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        <title>Frontiers in Physics | Stellar and Solar Physics section | New and Recent Articles</title>
        <link>https://www.frontiersin.org/journals/physics/sections/stellar-and-solar-physics</link>
        <description>RSS Feed for Stellar and Solar Physics section in the Frontiers in Physics journal | New and Recent Articles</description>
        <language>en-us</language>
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        <pubDate>2026-05-14T01:23:24.736+00:00</pubDate>
        <ttl>60</ttl>
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        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2023.1286802</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2023.1286802</link>
        <title><![CDATA[Neutron star characteristics from the neutron structure]]></title>
        <pubdate>2023-10-12T00:00:00Z</pubdate>
        <category>Hypothesis and Theory</category>
        <author>Arto Annila</author>
        <description><![CDATA[We draw insight into the neutron star structure and characteristics from the neutron structure. The eigenvectors of the special unitary group, SU(3), describing baryons, imply that neutron quarks reside on three faces of a tetrahedron. The tetrahedral structure accounts for the neutron magnetic moment and mass. Thus, we reason that neutrons precipitate with aligned magnetic moments into the triakis truncated tetrahedron tessellation under immense gravitational pressure. As the particle’s tetrahedral symmetry does not match the crystal’s rhombic symmetry, the total magnetic moment invariably misaligns with the star’s spinning axis. We infer further from the neutron structure that with increasing gravitational pressure, two neutrons condense into the same tetrahedron. Due to doubling density, the contracting star spins up abruptly but then settles down slowly as the gradients in density smoothen. As down quarks are positioned for pairwise fusions into anti-up quarks in the dineutron, we reason that tetraquark indeed forms as gravitational pressure increases further. The star balances the accompanying loss of mass by spinning down suddenly but recovers as the gradients in density smoothen again. Ultimately, when gravitational pressure increases even more, the anti-up quarks will annihilate with up quarks. As the core becomes ever more structured, such high-energy events fade out, and eventually, only magnetic field-collimated radio-frequency dissipation drives the spin down. The nuclear moments manifest fully in a magnetar, free from floating, hence counteraligning baryonic matter. In conclusion, the neutron structure makes sense of the neutron star density, magnetism, beams at an angle to the spinning axis, and pulsing transients, and paves the way for making sense of reactions in a black hole.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2023.1198194</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2023.1198194</link>
        <title><![CDATA[The thickness of current sheets and implications for coronal heating]]></title>
        <pubdate>2023-09-01T00:00:00Z</pubdate>
        <category>Brief Research Report</category>
        <author>James A. Klimchuk</author><author>James E. Leake</author><author>Lars K. S. Daldorff</author><author>Craig D. Johnston</author>
        <description><![CDATA[The thickness of current sheets is extremely important, especially as it relates to the onset of fast magnetic reconnection. Onset determines how much magnetic free energy can build up in a field before it is explosively released. This has implications for many phenomena on the Sun and throughout the Universe, including the heating of the solar corona. Significant effort has been devoted to the question of whether equilibrium current sheets in realistic geometries have finite or zero thickness. Using a simple force balance analysis, we show why current sheets without a guide field (2D) and with a guide field that is invariant in the guide field direction (2.5D) cannot be in equilibrium if they have both finite thickness and finite length. We then estimate the conditions under which the tension of a curved line-tied guide field can facilitate equilibrium in 3D sheets that are finite in all dimensions. Finally, we argue that some quasi-statically evolving current sheets undergoing slow stressing—e.g., when the coronal magnetic field is subjected to photospheric boundary driving—may reach a critical shear, at which point they lose equilibrium, spontaneously collapse, and reconnect. The critical shear is generally consistent with the heating requirements of solar active regions.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2023.1119637</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2023.1119637</link>
