Solar Activity Intensity Research Articles

The Response of Stratospheric Gravity Waves to the 11-Year Solar Cycle

Atmospheric gravity waves are one of the important dynamic processes in near space and are widely present in the atmosphere. They play a crucial role in the transfer of energy and momentum between different regions of the atmosphere. The Sun, as the ultimate source of gravity wave energy, significantly influences the intensity of gravity wave disturbances through its activity variations. This paper utilizes data from the Global Navigation Satellite System Occultation Sounder (GNOS) onboard the Fengyun-3C (FY-3C) satellite to invert global stratospheric gravity wave disturbances. It provides the global stratospheric gravity wave distribution from 2015 to 2023, nearly covering one solar activity cycle, and focuses on analyzing the response of gravity waves at different latitudes, altitudes, and wavelengths to the solar activity cycle. We found that short-wavelength gravity waves respond more noticeably to solar activity compared to long-wavelength gravity waves. Through analyzing the intensity of stratospheric gravity wave disturbances across different latitude bands, we found that in high-latitude regions, stratospheric gravity wave disturbances are most sensitive and respond most quickly to variations in solar activity. Furthermore, the Southern Hemisphere exhibits a stronger response to the current year’s solar activity changes compared to the Northern Hemisphere. In the mid-latitude and equatorial regions, the response to changes in solar activity intensity is delayed. The correlation gradually strengthens with this lag, reaching a very strong level after a 2-year lag. Additionally, the correlation between the Southern Hemisphere and solar activity is generally higher than that of the Northern Hemisphere.

Latitudinal Characteristics of Nighttime Electron Temperature in the Topside Ionosphere and Its Dependence on Solar and Geomagnetic Activities

This study investigates the latitudinal characteristics of the nighttime electron temperature, as observed by the Defense Meteorological Satellite Program F16 satellite, and its dependence on solar and geomagnetic activities between 2013 and 2022 in the topside ionosphere, only for the winter hemispheres. The electron temperature in both hemispheres exhibited a low-temperature zone at the equator and a double high-temperature zone at the sub-auroral and auroral latitudes along the magnetic latitude. In addition, we further studied the temperature crest/trough positions in the temperature zone at different latitudes. As the solar activity intensity decreased (increased), the temperature trough position at the equator shifted from the Southern (Northern) to the Northern (Southern) Hemisphere, and the temperature double-crest positions at the sub-auroral and auroral latitudes gradually approached (moved away from) each other. Furthermore, during the geomagnetic disturbance time, the temperature double-crest positions both moved toward lower latitudes, but the temperature trough position was not sensitive to geomagnetic activity. Our analysis demonstrates that the values and correlations of the electron temperature and density varied in different temperature characteristic zones (the temperature crest/trough positions ±2°), possibly due to the different energy control factors of the electrons at different latitudes. This may also indirectly indicate the energy coupling process between the topside ionosphere and different regions at different latitudes.

Solar activity influence on the temporal and spatial variations of the Arctic and Antarctic ionosphere

Based on Total Electron Content (TEC) data in polar areas derived from Global Ionospheric Maps (GIMs) and observations of single GPS stations from 2000 to 2020, combined with solar activity parameters F10.7, the influence of solar activity on the polar ionosphere is studied. Firstly, the spatiotemporal variation characteristics of the Arctic and Antarctic ionosphere TEC are analyzed in different solar activity intensities. Secondly, the correlations between polar TEC and F10.7 are studied in different solar activity stages. Thirdly, the variations of TEC during the polar day and polar night in year of very low solar activity (2008) are analyzed. The results show the monthly average value of the polar ionospheric TEC reaches its maximum in May and June under the influence of solar activity. However, during the peak year of solar activity, the monthly average peak value of TEC may arrive early, reaching its maximum value in March or April. The dependence of polar TEC on the solar activity varies at different periods of solar activity (rising or declining period). The correlation between polar TEC and F10.7 is higher in the declining period of solar activity than in the rising period of solar activity. During the rising period of solar activity, the TEC at different times under the same solar activity intensity is also different, and the low value of TEC has a lower correlation with solar activity. The ionosphere at the Arctic and Antarctic is quiet during polar night in 2008, and ionization patch appears in the Arctic. During the polar days, the ionospheric peaks of the Arctic and Antarctic occur in the areas with a high solar irradiation altitude angle. However, the ionospheric peak region in the Antarctic area from 10:00 UT to 20:00 UT does not follow this rule.

