Maximum Of Cycle Research Articles

Status of NeQuick G After the Solar Maximum of Cycle 24

AbstractThe solar cycle 24 will not be registered as the most intense of the last cycles. In fact, its intensity is roughly half of the previous cycle and the ionospheric effects experienced in this cycle have been far milder than originally expected, despite having several major ionospheric storms in this period, as the so‐called St. Patrick's Day's ionospheric storm. On the other hand, in this same period of time, the Galileo system has started the deployment phase and it started the In‐Orbit‐Validation campaign on 2013 with the first four full operational satellites, following the launch of a number of additional satellites allowing the declaration of Initial Services in December 2016 and targeting the Full Operational Capability by 2020. Thus, during this period of time, Galileo has been broadcasting the 3 Az coefficients needed to use the NeQuick G for correcting the ionospheric delay for single‐frequency users. In this work, the full analysis of the performance of the NeQuick G for the last solar cycle will be presented along with the detailed analysis of some of the most relevant ionospheric storms occurred during the very same period. In general, the NeQuick G presents around 50 cm better root mean square than the Global Positioning System broadcast model for all the period of study. As an internal measure of the goodness of the NeQuick G, the percentage of slant total electron content inside of target Galileo specification will also be analyzed.

Update on the Worsening Particle Radiation Environment Observed by CRaTER and Implications for Future Human Deep‐Space Exploration

AbstractOver the last decade, the solar wind has exhibited low densities and magnetic field strengths, representing anomalous states that have never been observed during the space age. As discussed by Schwadron, Blake, et al. (2014, https://doi.org/10.1002/2014SW001084), the cycle 23–24 solar activity led to the longest solar minimum in more than 80 years and continued into the “mini” solar maximum of cycle 24. During this weak activity, we observed galactic cosmic ray fluxes that exceeded theERobserved small solar energetic particle events. Here we provide an update to the Schwadron, Blake, et al. (2014, https://doi.org/10.1002/2014SW001084) observations from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter. The Schwadron, Blake, et al. (2014, https://doi.org/10.1002/2014SW001084) study examined the evolution of the interplanetary magnetic field and utilized a previously published study by Goelzer et al. (2013, https://doi.org/10.1002/2013JA019404) projecting out the interplanetary magnetic field strength based on the evolution of sunspots as a proxy for the rate that the Sun releases coronal mass ejections. This led to a projection of dose rates from galactic cosmic rays on the lunar surface, which suggested a ∼20% increase of dose rates from one solar minimum to the next and indicated that the radiation environment in space may be a worsening factor important for consideration in future planning of human space exploration. We compare the predictions of Schwadron, Blake, et al. (2014, https://doi.org/10.1002/2014SW001084) with the actual dose rates observed by CRaTER in the last 4 years. The observed dose rates exceed the predictions by ∼10%, showing that the radiation environment is worsening more rapidly than previously estimated. Much of this increase is attributable to relatively low‐energy ions, which can be effectively shielded. Despite the continued paucity of solar activity, one of the hardest solar events in almost a decade occurred in September 2017 after more than a year of all‐clear periods. These particle radiation conditions present important issues that must be carefully studied and accounted for in the planning and design of future missions (to the Moon, Mars, asteroids, and beyond).

Solar cycle variations in mesospheric carbon monoxide

As an extension of Lee et al. (2013), solar cycle variation of carbon monoxide (CO) is analyzed with MLS observation, which covers more than thirteen years (2004–2017) including maximum of solar cycle 24. Being produced primarily by the carbon dioxide (CO2) photolysis in the lower thermosphere, the variations of the mesospheric CO concentration are largely driven by the solar cycle modulated ultraviolet (UV) variation. This solar signal extends down to the lower altitudes by the dynamical descent in the winter polar vortex, showing a time lag that is consistent with the average descent velocity. To characterize a global distribution of the solar impact, MLS CO is correlated with the SORCE measured total solar irradiance (TSI) and UV. As high as 0.8 in most of the polar mesosphere, the linear correlation coefficients between CO and UV/TSI are more robust than those found in the previous work. The photochemical contribution explains most (68%) of the total variance of CO while the dynamical contribution accounts for 21% of the total variance at upper mesosphere. The photochemistry driven CO anomaly signal is extended in the tropics by vertical mixing. The solar cycle signal in CO is further examined with the Whole Atmosphere Community Climate Model (WACCM) 3.5 simulation by implementing two different modeled Spectral Solar Irradiances (SSIs): SRPM 2012 and NRLSSI. The model simulations underestimate the mean CO amount and solar cycle variations of CO, by a factor of 3, compared to those obtained from MLS observation. Different inputs of the solar spectrum have small impacts on CO variation.

