Search

Abstract The anomalous heating of the solar upper atmosphere is one of the eight key problems in modern astronomy. Moreover, the stratification of the solar atmosphere is an outstanding key-problem in solar physics. In this study, a hot butterfly-like pattern is found to run through the chromosphere to the corona lying right on top of the magnetic butterfly pattern of sunspots in the photosphere. We thus propose to introduce the term butterfly body to describe the butterfly diagram in the 3-dimensional atmosphere. Besides, we discuss the so-called polar brightening in different layers. It is found to be statistically in anti-phase with the solar cycle in the photosphere and the chromosphere, while in phase with the solar cycle in the corona. Accordingly, we describe the role and relationship of solar magnetic elements of different magnetic flux strengths to explain the statistical structuring of the solar atmosphere with the butterfly body over the solar cycle.

Based on the data from the Kodaikanal and Mount Wilson observatories, we investigate the relationships of the tilt angles of sunspot groups, including the mean tilt angle and the tilt-angle scatter, during the declining phase with the parameters of the next solar cycle (SC). The main findings are summarized in the following three points. (1) During the declining phase, the correlation between the mean tilt angle and the tilt-angle scatter is statistically insignificant. (2) Six quantities measured during the declining phase show significant anticorrelations with the strength and amplitude of the next SC and positive correlations with the duration of the ascending phase of the next SC: the standard deviation of the tilt angles, the rms tilt angle, the mean absolute value of the tilt angles, the area-weighted absolute value of the tilt angles, the latitude-weighted absolute value of the tilt angles, and the area- and latitude-weighted absolute value of the tilt angles. (3) The correlations of the mean tilt angle, the area-weighted tilt angle, the latitude-weighted tilt angle, and the area- and latitude-weighted tilt angle during the declining phase with the strength, amplitude, and duration of the ascending phase of the next SC are statistically insignificant. These findings demonstrate that the modulation of the parameters of the next SC by the tilt-angle scatter during the declining phase plays a vital role in regulating SC variability.

The corona is a structure possessed by stars, including the Sun. The abnormal heating of the solar corona and chromosphere is one of the greatest mysteries in modern astronomy. While state-of-the-art observations have identified some candidates of magnetic activity events that could be responsible for this abnormal heating, and theoretical studies have proposed various heating modes, a complete physical picture of how they are heated as a whole remains elusive. In this study, the characteristics of the heated corona and chromosphere are investigated, and for the first time, the question of how they are abnormally heated is explicitly answered by analyzing the long-term observations of the global chromosphere in the Ca ii K line and the global corona in the coronal green line. The findings reveal that both the quiet chromosphere and corona are in antiphase with the solar cycle, whereas the active chromosphere and corona are in phase with it. Different parts of the solar corona and chromosphere exhibit significantly different variation characteristics and are found to be heated by different magnetic categories and probably in different modes. This study posits that unraveling the heating mystery is best approached through the lens of magnetic categories, rather than magnetic activity events.

Suspended sediment transport in rivers is controlled by terrain, climate, and human activities. These variables affect hillslope and riverbank erosion at the source, transport velocities and sedimentation opportunities in the river channel, and trapping in reservoirs. The relative importance of those factors varies by context, but the specific attribution to sediment transfer is important for policymaking, and has wide implications on watershed management. In our research, we analyzed data from the Kejie watershed in the upper Salween River (Yunnan Province, China), where a combination of land cover change (reforestation, as well as soil and water conservation measures) and river channel engineering (sand mining and check dam construction) interact with a changing climate. Records (1971–2010) of river flow and suspended sediment loads were combined with five land-use maps from 1974, 1991, 2001, 2006 and 2009. Average annual sediment yield decreased from 13.7 t ha−1 yr−1 to 8.3 t ha−1 yr−1 between the period 1971–1985 and the period 1986–2010. A distributed hydrological model (Soil and Water Assessment Tools, SWAT) was set up to simulate the sediment sourcing and transport process. By recombining land-use and climate data for the two periods in model scenarios, the contribution of these two factors could be assessed with engineering effects derived from residual measured minus modeled transport. Overall, we found that 47.8% of the decrease was due to land-use and land cover change, 19.8% to climate change, resulting in a milder rainfall regime, 26.1% to watershed engineering measures, and the remaining 6.3% was due to the simulation percent bias. Moreover, mean annual suspended sediment yield decreased drastically with the increase of forest cover, making diverse forest cover one of the most effective ecosystems to control erosion. For consideration of stakeholders and policymakers, we also discuss at length the modeling uncertainty and implications for future soil and water conservation initiatives in China.

