On the connection between Rieger-type and Magneto-Rossby waves driving the frequency of the large solar eruptions during solar cycles 19–25

Global solar activity variation mainly occurs over about an 11 yr cycle. However, both longer and shorter periodicities than the solar cycle are also present in many different solar activity indices. The longer timescales may be up to hundreds of years, while the shorter timescales for global solar variability could be within 0.5–2 yr, which include, e.g., from the Rieger-type periods (150–160 days) to quasi-biennial oscillations of 2 yr. The most likely origin of this short-timescale quasi-periodicity is attributed to magnetic Rossby waves, which have periods of 0.8–2.4 yr. In this work, we present findings of a unique evolution of identified shorter periodicities, like the Rieger-type, arising from magnetic Rossby waves, throughout Solar Cycles 19–25. We report further observational evidence of the strong relationship between the Rieger-type periodicity, magneto-Rossby waves, and major solar flare activity. Moreover, this study also reveals that the global solar magnetic field has a continuous periodic longitudinal conveyor belt motion along the solar equator, together with an up-and-down movement in the latitudinal directions. We found that when these longitudinal and latitudinal movements have Rieger-type periodicity and magneto-Rossby waves during the same period of a solar cycle, major flare activity is present

Evolution of coronal jets during Solar Cycle 24

The focus of this study is on the spatial and temporal distributions of 2704 solar jets throughout Solar Cycle 24, from beginning to end. This work is a follow-up paper by Liu et al. With this extended data set, we have further confirmed the two distinct distributions of coronal jets: one located in polar regions and another at lower latitudes. Further analysis of the series of coronal jets revealed kink oscillations of the global solar magnetic field. Additionally, studying the northern and southern hemispheres separately showed an antiphase correlation that can be interpreted as a global sausage oscillatory pattern of the loci of the coronal jets. We also investigated how the variability of the solar cycle may impact the power law index of coronal jets by dividing the data set into the rising and declining phases of Solar Cycle 24. However, there is no compelling evidence to suggest that the power law index changes after the maximum. It is worth noting that based on this vast database of solar jets, the degradation of the 304 Å channel of the Atmospheric Imaging Assembly instrument on board the Solar Dynamics Observatory can also be identified and confirmed. Finally, we searched for compelling signatures of the presence of active longitude in the coronal jet database. There was no obvious evidence with a high probability of an active longitude; therefore, this question remains yet to be addressed further

Long-period oscillations in the lower solar atmosphere prior to flare events

Context. Multiple studies have identified a range of oscillation periods in active regions, from 3−5 min to long-period oscillations that last from tens of minutes to several hours. Recently, it was also suggested that these periods are connected with eruptive activity in the active regions. Thus, it is essential to understand the relation between oscillations in solar active regions and their solar eruption activity. Aims. We investigate the long-period oscillations of NOAA 12353 prior to a series of C-class flares and correlate the findings with the 3- to 5-min oscillations that were previously studied in the same active region. The objective of this work is to elucidate the presence of various oscillations with long periods in the lower solar atmosphere both before and after the flare events. Methods. To detect long-period oscillations, we assessed the emergence, shearing, and total magnetic helicity flux components from the photosphere to the top of the chromosphere. To analyze the magnetic helicity flux in the lower solar atmosphere, we used linear force-free field extrapolation to construct a model of the magnetic field structure of the active region. Subsequently, the location of long-period oscillations in the active region was probed by examining the spectral energy density of the measured intensity signal in the 1700 Å, 1600 Å, and 304 Å channels of the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO). Significant oscillation periods were determined by means of a wavelet analysis. Results. Based on the evolution of the three magnetic helicity flux components, 3- to 8-h periods were found both before and after the flare events, spanning from the photosphere to the chromosphere. These 3- to 8-h periods were also evident throughout the active region in the photosphere in the 1700 Å channel. Observations of AIA 1600 Å and 304 Å channels, which cover the chromosphere to the transition region, revealed oscillations of 3−8 h near the region in which the flare occurred. The spatial distribution of the measured long-period oscillations mirror the previously reported distribution of 3- to 5-min oscillations in NOAA 12353 that were seen both before and after the flares. Conclusions. This case study suggest that the varying oscillation properties in a solar active region could be indicative of future flaring activity

