Maximum Of Cycle Research Articles

Observations of Slow Solar Wind from Equatorial Coronal Holes

Abstract Because of its distinctive compositional properties and variability, low-speed (≲450 km s−1) solar wind is widely believed to originate from coronal streamers, unlike high-speed wind, which comes from coronal holes. An alternative scenario is that the bulk of the slow wind (excluding that in the immediate vicinity of the heliospheric current sheet) originates from rapidly diverging flux tubes rooted inside small coronal holes or just within the boundaries of large holes. This viewpoint is based largely on photospheric field extrapolations, which are subject to considerable uncertainties and do not include dynamical effects, making it difficult to be certain whether a source is located just inside or outside a hole boundary, or whether a high-latitude hole will be connected to Earth. To minimize the dependence on field-line extrapolations, we have searched for cases where equatorial coronal holes at central meridian are followed by low-speed streams at Earth. We describe 14 examples from the period 2014–2017, involving Fe xiv 21.1 nm coronal holes located near active regions and having equatorial widths of ∼3°–10°. The associated in situ wind was characterized by speeds v ∼ 300–450 km s−1 and by O7+/O6+ ratios of ∼0.05–0.15, with v showing the usual correlation with proton temperature. In addition, consistent with other recent studies, this slow wind had remarkably high Alfvénicity, similar to that in high-speed streams. We conclude that small coronal holes are a major contributor to the slow solar wind during the maximum and early post-maximum phases of the solar cycle.

Beyond the Minisolar Maximum of Solar Cycle 24: Declining Solar Magnetic Fields and the Response of the Terrestrial Magnetosphere

AbstractThe present study examines the response of the terrestrial magnetosphere to the long‐term steady declining trends observed in solar magnetic fields and solar wind microturbulence levels since mid‐1990s that has been continuing beyond the minisolar maximum of cycle 24. A detailed analysis of the response of the terrestrial magnetosphere has been carried out by studying the extent and shape of the Earth's magnetopause and bow shock over the past four solar cycles. We estimate subsolar stand‐off distance of the magnetopause and bow shock and the shape of the magnetopause, using numerical as well as empirical models. The computed magnetopause and bow shock stand‐off distances have been found to be increasing steadily since around mid‐1990s, consistent with the steady declining trend seen in solar magnetic fields and solar wind microturbulence levels. Similarly, we find an expansion in the shape of the magnetopause since 1996. The implications of the increasing trend seen in the magnetopause and bow shock stand‐off distances are discussed and a forecast of the shape of the magnetopause in 2020, the minimum of cycle 24, has been made. Importantly, we also find two instances between 1968 and 1991 when the magnetopause stand‐off distance dropped to values close to 6.6 Earth radii, the geostationary orbit, for duration ranging from 9–11 hr and one event in 2005, post 1995 when the decline in photospheric fields began. Though there have been no such events since 2005, it represents a clear and present danger to our satellite systems.

Diurnal variation of F2-layer critical frequency under solar activity recurrent conditions during solar cycles 21 and 22 at Ouagadougou Station: Prediction with IRI-2012

This paper presents foF2 data recorded at Ouagadougou Ionosonde Station and compares them with IRI-2012 model results through its two subroutines, Union Radio Scientifique Internationale (URSI) and Comite Consultatif International des Radio Communications (CCIR) during recurrent solar activity. Except for the solar cycle maximum period, measured data profiles corroborate with the signatures of E×B drift. IRI- 2012 subroutine URSI is not consistent with observed electrodynamics during any solar cycle phase, while CCIR predictions are consistent with the measured data during the solar maximum and declining phases. Investigation on the relative deviation module mean (RDMM) shows poor agreement between measurements and predictions with IRI most of the time. However, the deviation percentages indicate good correlation between URSI predictions and data from the ionosonde, except for solar ascending phase. Good correlation with CCIR is only obtained during the solar cycle minimum and maximum phases. From a quantitative point of view, this study shows that predictions with URSI are closer to experimental measurements. The investigations show good agreement between model and in situ measurement during the day. Significant differences are recorded at night, especially from midnight to sunrise. There is necessity to improve IRI model for equatorial regions to better predict foF2 variation. Key words: Ionosphere, foF2, Solar cycle, IRI model.