        <title><![CDATA[The mechanism of magnetic flux rope rotation during solar eruption]]></title>
        <pubdate>2023-02-23T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Zhenjun Zhou</author><author>Chaowei Jiang</author><author>Xiaoyu Yu</author><author>Yuming Wang</author><author>Yongqiang Hao</author><author>Jun Cui</author>
        <description><![CDATA[Solar eruptions often show the rotation of filaments, which is a manifestation of the rotation of erupting magnetic flux rope (MFR). Such a rotation of MFR can be induced by either the torque exerted by a background shear-field component (which is an external cause) or the relaxation of the magnetic twist of the MFR (an internal cause). For a given chirality of the erupting field, both the external and internal drivers cause the same rotation direction. Therefore, it remains elusive from direct observations which mechanism yields the dominant contribution to the rotation. In this paper, we exploit a full MHD simulation of solar eruption by tether-cutting magnetic reconnection to study the mechanism of MFR rotation. In the simulation, the MFR’s height–rotation profile suggests that the force by the external shear-field component is a dominant contributor to the rotation. Furthermore, the torque analysis confirms that it is also the only factor in driving the counterclockwise rotation. On the contrary, the Lorentz torque inside the MFR makes a negative effect on this counterclockwise rotation.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2022.960315</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2022.960315</link>
        <title><![CDATA[A magnetic flux rope configuration derived by optimization of two-spacecraft In-situ measurements]]></title>
        <pubdate>2022-08-25T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Qiang Hu</author><author>Wen He</author><author>Yu Chen</author>
        <description><![CDATA[Increasingly one interplanetary coronal mass ejection (ICME) structure can propagate across more than one spacecraft in the solar wind. This usually happens when two or more spacecraft are nearly radially aligned with a relatively small longitudinal separation angle from one another. This provides multi-point measurements of the same structure and enables better characterization and validation of modeling results of the structures embedded in these ICMEs. We report such an event during October 13-14, 2019 when the Solar TErrestrial RElations Observatory Ahead (STA) spacecraft and the Parker Solar Probe (PSP) crossed one ICME structure at two different locations with nominal separations in both heliocentric distances and the longitudinal angles. We first perform an optimal fitting to the STA in-situ measurements, based on an analytic quasi-three dimensional (3D) model, yielding a minimum reduced χ2 = 0.468. Then we further apply the optimization approach by combining the magnetic field measurements from both spacecraft along their separate paths across the ICME structure. We find that the output based on the optimization (with the minimum reduced χ2 = 3.15) of the combined two-spacecraft dataset yields a more consistent result, given the much improved agreement of the model output with PSP data. The result demonstrates a magnetic flux rope configuration with clear 3D spatial variations.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2022.869738</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2022.869738</link>
        <title><![CDATA[Solar Irradiance Variability Monitor for the Galileo Solar Space Telescope Mission: Concept and Challenges]]></title>
        <pubdate>2022-06-24T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Franciele Carlesso</author><author>Jenny Marcela Rodríguez Gómez‬</author><author>Adriany Rodrigues Barbosa</author><author>Luis Eduardo Antunes Vieira</author><author>Alisson Dal Lago</author>
        <description><![CDATA[Long and reliable total solar irradiance (TSI) time series is one of the essential parameters for understanding solar contributions to climate change. The minor fluctuations of TSI in long timescales could impact the energy balance. Despite the improvement of accurate measurements provided by the instruments, at the time, long-term TSI variability and its effects had not been established. The space-borne radiometer era provided observations in short timescales from minutes to years. Therefore, this study presents an overview of irradiance observations, highlighting the importance of following its variability in different time scales. In this context, the Galileo Solar Space Telescope that has been developed by the Institute for Space Research (INPE), Brazil, includes the Irradiance Monitor Module with a radiometer cavity like the classical design and a next-generation compact radiometer.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.820476</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.820476</link>