In order to probe the mechanism of variations of the solar constant on the inter-solar-cycle scale, the total solar irradiance (TSI; the so-called solar constant) in the time interval of 1978 November 7 to 2010 September 20 is decomposed into three components through empirical mode decomposition and time-frequency analyses. The first component is the rotation signal, counting up to 42.31% of the total variation of TSI, which is understood to be mainly caused by large magnetic structures, including sunspot groups. The second is an annual-variation signal, counting up to 15.17% of the total variation, the origin of which is not known at this point in time. Finally, the third is the inter-solar-cycle signal, counting up to 42.52%, which is inferred to be caused by the network magnetic elements in quiet regions, whose magnetic flux ranges from (4.27-38.01) x 1019 Mx. [ABSTRACT FROM AUTHOR]

Jiang Z, Wu C L, Woda B A, Iczkowski K A, Chu P G, Tretiakova M S, Young R H, Weiss L M, Blute R D Jr, Brendler C B, Krausz T, Xu J C, Rock K L, Amin M B & Yang X J (2004) Histopathology 45, 218–225 Alpha-methylacyl-CoA racemase: a multi-institutional study of a new prostate cancer marker : To test whether α-methylacyl-CoA racemase (AMACR) is a sensitive and specific marker of prostate cancer. : The expression levels of AMACR mRNA were measured by real-time polymerase chain reaction. A total of 807 prostatic specimens were further examined by immunohistochemistry specific for AMACR. Quantitative immunostaining analyses were carried out by using the ChromaVision Automated Cellular Imaging System and the Ariol SL-50 Imaging System, respectively. AMACR mRNA levels measured in prostatic adenocarcinoma were 55 times higher than those in benign prostate tissue. Of 454 cases of prostatic adenocarcinoma, 441 were positive for AMACR, while 254 of 277 cases of benign prostate were negative for AMACR. The sensitivity and specificity of AMACR immunodetection of prostatic adenocarcinomas were 97% and 92%, respectively. Both positive and negative predictive values were 95%. By automatic imaging analyses, the AMACR immunostaining intensity and percentage in prostatic adenocarcinomas were also significantly higher than those in benign prostatic tissue (105.9 versus 16.1 for intensity, 45.7% versus 0.02% and 35.03% versus 4.64% for percentage, respectively). : We have demonstrated the promising features of AMACR as a biomarker for prostate cancer in this large series and the potential to develop automated quantitative diagnostic tests. [ABSTRACT FROM AUTHOR]

One of the major challenges for the design and operation of next-step high-power steady-state fusion devices is to develop and validate advanced divertor solutions for handling power exhaust, while maintaining acceptable divertor target plate erosion. This requires to access divertor detachment at relatively low main plasma densities compatible with current drive and high plasma confinement. Recently a new initiative has been launched on the EAST superconducting tokamak to develop a new divertor for evaluating boundary plasma solutions applicable to the next step fusion experiments beyond ITER. In the present work, four different divertor configurations with different degrees of closure are evaluated through detailed modeling with the SOLPS plasma boundary code. The modeling results show that increasing divertor closure can significantly trap more neutrals from to with the same upstream separatrix density and hence facilitate the onset of detachment decreasing from to Moreover, with increasing divertor closure the divertor radiated power is also increased from 200 to 450 kW and the peak heat flux density at the divertor target is reduced from 9.3 to 3.8 MW m−2. Therefore, increasing divertor closure can benefit divertor operation for EAST and may be used as one of the scientific metrics for the divertor design of future fusion devices. [ABSTRACT FROM AUTHOR]

Pace making of the edge-localized modes (ELMs) by low-hybrid-wave (LHW) power modulation has been observed in the EAST superconducting tokamak when the modulation frequency is sufficiently close to the natural-ELM frequency, i.e. within ±30%fELM. The highest pace-making frequency obtained so far is 120 Hz. The ELM triggering is typically delayed by 1–2 ms relative to the LHW power rising edge, during which the pedestal profiles evolve. The mechanism of the synchronized triggering of ELMs was found due to the LHW-induced pedestal density pumpout. A previous study indicates that LHW generates field-aligned helical current filaments in the scrape-off layer (SOL) (Liang et al 2013 Phys. Rev. Lett. 110 235002), which produces three- dimensional (3D) magnetic topology change at the plasma edge similar to the effect of the resonant magnetic perturbations. The observed pedestal density pumpout, local flattening of the density gradient near the separatrix and steepening near the pedestal top may be induced by the 3D effect. Pedestal linear stability analysis using ELITE code indicates that the pedestal is approaching the peeling-ballooning stability boundary as the profile is getting steep near the pedestal top until the ELM is triggered. The power threshold for the ELM pacing with 2.45 GHz LHW is ∼1 MW. [ABSTRACT FROM AUTHOR]