Long-term variations in solar activity and planetary configurations

AbstractWe have analyzed the data on yearly mean international sunspot number (RZ) during the period 1610 – 2015 and orbital positions (ecliptic longitudes) of the giant planets in each 10-day interval during the period 1600 – 2099. We determined mean absolute difference ($\overline{\psi _D}$) of the orbital positions of the giant planets in each interval. We find that there exits a good correlation between cycle amplitude (RM, i.e. the maximum value of RZ) and the value of $\overline{\psi _D}$ at cycle maximum, suggesting that on longer time scales low/high solar activity associated with less/large spread in orbital positions of the giant planets (i.e. with a low/high value of $\overline{\psi _D}$).

Long-term variations in meridional motion of sunspot groups: comparison of DPD and SOON data

AbstractWe have analyzed the Debrecen Photoheliographic Data (DPD) and the Solar Optical Observing Network (SOON) sunspot group data during the period 1977 – 2015 and find that during the maximum of solar cycle 23 there is a large difference in the mean meridional motion of sunspot groups determined from DPD and SOON data.

Properties of Coronal Holes in Solar Cycle 21-23 using McIntosh archive

AbstractWe study the properties of coronal holes during solar cycle 21-23 from the McIntosh archive. In the spatial distribution of coronal hole area we find that there is a sharp increase in coronal hole area at high latitude in agreement with expected open flux configuration there. In overall spatiotemporal distribution of coronal hole centroids, we find the dominance of high latitude coronal holes except for the maximum of the solar cycle, when coronal holes mostly appear in low latitudes. This is in agreement with the expected solar cycle evolution of surface magnetic flux.

The new Sunspot Number: continuing upgrades and possible impacts

AbstractThe first-ever revision of the sunspot number was released in 2015 by the World Data Center (WDC) SILSO. We describe the main diagnosed corrections to the sunspot and group number series, and also review newly published alternate reconstructions. We show the convergence of the determinations of the 1947 scale jump in the sunspot number around a value of 1.18 for cycle maxima. We also assess new proposed reconstructions of the group number, like the “backbone” and “active-day fraction” methods. No agreement was reached yet for this series.We highlight the main impacts of those recent upgrades on different scientific applications. As this first revision also marks a transition towards a dynamical series open to future improvements, we finally introduce the ongoing collaborative process for preparing the next upgrade (Version 3). From now on, our scientific users must be prepared for a flexible integration of an evolving sunspot number series.

Study the Influence of Solar Activity on the Ionospheric Electron, Ion and Neutral Particle Temperatures over Iraqi Region Using Ionospheric Models

The influence of solar activity on the predicted ionospheric temperature parameters (electron Te, Ion Ti and neutral particle Tn) have been investigated over ionospheric Iraqi region by data generated using International Reference Ionosphere (IRI) and Madrigal models, the models result have been compared during the minimum and the maximum of solar cycle 24 for the years 2009 and 2016 respectively and for an altitudes ranged from 200-1000 km. The region under consideration spans over (latitude 29.1-37.2oN; longitude 38.9-47.7oE) within Iraq territory, the purpose of this paper is to determine the affection of the solar activity represented by the (sunspot number and solar flux) on the annual behaviors of the ionospheric temperature parameters (Te, Ti and Tn).The results of the conducted study showed that the solar activity of the adopted years exhibited a weak affection on the ionospheric temperature parameters, where (Tn) was the highly affected parameter and (Te) was the poorly affected one. Also, the ionospheric temperature parameters were increased with altitudes increment except for (Tn) which was increased with altitudes till 400 km, than it reaches its maximum value and keep constant.