        <title><![CDATA[Editorial: The Magnetic Structures and Their Role in The Evolution of Coronal Mass Ejections]]></title>
        <pubdate>2021-12-21T00:00:00Z</pubdate>
        <category>Editorial</category>
        <author>Hengqiang Feng</author><author>Qiang Hu</author><author>Hongqiang Song</author>
        <description></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.762488</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.762488</link>
        <title><![CDATA[Origin of Extremely Intense Southward Component of Magnetic Field (Bs) in ICMEs]]></title>
        <pubdate>2021-11-26T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Chenglong Shen</author><author>Yutian Chi</author><author>Mengjiao Xu</author><author>Yuming Wang</author>
        <description><![CDATA[The intensity of the southward component of the magnetic field (Bs) carried by Interplanetary Coronal Mass Ejections (ICMEs) is one of the most critical parameters in causing extreme space weather events, such as intense geomagnetic storms. In this work, we investigate three typical ICME events with extremely intense Bs in detail and present a statistical analysis of the origins of intense Bs in different types of ICMEs based on the ICME catalogue from 1995 to 2020. According to the in-situ characteristics, the ICME events with extremely high Bs are classified into three types: isolated ICMEs, multiple ICMEs, and shock-ICME interaction events with shocks inside ICMEs or shocks passing through ICMEs. By analyzing all ICME events with Bs ≥ 10nT and Bs ≥ 20nT, we find that 39.6% of Bs,mean ≥ 10nT events and 50% of Bs,mean ≥ 20nT events are associated with shock-ICME events. Approximately 35.7% of shock-ICME events have Bs,mean ≥ 10nT, which is much higher than the other two types (isoloted ICMEs: 7.2% and multiple ICMEs: 12.1%). Those results confirm that the ICMEs interaction events are more likely to carry extreme intense Bs and cause intense geomagntic storms. Only based on the in-situ observations at Earth, some interaction ICME events, such as shock-ICME interaction events with shocks passing through the preceding ICME or ICME cannibalism, could be classified as isolated ICME events. This may lead to an overestimate of the probability of ICME carrying extremely intense Bs. To further investigate such events, direct and multi-point observations of the CME propagation in the inner heliosphere from the Solar Ring Mission could be crucial in the future.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.750410</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.750410</link>
        <title><![CDATA[The Relationship Between Solar Wind Dynamic Pressure Pulses and Solar Wind Turbulence]]></title>
        <pubdate>2021-11-16T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Mengsi Ruan</author><author>Pingbing Zuo</author><author>Zilu Zhou</author><author>Zhenning Shen</author><author>Yi Wang</author><author>Xueshang Feng</author><author>Chaowei Jiang</author><author>Xiaojun Xu</author><author>Jiayun Wei</author><author>Yanyan Xiong</author><author>Ludi Wang</author>
        <description><![CDATA[Solar wind dynamic pressure pulses (DPPs) are small-scale plasma structures with abrupt and large-amplitude plasma dynamic pressure changes on timescales of seconds to several minutes. Overwhelming majority of DPP events (around 79.13%) reside in large-scale solar wind transients, i.e., coronal mass ejections, stream interaction regions, and complex ejecta. In this study, the intermittency, which is a typical feature of solar wind turbulence, is determined and compared during the time intervals in the undisturbed solar wind and in large-scale solar wind transients with clustered DPP events, respectively, as well as in the undisturbed solar wind without DPPs. The probability distribution functions (PDFs) of the fluctuations of proton density increments normalized to the standard deviation at different time lags in the three types of distinct regions are calculated. The PDFs in the undisturbed solar wind without DPPs are near-Gaussian distributions. However, the PDFs in the solar wind with clustered DPPs are obviously non-Gaussian distributions, and the intermittency is much stronger in the large-scale solar wind transients than that in the undisturbed solar wind. The major components of the DPPs are tangential discontinuities (TDs) and rotational discontinuities (RDs), which are suggested to be formed by compressive magnetohydrodynamic (MHD) turbulence. There are far more TD-type DPPs than RD-type DPPs both in the undisturbed solar wind and large-scale solar wind transients. The results imply that the formation of solar wind DPPs could be associated with solar wind turbulence, and much stronger intermittency may be responsible for the high occurrence rate of DPPs in the large-scale solar wind transients.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.745152</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.745152</link>