Analysis of spatiotemporal characteristics of internal coincidence accuracy in global TEC grid data

Evaluating the coincidence accuracy and time-varying characteristics of global total electron content (TEC) grid data can contribute to the improvement of the performance of global ionosphere maps (GIMs) and provide effective data support and theoretical verification for GIMs model update. This paper applies the global TEC grid data and GPS single-station ionospheric TEC data published by IGS from 1999 to 2020, as well as the F10.7 and SSN data series provided by the World Sunspot Index Data Center in Belgium. Using correlation, time series, and contour chart analyses, the correlation between TEC RMS and F10.7, SSN, and the accuracy-compliant space–time variation characteristics in the global TEC grid data are studied and analyzed. The results show the accuracy of the global TEC grid data is highly correlated with the solar activity intensity. The mean values of the correlation coefficients R between TEC RMS and F10.7, SSN are 0.755 and 0.707, respectively. The internal coincidence accuracy of single station GPS-TEC and global grid TEC is better than 3 TECU and is closely related to the solar activity. Globally, TEC RMS in land and ocean areas have significant differences. In general, the accuracy of the northern hemisphere is significantly higher than that of the southern hemisphere, and the accuracy of land is higher than that of the ocean. Among them, the accuracy of Europe and North America is the highest, the precision of the Pacific region is obviously on the low side, and “double hump” phenomenon can be observed. The accuracy of the global TEC grid data is closely related to the number of stations and satellites. The accuracy of the TEC grid data is higher in areas where the number of stations is dense, or when there are more satellites.

Statistics of Low Frequency Cutoffs for Type III Radio Bursts Observed by Parker Solar Probe during Its Encounters 1–5

Abstract The low frequency cutoffs f lo and the observed plasma frequency f p of 176 type III radio bursts are investigated in this paper. These events are observed by the Parker Solar Probe when it is in the encounter phase from the first to the fifth orbit. The result shows that the distribution of cutoffs f lo is widely spread between 200 kHz and 1.6 MHz. While the plasma frequency f p at the spacecraft is between 50 and 250 kHz, which is almost all smaller than f lo . The result also shows that the maximum probability distribution of f lo (∼680 kHz) is remarkably higher than that observed by Ulysses and Wind (∼100 kHz) in previous research. Three possible reasons, i.e., solar activity intensity, event electing criteria, and radiation attenuation effect, are also preliminarily discussed.

Applicability of sunspot activity on the climatic conditions of Gilgit-Baltistan region using fractal dimension rescaling method

ABSTRACT The total solar irradiance fluctuates on the scale of 11 year cycle and is associated to sunspots, solar activity and climate. The sunspot number is an essential parameter for presenting the intensity of solar activity. The minimum and maximum values of sunspot number during each solar cycle represent a fractional variation in solar radiation energy. However, variability in ultraviolet solar irradiance seems to suggest a potential driving force for larger regional surface climate effects. It is to be explored the possible impacts of the sunspot activity on climate parameters, i.e., temperature and precipitation of Gilgit-Baltistan region. The segregated datasets of temperatures and precipitations of the region have been obtained for the period from 1954 to 2015. The corresponding sunspot cycles have been used are: 19, 20, 21, 22, and 23. The cycle 24 is incomplete and gives insignificant result. The climate datasets of both metrological stations have been partitioned for making cycle-wise comparison with the corresponding sunspot cycles by Fractal Rescaling method. The analysis was carried out under similarity 0.5 and 1.5 for the Hurst exponent and fractal dimension, respectively. The results obtained show that the inconstant solar irradiance due to the sunspot number variation at minima and maxima seem to have persistent effects on the regional temperatures and precipitations. Moreover, it is found that the sunspot cyclic activity is more strongly correlated with regional precipitations than the temperatures. This study indicates the need for more robust study of regional climate variability due to sunspot activity and the other solar indices that may be contributing to affect these climate parameters.

