Solar Core Research Articles

Big Science “for the benefit of all mankind”

Abstract A little more than a century ago at the turn of the 1920s two eminent scientists—Jean Perrin (1870-1942) in France and Arthur Eddington (1882-1944) in the United Kingdom—speculated that the energy source at the core of the Sun was a product of nuclear reactions. Their intuition was a huge departure from the theories that had prevailed until then. In the years that followed a clearer understanding1 of the hydrogen fusion process at the core of Sun-like stars led to a Promethean ambition: reproducing and harnessing fusion reactions to gain access here on Earth to a new sustainable source of energy for generating electricity on a massive scale.

Fitting the Crab Supernova with a Gamma-Ray Burst

Here, we reconsider the historical data, assuming a gamma-ray burst (GRB) as its source. A Supernova correlated with the GRB explains well the fading time observed by the ancient Chinese astronomers in the daytime and the nighttime, while the GRB power law explains the present X-rays and GeV emission of the Crab. On the grounds of a recent understanding of the first episode of binary-driven hypernova GRB (BDHN GRB) in terms of the collapse of a ten solar masses core, we propose the possible identification of the real Supernova event at an earlier time than Chinese chronicles. This work allows a new understanding of the significance of historical astronomical observations, including a fireball due to gamma-ray air shower observation and a plague of acute radiation syndrome, documented with several thousands of victims in the Eurasian area (Egypt, Iraq, and Syria).

An Expanded Set of Los Alamos OPLIB Tables in MESA: Type-1 Rosseland-mean Opacities and Solar Models

We present a set of 1194 Type-1 Rosseland-mean opacity tables for four different metallicity mixtures. These new Los Alamos OPLIB atomic radiative opacity tables are an order of magnitude larger in number than any previous opacity table release, and span regimes where previous opacity tables have not existed. For example, the new set of opacity tables expands the metallicity range to Z = 10−6 to Z = 0.2, which allows improved accuracy of opacities at low and high metallicity, increases the table density in the metallicity range Z = 10−4 to Z = 0.1 to enhance the accuracy of opacities drawn from interpolations across neighboring metallicities, and adds entries for hydrogen mass fractions between X = 0 and X = 0.1 including X = 10−2, 10−3, 10−4, 10−5, 10−6 that can improve stellar models of hydrogen deficient stars. We implement these new OPLIB radiative opacity tables in MESA and find that calibrated solar models agree broadly with previously published helioseismic and solar neutrino results. We find differences between using the new 1194 OPLIB opacity tables and the 126 OPAL opacity tables range from ≈20% to 80% across individual chemical mixtures, up to ≈8% and ≈15% at the bottom and top of the solar convection zone respectively, and ≈7% in the solar core. We also find differences between standard solar models using different opacity table sources that are on par with altering the initial abundance mixture. We conclude that this new, open-access set of OPLIB opacity tables does not solve the solar modeling problem, and suggest the investigation of physical mechanisms other than the atomic radiative opacity.

Signatures of solar chameleons in the Earth’s magnetic field

Chameleon dark energy models are a popular alternative to the standard cosmological constant model. These models consist of a new light degree of freedom, called chameleon, with a density dependent mass and a nontrivial coupling to both matter and photons. Owing to these couplings, chameleons can be produced inside the sun. However due to their density dependent mass, the chameleons produced in the solar core are screened and cannot escape whereas those produced outside the solar core, such as in the region with energies of the order of few a keV, can escape from the sun and travel all the way toward Earth. Hence the Earth is expected to receive a flux of . In this work we propose a (LSW) type of experiment in which the Earth itself acts as a wall. Both photons and chameleons are incident on the light side of the Earth. While all the photons are stopped by the Earth, only a fraction of the chameleons are stopped by the earth due to screening. Those chameleons which are not screened by the earth pass directly through the Earth and exit the night side. Here these chameleons interact with the geomagnetic field and convert into x-ray photons. A space-based x-ray telescope orbiting the Earth can detect these x-ray photons, while passing through the night side, thereby acting as a detector in this LSW type experiment. We show that such a kind of setup can be complementary to other terrestrial experiments looking for chameleons. Published by the American Physical Society 2024