        <title><![CDATA[Statistical Study of Small-Scale Interplanetary Magnetic Flux Ropes in the Vicinity of the Heliospheric Current Sheet]]></title>
        <pubdate>2021-11-11T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Qiang Liu</author><author>Yan Zhao</author><author>Guoqing Zhao</author>
        <description><![CDATA[The small-scale interplanetary magnetic flux ropes (SIMFRs) are common magnetic structures in the interplanetary space, yet their origination is still an open question. In this article, we surveyed 63 SIMFRs found within 6-day window around the heliospheric current sheet (HCS) and investigated their axial direction, as well as the local normal direction of the HCS. Results showed that the majority (48/63) of the SIMFRs were quasi-parallel to the associated HCS (i.e., the axial direction of SIMFRs was quasi-perpendicular to the normal direction of the associated HCS). They also showed that the SIMFRs quasi-parallel to the associated HCS statistically had shorter duration than the cases quasi-perpendicular. The results indicate that most of these SIMFRs may be generated in the nearby HCSs.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.712599</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.712599</link>
        <title><![CDATA[Magnetic Field Intensity Modification to Force Free Model of Magnetic Clouds: Website of Wind Examples From Launch to July of 2015]]></title>
        <pubdate>2021-10-20T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Chin-Chun Wu</author><author>R. P. Lepping</author><author>D. B. Berdichevsky</author>
        <description><![CDATA[We describe a new NASA website that shows normalized magnetic field (B) magnitude profiles within Wind magnetic clouds (MCs) (i.e., observations versus basic model versus modified model) for 209 MCs observed from launch in late 1994 to July of 2015, where model modification is based on the studies of Lepping et al. (Solar Phys, 2017, 292:27) and Lepping et al. (Solar Phys, 2018, 293:162); the basic force free magnetic cloud parameter fitting model employing Bessel functions (Lepping et al., J. Geophys. Res., 1990, 95:11957) is called the LJB model here. The fundamental principles should be applicable to the B-data from any spacecraft at 1 AU. Earlier (in the LJB study), we justified why the field magnitude can be thought of as decoupled from the field direction within an MC, and further, we justified this idea in terms of actual observations seen over a few decades with examples of MCs from Wind data. The model modification is achieved by adding a correction (“Quad”) value to the LJB model (Bessel function) value in the following manner: B (est)/B0 ≈ [LJB Model + Quad (CA,u)], where B0 is the LJB-estimated field magnitude value on the MC’s axis, CA is the relative closest approach (See Supplementary Appendix A), and u is the distance that the spacecraft travels through the MC from its entrance point. In an average sense, the Quad technique is shown to be successful for 82% of the past modeled MCs, when Quality (Q0) is good or excellent (see Supplementary Appendix A). The Quad technique is successful for 78% of MCs when all cases are considered. So Q0 of the MC LJB-fit is not a big factor when the success of the Quad scheme is considered. In addition, it is found that the Quad technique does not work better for MC events with higher solar wind speed. Yearly occurrence frequency of all MC events (NYearly) and those MC events with ΔσN/σN2 ≥ 0.5 (NΔσN/σN2≥0.5) are well correlated, but there is no solar cycle dependence for normalizing NΔσN/σN2≥0.5 with NYearly.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.749479</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.749479</link>
        <title><![CDATA[Magnetic Structure in Successively Erupting Active Regions: Comparison of Flare-Ribbons With Quasi-Separatrix Layers]]></title>
        <pubdate>2021-10-15T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>P. Vemareddy</author>