Exploring spatial and temporal patterns in the Debrecen Solar Faculae Database: Part I

Photospheric faculae are markers of the solar magnetic field, appearing as bright regions along the edges of granules on the Sun's surface. Using data from the Debrecen Solar Faculae Database, we investigated the spatiotemporal distribution of photospheric faculae between 2010 May 1 and 2014 December 31 and found the following. (i) At lower latitudes, there is an enhanced abundance of faculae appearing as stripes at given Carrington longitudes, which are interpreted as indicative of the presence of active longitudes. (ii) At higher latitudes, we identified so-called crisscross patterns of facular appearance. These patterns are likely the result of faculae in regions situated along the boundaries of supergranules. Last but not least, (iii) various periods of oscillatory phenomena were identified in this facular data set, including a longer periodic range consistent with the quasi-biennial oscillations and shorter ones with periods of 4–12 days. Our findings are supported by the visualization of a simple heuristic thought experiment and more complex dynamo simulations, strengthening the proposed interpretation of the three observed solar phenomena reported

On the differences in the periodic behavior of magnetic helicity flux in flaring active regions with and without X-class events

Observational precursors of large solar flares provide a basis for future operational systems for forecasting. Here, we study the evolution of the normalized emergence (EM), shearing (SH), and total (T) magnetic helicity flux components for 14 flaring (with at least one X-class flare) and 14 nonflaring (10 hr) do not change. (iv) When the EM periodicity does not contain harmonics, the ARs do not host a large energetic flare. (v) Finally, significant power at long periods (∼20 hr) in the T and EM components may serve as a precursor for large energetic flares

First insights into the applicability and importance of different 3D magnetic field extrapolation approaches for studying the preeruptive conditions of solar active regions

The three-dimensional (3D) coronal magnetic field has not yet been directly observed. However, for a better understanding and prediction of magnetically driven solar eruptions, 3D models of solar active regions are required. This work aims to provide insight into the significance of different extrapolation models for analyzing the preeruptive conditions of active regions with morphological parameters in 3D. Here, we employed potential field (PF), linear force-free field (LFFF), and nonlinear force-free field (NLFFF) models and a neural network-based method integrating observational data and NLFFF physics (NF2). The 3D coronal magnetic field structure of a "flaring" (AR11166) and "flare-quiet" (AR12645) active region, in terms of their flare productivity, is constructed via the four extrapolation methods. To analyze the evolution of the field, six prediction parameters were employed throughout, from the photosphere up to the base of the lower corona. First, we find that the evolution of the adopted morphological parameters exhibits similarity across the investigated time period when considering the four types of extrapolations. Second, all the parameters exhibited preeruptive conditions not only at the photosphere but also at higher altitudes in the case of active region (AR) 11166, while three out of the six proxies also exhibited preeruptive conditions in the case of AR12645. We conclude that: (i) the combined application of several different precursor parameters is important in the lower solar atmosphere to improve eruption predictions, and (ii) to gain a quick yet reliable insight into the preflare evolution of active regions in 3D, the PF and LFFF are acceptable; however, the NF2 method is likely the more suitable option

CME arrival modeling with machine learning

Space weather phenomena have long captured the attention of the scientific community, and along with recent technological developments, the awareness that such phenomena can interfere with human activities on Earth has grown considerably. Coronal mass ejections (CMEs) are among the main drivers of space weather. Therefore, developing tools to provide information on their arrival at Earth's nearby space has become increasingly important. Liu et al. developed a tool, called CME Arrival Time Prediction Using Machine Learning Algorithms (CAT-PUMA), to obtain fast and accurate predictions of CME transit time. This present work aims at the expansion of the CAT-PUMA concept, employing supervised learning to obtain vital information about the arrival of CMEs at Earth. In this study, we report the results of our work following the implementation of supervised regression and classification models in the CAT-PUMA framework. We conducted a comparison of various machine learning models in the context of predicting the transit time of CMEs and classifying CMEs as either Earth impacting or non-impacting. In this way, we are able to provide information on the possibility of a CME reaching Earth relying on CME features and solar wind parameters measured at take-off. This application thus provides quantitative indications about the geoeffectiveness of these space weather events. While machine-learning models can demonstrate fairly strong performance in regression and classification tasks, it is not always straightforward to extrapolate their practical potential and real-world applicability. To address this challenge, we employed model interpretation techniques, specifically Shap values, to gain quantitative insights into the limitations that affect these models