Solar Wind Density and Core Temperature Derived from the PSP Quasi-thermal Noise Measurements

Quasi-thermal noise (QTN) spectroscopy is a valuable method to deduce important parameters in space plasma, such as plasma density and temperature, especially when direct particle measurements are not available. The present study develops a new fitting method to fit the QTN spectra observed by the Parker Solar Probe (PSP) with a comprehensive theoretical QTN spectral model. By combining the steepest descent and Levenberg–Marquardt algorithms, the new method is more flexible with initial guess values but still yields reliable solar wind electron density and temperature values. The new method is applied to derive the solar wind density and core temperature from the QTN measurements during 10 encounters of PSP. The electron density and temperature values obtained vary with the radial distance from the Sun as n e ∝ r −2.12 and T e ∝ r −0.71, both of which are consistent with existing models and previous results.

The study of angular distance distribution to the solar flares during different solar cycles

The angular distance of the solar flares to the projective point of the center of the solar disk on the solar spherical surface has been studied by the heliographical or helioprojective coordinates, during the periods 1975–2021 for GOES events and 2002–2021 for RHESSI events, hereafter “distance.” It gives a specific distribution curvature. It has also been noted that when using the number of solar flare events in each satellite, GOES or RHESSI, or even using the sum of the flux (class) or importance parameter, it obtains the same result, which is that the shape of the distribution curve remains in its shape without any significant change. In addition, it has been shown that the distribution curve contains a specific number of peaks. These peaks have a specific distance from the center of the solar disk that is very similar to the projection of the solar interior layers on the solar disk. For this reason, the names of these four main peaks have been given as follows: (1) the core circle (0–15°): it is a projection of the solar core onto the solar disk, (2) radiative ring (15–45°), and (3) the convection ring (45–55°). The limb ring is 80–90°. This result makes us wonder why the number of events in the middle of the solar disk is few, and also small at the solar limb, while many in the other parts in the solar disk. This suggests that we need to understand the sun better than before, and it also suggests that solar flares are connected to each other through the solar interior layers, the extent of which may reach the convection zone or perhaps beyond that, or the opacity of the convection zone may be less than the currently estimated value.

Biological timekeeping in polar environments: lessons from terrestrial vertebrates.

The polar regions receive less solar energy than anywhere else on Earth, with the greatest year-round variation in daily light exposure; this produces highly seasonal environments, with short summers and long, cold winters. Polar environments are also characterised by a reduced daily amplitude of solar illumination. This is obvious around the solstices, when the Sun remains continuously above (polar 'day') or below (polar 'night') the horizon. Even at the solstices, however, light levels and spectral composition vary on a diel basis. These features raise interesting questions about polar biological timekeeping from the perspectives of function and causal mechanism. Functionally, to what extent are evolutionary drivers for circadian timekeeping maintained in polar environments, and how does this depend on physiology and life history? Mechanistically, how does polar solar illumination affect core daily or seasonal timekeeping and light entrainment? In birds and mammals, answers to these questions diverge widely between species, depending on physiology and bioenergetic constraints. In the high Arctic, photic cues can maintain circadian synchrony in some species, even in the polar summer. Under these conditions, timer systems may be refined to exploit polar cues. In other instances, temporal organisation may cease to be dominated by the circadian clock. Although the drive for seasonal synchronisation is strong in polar species, reliance on innate long-term (circannual) timer mechanisms varies. This variation reflects differing year-round access to photic cues. Polar chronobiology is a productive area for exploring the adaptive evolution of daily and seasonal timekeeping, with many outstanding areas for further investigation.