        <description><![CDATA[This paper studies the magnetic topology of successively erupting active regions (ARs) 11,429 and 12,371. Employing vector magnetic field observations from Helioseismic and Magnetic Imager, the pre-eruptive magnetic structure is reconstructed by a model of non-linear force-free field (NLFFF). For all the five CMEs from these ARs, the pre-eruptive magnetic structure identifies an inverse-S sigmoid consistent with the coronal plasma tracers in EUV observations. In all the eruption cases, the quasi-separatrix layers (QSLs) of large Q values are continuously enclosing core field bipolar regions in which inverse-S shaped flare ribbons are observed. These QSLs essentially represent the large connectivity gradients between the domains of twisted core flux within the inner bipolar region and the surrounding potential like arcade. It is consistent with the observed field structure largely with the sheared arcade. The QSL maps in the chromosphere are compared with the flare-ribbons observed at the peak time of the flares. The flare ribbons are largely inverse-S shape morphology with their continuity of visibility is missing in the observations. For the CMEs in the AR 12371, the QSLs outline the flare ribbons as a combination of two inverse J-shape sections with their straight parts being separated. These QSLs are typical with the weakly twisted flux rope. Similarly, for the CMEs in the AR 11429, the QSLs are co-spatial with the flare ribbons both in the middle of the PIL and in the hook sections. In the frame work of standard model of eruptions, the observed flare ribbons are the characteristic of the pre-eruptive magnetic structure being sigmoid which is reproduced by the NLFFF model with a weakly twisted flux rope at the core.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.746576</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.746576</link>
        <title><![CDATA[Formation of Magnetic Flux Rope During Solar Eruption. I. Evolution of Toroidal Flux and Reconnection Flux]]></title>
        <pubdate>2021-10-01T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Chaowei Jiang</author><author>Jun Chen</author><author>Aiying Duan</author><author>Xinkai Bian</author><author>Xinyi Wang</author><author>Jiaying Li</author><author>Peng Zou</author><author>Xueshang Feng</author>
        <description><![CDATA[Magnetic flux ropes (MFRs) constitute the core structure of coronal mass ejections (CMEs), but hot debates remain on whether the MFR forms before or during solar eruptions. Furthermore, how flare reconnection shapes the erupting MFR is still elusive in three dimensions. Here we studied a new MHD simulation of CME initiation by tether-cutting magnetic reconnection in a single magnetic arcade. The simulation follows the whole life, including the birth and subsequent evolution, of an MFR during eruption. In the early phase, the MFR is partially separated from its ambient field by a magnetic quasi-separatrix layer (QSL) that has a double-J shaped footprint on the bottom surface. With the ongoing of the reconnection, the arms of the two J-shaped footprints continually separate from each other, and the hooks of the J shaped footprints expand and eventually become closed almost at the eruption peak time, and thereafter the MFR is fully separated from the un-reconnected field by the QSL. We further studied the evolution of the toroidal flux in the MFR and compared it with that of the reconnected flux. Our simulation reproduced an evolution pattern of increase-to-decrease of the toroidal flux, which is reported recently in observations of variations in flare ribbons and transient coronal dimming. The increase of toroidal flux is owing to the flare reconnection in the early phase that transforms the sheared arcade to twisted field lines, while its decrease is a result of reconnection between field lines in the interior of the MFR in the later phase.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.736319</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.736319</link>
        <title><![CDATA[Observations of a Quickly Flapping Interplanetary Magnetic Reconnection Exhaust]]></title>
        <pubdate>2021-09-30T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Jiemin Wang</author><author>Yan Zhao</author>
        <description><![CDATA[On the basis of the Petschek reconnection model and the characteristics of reconnection, hundreds of reconnection exhausts were reported in the solar wind. Many multi-spacecraft observations also indicated that interplanetary magnetic reconnection is a quasi–steady-state plasma process and the reconnection X-line can extend hundreds of Earth radii. In this study, we report an interplanetary flapping reconnection exhaust observed by Wind on April 1, 2003 at one AU. The magnetic reconnection event has two adjacent accelerated flows. We compared the plasma and magnetic characteristics of the two accelerated flows and found that the second accelerated flow was due to the back-and-forth movement of the reconnection exhaust. Our observations reveal that not all interplanetary reconnections operate in a quasi–steady-state manner; some reconnection current sheets can move rapidly back and forth.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.750097</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.750097</link>
