Solar Dynamics Observatory Images Research Articles

Neural-Based Video Compression on Solar Dynamics Observatory Images

Neural-Based Video Compression on Solar Dynamics Observatory Images

A Community Data Set for Comparing Automated Coronal Hole Detection Schemes

Automated detection schemes are nowadays the standard approach for locating coronal holes in extreme-UV images from the Solar Dynamics Observatory (SDO). However, factors such as the noisy nature of solar imagery, instrumental effects, and others make it challenging to identify coronal holes using these automated schemes. While discrepancies between detection schemes have been noted in the literature, a comprehensive assessment of these discrepancies is still lacking. The contribution of the Coronal Hole Boundary Working Team in the COSPAR ISWAT initiative to close this gap is threefold. First, we present the first community data set for comparing automated coronal hole detection schemes. This data set consists of 29 SDO images, all of which were selected by experienced observers to challenge automated schemes. Second, we use this community data set as input to 14 widely applied automated schemes to study coronal holes and collect their detection results. Third, we study three SDO images from the data set that exemplify the most important lessons learned from this effort. Our findings show that the choice of the automated detection scheme can have a significant effect on the physical properties of coronal holes, and we discuss the implications of these findings for open questions in solar and heliospheric physics. We envision that this community data set will serve the scientific community as a benchmark data set for future developments in the field.

A Dataset for Exploring Stellar Activity in Astrometric Measurements from SDO Images of the Sun

We present a data set for investigating the impact of stellar activity on astrometric measurements using NASA’s Solar Dynamics Observatory (SDO) images of the Sun. The sensitivity of astrometry for detecting exoplanets is limited by stellar activity (e.g., starspots), which causes the measured “center of flux” of the star to deviate from the true, geometric, center, producing false positive detections. We analyze Helioseismic and Magnetic Imager continuum image data obtained from SDO between 2015 July and 2022 December to examine this “astrometric jitter” phenomenon for the Sun. We employ data processing procedures to clean the images and compute the time series of the sunspot-induced shift between the center of flux and the geometric center. The resulting time series show quasiperiodic variations up to 0.05% of the Sun’s radius at its rotation period.

Spatial and Temporal Analysis of Quiescent Coronal Rain over an Active Region

The solar corona produces coronal rain, hundreds of times colder and denser material than the surroundings. Coronal rain is known to be deeply linked to coronal heating, but its origin, dynamics, and morphology are still not well understood. The leading theory for its origin is thermal instability (TI) occurring in coronal loops in a state of thermal nonequilibrium (TNE), the TNE-TI scenario. Under steady heating conditions, TNE-TI repeats in cycles, leading to long-period EUV intensity pulsations and periodic coronal rain. In this study, we investigate coronal rain on the large spatial scales of an active region (AR) and over the long temporal scales of EUV intensity pulsations to elucidate its distribution at such scales. We conduct a statistical study of coronal rain observed over an AR off limb with Interface Region Imaging Spectrograph and Solar Dynamics Observatory imaging data, spanning chromospheric to transition region (TR) temperatures. The rain is widespread across the AR, irrespective of the loop inclination, and with minimal variation over the 5.45 hr duration of the observation. Most rain has a downward (87.5%) trajectory; however, upward motions (12.5%) are also ubiquitous. The rain dynamics are similar over the observed temperature range, suggesting that the TR emission and chromospheric emission are colocated on average. The average clump widths and lengths are similar in the SJI channels and wider in the AIA 304 Å channel. We find ubiquitous long-period EUV intensity pulsations in the AR. Short-term periodicity is found (16 minutes) linked to the rain appearance, which constitutes a challenge to explain under the TNE-TI scenario.

GST Data-processing Workflow: Image Registration and Alignment

Multiple solar instrument observation campaigns are increasingly popular among the solar physics and space science communities. Scientists organize high-resolution ground-based telescopes and spacecraft to study the evolution of the complex solar atmosphere and the origin of space weather. Image registration and coalignment between different instruments are vital for accurate data product comparison. We developed a Python language package for registration of ground-based high-resolution imaging data acquired by the Goode Solar Telescope (GST) to space-based full-disk continuum intensity data provided by the Solar Dynamics Observatory (SDO) with the scale-invariant feature transform method. The package also includes tools to align data sets obtained in different wavelengths and at different times utilizing the optical flow method. We present the image registration and coalignment workflow. The aliment accuracy of each alignment method is tested with the aid of radiative magnetohydrodynamics simulation data. We update the pointing information in GST data fits headers and generate GST and SDO imaging data products as science-ready four-dimensional (x, y, λ, t) data cubes.