Solar Energy Is Any Type Of Energy Generated By The Sun

Solar energy is any type of energy generated by the sun Solar energy is created by nuclear fusion that takes place in the sun Fusion occurs when protons of hydrogen atoms violently collide in the sun's core and fuse to create a helium atom

Overview of Solar Neutrino Experiments

Solar neutrinos have played a major historic role in the development of neutrino physics and understanding of the fusion processes in the Sun. Neutrino experiments worldwide continue to measure neutrinos originating in the core of the Sun in the search for new insights. Recent years have marked the discovery of the carbon-nitrogen-oxygen fusion cycle, tackling the Sun metallicity problem, and the search for physics beyond the Standard Model.

Reinvestigating the Gamow Factor of Reactions on Light Nuclei

We present a modified Gamow factor by reinvestigating the conventional assumptions used in its derivation. The conventional Gamow factor, factorized from the total cross section, effectively describes the penetration probabilities (PPs) in low-energy nuclear reactions under the assumption of particle energies significantly lower than the Coulomb barrier. However, we find that the assumption is invalid for light nuclei, resulting in PPs that depend on the nuclear potential depth for such nuclei. By adopting a potential depth fitted to experimental fusion cross sections, we demonstrate that PPs for light nuclei (D+D, D+T, D+3He, p+D, p+6Li, and p+7Li) become higher than those predicted by the conventional form near the Coulomb barrier. This reduces the Gamow peak energy by a factor of 5.3 maximally compared to the conventional form. Furthermore, we show that the enhancement factor due to the Debye screening effects in the solar core can be reduced by approximately 5%–10% due to the modified PP. Our findings hold implications for evaluating the available energy region in low-energy reaction experiments based on the Gamow peak energy region and for understanding electron screening effects in typical astrophysical environments.

Fabrication of a 64-Pixel TES Microcalorimeter Array With Iron Absorbers Uniquely Designed for 14.4-keV Solar Axion Search

If a hypothetical elementary particle called an axion exists, to solve the strong CP problem, a 57Fe nucleus in the solar core could emit a 14.4-keV monochromatic axion through the M1 transition. If such axions are once more transformed into photons by a 57Fe absorber, a transition edge sensor (TES) X-ray microcalorimeter should be able to detect them efficiently. We have designed and fabricated a dedicated 64-pixel TES array with iron absorbers for the solar axion search. In order to decrease the effect of iron magnetization on spectroscopic performance, the iron absorber is placed next to the TES while maintaining a certain distance. A gold thermal transfer strap connects them. We have accomplished the electroplating of gold straps with high thermal conductivity. The residual resistivity ratio (RRR) was over 23, more than eight times higher than a previous evaporated strap. In addition, we successfully electroplated pure-iron films of more than a few micrometers in thickness for absorbers and a fabricated 64-pixel TES calorimeter structure.

Probing the Structure and Dynamics of the Solar Core with Gravity Modes

Probing the Structure and Dynamics of the Solar Core with Gravity Modes

Energy Repartition and Entropy Generation across the Earth’s Bow Shock: MMS Observations

The evolution of plasma entropy and the process of plasma energy redistribution at the collisionless plasma shock front are evaluated based on the high temporal resolution data from the four Magnetospheric Multiscale spacecraft during the crossing of the terrestrial bow shock. The ion distribution function has been separated into the populations with different characteristic behaviors in the vicinity of the shock: the upstream core population, the reflected ions, the gyrating ions, the ions trapped in the vicinity of the shock, and the downstream core population. The values of ion and electron moments (density, bulk velocity, and temperature) have been determined separately for these populations. It is shown that the solar wind core population bulk velocity slows down mainly in the ramp with the electrostatic potential increase but not in the foot region as it was supposed. The reflected ion population determines the foot region properties, so the proton temperature peak in the foot region is an effect of the relative motion of the different ion populations, rather than an actual increase in the thermal speed of any of the ion population. The ion entropy evaluated showed a significant increase across the shock: the enhancement of the ion entropy occurs in the foot of the shock front and at the ramp, where the reflected ions are emerging in addition to the upstream solar wind ions, the anisotropy growing to generate the bursts of ion-scale electrostatic waves. The entropy of electrons across the shock does not show a significant change: electron heating goes almost adiabatically.