        <title><![CDATA[Spectral Evolution of an Eruptive Polar Crown Prominence With IRIS Observations]]></title>
        <pubdate>2021-09-21T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Jianchao Xue </author><author>Hui Li </author><author>Yang Su </author>
        <description><![CDATA[Prominence eruption is closely related to coronal mass ejections and is an important topic in solar physics. Spectroscopic observation is an effective way to explore the plasma properties, but the spectral observations of eruptive prominences are rare. In this paper we will introduce an eruptive polar crown prominence with spectral observations from the Interface Region Imaging Spectrograph (IRIS), and try to explain some phenomena that are rarely reported in previous works. The eruptive prominence experiences a slow-rise and fast-rise phase, while the line-of-sight motions of the prominence plasma could be divided into three periods: 2 hours before the fast-rise phase, opposite Doppler shifts are found at the two sides of the prominence axis; then, red shifts dominate the prominence gradually; in the fast-rise phase, the prominence gets to be blue-shifted. During the second period, a faint component appears in Mg ii k window with a narrow line width and a large red shift. A faint region is also found in AIA 304Å images along the prominence spine, and the faint region gets darker during the expansion of the spine. We propose that the opposite Doppler shifts in the first period is a feature of the polar crown prominence that we studied. The red shifts in the second period are possibly due to mass drainage during the elevation of the prominence spine, which could accelerate the eruption in return. The blue shifts in the third period are due to that the prominence erupts toward the observer. We suggest that the faint component appears due to the decreasing of the plasma density, and the latter results from the expansion of the prominence spine.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.741427</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.741427</link>
        <title><![CDATA[Polar Quasinormal Modes of Neutron Stars in Massive Scalar-Tensor Theories]]></title>
        <pubdate>2021-09-14T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Jose Luis Blázquez-Salcedo </author><author>Fech Scen Khoo </author><author>Jutta Kunz </author><author>Vincent Preut </author>
        <description><![CDATA[We study polar quasinormal modes of relativistic stars in scalar-tensor theories, where we include a massive gravitational scalar field and employ the standard Brans-Dicke coupling function. For the potential of the scalar field we consider a simple mass term as well as a potential associated with R2 gravity. The presence of the scalar field makes the spectrum of quasinormal modes much richer than the spectrum in General Relativity. We here investigate radial modes (l = 0) and quadrupole modes (l = 2). The general relativistic l = 0 normal modes turn into quasinormal modes in scalar-tensor theories, that are able to propagate outside of the stars. In addition to the pressure-led modes new scalar-led ϕ-modes arise. We analyze the dependence of the quasinormal mode frequencies and decay times on the scalar field mass.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.646556</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.646556</link>
        <title><![CDATA[Auto Recognition of Solar Radio Bursts Using the C-DCGAN Method]]></title>
        <pubdate>2021-09-01T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Weidan Zhang</author><author>Fabao Yan</author><author>Fuyun Han</author><author>Ruopu He</author><author>Enze Li</author><author>Zhao Wu</author><author>Yao Chen</author>