Suzaku observation of Jupiter’s X-rays around solar maximum

Abstract We report on results of imaging and spectral studies of X-ray emission from Jupiter observed by Suzaku. In 2006, Suzaku found diffuse X-ray emission in 1–5 keV associated with Jovian inner radiation belts. It has been suggested that the emission is caused by the inverse-Compton scattering by ultra-relativistic electrons (∼50 MeV) in Jupiter’s magnetosphere. To confirm the existence of this emission and to understand its relation to the solar activity, we conducted an additional Suzaku observation in 2014 around the maximum of the 24th solar cycle. As a result, we successfully found the diffuse emission around Jupiter in 1–5 keV again, and also found point-like emission in 0.4–1 keV. The luminosity of the point-like emission, which was probably composed of solar X-ray scattering, charge exchange, or auroral bremsstrahlung emission, increased by a factor of ∼5 with respect to the findings from 2006, most likely due to an increase of the solar activity. The diffuse emission spectrum in the 1–5 keV band was well-fitted with a flat power-law function (Γ = 1.4 ± 0.1) as in the past observation, which supported the inverse-Compton scattering hypothesis. However, its spatial distribution changed from ∼12 × 4 Jovian radius (Rj) to ∼20 × 7 Rj. The luminosity of the diffuse emission increased by the smaller factor of ∼3. This indicates that the diffuse emission is not simply responding to the solar activity, which is also known to cause little effect on the distribution of high-energy electrons around Jupiter. Further sensitive study of the spatial and spectral distributions of the diffuse hard X-ray emission is important to understand how high-energy particles are accelerated in Jupiter’s magnetosphere.

Conventional and advanced exergy analysis of a novel transcritical compressed carbon dioxide energy storage system

The work presents a comprehensive investigation on a novel two-stage transcritical compressed carbon dioxide energy storage system using conventional and advanced exergy analyses. Conventional exergy analysis quantifies the exergy destruction of each component in an independent manner, and identifies cold storage as the most significant component for improvement due to the largest exergy destruction rate of 256.71 kW, sharing 19.23% of the total exergy destruction rate. The advanced exergy analysis can reveal more valuable information by taking the interconnections among system components and technological limitations of each component into consideration. The results indicate that the interactions among components are complex but not very significant, and the first compressor possesses the highest potential for improvement due to the largest avoidable exergy destruction rate of 159.01 kW that accounts for 22.55% of total avoidable exergy destruction and 11.91% of total exergy destruction. A comparison between the results of above two analysis approaches confirms that the conventional exergy analysis could mislead the designer and the results based on the advanced approach are more pragmatic. Besides, the system exergy efficiency is 59% for real cycle and the theoretical maximum for unavoidable cycle is 77.8%, meaning great potential for the improvement of system performance.

A Phase I Comparative Pharmacokinetic and Safety Study of Two Intravenous Formulations of Vinorelbine in Patients With Advanced Non-Small Cell Lung Cancer.

Purpose: The aim of this study was to compare the pharmacokinetics and safety between two vinorelbine formulations [a new oil-in-water emulsion formulation (ANX) versus a previously marketed solution formulation (Navelbine)] in Chinese patients with advanced non-small cell lung cancer (NSCLC). Method: This was a single-center, randomized, open-label study. Eligible patients aged 18–70 years who had histologically or cytologically confirmed NSCLC were enrolled. In cycle 1, the patients alternatively received the two formulations (30 mg/m2, given as a 10-min infusion) with a 7-day interval. Samples for pharmacokinetic analysis were taken during cycle 1. For all subsequent 21-day cycles (maximum four cycles), ANX was administered on days 1 and day 8. Bioequivalence analysis was performed on Cmax, AUClast, and AUCinf. The safety profiles and anti-tumor effects were also determined. Results: From March 2013 to January 2015, 24 patients were enrolled and 20 were eligible for pharmacokinetic evaluation. The 20 subjects in the pharmacokinetic analysis set had a median age of 61 years (range, 37–70 years), and 15 patients were male (75%). Mean vinorelbine Cmax values for ANX and Navelbine were 1,317.40 and 1,446.30 ng/mL, respectively. Corresponding AUClast values were 797.08 and 924.26 ng·h/mL, respectively. AUCinf values were 830.14 and 957.16 ng·h/mL, respectively. Treatment ratios of the geometric means were 90.00% (90% CI, 83.22–99.07%) for Cmax, 86.92% (90% CI, 80.91–93.37%) for AUClast, and 87.44% (90% CI, 82.08–93.16%) for AUCinf. These results met the required 80–125% bioequivalence criteria. The most frequently reported adverse events after vinorelbine administration were neutropenia, leucopenia, neutropenic fever, and constipation. Conclusion: At therapeutic dosage levels, pharmacokinetic behavior and safety profiles were similar for both formulations. Chinese National Registry Code: ChiCTR-IPR-15005856.