Myotonic Dystrophy Type 1 - An Atypical Presentation Having Symmetric Parkinsonism and Early Proximal Muscle Involvement.

Myotonic Dystrophy Type 1 - An Atypical Presentation Having Symmetric Parkinsonism and Early Proximal Muscle Involvement.

Outcome of adalimumab monotherapy in paediatric non-infectious uveitis

BackgroundAdalimumab in combination with other disease-modifying antirheumatic drugs (DMARD) such as methotrexate has a proven efficacy in the management of paediatric non-infectious uveitis. However, many children experience significant intolerance to methotrexate while on this combination, leaving a dilemma for clinicians for choosing the subsequent therapeutic roadmap. Continuation of adalimumab monotherapy might be an alternative feasible option under such settings. This study aims to investigate the efficacy of adalimumab monotherapy in paediatric non-infectious uveitis.MethodsChildren with non-infectious uveitis on adalimumab monotherapy (from August 2015 to June 2022) following intolerance to accompanying methotrexate or mycophenolate mofetil were included in this retrospective study. Data were collected at the initiation of adalimumab monotherapy and at three monthly intervals until the last visit. The primary outcome was to evaluate disease control on adalimumab monotherapy as determined by the proportion of patients who had less than a 2-step worsening in uveitis (as per SUN score) and no additional systemic immunosuppression during follow-up. Secondary outcome measures were visual outcome, complications and side-effect profile of adalimumab monotherapy.ResultsData was collected for 28 patients (56 eyes). The most common uveitis type and course were anterior and chronic uveitis respectively. Juvenile idiopathic arthritis-associated uveitis was the most common underlying diagnosis. During the study period, 23 (82.14%) of the study subjects met the primary outcome. On Kaplan–Meier survival analysis 81.25% (95% CI; 60.6–91.7%) children maintained remission at 12 months on adalimumab monotherapy.ConclusionContinuation of adalimumab monotherapy is an effective therapeutic option for the treatment of non-infectious uveitis in children who are intolerant to the combination of adalimumab and methotrexate or mycophenolate mofetil.

Academic Text as a Part of the Fictional World in Johanna Sinisalo’s The Core of the Sun

Academic Text as a Part of the Fictional World in Johanna Sinisalo’s The Core of the Sun

Performance of TES X-Ray Microcalorimeters Designed for 14.4-keV Solar Axion Search

A ^{57}Fe nucleus in the solar core could emit a 14.4-keV monochromatic axion through the M1 transition if a hypothetical elementary particle, axion, exists to solve the strong CP problem. Transition edge sensor (TES) X-ray microcalorimeters can detect such axions very efficiently if they are again converted into photons by a ^{57}Fe absorber. We have designed and produced a dedicated TES array with ^{57}Fe absorbers for the solar axion search. The iron absorber is set next to the TES, keeping a certain distance to reduce the iron-magnetization effect on the spectroscopic performance. A gold thermal transfer strap connects them. A sample pixel irradiated from a ^{55}Fe source detected 698 pulses. In contrast to thermal simulations, we consider that the pulses include either events produced in an iron absorber or gold strap at a fraction dependent on the absorption rate of each material. Furthermore, photons deposited on the iron absorber are detected through the strap as intended. The identification of all events still needs to be completed. However, we successfully operated the TES with the unique design under iron magnetization for the first time.