        <description><![CDATA[Solar radio bursts can be used to study the properties of solar activities and the underlying coronal conditions on the basis of the present understanding of their emission mechanisms. With the construction of observational instruments, around the world, a vast volume of solar radio observational data has been obtained. Manual classifications of these data require significant efforts and human labor in addition to necessary expertise in the field. Misclassifications are unavoidable due to subjective judgments of various types of radio bursts and strong radio interference in some events. It is therefore timely and demanding to develop techniques of auto-classification or recognition of solar radio bursts. The latest advances in deep learning technology provide an opportunity along this line of research. In this study, we develop a deep convolutional generative adversarial network model with conditional information (C-DCGAN) to auto-classify various types of solar radio bursts, using the solar radio spectral data from the Culgoora Observatory (1995, 2015) and the Learmonth Observatory (2001, 2019), in the metric decametric wavelengths. The technique generates pseudo images based on available data inputs, by modifying the layers of the generator and discriminator of the deep convolutional generative adversarial network. It is demonstrated that the C-DCGAN method can reach a high-level accuracy of auto-recognition of various types of solar radio bursts. And the issue caused by inadequate numbers of data samples and the consequent over-fitting issue has been partly resolved.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.718306</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.718306</link>
        <title><![CDATA[Comparative Analysis of Super-Kamiokande Solar Neutrino Measurements and Geological Survey of Israel Radon Decay Measurements]]></title>
        <pubdate>2021-08-18T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>P. A. Sturrock</author><author>O. Piatibratova</author><author>F. Scholkmann</author>
        <description><![CDATA[Analyses of neutrino measurements acquired by the Super-Kamiokande Neutrino Observatory (SK, in operation 1996–2001) and radon decay measurements acquired by the Geological Survey of Israel (GSI, in operation 2007–2017) yield strikingly similar detections of an oscillation with frequency 9.43 ± 0.04 year−1 (SK), 9.44 ± 0.04 year−1 (GSI); amplitude 6.8 ± 1.7% (SK), 7.0 ± 1.0% (GSI); and phase 124 ± 15° (SK), 124 ± 9° (GSI). This remarkably close correspondence supports the proposition that neutrinos may somehow influence nuclear decays. It is interesting to note that an oscillation at this frequency has also been reported by (Alexeyev EN, Gavrilyuk YM, Gangapshev AM, Phys Particles Nuclei, 2018 49(4):557–62) in the decay of 214Po. The physical process responsible for this influence of neutrinos on nuclear processes is currently unknown. Related oscillations in GSI data at 7.45 ± 0.03 year−1 and 8.46 ± 0.03 year−1 suggest that these three oscillations are attributable to a solar core that rotates with a sidereal rotation rate of 8.44 ± 0.03 year−1 about an axis almost orthogonal to that of the convection zone. We briefly discuss possible implications of these results.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.705744</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.705744</link>
        <title><![CDATA[Numerical Study of Divergence Cleaning and Coronal Heating/Acceleration Methods in the 3D COIN-TVD MHD Model]]></title>
        <pubdate>2021-07-30T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Chang Liu</author><author>Fang Shen</author><author>Yousheng Liu</author><author>Man Zhang</author><author>Xiaojing Liu</author>
        <description><![CDATA[In the solar coronal numerical simulation, the coronal heating/acceleration and the magnetic divergence cleaning techniques are very important. The coronal–interplanetary total variation diminishing (COIN-TVD) magnetohydrodynamic (MHD) model is developed in recent years that can effectively realize the coronal–interplanetary three-dimensional (3D) solar wind simulation. In this study, we focus on the 3D coronal solar wind simulation by using the COIN-TVD MHD model. In order to simulate the heating and acceleration of solar wind in the coronal region, the volume heating term in the model is improved efficiently. Then, the influence of the different methods to reduce the ∇⋅B constraint error on the coronal solar wind structure is discussed. Here, we choose Carrington Rotation (CR) 2199 as a study case and try to make a comparison of the simulation results among the different magnetic divergence cleaning methods, including the diffusive method, the Powell method, and the composite diffusive/Powell method, by using the 3D COIN-TVD MHD model. Our simulation results show that with the different magnetic divergence cleaning methods, the ∇⋅B error can be reduced in different levels during the solar wind simulation. Among the three divergence cleaning methods we used, the composite diffusive/Powell method can maintain the divergence cleaning constraint better to a certain extent, and the relative magnetic field divergence error can be controlled in the order of 10−9. Although these numerical simulations are performed for the background solar corona, these methods are also suitable for the simulation of CME initiation and propagation.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.706056</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.706056</link>