HiRISE - High-Resolution Imaging and Spectroscopy Explorer - Ultrahigh resolution, interferometric and external occulting coronagraphic science

Recent solar physics missions have shown the definite role of waves and magnetic fields deep in the inner corona, at the chromosphere-corona interface, where dramatic and physically dominant changes occur. HiRISE (High Resolution Imaging and Spectroscopy Explorer), the ambitious new generation ultra-high resolution, interferometric, and coronagraphic, solar physics mission, proposed in response to the ESA Voyage 2050 Call, would address these issues and provide the best-ever and most complete solar observatory, capable of ultra-high spatial, spectral, and temporal resolution observations of the solar atmosphere, from the photosphere to the corona, and of new insights of the solar interior from the core to the photosphere. HiRISE, at the L1 Lagrangian point, would provide meter class FUV imaging and spectro-imaging, EUV and XUV imaging and spectroscopy, magnetic fields measurements, and ambitious and comprehensive coronagraphy by a remote external occulter (two satellites formation flying 375 m apart, with a coronagraph on a chaser satellite). This major and state-of-the-art payload would allow us to characterize temperatures, densities, and velocities in the solar upper chromosphere, transition zone, and inner corona with, in particular, 2D very high resolution multi-spectral imaging-spectroscopy, and, direct coronal magnetic field measurement, thus providing a unique set of tools to understand the structure and onset of coronal heating. HiRISE’s objectives are natural complements to the Parker Solar Probe and Solar Orbiter-type missions. We present the science case for HiRISE which will address: i) the fine structure of the chromosphere-corona interface by 2D spectroscopy in FUV at very high resolution; ii) coronal heating roots in the inner corona by ambitious externally-occulted coronagraphy; iii) resolved and global helioseismology thanks to continuity and stability of observing at the L1 Lagrange point; and iv) solar variability and space climate with, in addition, a global comprehensive view of UV variability. © 2022, The Author(s)

HiRISE - High-Resolution Imaging and Spectroscopy Explorer - Ultrahigh resolution, interferometric and external occulting coronagraphic science

peer reviewedRecent solar physics missions have shown the definite role of waves and magnetic fields deep in the inner corona, at the chromosphere-corona interface, where dramatic and physically dominant changes occur. HiRISE (High Resolution Imaging and Spectroscopy Explorer), the ambitious new generation ultra-high resolution, interferometric, and coronagraphic, solar physics mission, proposed in response to the ESA Voyage 2050 Call, would address these issues and provide the best-ever and most complete solar observatory, capable of ultra-high spatial, spectral, and temporal resolution observations of the solar atmosphere, from the photosphere to the corona, and of new insights of the solar interior from the core to the photosphere. HiRISE, at the L1 Lagrangian point, would provide meter class FUV imaging and spectro-imaging, EUV and XUV imaging and spectroscopy, magnetic fields measurements, and ambitious and comprehensive coronagraphy by a remote external occulter (two satellites formation flying 375 m apart, with a coronagraph on a chaser satellite). This major and state-of-the-art payload would allow us to characterize temperatures, densities, and velocities in the solar upper chromosphere, transition zone, and inner corona with, in particular, 2D very high resolution multi-spectral imaging-spectroscopy, and, direct coronal magnetic field measurement, thus providing a unique set of tools to understand the structure and onset of coronal heating. HiRISE’s objectives are natural complements to the Parker Solar Probe and Solar Orbiter-type missions. We present the science case for HiRISE which will address: i) the fine structure of the chromosphere-corona interface by 2D spectroscopy in FUV at very high resolution; ii) coronal heating roots in the inner corona by ambitious externally-occulted coronagraphy; iii) resolved and global helioseismology thanks to continuity and stability of observing at the L1 Lagrange point; and iv) solar variability and space climate with, in addition, a global comprehensive view of UV variability