Solar Physics最新文献

This work builds on a recently developed self-consistent synchronization model of the solar dynamo which attempts to explain Rieger-type periods, the Schwabe/Hale cycle, and the Suess-de Vries and Gleissberg cycles in terms of resonances of various wave phenomena with gravitational forces exerted by the orbiting planets. We start again from the basic concept that the spring tides of the three pairs of the tidally dominant planets Venus, Earth, and Jupiter excite magneto-Rossby waves at the solar tachocline. While the quadratic action of the sum of these three waves comprises the secondary beat period of 11.07 years, the main focus is now on the action of the even more pronounced period of 1.723 years. Our dynamo model provides oscillations with exactly that period, which is also typical for the quasi-biennial oscillation (QBO). Most remarkable is its agreement with Ground Level Enhancement (GLE) events which preferentially occur in the positive phase of an oscillation with a period of 1.724 years. While bimodality of the sunspot distribution is shown to be a general feature of synchronization, it becomes most strongly expressed under the influence of the QBO. This may explain the observation that the solar activity is relatively subdued when compared to that of other sun-like stars. We also discuss anomalies of the solar cycle, and subsequent phase jumps by 180^∘. In this connection it is noted that the very 11.07-year beat period is rather sensitive to the time-averaging of the quadratic functional of the waves and prone to phase jumps of 90^∘. On this basis, we propose an alternative explanation of the observed 5.5-year phase jumps in algae-related data from the North Atlantic and Lake Holzmaar that were hitherto attributed to optimal growth conditions.

One of the most commonly observed solar radio sources in the metric and decametric wavelengths is the solar noise storm. These are generally associated with active regions and are believed to be powered by the plasma emission mechanism. Since plasma emission is emitted primarily at the fundamental and harmonic of the local plasma frequency, it is significantly affected by density inhomogeneities in the solar corona. The source can become significantly scatter-broadened due to the multi-path propagation caused by refraction from the density inhomogeneities. Past observational and theoretical estimates suggest some minimum observable source size in the solar corona. The details of this limit, however, depend on the modeling approach and details of the coronal turbulence model chosen. Hence pushing the minimum observable source size to smaller values can help constrain the plasma environment of the observed sources. In this work, we for the first time, use data from the upgraded Giant Metrewave Radio Telescope in the 250 – 500 MHz band, to determine multiple instances of very small-scale structures in the noise storms. We also find that these structures are stable over timescales of 15 – 30 minutes. By comparing the past observations of type III radio bursts and noise storms, we hypothesize that the primary reason behind the detection of these small sources in noise storm is due to the local environment of the noise storm. We also build an illustrative model and propose some conditions under which the minimum observable source size predicted by theoretical models, can be lowered significantly.

Solar type II radio bursts are generated through plasma emission caused by energetic electrons that are accelerated by shock waves during solar eruptions. These bursts serve as tracers of shock waves in the corona. However, the complexity of solar eruptions and the lack of radio imaging observations have hampered our understanding of type II bursts. The newly built Daocheng Solar Radio Telescope (DSRT) detected a rare type II burst. Its harmonic shows an initial herringbone (HB), followed by three nearly parallel lanes. These lanes form a framed pattern: a central main lane (termed MAIN) with a higher brightness temperature and wider bandwidth, flanked by two well-defined fringes, F1 and F2. Radio and extreme ultraviolet imaging observations indicate that the sources of the HB are precisely located on the flank of the leading shock wave driven by a coronal mass ejection (CME). In contrast, the MAIN and F2 sources correlate in terms of time, location, electron number density, and propagation velocity with an ascending coronal loop. In contrast, the F1 sources are associated with a nearby but distinct coronal loop. These observations suggest that at least three sources of the type II burst accompany the CME. A scenario involving multiple shock waves within the CME is proposed to explain the presence of the different radio sources.