Development of a neutrino detector capable of operating in space

The $\nu$SOL experiment to operate a neutrino detector close to the Sun is building a small test detector to orbit the Earth to test the concept in space. This detector concept is to provide a new way to detect neutrinos unshielded in space. A double delayed coincidence on Gallium nuclei that have a large cross section for solar neutrino interactions emitting a conversion electron and converting the nuclei into an excited state of Germanium, which decays with a well-known energy and half-life. This unique signature permits operation of the detector volume mostly unshielded in space with a high single particle counting rate from gamma and cosmic ray events. The test detector concept which has been studied in the lab and is planned for a year of operations orbiting Earth which is scheduled for launch in late 2024. It will be surrounded by an active veto and shielding will be operated in a polar orbit around the Earth to validate the detector concept and study detailed background spectrums that can fake the double timing and energy signature from random galactic cosmic or gamma rays. The success of this new technology development will permit the design of a larger spacecraft with a mission to fly close to the Sun and is of importance to the primary science mission of the Heliophysics division of NASA Space Science Mission Directorate, which is to better understand the Sun by measuring details of our Sun's fusion core.

Machine learning application for dark matter - background classification in JUNO experiment

Jiangmen underground neutrino observatory (JUNO) has a potential to indirectly detect dark matter (DM), observing neutrino events from annihilations of DM trapped by the gravitational force in the solar core. Weakly interacting massive particle (WIMP) DM candidate with mass > 4 GeV has significant solar capture rate. In this work, we simulate JUNO neutrino events from the most dominated WIMP annihilation channel, . Given the high-energy neutrinos from massive WIMPs, we extend the neutrino-nucleon interactions in the detector to include quasi-elastic (QE) and deep inelastic scatterings (DIS). The most challenging background events in the energy range above 100 MeV is the atmospheric neutrinos (atmo). The pulse shape discrimination (PSD) method is usually applied to distinguish between DM and atmo. In this work, we apply machine learning (ML) techniques to distinguish between the background (BG) atmo and DM neutrino events. We found that the random forest algorithm gives the best results. Using ML, the accuracy of DM-atmo events classification is 93.8% while similar f1-score could be achieved. On the other hand, only 78.1 % accuracy is obtained using conventional PSD with linear regression (LR). The upper limit for spin-dependent DM-proton cross-section with the applied ML is 5.84 × 10−40 cm2 for a 10 GeV WIMP DM which is an improvement over the sensitivity of the LR method of by a factor of ∼ 2.8x.

Investigation of the N14(p,γ)O15 reaction and its impact on the CNO cycle

The CNO cycle is the main energy source in massive stars during their hydrogen burning phase, and, for our sun, it contributes at the $\ensuremath{\approx}1%$ level. As the $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$ reaction is the slowest in the cycle, it determines the CNO energy production rate and thus the CNO contribution to the solar neutrino flux. These CNO neutrinos are produced primarily from the $\ensuremath{\beta}$ decay of $^{15}\mathrm{O}$ and, to a lesser extent, from the decay of $^{13}\mathrm{N}$. Solar CNO neutrinos are challenging to detect, but they can provide independent new information on the metallicity of the solar core. Recently, CNO neutrinos from $^{15}\mathrm{O}$ have been identified for the first time with the Borexino neutrino detector at the INFN Gran Sasso underground laboratory. There are, however, still some considerable uncertainties in the $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$ reaction rate under solar temperature conditions. The low energy reaction data presented here, measured at the CASPAR underground accelerator, aim at connecting existing measurements at higher energies and attempts to shed light on the discrepancies between the various data sets, while moving towards a better understanding of the $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$ reaction cross section. The present measurements span proton energies between 0.27 and 1.07 MeV, closing a critical gap in the existing data. A multichannel $R$-matrix analysis was performed with the entire new and existing data sets and is used to extrapolate the astrophysical $S$ factors of the ground state and the 6.79 MeV transition to low energies. The extrapolations are found to be in agreement with previous work, but find that the discrepancies between measured data and $R$-matrix fits, both past and present, still exist. We examine the possible reasons for these discrepancies and thereby provide recommendations for future studies.