Coronal heating is a big question for modern astronomy. Daily measurement of 985 solar spectral irradiances (SSIs) at the spectral intervals 1–39 and 116–2416 nm during 2003 March 1 to 2017 October 28 is utilized to investigate characteristics of solar rotation in the solar atmosphere by means of the Lomb–Scargle periodogram method to calculate their power spectra. The rotation period of coronal plasma is determined to be 26.3 days, and that of the solar atmosphere at the bottom of the photosphere modulated by magnetic structures is 27.5 days. Here we report for the first time that, unexpectedly, the coronal atmosphere is found to rotate faster than the underlying photosphere. When time series of SSIs are divided into different cycles as well as the ascending and descending periods of a solar cycle, the rotation rate in the corona is also found to be larger than that in the photosphere, and this actually uncovers hidden evidence: it is small-scale magnetic activity that heats the corona. [ABSTRACT FROM AUTHOR]

Waves in the ion-cyclotron range of frequencies (ICRF) used for tokamak heating are known to interact strongly with the scrape-off layer (SOL) plasma, potentially limiting ICRF performance. We present the effect of ICRF heating on triple-probe signals in the Experimental Advanced Superconducting Tokamak (EAST) experiment, an advanced superconducting tokamak with two ICRF antennas and 12 MW of ICRF source power in support of high-power and long-pulse operation. Applying time-resolved magnetic mapping to the divertor probe arrays enables detailed sensing of the spatial structure of the SOL modifications. We observe a sharp transition in floating potential from negative to positive over a length scale of a centimeter at a major radius just inboard of the ICRF antenna. The largest changes in floating potential are observed not for probes connecting to the active ICRF antennas but rather to the main limiter or limiters for inactive lower hybrid launchers. Ion saturation current can be greatly reduced for probes mapping just in front of an antenna. Where relevant, comparison with results from the National Spherical Torus Experiment are made. This work will provide insight into sputtering, impurity production and antenna coupling as higher ICRF power levels are attempted on EAST. [ABSTRACT FROM AUTHOR]

The study of the divertor heat flux is of great importance for the operation of ITER and future fusion devices. In this paper, the behaviors of the widths of the particle flux footprints on the tungsten divertor in EAST have been statistically studied for the first time. A large number of divertor Langmuir probe (Div-LP) data from EAST general discharges in the 2016 campaign have been stepwise selected and analyzed for both L- and H-mode plasmas. It is found that the scaling dependences on poloidal magnetic field for the particle flux fall-off width at the inner tungsten divertor agree well with those at the outer graphite divertor in both L- and H-mode plasmas. The difficulty of extracting reliable footprint widths has been overcome by fitting data from two Div-LP arrays distributed toroidally. The nonlinear regressions of the particle flux fall-off width and particle flux spreading width at the inner tungsten divertor in H-mode plasmas have then been performed. A negative dependence on the plasma stored energy is found in the regression of the particle flux fall-off width and the exponent of the stored energy in the regression is consistent with previous experimental studies. The comparison between the particle flux fall-off width at the tungsten divertor with that at the graphite divertor indicates that statistically the divertor material and the direction of the toroidal magnetic field seem to have no significant influence on the particle flux fall-off width at the inner divertor. In addition, the similar particle flux fall-off width in L- and H-mode plasmas and the in–out asymmetry of the particle flux fall-off width at the graphite divertor have also been shown. [ABSTRACT FROM AUTHOR]

The N–S asymmetry (the north–south hemispheric asymmetry) of sunspot areas for each of the cycles 7–24 have been investigated, and a trend of a long-term characteristic timescale of about eight cycles is inferred, which is confirmed again by studying the fitted lines of the yearly values of the N–S asymmetry of sunspot numbers and sunspot group numbers at solar cycle 24. Then, a periodic behavior of about 12 solar cycles is found in the cumulative counts of yearly sunspot areas for each of the cycles 7–24. Nevertheless, the cumulative counts of sunspot numbers and sunspot group numbers for cycle 24 have different behaviors. Moreover, the dominant hemispheres for cycles 7–23 show a trend of a long-term characteristic timescale of about 12 cycles. However, we cannot determine the dominant hemisphere of cycle 24, as these three parameters give different results for the dominant hemisphere. Cycle 24 is a particular solar activity cycle, as sunspot areas suggest a long characteristic timescale of about 12-cycle length, while sunspot numbers and sunspot group numbers support an eight-cycle period of the N–S asymmetry. [ABSTRACT FROM AUTHOR]