Cloud climatology from visual observations at São Paulo, Brazil

AbstractClouds remain as the main uncertainty source in climate studies. Specifically, over urban and other polluted regions, where their properties are subject to anthropic influence, more studies are needed. This study focuses on clouds at the southeast of Brazil, especially on the diurnal and annual cycles, trends of cloud amount and cloud occurrence in one of the biggest metropolitan areas of the world, the Metropolitan Area of São Paulo (MASP). For this purpose, 59 years of visual observations of cloud amount and type, made from surface at MASP, are analysed. In addition, trends of total cloud amount in the state of São Paulo, Brazil, are estimated using 30 years of total cloud amount, adding nine synoptic meteorological stations. To assess the reliability of the visual observations, annual‐average time series of cloud amount are compared with ones from the International Satellite Cloud Climatology Project (ISCCP) and solar irradiation reaching the surface. The results show that the diurnal cycle of total cloud amount at MASP is highly influenced by low clouds, especially stratiform clouds, which are the predominant cloud type. Moreover, the seasonality of the diurnal cycles was also analysed, with higher amplitude and late‐afternoon occurrence in spring–summer. In winter‐autumn, the maxima of cloud amount diurnal cycles tends to occur at early morning with lower amplitude. The low cloud amount at MASP has undergone an increase, especially in the last 30 years, evidenced when compared annual‐average time series of visual observations and solar irradiation. In contrast, a decrease of total cloud amount in the state of São Paulo, mainly since the beginning of 1990s, is observed in ISCCP and visual observations databases.

Unaided-eye Sunspot Observations in 1769 November: A Comparison of Graphical Records in the East and the West

Sunspots can be seen with the unaided eye when they are sufficiently large. Due to the known correlation between the occurrence of unaided-eye sunspot observations and the phase of the solar cycle, these observations frequently provide some insight into the level of solar activity in the past. In this context, we have identified a few unaided-eye sunspot observations in late 1769 in East Asia, analyzed their observational conditions, and compared them with contemporary telescopic sunspot observations. The East Asian records indicate that large sunspots were seen with the aid of a temporary coverage of cloud mist on 1769 November 18 and 20. The contemporary sunspot drawings by Christian Horrebow show extremely large sunspot groups near the disk centre for each occasion. These unaided-eye sunspot observations occurred immediately after the maximum of Solar Cycle 2 and provide a snapshot of the enhanced level of solar activity at that time.

Update on Galactic Cosmic Ray Integral Flux Measurements in Lunar Orbit With CRaTER

AbstractWe report updated measurements of the integral fluxes of energetic protons, helium ions, and heavier ions as measured by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER). CRaTER is a particle telescope that has been operating aboard the Lunar Reconnaissance Orbiter since 2009. In an earlier report, we presented the methodology used to extract linear energy transfer spectra and integral fluxes for particles with sufficient energies to fully penetrate the telescope. Results were presented for the time span from late 2009 to the end of calendar year 2014, a period that encompassed the rise of solar activity from deep solar minimum to the weak maximum of Cycle 24. Here, we update the results with data obtained from that point in time through the end of 2018, in the declining phase of Cycle 24. Fluxes obtained in the most recent data are approaching the peak levels observed in late 2009 and early 2010. The results can be used as input to models of solar modulation of galactic cosmic rays and are also relevant to human exploration of deep space.

