity is attributed to shock deceleration as a result of a shock–cloud interaction. This result provides solid evidence that the forward shock of RX J1713.7−3946 is indeed colliding with dense gas discovered through radio observations reported in the literature. The locations and velocity differences of the two blobs lead to an estimate that the shock encountered with the dense gas ∼100 yr ago. The shock velocities, together with cutoff energies of the synchrotron X-ray spectra of the blobs, indicate that particle acceleration in these regions is close to the Bohm limit. Blob B, in particular, is almost at the limit, accelerating particles at the fastest possible rate. We discuss possible influence of the shock–cloud interaction on the efficiency of particle acceleration.

Nighttime Vehicle Detection and Tracking with Occlusion Handling by Pairing Headlights and Taillights

In recent years, vision-based vehicle detection has received considerable attention in the literature. Depending on the ambient illuminance, vehicle detection methods are classified as daytime and nighttime detection methods. In this paper, we propose a nighttime vehicle detection and tracking method with occlusion handling based on vehicle lights. First, bright blobs that may be vehicle lights are segmented in the captured image. Then, a machine learning-based method is proposed to classify whether the bright blobs are headlights, taillights, or other illuminant objects. Subsequently, the detected vehicle lights are tracked to further facilitate the determination of the vehicle position. As one vehicle is indicated by one or two light pairs, a light pairing process using spatiotemporal features is applied to pair vehicle lights. Finally, vehicle tracking with occlusion handling is applied to refine incorrect detections under various traffic situations. Experiments on two-lane and four-lane urban roads are conducted, and a quantitative evaluation of the results shows the effectiveness of the proposed method.

Observation of All Pre- and Post-reconnection Structures Involved in Three-dimensional Reconnection Geometries in Solar Eruptions

Abstract We report on observations of the two newly identified reconnection geometries involving erupting flux ropes. In 3D, a flux rope can reconnect either with a surrounding coronal arcade (recently named “ar–rf” reconnection) or with itself (“rr–rf” reconnection), and both kinds of reconnection create a new flux-rope field line and a flare loop. For the first time, we identify all four constituents of both reconnections in a solar eruptive event, the filament eruption of 2011 June 7 observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly. The ar–rf reconnection manifests itself as shift of one leg of the filament by more than 25″ northward. At its previous location, a flare arcade is formed, while the new location of the filament leg previously corresponded to a footpoint of a coronal loop in 171 Å. In addition, the evolution of the flare ribbon hooks is also consistent with the occurrence of ar–rf reconnection as predicted by MHD simulations. Specifically, the growing hook sweeps footpoints of preeruptive coronal arcades, and these locations become inside the hook. Furthermore, the rr–rf reconnection occurs during the peak phase above the flare arcade, in an apparently X-type geometry involving a pair of converging bright filament strands in the erupting filament. A new flare loop forms near the leg of one of the strands, while a bright blob, representing a remnant of the same strand, is seen ascending into the erupting filament. All together, these observations vindicate recent predictions of the 3D standard solar-flare model.

Vortex Formations and Its Associated Surges in a Sunspot Light Bridge

Abstract We report on the successive occurrence of 0.″5 wide photospheric vortices with strong transverse shear flows at the edge of a sunspot light bridge (LB), and the subsequent ejection of chromospheric surges observed using a Visible Inteferometry Spectrograph, a broadband TiO filter, and a Near InfRared Imaging Spectrograph of the Goode Solar Telescope operating at Big Bear Solar Observatory. The Hα surges ejected at the location of the vortices often appeared in a hollow cylindrical structure. We also observed quasi-periodic vortex-associated bright Hα plasma blobs moving upward with a speed of up to 4 km s−1. In view of the strong shear flow at the edge of the LB, it is likely that the vortices form under the Kelvin–Helmholtz instability. The surges may result from either the magnetic tension generated after magnetic reconnection or an acoustic impulse of a fast photospheric transverse flow. Otherwise, the surges could also be associated with Alfvénic waves, in which case their origin could be torsional magnetic fields generated in the process of the vortex formation.

Blobs, spiral arms, and a possible planet around HD 169142

Context. Young planets are expected to cause cavities, spirals, and kinematic perturbations in protostellar disks that may be used to infer their presence. However, a clear detection of still-forming planets embedded within gas-rich disks is still rare. Aims. HD 169142 is a very young Herbig Ae-Be star surrounded by a pre-transitional disk, composed of at least three rings. While claims of sub-stellar objects around this star have been made previously, follow-up studies remain inconclusive. The complex structure of this disk is not yet well understood. Methods. We used the high contrast imager SPHERE at ESO Very large Telescope to obtain a sequence of high-resolution, high-contrast images of the immediate surroundings of this star over about three years in the wavelength range 0.95–2.25 μm. This enables a photometric and astrometric analysis of the structures in the disk. Results. While we were unable to definitively confirm the previous claims of a massive sub-stellar object at 0.1–0.15 arcsec from the star, we found both spirals and blobs within the disk. The spiral pattern may be explained as due to the presence of a primary, a secondary, and a tertiary arm excited by a planet of a few Jupiter masses lying along the primary arm, likely in the cavities between the rings. The blobs orbit the star consistently with Keplerian motion, allowing a dynamical determination of the mass of the star. While most of these blobs are located within the rings, we found that one of them lies in the cavity between the rings, along the primary arm of the spiral design. Conclusions. This blob might be due to a planet that might also be responsible for the spiral pattern observed within the rings and for the cavity between the two rings. The planet itself is not detected at short wavelengths, where we only see a dust cloud illuminated by stellar light, but the planetary photosphere might be responsible for the emission observed in the K1 and K2 bands. The mass ofthis putative planet may be constrained using photometric and dynamical arguments. While uncertainties are large, the mass should be between 1 and 4 Jupiter masses. The brightest blobs are found at the 1:2 resonance with this putative planet.

