Solar Physics最新文献

Two similar-looking, two-part interplanetary type II burst events from 2003 and 2012 are reported and analysed. The 2012 event was observed from three different viewing angles, enabling comparisons between the spacecraft data. In these two events, a diffuse wide-band type II radio burst was followed by a type II burst, which showed emission at the fundamental and harmonic (F-H) plasma frequencies, and these emission bands were also slightly curved in their frequency-time evolution. Both events were associated with high-speed, halo-type coronal mass ejections (CMEs). In both events, the diffuse type II burst was most probably created by a bow shock at the leading front of the CME. However, for the later appearing F-H type II burst, there are at least two possible explanations. In the 2003 event, there is evidence of CME interaction with a streamer, with a possible shift from a bow shock to a CME flank shock. In the 2012 event, a separate white-light shock front was observed at lower heights, and it could have acted as the driver of the F-H type II burst. There is also some speculation on the existence of two separate CMEs, launched from the same active region, close in time. The reason for the diffuse type II burst being visible only from one viewing direction (STEREO-A) and the ending of the diffuse emission before the F-H type II burst appears still need explanations.

We suggest the Kuramoto chain model with four coupled oscillators as a way to describe the phase evolution and departures from synchronization of solar indices at low and high latitudes in the northern and southern hemispheres. Our model simulates the basic properties of the phase differences between the near-equatorial sunspot areas and the polar facula series provided by the Pulkovo and Mount Wilson (MWO) observatories. Temporal variations of the meridional circulation are represented through slow, regular oscillations of natural frequencies. We consider the Gleissberg range (GR) oscillations to have the North-South asymmetry and the 22-year oscillation to be symmetric. The overall synchronization of polar and equatorial solar indices is confirmed. We use it to reconstruct model parameters from the phase difference of solar indices. The synchronization allows for reducing the space of model parameters to a 2D plane, where the eventual departures from the synchronization cut out a narrow zone of accurate estimates. We discuss revealed relations between the low-frequency variations of the solar meridional circulation, the North-South asymmetry, and the desynchronization events.

In this paper, we present a magnetohydrodynamics simulation of NOAA active region 11166 to understand the origin of a confined X-class flare that peaked at 23:23 UT on 2011 March 9. The simulation is initiated with a magnetic field extrapolated from the corresponding photospheric magnetogram, using a non-force-free-field extrapolation technique. Importantly, the initial magnetic configuration identifies three-dimensional (3D) magnetic nulls and quasi-separatrix layers (QSLs), which nearly agree with the bright structures appeared in multi-wavelength observations. The Lorentz force associated with the extrapolated field self-consistently generates the dynamics that leads to the magnetic reconnections at the 3D nulls and the QSLs. These reconnections are found to contribute to the pre-flare activities and, ultimately, lead to the development of the flare ribbons. Notably, the anchored spine of the 3D null and the complete absence of flux rope in the flaring region are congruent with the confined nature of the flare. Furthermore, the simulation also suggests the role of reconnections at the 3D null with an open spine in the onset of a jet away from the flaring site.

We investigate the evolution of the Rieger periodicity at 152 – 156 days, the 27-day synodic rotation period as well as the 13.5- and 9-day harmonic periodicities in anomalous cosmic ray (ACR) oxygen (O) fluxes at the energy range between 8 – 25 MeV/n observed by the Advanced Composition Explorer (ACE) satellite during Solar Cycles 23 and 24. The ACR oxygen flux data is analysed using the Lomb–Scargle periodogram and Morlet wavelet spectral analysis techniques. Daily mean oxygen fluxes during solar quiet times are used to identify how the ACR oxygen at different energies varies with the Rieger periodicity and the solar rotation periodicities in each year. This is the first investigation of the periodicity evolution of ACR oxygen ions. Previous investigations have mostly concentrated on the spectral behaviour of GCR particles during various solar cycles of opposite polarities, in particular the 27-day and 13.5-day periodicities. Our analysis revealed a significant temporal and energy dependence in the spectral behaviour of ACR oxygen during both cycles. An important finding of this investigation, not reported before in the literature, is the significant increase in the power of the different ACR oxygen periodicities during the minimum of Cycle 24/25 (characterised by a positive solar polarity) in comparison to the minimum of Cycle 23/34 (dominated by a negative solar polarity).

The growth of a large-scale magnetic field in the Sun and stars is usually possible when the dynamo number ((D)) is above a critical value (D_{c}). As the star ages, its rotation rate and thus (D) decrease. Hence, the question is how far the solar dynamo is from the critical dynamo transition. To answer this question, we have performed a set of simulations using Babcock–Leighton type dynamo models at different values of dynamo supercriticality and analyzed various features of magnetic cycle. By comparing the recovery rates of the dynamo from the Maunder minimum and statistics (numbers and durations) of the grand minima and maxima with that of observations and we show that the solar dynamo is only about two times critical and thus not highly supercritical. The observed correlation between the polar field proxy and the following cycle amplitudes and Gnevyshev–Ohl rule are also compatible with this conclusion.