One challenge in long-pulse and high performance tokamak operation is to control the edge localized modes (ELMs) to reduce the transient heat load on plasma facing components. Minute-scale discharges in H-mode have been achieved repeatedly on Experimental Advanced Superconducting Tokamak (EAST) since the 2016 campaign and understanding the characteristics of the ELMs in these discharges can be helpful for effective ELM control in long-pulse discharges. The kinetic profile diagnostics recently developed on EAST make it possible to perform the pedestal stability analysis quantitatively. Pedestal stability calculation of a typical long-pulse discharge with ELITE code is presented. The ideal linear stability results show that the ELM is dominated by toroidal mode number n around 10–15 and the most unstable mode structure is mainly localized in the steep pressure gradient region, which is consistent with experimental results. Compared with a typical type-I ELM discharge with larger total plasma current (Ip = 600 kA), pedestal in the long-pulse H-mode discharge (Ip = 450 kA) is more stable in peeling-ballooning instability and its critical peak pressure gradient is evaluated to be 65% of the former. Two important features of EAST tokamak in the long-pulse discharge are presented by comparison with other tokamaks, including a wider pedestal correlated with the poloidal pedestal beta and a smaller inverse aspect ratio and their effects on the pedestal stability are discussed. The effects of uncertainties in measurements on the linear stability results are also analyzed, including the edge electron density profile position, the separatrix position and the line-averaged effective ion charge value. [ABSTRACT FROM AUTHOR]

A comprehensive work of the effects of plasma current and heating schemes on divertor power footprint widths is carried out in the experimental advanced superconducting tokamak (EAST). The divertor power footprint widths, i.e., the scrape-off layer heat flux decay length λq and the heat spreading S, are crucial physical and engineering parameters for fusion reactors. Strong inverse scaling of λq and S with plasma current have been demonstrated for both neutral beam (NB) and lower hybrid wave (LHW) heated L-mode and H-mode plasmas at the inner divertor target. For plasmas heated by the combination of the two kinds of auxiliary heating schemes (NB and LHW), the divertor power widths tend to be larger in plasmas with higher ratio of LHW power. Comparison between experimental heat flux profiles at outer mid-plane (OMP) and divertor target for NB heated and LHW heated L-mode plasmas reveals that the magnetic topology changes induced by LHW may be the main reason to the wider divertor power widths in LHW heated discharges. The effect of heating schemes on divertor peak heat flux has also been investigated, and it is found that LHW heated discharges tend to have a lower divertor peak heat flux compared with NB heated discharges under similar input power. All these findings seem to suggest that plasmas with LHW auxiliary heating scheme are better heat exhaust scenarios for fusion reactors and should be the priorities for the design of next-step fusion reactors like China Fusion Engineering Test Reactor. [ABSTRACT FROM AUTHOR]

Understanding the effect of sunspot activities on the variations in the total solar irradiance (TSI) is essential for the interpretation of the variability of TSI as well as its reconstruction. Phase relations between the sunspot numbers (SN) and two TSI composite data are investigated. It is found that TSI and SN are positively correlated, and the former lags the latter by about 29 days, which is approximately a solar rotation period; analyses of the data sets in the four individual cycles show that in cycles 21, 23, and 24, TSI lags SN by 28.9–30.3 days, while in cycle 22, the lag is only 21.8–22.3 days. The abnormality in cycle 22 is probably caused by its stronger magnetic field in sunspots compared with its adjacent cycles. The nonlinearity between TSI and SN is confirmed and explained with the different behavior and effect of spots, faculae, and magnetic network. Based on the cross-wavelet transform and wavelet coherence analysis, a common periodicity between TSI and SN at the timescale of the solar cycle is clearly revealed; at timescales longer than about four years, high values of coherence above the 95% confidence level together with a strong phase synchronization feature are exhibited. At timescales shorter than three rotational periods, the relation between TSI and SN indicates low correlations and a noisy behavior with strong phase mixing due to the lifetime of spots and faculae; moreover, if the short-term effect of spots and faculae is smoothed out, then their coherence reaches high values in partial areas at periods from three rotations to about four years. [ABSTRACT FROM AUTHOR]