Subarcsecond Blobs in Flare-related Coronal Jets

Abstract In this paper, we report multiwavelength observations of subarcsecond blobs in coronal jets. In AR 12149, a C5.5 circular-ribbon flare occurred at ∼04:55 UT on 2014 August 24, which consisted of a discrete circular ribbon and a short inner ribbon inside. Two jets (jet1 and jet2) were related to the flare. Jet1 appeared first and experienced untwisting motion during its early propagation along a closed coronal loop. Jet2 appeared 6 minutes later and propagated upward along another closed loop. During its initial phase, a big plasmoid was ejected out of jet2 at a speed of ∼150 km s−1. After the flare peak time (05:02 UT), multiple bright and compact blobs appeared in the lower part of jet2, which were observed by the Slit-Jaw Imager (SJI) on board the Interface Region Imaging Spectrograph. The blobs observed by SJI in 1330 Å have sizes of 0.″45–1.″35, nearly 84% of which are subarcsecond (<1″). The mean value and standard deviation of the sizes are 0.″78 and 0.″19, respectively. The velocities of the blobs range from 10 to more than 220 km s−1, some of which decelerate and disappear during the upward propagation. Three of the blobs had their counterparts in extreme-ultraviolet (EUV) wavelengths observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory spacecraft. The velocities are almost identical in ultraviolet (UV) and EUV wavelengths. We propose that the blobs observed in 1330 Å are the cool component (∼0.025 MK), while the blobs observed in EUV are the hot component of several MK. In jet1, only one blob was present, with a size of ∼1″ and a velocity of ∼40 km s−1. We conclude that the blobs are created by the tearing-mode instability of the current sheet at the base or inside the coronal jets. Our results have important implications for uncovering the fine structures of coronal jets and understanding the relationship between the blobs observed at UV and EUV wavelengths.

On Dynamics and Spectra of Fine Spatial Structures in the Vela Pulsar Wind Nebula

Evolution of X-ray surface brightness and spectra of fine spatial structures in the Vela pulsar wind nebula (PWN) are studied. Variability of morphology and the spectrum of a small-scale structure at the base of the southern jet of the nebula – a bright transverse bar is investigated for the first time. The size of the bar located within 4″–5″ from the Vela pulsar is ∼ 4.5″ × 1.5″. It is shown that brightness, shapes, and positions of the bar and the southern jet base vary on the timescale of 1–2 weeks, the bar can disappear and emerge again within 10 days. The power-law photon index of the jet base is much harder than that of the bar, 1.20 ± 0.12 vs 1.65 ± 0.15. The latter index is close to 1.6, a typical value for synchrotron emission of electrons accelerated at an ultrarelativistic shock. We speculate that bright blobs seen on both sides of the southern jet base may have the same nature as the bright blobs in the Crab PWN, which are believed to mark the position of the termination shock of the pulsar wind.

Solar Radio Burst Associated with the Falling Bright EUV Blob

Abstract At the beginning of the 2015 November 4 flare, in the 1300–2000 MHz frequency range, we observed a very rare slow positively drifting burst. We searched for associated phenomena in simultaneous EUV observations made by IRIS, SDO/AIA, and Hinode/XRT, as well as in H α observations. We found that this radio burst was accompanied with the bright blob, visible at transition region, coronal, and flare temperatures, falling down to the chromosphere along the dark loop with a velocity of about 280 km s−1. The dark loop was visible in H α but disappeared afterward. Furthermore, we found that the falling blob interacted with the chromosphere as expressed by a sudden change of the H α spectra at the location of this interaction. Considering different possibilities, we propose that the observed slow positively drifting burst is generated by the thermal conduction front formed in front of the falling hot EUV blob.

Blind spot monitoring at night-time using rear-view camera

The blind spot monitoring (BSM) is one of the key functions of advanced driver assistance system (ADAS). In this paper, we propose vision-based blind spot detection and tracking algorithm which is applicable at night-time. The feature of highly bright blobs due to the headlights of behind vehicle is employed for the detection of vehicles in blind spot area, because the appearance-based approach that can be used at daytime is not any more appropriate. We calculate the motion vectors of detected blobs to find an approaching vehicle and make headlight grouping to estimate its position by use of the projection map. We can successfully generate an alarm signal by detection and tracking the overtaking vehicle in blind spot area at night-time.