Solar differential rotation (SDR) profile can give an important clue on how the solar dynamo varies from one solar cycle to another. In order to investigate the variability of SDR across multiple solar cycles, we calculated rotation rates of sunspots observed in Solar Cycles 22 – 24 (1987 – 2019) by using sunspot data records from the Watukosek Solar Observatory (WKSO). WKSO has the longest continuous sunspot observation record in Indonesia. Its historical record of sunspot observations provides a unique and valuable dataset for solar physics research. In this paper, we introduced the repository of sunspot observations from WKSO for almost three solar cycles. Using these data, we calculated the rotation rate of each long-lived sunspot group during Solar Cycles 22 – 24 by measuring the linear least-square fitting of daily movements of the sunspot position in various latitudes. The results confirm the well-established pattern of SDR, with a faster rotation at the equator compared to higher latitudes. We also found that the rotation rates of long-lived sunspot groups are slower than the differential rotation rates derived from the entire sunspot data. Furthermore, our analysis of this dataset confirmed that the bipolar sunspot groups rotate faster than unipolar sunspots. These results suggest that unipolar and bipolar sunspots are anchored at different depths beneath the solar surface. These findings are consistent with prior results using older data from different observatories, suggesting the reliability and scientific importance of the sunspot observations from WKSO for understanding solar-dynamo processes and their variability.

Active regions (ARs) are the photospheric manifestations of emerging magnetic flux ropes (FRs) formed in the solar interior. We analyze the emergence of 126 bipolar ARs during Solar Cycle 23 using a flux rope model, whose parameters are inferred through a Bayesian inference method. This approach allows us to estimate key sub-photospheric properties of FRs. We find that the Bayesian method effectively captures the global magnetic characteristics of ARs, with discrepancies primarily arising in the later stages of emergence. We examine the ability of a flux-balanced FR model with a symmetric circular cross-section to reproduce polarity shapes during these late stages. Additionally, we analyze how the inclination of the FR legs provides insight into the emergence stage. We propose an improved method for estimating the separation of polarities, which decreases projection effects and flux distribution biases. Furthermore, we confirm a strong correlation between the AR flux and the distance between the main polarities, as well as the evolution of their separation speed. Finally, we identify a characteristic ratio between the thickness of the FR and its curvature radius, suggesting an underlying physical mechanism governing this ratio.

This study presents a detailed on-orbit performance analysis of the Hard X-ray Imager (HXI) aboard the Advanced Space-based Solar Observatory (ASO-S), confirming its overall stability within design specifications for key parameters like detection efficiency and energy resolution. However, the analysis focuses primarily on characterizing temporal variations, including distinct periodic fluctuations linked to orbital (∼ 99 minutes) and annual cycles, as well as non-periodic events. Temperature variations highlight orbital/seasonal effects and suggest potential long-term thermal leakage around the Solar Aspect System (SAS) via a gradual rise on the front plate. High-voltage (HV) remains stable during nominal operations, but its management during South Atlantic Anomaly (SAA) passages is critical. Gain analysis identifies a generally stable trend punctuated by five significant abrupt decreases attributed to operational parameter reset errors and radiation exposure during SAA passages (influenced by geomagnetic storms or operational choices). Detection efficiency and energy resolution remained largely stable, with notable deviations primarily linked to the parameter reset error. These findings demonstrate the instrument’s general robustness while highlighting specific anomalies and underscoring the need for ongoing monitoring, optimized operational protocols (especially HV management), and time-dependent calibration to ensure the highest data quality for solar flare science.

We present the design and pre-launch performance of the Narrow Field Imager (NFI), which is an instrument designed to provide the inner field of view of the NASA Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission. This paper provides details of the NFI instrument concept, design, and pre-flight performance to give the potential user of the data a better understanding of how the observations are collected and the sources that contribute to the signal. NFI will contribute significantly to the scientific success of the PUNCH mission. The paper discusses the NFI design concepts, which include the optics, mechanical, and thermal. The performance measurements of the various instrument parameters meet or exceed the requirements derived from the mission science objectives. NFI is poised to take its place as a vital contributor to the science success of the PUNCH mission.