An improved prediction of sunspot maximum by Vondrak smoothing method

Studies of solar activity characteristics and prediction are gaining more attention. Using the 13‐month smoothed value of monthly sunspot numbers, we studied correlations between the rising rate of sunspot numbers of the first 24 months of the solar cycle (SC) and the coming cycle maximum; published forecasting results demonstrated that the maximum value was 139.2 ± 18.8 for the 23rd SC, while the observed value was 120.8 and the error was about 15.2%. The present paper introduces our improved forecasting methods. The Vondrak smoothing method is used to deal with the monthly sunspot numbers. The relationships between the rise rate of earlier months of sunspot numbers of Vondrak smoothed sequence and the coming maximum value in each SC are studied. The results show that the rising rate of sunspot numbers are highly related with the coming maximum values, and simulated prediction of maximum for 22 ∼ 24 cycles show that, using the 24‐month rise rate of three SCs, the maximum forecasting error is about 8.6%. The differences between prediction and observation of ascending time are within ±10%. The new prediction method can shift at least 6 months ahead in comparison with the common method using the 13‐month smoothed value, that is, the amplitude and epoch of solar maximum in the SC can be predicted about 2 years after the solar minimum.

Examination of the relationship between solar activity and earth seismicity during the weak solar cycle 23

The relations between sunspot number, sunspot areas, and solar 10.7 cm radio flux, solar proton events and earthquakes of magnitude M ≥ 5 and M ≥ 8 during the interval from 1996 to 2008 of the solar cycle 23 have been analyzed in this work. We have found that there is a direct relation between solar activity and Earth seismic activity for M ≥ 5 and M ≥ 8, near the maximum of the solar cycle 23, and an inverse relation between them at the descending phase of the cycle.

ЗМІНА ЗНАКА ПОЛЯРНОГО МАГНІТНОГО ПОЛЯ СОНЦЯ У 24-МУ ЦИКЛІ АКТИВНОСТІ

The connection of solar activity expressed by international sunspot (Wolf) numbers in the northern and southern hemispheres of the Sun in the current 24th cycle with the time of polar magnetic field reversal in the corresponding hemisphere is investigated. It was obtained that: – The change of the sign of the polar magnetic field at the southern pole occurs almost a year later than in the north. – The polar magnetic field reversals do not coincide with the maximum activity in each of the hemispheres. In the northern hemisphere, the activity maximum was observed almost one and a half years earlier than the first polar field reversal and two and a half years earlier than the third or final one. In the southern hemisphere, the activity maximum was observed almost a year earlier from the change of the field sign at the pole. – The maximum of the 24th cycle almost coincides with the time of the change of the sign of the magnetic field at the northern pole. – In each of the hemispheres, the change in the sign of a magnetic field in the polar zone above 55 degrees occurred almost two years earlier than the final polar field reversal. The second and third changes of the sign of the total field in the polar zone above 55 degrees occurred shortly after the corresponding polar field reversal. – In the northern hemisphere, the polar field reversals occur at the time of maximum values of the inclination of the heliospheric current sheet, and in the south – almost two years after the maximum inclination of the HCS. – Three-fold polar field reversal at the northern pole occurs at small values of polar magnetic field measured at the Wilcox Solar Observatory while single reversal at the southern pole occurs at sufficiently high value of the corresponding measured polar field.

Geomagnetic storm forecasting service StormFocus: 5 years online

Forecasting geomagnetic storms is highly important for many space weather applications. In this study, we review performance of the geomagnetic storm forecasting service StormFocus during 2011–2016. The service was implemented in 2011 at SpaceWeather.Ru and predicts the expected strength of geomagnetic storms as measured by Dst index several hours ahead. The forecast is based on L1 solar wind and IMF measurements and is updated every hour. The solar maximum of cycle 24 is weak, so most of the statistics are on rather moderate storms. We verify quality of selection criteria, as well as reliability of real-time input data in comparison with the final values, available in archives. In real-time operation 87% of storms were correctly predicted while the reanalysis running on final OMNI data predicts successfully 97% of storms. Thus the main reasons for prediction errors are discrepancies between real-time and final data (Dst, solar wind and IMF) due to processing errors, specifics of datasets.