Experimental Advanced Superconducting Tokamak (EAST) aims to demonstrate steady-state advanced high-performance H-mode plasmas with an ITER-like configuration, plasma control and heating schemes. The plasma-facing components in EAST are actively cooled, providing good conditions for researching long-pulse and high-energy discharges. A long-pulse high-performance plasma discharge (#59892 discharge) of up to 103 s with a core electron temperature of up to 4.5 keV was sustained with an injected energy exceeding 0.22 GJ in the 2015–2016 experimental campaign. A calorimetric measurement utilizing the temperature increment of cooling water is carried out to calculate the heat load on the strike point region of the lower divertor during long-pulse discharges in EAST. For the long-pulse and high-energy discharges, the comparison of the measurement results for the heat load measured by divertor Langmuir probes and the calorimetry diagnostic indicates that most of the heat load is delivered to the divertor panels as plasma, not radiation, and charge exchange neutrals. The ratio of the heat load on the strike point region of the lower divertor to the total injected energy is on average 42.5% per discharge with the lower single null divertor configuration. If the radiated energy loss measured by the fast bolometer diagnostic is taken into consideration, the ratio is found to be 61.6%. The experimental results and the analysis of the physics involved in these discharges are reported and discussed. [ABSTRACT FROM AUTHOR]

The rotational characteristics of the solar photospheric magnetic field at four flux ranges are investigated together with the total flux of active regions (MFar) and quiet regions (MFqr). The first four ranges (MF1–4) are (1.5–2.9) × 1018, (2.9–32.0) × 1018, (3.20–4.27) × 1019, and (4.27–38.01) × 1019, respectively (the unit is Mx per element). Daily values of the flux data are extracted from magnetograms of the Michelson Doppler Imager on board the Solar and Heliospheric Observatory. Lomb–Scargle periodograms show that only MF2, MF4, MFqr, and MFar exhibit rotational periods. The periods of the first three types of flux are very similar, i.e., 26.20, 26.23, and 26.24 days, respectively, while that of MFar is longer, 26.66 days. This indicates that active regions rotate more slowly than quiet regions on average, and strong magnetic fields tend to repress the surface rotation. Sinusoidal function fittings and cross-correlation analyses reveal that MFar leads MF2 and MF4 by 5 and 1 days, respectively. This is speculated to be related with the decaying of active regions. MF2 and MFar are negatively correlated, while both MF4 and MFqr are positively correlated with MFar. At the timescale of the solar activity cycle, MFar leads (negatively) MF2 by around one year (350 days), and leads MF4 by about 3 rotation periods (82 days). The relation between MF2 and MFar may be explained by the possibility that the former mainly comes from a higher latitude, or emerges from the subsurface shear layer. We conjecture that MF4 may partly come from the magnetic flux of active regions; this verifies previous results that were obtained with indirect solar magnetic indices. [ABSTRACT FROM AUTHOR]

BACKGROUND:Tea is the world's most popular non-alcoholic beverage. China and India are known to be the largest tea producing countries and recognized as the centers for the domestication of the tea plant (Camellia sinensis (L.) O. Kuntze). However, molecular studies on the origin, domestication and relationships of the main teas, China type, Assam type and Cambod type are lacking. METHODOLOGY/PRINCIPAL FINDINGS:Twenty-three nuclear microsatellite markers were used to investigate the genetic diversity, relatedness, and domestication history of cultivated tea in both China and India. Based on a total of 392 samples, high levels of genetic diversity were observed for all tea types in both countries. The cultivars clustered into three distinct genetic groups (i.e. China tea, Chinese Assam tea and Indian Assam tea) based on STRUCTURE, PCoA and UPGMA analyses with significant pairwise genetic differentiation, corresponding well with their geographical distribution. A high proportion (30%) of the studied tea samples were shown to possess genetic admixtures of different tea types suggesting a hybrid origin for these samples, including the Cambod type. CONCLUSIONS:We demonstrate that Chinese Assam tea is a distinct genetic lineage from Indian Assam tea, and that China tea sampled from India was likely introduced from China directly. Our results further indicate that China type tea, Chinese Assam type tea and Indian Assam type tea are likely the result of three independent domestication events from three separate regions across China and India. Our findings have important implications for the conservation of genetic stocks, as well as future breeding programs.