Ionospheric effects of two solar flares in the maximum of solar cycle 23 and in the minimum of solar cycle 24

Using data from the GPS and GLONASS navigation satellite systems, we analyze the responses of the mid-latitude ionosphere to the extreme solar flares that occurred at the maximum of solar cycle 23 (October 28, 2003) and at the minimum of solar cycle 24 (September 6, 2017) during the same season at close solar zenith angles. To obtain the response, we use the rate of change of the total electronic content, which is practically independent of characteristics of equipment and is determined only by parameters of a propagation medium (the ionosphere in our case). The ionospheric response is shown to be almost independent of the total duration of the flare. In both cases, the duration of the main response at a level of 0.5 is about 1.5–2 min, whereas the total duration of the response is about 10 min and fairly independent of solar flare importance.

Ионосферные эффекты двух солнечных вспышек максимума 23-го и минимума 24-го циклов солнечной активности

Using data from the GPS and GLONASS navigation satellite systems, we analyze the responses of the mid-latitude ionosphere to the extreme solar flares that occurred at the maximum of solar cycle 23 (October 28, 2003) and at the minimum of solar cycle 24 (September 6, 2017) during the same season at close solar zenith angles. To obtain the response, we use the rate of change of the total electronic content, which is practically independent of characteristics of equipment and is determined only by parameters of a propagation medium (the ionosphere in our case). The ionospheric response is shown to be almost independent of the total duration of the flare. In both cases, the duration of the main response at a level of 0.5 is about 1.5–2 min, whereas the total duration of the response is about 10 min and fairly independent of solar flare importance.

Emissions From Smart Meters and Other Residential Radiofrequency Sources.

The advent of the Internet of things comes with a huge increase in wirelessly communicating devices in our environment. For example, smart energy-consumption meters are being widely deployed in residences from which they communicate their state using radiofrequency networks. Accurate characterization of the radiofrequency emissions from emerging residential wireless solutions is important to inform the public about the potential impact on their exposure to radiofrequency electromagnetic fields. A new measurement procedure to determine the exposure from residential radiofrequency devices is proposed by assessing the peak emitted fields at various distances and the proportion of time they transmit (duty cycle). Radiofrequency emissions from 55 residential devices were measured in 10 residences (Belgium and France) and compared to environmental levels, emissions from 41 mobile phones, and international standards. Overall, residential levels of radiofrequency electromagnetic field exposure are low. In addition to the continuous environmental exposure, wireless access points (due to frequent use) and especially mobile phones and other personal communication devices (due to their use close to the body) continue to represent the bulk of the radiofrequency electromagnetic field exposure in the smart home. However, some residential devices can significantly increase the exposure if their duty cycles are high enough (>10%), especially when held or used close to the body. Individual smart meters, on the other hand, will contribute only little in general, despite emissions of up to 20 V m at 50 cm, due to their low duty cycles (maximum 1%) and locations.

Astronomical forcing of terrestrial climate recorded in the Pleistocene of the western Tarim Basin, NW China

Astronomically forced variations of climate are well documented in lacustrine and marine settings. However, few studies have examined astronomical forced cycles within Quaternary fluvial-fan successions. To explore whether Milankovitch cyclicity might also be present in fluvial-fan successions, we carried out high-resolution gamma-ray (GR) from downhole logging, magnetic susceptibility (MS), Rb/Sr and total organic carbon (TOC) analysis of a core from an 800-m borehole (KT11) from the Kashgar region in the western Tarim Basin, China. Spectral analyses of the GR, MS and Rb/Sr data reveal cycles with ~70 m, ~30 m and ~14 m wavelengths. These pertain to relative variations in grain size. Electron spin resonance (ESR) dating and magnetostratigraphy imply that the cored interval spans the past 1.1 Myr. This age-span constraint, coupled with the comparison of the ratios of these cycle wavelengths to expected ratios of Milankovitch frequencies, suggests that these cycles represent ~100-kyr short-eccentricity, ~40-kyr obliquity and ~20-kyr precession frequencies, respectively. We constructed an astronomical time scale (ATS) spanning the past 1.13 Myr using the ~100-kyr short-eccentricity period. The average accumulation rate is about 70 cm/kyr for this 800-m core succession, and the evolutive spectrum emphasizes that long-term sedimentation rates were stable. We also applied correlation coefficient (COCO) analysis to identify the astronomical forcing. Thus, we conclude that orbitally forced climate change was the main driver of stratigraphic alternations between sand- and clay-rich intervals in the Kashgar region. During maxima of the 100-kyr short-eccentricity cycles, which correspond to interglacial intervals, more chemical weathering and increased seasonal runoff delivered a larger amount of relatively coarser-grained sediments to the fluvial fan in the Kashgar region, and vice versa. The Mid-Pleistocene Transition (MPT) at ca. 0.9 to 0.65 Ma is also well recorded in our GR and Rb/Sr data, and is characterized by a shift in dominant cycle period from 41 kyr obliquity to 100 kyr eccentricity. After 0.65 Ma, the average TOC content decreases whilst Rb/Sr values increase, which suggests that there was an increase in regional aridity of the Kashgar region in the western Tarim Basin following the MPT. This regional change is synchronous with the trend toward aridification observed throughout central Asia.