Evolution of cyclic mixmaster universes with noncomoving radiation

We study a model of a cyclic, spatially homogeneous, anisotropic 'mixmaster' universe of Bianchi type IX, containing a radiation field with non-comoving ('tilted' with respect to the tetrad frame of reference) velocities and vorticity. We employ a combination of numerical and approximate analytic methods to investigate the consequences of the second law of thermodynamics on the evolution. We model a smooth cycle-to-cycle evolution of the mixmaster universe, bouncing at a finite minimum, by the device of adding a comoving 'ghost' field with negative energy density. In the absence of a cosmological constant, an increase in entropy, injected at the start of each cycle, causes an increase in the volume maxima, increasing approach to flatness, falling velocities and vorticities, and growing anisotropy at the expansion maxima of successive cycles. We find that the velocities oscillate rapidly as they evolve and change logarithmically in time relative to the expansion volume. When the conservation of momentum and angular momentum constraints are imposed, the spatial components of these velocities fall to smaller values when the entropy density increases, and vice versa. Isotropisation is found to occur when a positive cosmological constant is added because the sequence of oscillations ends and the dynamics expand forever, evolving towards a quasi de Sitter asymptote with constant velocity amplitudes. The case of a single cycle of evolution with a negative cosmological constant added is also studied.

Midlatitude ionospheric F2-layer response to eruptive solar events-caused geomagnetic disturbances over Hungary during the maximum of the solar cycle 24: A case study

In our study we analyze and compare the response and behavior of the ionospheric F2 and of the sporadic E-layer during three strong (i.e., Dst < −100nT) individual geomagnetic storms from years 2012, 2013 and 2015, winter time period. The data was provided by the state-of the art digital ionosonde of the Széchenyi István Geophysical Observatory located at midlatitude, Nagycenk, Hungary (IAGA code: NCK, geomagnetic latitude: 46.17° geomagnetic longitude: 98.85°). The local time of the sudden commencement (SC) was used to characterize the type of the ionospheric storm (after Mendillo and Narvaez, 2010). This way two regular positive phase (RPP) ionospheric storms and one no-positive phase (NPP) storm have been analyzed. In all three cases a significant increase in electron density of the foF2 layer can be observed at dawn/early morning (around 6:00 UT, 07:00 LT). Also we can observe the fade-out of the ionospheric layers at night during the geomagnetically disturbed time periods. Our results suggest that the fade-out effect is not connected to the occurrence of the sporadic E-layers.

Forecasting the sunspot maximum through an analysis of geomagnetic activity

In the present work we show that it is possible to predict the maximum sunspot number for a particular solar cycle from the maximum value of the solar dipole magnetic field of the previous cycle. Based on the measured dipole field maximum, we determine the geomagnetic activity in the upcoming solar minimum during the intervals when the Earth is not exposed to CME and HSS influences. The physical meaning of the relationship between the geomagnetic activity in the solar activity minimum and the maximum value of the solar dipole magnetic field is that the basic factor determining the geomagnetic activity during the minimum is not the heliospheric current sheet thickness but the physical parameters of the slow solar wind in this period.Then, based on the established relationship between the average geomagnetic activity at the specified minimum and the next solar maximum, we can predict the sunspot maximum of the next solar cycle.

Precursors of an upcoming solar cycle at high latitudes from coronal green line data

After reviewing potential early indicators of an upcoming solar cycle at high latitudes, we focus attention on the rush–to-the-poles (RTTP) phenomenon in coronal green line emission. Considering various correlations between properties of the RTTP with the upcoming solar cycle we find a correlation between the rate of the RTTP and the time delay until the maximum of the next solar cycle. On the basis of this correlation and the known internal regularities of the sunspot number series we predict that, following a minimum in 2019, cycle 25 will peak in late 2024 at an amplitude of about 130 (in terms of smoothed monthly revised sunspot numbers). This slightly exceeds the amplitude of cycle 24 but it would still make cycle 25 a fairly weak cycle.