        <title><![CDATA[Configuration of a Magnetic Cloud From Solar Orbiter and Wind Spacecraft In-situ Measurements]]></title>
        <pubdate>2021-07-22T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Qiang Hu</author><author>Wen He</author><author>Lingling Zhao</author><author>Edward Lu</author>
        <description><![CDATA[Coronal mass ejections (CMEs) represent one type of the major eruption from the Sun. Their interplanetary counterparts, the interplanetary CMEs (ICMEs), are the direct manifestations of these structures when they propagate into the heliosphere and encounter one or more observing spacecraft. The ICMEs generally exhibit a set of distinctive signatures from the in-situ spacecraft measurements. A particular subset of ICMEs, the so-called Magnetic Clouds (MCs), is more uniquely defined and has been studied for decades, based on in-situ magnetic field and plasma measurements. By utilizing the latest multiple spacecraft measurements and analysis tools, we report a detailed study of the internal magnetic field configuration of an MC event observed by both the Solar Orbiter (SO) and Wind spacecraft in the solar wind near the Sun-Earth line. Both two-dimensional (2D) and three-dimensional (3D) models are applied to reveal the flux rope configurations of the MC. Various geometrical as well as physical parameters are derived and found to be similar within error estimates for the two methods. These results quantitatively characterize the coherent MC flux rope structure crossed by the two spacecraft along different paths. The implication for the radial evolution of this MC event is also discussed.]]></description>
      </item><item>
        <guid isPermaLink="true">https://www.frontiersin.org/articles/10.3389/fphy.2021.684345</guid>
        <link>https://www.frontiersin.org/articles/10.3389/fphy.2021.684345</link>
        <title><![CDATA[The Inhomogeneity of Composition Along the Magnetic Cloud Axis]]></title>
        <pubdate>2021-07-15T00:00:00Z</pubdate>
        <category>Original Research</category>
        <author>Hongqiang Song</author><author>Qiang Hu</author><author>Xin Cheng</author><author>Jie Zhang</author><author>Leping Li</author><author>Ake Zhao</author><author>Bing Wang</author><author>Ruisheng Zheng</author><author>Yao Chen</author>
        <description><![CDATA[Coronal mass ejections (CMEs) are one of the most energetic explosions in the solar system. It is generally accepted that CMEs result from eruptions of magnetic flux ropes, which are dubbed as magnetic clouds (MCs) in interplanetary space. The composition (including the ionic charge states and elemental abundances) is determined prior to and/or during CME eruptions in the solar atmosphere and does not alter during MC propagation to 1 AU and beyond. It has been known that the composition is not uniform within a cross section perpendicular to the MC axis, and the distribution of ionic charge states within a cross section provides us an important clue to investigate the formation and eruption processes of flux ropes due to the freeze-in effect. The flux rope is a three-dimensional magnetic structure intrinsically, and it remains unclear whether the composition is uniform along the flux rope axis as most MCs are only detected by one spacecraft. In this study, we report an MC that was observed by Advanced Composition Explorer at ∼1 AU during March 4–6, 1998, and Ulysses at ∼5.4 AU during March 24–28, 1998, sequentially. At these times, both spacecraft were located around the ecliptic plane, and the latitudinal and longitudinal separations between them were ∼2.2° and ∼5.5°, respectively. It provides us an excellent opportunity to explore the axial inhomogeneity of flux rope composition, as both spacecraft almost intersected the cloud center at different sites along its axis. Our study shows that the average values of ionic charge states exhibit significant difference along the axis for carbon, and the differences are relatively slight but still obvious for charge states of oxygen and iron as well as the elemental abundances of iron and helium. Besides the means, the composition profiles within the cloud measured by both spacecraft also exhibit some discrepancies. We conclude that the inhomogeneity of composition exists along the cloud axis.]]></description>
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