White-light polar jets on rising phase of solar cycle 24

We studied coronal white-light jets in the polar regions of solar corona in 2009–2014. Jets were tracked on data producing by coronographs COR2/STEREO with the 2.5–16 solar radii field of view. We also considered their characteristics on solar cycle progress: jet occurrence rate of jets per year above the northern and southern poles, angular distributions and measured apparent velocities. The jet mean occurrence rate per year is 234 registered events. It is defined that both occurrence rate per year and the mean apparent velocities are increased to solar cycle maximum. This changes were shown to be different for the north and south polar regions and to depend on polar magnetic fields. The mean apparent velocities are increased by 1.7 times for north pole (from 134 ± 66 km/s to 229 ± 59 km/s) and by 2.4 times for south pole (from 101 ± 37 km/s to 243 ± 79 km/s). Most of the jets with velocities > 450 km/s was registered at the solar cycle maximum.

Multifractal Analysis of Heliospheric Magnetic Field Fluctuations Observed by Ulysses

Abstract We present the multifractal study of the intermittency of the magnetic field turbulence in the fast and slow solar wind beyond the ecliptic plane during two solar minima (1997–1998, 2007–2008) and solar maximum (1999–2001). More precisely, we consider 126 time intervals of Ulysses magnetic field measurements, obtain the multifractal spectra, and examine the degree of multifractality as the measure of intermittency in the MHD range of scales, for a wide range of heliocentric distances and heliolatitudes. The results show a slow decrease of intermittency with the radial distance, which is more significant for the fast than for the slow solar wind. Analysis of Alfvénic and compressive fluctuations confirms the decrease of intermittency with distance and latitude. This radial dependence of multifractality/intermittency may be explained by a slower evolution of turbulence beyond the ecliptic plane and by the reduced efficiency of intermittency drivers with the distance from the Sun. Additionally, our analysis shows that the greatest differences between magnetic field components are revealed close to the Sun, where intermittency is the strongest. Moreover, we observe that the slow solar wind from the maximum of the solar cycle 23 exhibits in general, a lower level of multifractality (intermittency) than fast solar wind, which can be related to the idea of a new type of Alfvénic slow solar wind.

North–South Asymmetry in Solar Activity and Solar Cycle Prediction, IV: Prediction for Lengths of Upcoming Solar Cycles

We analyzed the daily sunspot-group data reported by the Greenwich Photoheliographic Results (GPR) during the period 1874 – 1976 and Debrecen Photoheliographic Data (DPD) during the period 1977 – 2017 and studied North–South asymmetry in the maxima and minima of the Solar Cycles 12 – 24. We derived the time series of the 13-month smoothed monthly mean corrected whole-spot areas of the sunspot groups in the Sun’s whole sphere (WSGA), northern hemisphere (NSGA), and southern hemisphere (SSGA). From these smoothed time series we obtained the values of the maxima and minima, and the corresponding epochs, of the WSGA, NSGA, and SSGA Cycles 12 – 24. We find that there exists a 44 – 66 years periodicity in the North–South asymmetry of the minimum. A long periodicity (130 – 140 years) may exist in the asymmetry of the maximum. A statistically significant correlation exists between the maximum of SSGA Cycle $n$ and the rise time of WSGA Cycle $n+2$ . A reasonably significant correlation also exists between the maximum of WSGA Cycle $n$ and the decline time of WSGA Cycle $n+2$ . These relations suggest that the solar dynamo carries memory over at least three solar cycles. Using these relations we obtained the values $11.7\pm 0.15~\text{years}$ , $11.2\pm 0.2~\text{years}$ , and $11.45\pm 0.3~\text{years}$ for the lengths of WSGA Cycles 24, 25, and 26, respectively, and hence, July 2020, October 2031, and March 2043 for the minimum epochs (start dates) of WSGA Cycles 25, 26, and 27, respectively. We also obtained May 2025 and March 2036 for the maximum epochs of WSGA Cycles 25 and 26, respectively. It seems during the late Maunder Minimum sunspot activity was absent around the epochs of the maxima of the NSGA-cycles and the minima of the SSGA-cycles, and some activity was present at the epochs of the maxima of some SSGA-cycles and the minima of some NSGA-cycles.