Galactic cosmic ray spectral index: the case of Forbush decreases of March 2012

During the burst of solar activity in March 2012, close to the maximum of solar cycle 24, a number of X-class and M-class flares and halo CMEs with velocity up to $2684~\mbox{km}/\mbox{s}$ were recorded. During a relatively short period (7–21 March 2012) two Forbush decreases were registered in the ground-level neutron monitor data. In this work, after a short description of the solar and geomagnetic background of these Forbush decreases, we deduce the cosmic ray density and anisotropy variations based on the daily cosmic ray data of the neutron monitor network ( http://www.nmdb.eu ; http://cosray.phys.uoa.gr ). Applying to our data two different coupling functions methods, the spectral index of these Forbush decreases was calculated following the technique of Wawrzynczak and Alania (Adv. Space Res. 45:622–631, 2010). We pointed out that the estimated values of the spectral index $\gamma$ of these events are almost similar for both cases following the fluctuation of the Forbush decrease. The study and the calculation of the cosmic ray spectrum during such cosmic ray events are very important for Space Weather applications.

Latitude and Power Characteristics of Solar Activity at the End of the Maunder Minimum

Two important sources of information about sunspots in the Maunder minimum are the Sporer catalog (Sporer, 1889) and observations of the Paris observatory (Ribes and Nesme-Ribes, 1993), which cover in total the last quarter of the 17th and the first two decades of the 18th century. These data, in particular, contain information about sunspot latitudes. As we showed in (Ivanov et al., 2011; Ivanov and Miletsky, 2016), dispersions of sunspot latitude distributions are tightly related to sunspot indices, and we can estimate the level of solar activity in the past using a method which is not based on direct calculation of sunspots and weakly affected by loss of observational data. The latitude distributions of sunspots in the time of transition from the Maunder minimum to the regular regime of solar activity proved to be wide enough. It gives evidences in favor of, first, not very low cycle no.–3 (1712–1723) with the Wolf number in maximum W = 100 ± 50, and, second, nonzero activity in the maximum of cycle no.–4 (1700–1711) W = 60 ± 45. Therefore, the latitude distributions in the end of the Maunder minimum are in better agreement with the traditional Wolf numbers and new revisited indices of activity SN and GN (Clette et al., 2014; Svalgaard and Schatten, 2016) than with the GSN (Hoyt and Schatten, 1998); the latter provide much lower level of activity in this epoch.

The Waldmeier Effect for Two Sunspot Populations

This paper continues our studies in which we showed that sunspot groups form two populations differing by physical properties—populations of small and large groups. The known Waldmeier effect has been individually considered for these populations. Two formulations of this effect were verified: the classical one, which connects the solar activity index at the maximum of the 11-year cycle with the length of the ascending phase of a cycle, and the modified one, connecting the index value at the cycle maximum with the highest rate of the index change along the ascending branch. We used the data from the Greenwich Observatory and the Kislovodsk Mountain Astronomical Station for the solar activity cycles from 12 to 24 to construct the series of indices for the areas and the numbers of sunspot groups. It has been shown that the Waldmeier effect works more strictly for the population of large sunspot groups than for that of small groups. The results of this analysis may find an application in the dynamo theory.

Climatology and modeling of ionospheric scintillations and irregularity zonal drifts at the equatorial anomaly crest region

Abstract. In this study the climatology of ionospheric scintillations and the zonal drift velocities of scintillation-producing irregularities are depicted for a station located under the southern crest of the equatorial ionization anomaly. Then, the α − μ ionospheric fading model is used for the first- and second-order statistical characterization of amplitude scintillations. In the statistical analyzes, data are used from single-frequency GPS receivers acquired during ∼ 17 years (September 1997–November 2014) at Cachoeira Paulista (22.4° S; 45.0° W), Brazil. The results reveal that the nocturnal occurrence of scintillations follows the seasonal distribution of plasma bubble irregularities observed in the longitudinal sector of eastern South America. In addition to the solar cycle dependence, the results suggest that the occurrence climatology of scintillations is also modulated by the secular variation in the dip latitude of Cachoeira Paulista, since the maximum occurrence of scintillations during the peak of solar cycle 24 was ∼ 20 % lower than that observed during the maximum of solar cycle 23. The dynamics of the irregularities throughout a solar cycle, as investigated from the estimates of the mean zonal drift velocities, presented a good correlation with the EUV and F10.7 cm solar fluxes. Meanwhile, the seasonal behavior showed that the magnitude of the zonal drift velocities is larger during the December solstice months than during the equinoxes. In terms of modeling, the results for the α − μ distribution fit quite well with the experimental data and with the temporal characteristics of fading events independently of the solar activity level.