The Sunspot Solar Observatory Data Archive (SSODA) stores data acquired with the suite of instruments at the Richard B. Dunn Solar Telescope (DST) from February 2018 to the present. The instrumentation at the DST continues to provide high cadence imaging, spectroscopy, and polarimetry of the solar photosphere and chromosphere across a wavelength range from 3500 Å to 11,000 Å. At the time of writing, the archive contains approximately 374 TiB of data across more than 520 observing days (starting on February 1, 2018). These numbers are approximate as the DST remains operational, and is actively adding new data to the archive. The SSODA includes both raw and calibrated data. A subset of the archive contains the results of photospheric and chromospheric spectropolarimetric inversions using the Hazel-2.0 code to obtain maps of magnetic fields, temperatures, and velocity flows. The SSODA represents a unique resource for the investigation of plasma processes throughout the solar atmosphere, the origin of space weather events, and the properties of active regions throughout the rise of Solar Cycle 25.

In this work we discuss the growing ensemble of solar energetic particle events registered on the Martian surface, including their temporal appearance and solar sources. Solar energetic particle events have been observed from the surface of Mars since soon after the August 2012 landing of the Radiation Assessment Detector onboard Curiosity. The Martian atmosphere prevents protons and heavy ions below 140 – 190 MeV/n kinetic energy from directly reaching the Martian surface. This cut-off is high enough to limit the number of solar energetic particle events measured on the surface to only 19 in ∼ 12 1/2 years. Yet we find in this analysis that proton acceleration that gives rise to Mars ground level enhancements takes place predominantly at or near the solar eruption site, while transport to Mars incurs a delay in onset, and, as we show here, peak intensity. These delays are a function of the longitudinal magnetic connection distance, defined here as the angular distance between the foot point of solar wind magnetic field lines that intersect the Mars environment and the source longitude of the solar magnetic eruption. A distinct clustering of solar source locations at or near the Mars foot points at the Sun’s western limb relative to Mars is apparent, indicating lower flux thresholds from such preferred locations. We have developed a simple peak flux prediction tool for the Martian surface that could be used to reduce radiation exposure during future human exploration missions.

We studied the heliolatitudinal distribution and hemispheric asymmetry of source locations for super geomagnetic storms (SGSs) (Dst (leq -250) nT) during the ascending phase, solar maximum, descending phase, and solar minimum. The proportions of SGSs during the ascending phase, solar maximum, descending phase, and solar minimum were 16.1%, 33.9%, 48.2% and 1.8%, respectively. For SGSs with source locations in the heliolatitude above 20° in both hemispheres, the proportions during the ascending phase, solar maximum, descending phase, and solar minimum were 50%, 26.3%, 31.2%, and 0%, respectively. For SGSs with source locations within the heliolatitude range of [11°, 20°] in both hemispheres, the proportions during these phases were 50%, 52.6%, 43.8%, and 100%, respectively. For SGSs with source locations within the heliolatitude range of [0°, 10°] in both hemispheres, the proportions during these phases were 0%, 21.1%, 25%, and 0%, respectively. For all SGSs, the N–S asymmetry was significant over the period from 1932 to 2024. Specifically, during the ascending phase, solar maximum, and descending phase, the N–S asymmetries were significant, marginally significant, and not significant, respectively. Throughout these periods, the source locations of the SGSs were consistently dominated by the northern hemisphere. For all SGSs, the E–W asymmetry was insignificant over the period from 1932 to 2024. Specifically, during the ascending phase, the E–W asymmetry remained insignificant. In contrast, during the solar maximum, the E–W asymmetry became significant, with SGS source locations predominantly in the western hemisphere and an anti-correlation observed between the number of SGSs in the two hemispheres. During the descending phase, the E–W asymmetry was significant once again, but this time with SGS source locations dominated in the eastern hemisphere, maintaining the anti-correlation between the two hemispheres. Only one SGS was observed during the solar minimum, with a source location at S11W21.