Prediction of maximum amplitude of solar cycle 25 using machine learning

Prediction of maximum amplitude of Solar Cycle 25 is obtained by using four different machine learning regression methods, i.e. Linear Regression (LR), Random Forest (RF), Radial Basis Function (RBF) and Support Vector Machine (SVM). Monthly mean sunspot number data during the 1856-June 2018 (solar cycles 10-24) from the World Data Center SILSO, Royal Observatory of Belgium, Brussels are used as machine learning inputs. According to LR, RF, RBF and SVM, the maximum of Solar Cycle 25 is predicted to occur in September 2023 (sunspot number of 159.4 ± 22.3), in December 2024 (sunspot number of 110.2 ± 12.8), in December 2024 (sunspot number of 95.5 ± 21.9) and in July 2024 (sunspot number of 93.7 ± 23.2), respectively. The prediction using LR method suggested that Solar Cycle 25 maximum will be slightly higher than the current cycle, while RBF and SVM suggested much lower cycles. RF prediction suggested a lower maximum with well-constructed double-peak. It was also found that the Solar Cycle 25 is predicted to begin in the late 2019 or early 2020 according to all four methods.

Long-Term Trends in Forbush Decrease Activity over the Last Six Solar Cycles

Forbush decrease (FD) parameters (magnitude, rate of decrease, anisotropy, and duration of the main phase) are compared for solar cycles 19–24 and in the maxima of cycles 23 and 24 and the minimum between them. The Forbush Effects and Interplanetary Disturbances database created and maintained at IZMIRAN allows statistical means to be used for data analysis. The results obtained in this work show that the relation between FDs and solar cyclicity is observed for all FD parameters; most FDs in the maximum of cycle 23 were caused by interplanetary disturbances associated with coronal mass ejections, while most of FDs in the minimum between cycles 23 and 24 were caused by high-speed streams from coronal holes.

Mass loss via solar wind and coronal mass ejections during solar cycles 23 and 24

ABSTRACT Similar to the Sun, other stars shed mass and magnetic flux via ubiquitous quasi-steady wind and episodic stellar coronal mass ejections (CMEs). We investigate the mass loss rate via solar wind and CMEs as a function of solar magnetic variability represented in terms of sunspot number and solar X-ray background luminosity. We estimate the contribution of CMEs to the total solar wind mass flux in the ecliptic and beyond, and its variation over different phases of the solar activity cycles. The study exploits the number of sunspots observed, coronagraphic observations of CMEs near the Sun by SOHO/LASCO, in situ observations of the solar wind at 1 AU by WIND, and GOES X-ray flux during solar cycles 23 and 24. We note that the X-ray background luminosity, occurrence rate of CMEs and ICMEs, solar wind mass flux, and associated mass loss rates from the Sun do not decrease as strongly as the sunspot number from the maximum of solar cycle 23 to the next maximum. Our study confirms a true physical increase in CME activity relative to the sunspot number in cycle 24. We show that the CME occurrence rate and associated mass loss rate can be better predicted by X-ray background luminosity than the sunspot number. The solar wind mass loss rate which is an order of magnitude more than the CME mass loss rate shows no obvious dependency on cyclic variation in sunspot number and solar X-ray background luminosity. These results have implications for the study of solar-type stars.

Evaluation of CESM1 (WACCM) free-running and specified dynamics atmospheric composition simulations using global multispecies satellite data records

Evaluation of CESM1 (WACCM) free-running and specified dynamics atmospheric composition simulations using global multispecies satellite data records