In this paper, starting from solar storms, which are the main cause of geomagnetic storms, the effects of the speed (v) and density (Np) of solar plasma coming to the Earth on geomagnetic storms are investigated. During the ascending phase of the 25th solar cycle (2021 – 2022), various geomagnetic storms from G1 to G4 were examined. Multiple linear regression models are created to examine the effects of solar parameters that cause changes in geomagnetic storm processes. The effects of the speed and charge density of solar wind, coronal mass ejections (CMEs), corotating interaction regions (CIRs), and CME-CME interactions on the Dst index, which reflects disturbances in the Earth’s magnetic field and the scale of geomagnetic storms, are statistically analyzed. It is determined that a one-unit change in speed in 82 geomagnetic storms in the statistical models created a decrease in Dst of approximately −0.25 nT. In contrast, it is determined that a unit increase in particle density also reduces the effect and duration of a geomagnetic storm. However, if there is an increase in density during the main phase of the storm, then the storm level increases. We believe that our results will significantly contribute to predicting the formation of geomagnetic storms and their possible effects on space weather.

The first burst of solar microwave coherent emission observed simultaneously with two multifrequency two-dimensional radio telescopes is reported, making it possible to unambiguously interpret the mechanism of the radiation and to propose a scenario that explains all the observed features of the burst. Recently, many studies have appeared that explain coherent bursts of radio emission from the Earth’s magnetosphere and solar corona by an electron cyclotron maser (ECM) driven by horseshoe distribution. The result of this study is that the observed coherent burst near the frequency 4.8 GHz is caused by a hollow beam distribution formed by the oblique injection of electrons into a magnetic loop. If the pitch-angle is large enough, then the absence of HXR and the relatively large (about 1 s) pulse duration can be explained. The measured size of the ECM source, (approx 2.2^{prime prime }), corresponds to a brightness temperature of (approx 5.8times 10^{10}text{ K}). The displacement of the spike sources with respect to the gyroresonance source is consistent to the second-harmonic ECM emission, whereas the gyroresonance source is consistent to the third gyrolayer.

In this paper, we study the wave travel-time shift signature of two distinct magnetic models of sunspots, namely a monolithic model of varying sizes and a cluster (or spaghetti) model of different configurations (compact and loose) and sizes. To this end, we use numerical simulations to propagate an (f)-mode wave packet through these magnetic structures. We have shown that the region (y=0) behind the sunspot can be contaminated by caustics that emerge from both models, making the interpretation of the travel-time ambiguous. However, the location and characteristics (amplitude and pattern) of these caustics can be used as observational indicators to distinguish between a monolithic and a clustered model, as well as to differentiate between a compact and an open cluster configuration. These results are a contribution to probe the subsurface structure of sunspots and plages in the context of time-distance helioseismology.

The volume and diversity of solar physics data have grown exponentially in the last three decades. In view of making solar datasets easily accessible to the scientific community, we have developed the SOLARNET Virtual Observatory (SVO), an IT service that collects metadata from a large range of solar observational datasets in a common catalog to allow smooth data search and access. It follows the virtual observatories (VO) principle, with a provider layer, core metadata database, and user layer. The user layer contains a user-friendly web application, Python and IDL libraries, and a RESTful API. The SVO enables metadata to be searched either across all datasets or within a specific dataset by applying more precise search conditions. Additionally, it allows researchers to query solar events from the HEK database and identify data that overlaps with these events. Data can be previewed and downloaded from the web application. The Python and IDL libraries allow the integration of the SVO data search and functionality with complex data processing pipelines. On the provider side, datasets are ingested through tailored scripts. Recently, a TAP client layer has been added to the SVO, hence, it is possible to populate the SVO automatically with a dataset that is available as a TAP or EPN-TAP service. We describe the service, user, and provider side of the SVO and illustrate its capabilities with four scientific use cases.

We analyze Sunspot engravings and measurements in 1660 – 1676 to retrieve sunspot area and heliocoordinates. Based on these data, we revise the Hoyt and Schatten (The role of the sun in climate change, 1997) hypothesis of long-lived sunspots during the Maunder minimum as a sign of weakened convection. Historical reports also clarify what each observer defined as a sunspot and the purpose of the observations. The reconstructed longitudes of sunspots allow us to evaluate the rotation rate, revealing that the historical rotation profile resembles that of long-lived sunspot groups in the modern era.