Immersive Virtual-Reality-Based Streaming Distance Education System for Solar Dynamics Observatory: A Case Study

The combination of immersive virtual reality (VR) environments and distance education has led to a new educational paradigm. In this study, an immersive VR-based distance education system is proposed to enable multiple remote users to send, share, and experience images from the Solar Dynamics Observatory (SDO) via streaming. In contrast to the conventional system in which only experts use SDO data, the proposed system provides a head-mounted-display-based visualization platform that can be easily used by experts and non-experts. Real-time SDO image streaming must be possible to realistically observe changes in the Sun and increase involvement. Thus, multichannel-based SDO image transmission was applied to increase the network bandwidth utilization. To improve the social presence of participants, realistic avatar models controlled by the motions synchronized with the user are provided. In addition, free communication is possible through verbal interactions. This allows multiple remote users to participate simultaneously without having to be physically present. A user study with 20 subjects showed that the participants could observe SDO images in a more immersive manner by using the proposed system. In addition, they experienced social presence because of the user avatar models and an enriched educational experience by conversing with and listening to experts.

Measurement of the Height of the Chromospheric Network Emission from Solar Dynamics Observatory Images

We measured the height of the chromospheric network in the 1700, 1600, and 304 A wavelength bands of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) from the shift of features on the disk with respect to corresponding features in SDO/Helioseismic and Magnetic Imager (HMI) images of the absolute value of the longitudinal magnetic field. We found that near the limb the 304 A network emission forms 3.60$\pm$0.24 Mm above the 1600 A emission, which, in turn, forms 0.48$\pm$0.10 Mm above the HMI (6173 A) level. At the center of the disk the corresponding height differences are 2.99$\pm$0.02 Mm and 0.39$\pm$0.06 Mm respectively. We also found that the 1600 A network emission forms 0.25$\pm$0.02 Mm above the 1700 A emission near the limb and 0.20$\pm$0.02 Mm at the disk center. Finally, we examined possible variations with the solar cycle. Our results can help to check and refine atmospheric models.

On the propagation of a geoeffective coronal mass ejection during 15–17 March 2015

AbstractThe largest geomagnetic storm so far, called 2015 St. Patrick's Day event, in the solar cycle 24 was produced by a fast coronal mass ejection (CME) originating on 15 March 2015. It was an initially west‐oriented CME and expected to only cause a weak geomagnetic disturbance. Why did this CME finally cause such a large geomagnetic storm? We try to find some clues by investigating its propagation from the Sun to 1 AU. First, we reconstruct the CME's kinematic properties in the corona from the SOHO and Solar Dynamics Observatory imaging data with the aid of the graduated cylindrical shell model. It is suggested that the CME propagated to the west ∼33°±10° away from the Sun‐Earth line with a speed of about 817 km s−1 before leaving the field of view of the SOHO/Large Angle and Spectrometric Coronagraph (LASCO) C3 camera. A magnetic cloud (MC) corresponding to this CME was measured in situ by the Wind spacecraft 2 days after the CME left LASCO's field of view. By applying two MC reconstruction methods, we infer the configuration of the MC as well as some kinematic information, which implies that the CME possibly experienced an eastward deflection on its way to 1 AU. However, due to the lack of observations from the STEREO spacecraft, the CME's kinematic evolution in interplanetary space is not clear. In order to fill this gap, we utilize numerical MHD simulation, drag‐based CME propagation model (DBM) and the model for CME deflection in interplanetary space (DIPS) to recover the propagation process, especially the trajectory, of the CME from 30RS to 1 AU under the constraints of the derived CME's kinematics near the Sun and at 1 AU. It is suggested that the trajectory of the CME was deflected toward the Earth by about 12°, consistent with the implication from the MC reconstruction at 1 AU. This eastward deflection probably contributed to the CME's unexpected geoeffectiveness by pushing the center of the initially west‐oriented CME closer to the Earth.

ELLERMAN BOMBS AT HIGH RESOLUTION. II. TRIGGERING, VISIBILITY, AND EFFECT ON UPPER ATMOSPHERE

We use high-resolution imaging spectroscopy with the Swedish 1-m Solar Telescope (SST) to study the transient brightenings of the wings of the Balmer Halpha line in emerging active regions that are called Ellerman bombs. Simultaneous sampling of Ca II 854.2 nm with the SST confirms that most Ellerman bombs occur also in the wings of this line, but with markedly different morphology. Simultaneous images from the Solar Dynamics Observatory (SDO) show that Ellerman bombs are also detectable in the photospheric 170 nm continuum, again with differing morphology. They are also observable in 160 nm SDO images, but with much contamination from C IV emission in transition-region features. Simultaneous SST spectropolarimetry in Fe I 630.1 nm shows that Ellerman bombs occur at sites of strong-field magnetic flux cancelation between small bipolar strong-field patches that rapidly move together over the solar surface. Simultaneous SDO images in He II 30.4 nm, Fe IX 17.1 nm, and Fe XIV 21.1 nm show no clear effect of the Ellerman bombs on the overlying transition region and corona. These results strengthen our earlier suggestion, based on Halpha morphology alone, that the Ellerman bomb phenomenon is a purely photospheric reconnection phenomenon.