Empirical orthogonal function analysis and modeling of global ionospheric spherical harmonic coefficients

We developed a global empirical model for computing spherical harmonic (SH) coefficients based on the empirical orthogonal function (EOF) method and periodic functions by utilizing global ionospheric SH coefficients data provided by Center for Orbit Determination in Europe (CODE) during the years 2005–2016. Results show that the first four-order base functions and corresponding associated coefficients can represent 97.15% of the basic characteristics of the original data. The first four-order associated coefficients have noticeable periodic variations, and the correlation between these coefficients and the solar activity intensity is high. By fitting the associated coefficients with the periodic function that takes into account the influence of solar activity, it is possible to establish an EOF model to characterize the variations of the ionospheric SH coefficients with few model parameters and further calculate the global vertical total electron content (VTEC). Relative to the existing global VTEC EOF models, this EOF method can achieve high-accuracy modeling of global VTEC with a smaller number of model coefficients. By comparing the SH coefficients and the global VTEC between the EOF model and CODE, results demonstrate that the EOF model can achieve high accuracy and reliability under different solar activities. The difference between the EOF model and CODE is basically at the same level as that between the individual ionospheric analysis centers and CODE. In the extreme event of magnetic storms, the EOF model can also present higher accuracy than the international reference ionosphere (IRI) model.

NIGHTTIME TEC VARIATION ANALYSIS OF KLOBUCHAR MODEL BASED ON IGS DATA IN CHINA

Abstract. In order to further study the variation characteristics of the nighttime ionospheric accuracy of the Klobuchar model and the correlation between the nighttime ionospheric accuracy of the Klobuchar model and solar activity intensity. In this paper, a method for comparative analysis on solar activity intensity in the high, medium and low solar activity years has been proposed. The GIM provided by the IGS Center from 2008 to 2018 are treated as reference values to analyze the nighttime accuracy of the Klobuchar model for annual, seasonal, and monthly changes in high solar activity, medium solar activity and low solar activity. The results are: (1) The nighttime accuracy of the Klobuchar model is best in the medium solar activity, followed in the low solar activity and the worst in the high solar activity. (2) The Bias and RMS of the Klobuchar model at nighttime had obviously semi-annual and seasonal variations in high and medium solar activity. (3) The nighttime accuracy of the Klobuchar model did not vary with Bias and RMS changes at nighttime.

Independent temporal and spatial variation analysis of ionospheric TEC over Asia-Pacific area based on BDS GEO satellites

GPS has been widely used to monitor ionospheric total electron content (TEC) variations. However, GPS-derived TEC contains ionospheric horizontal gradient information due to the motion of GPS satellites. As a result, the temporal and spatial variation information is mixed. With the advent of the geostationary earth orbit (GEO) of the BeiDou navigation satellite system (BDS), observations from BDS GEO satellites provide a new opportunity for independent research on the temporal and spatial variations of the ionospheric TEC. Furthermore, the GEO satellite also enables continuous and long-term TEC monitoring. Due to its higher orbit, the BDS GEO-derived TEC also contains more plasmaspheric electron content. In this study, the temporal and spatial variation characteristics of the ionospheric TEC derived from the BDS GEO satellites over the Asia-Pacific area are investigated. The achievable TEC theoretical accuracy from the BDS GEO measurements is first deduced. The TEC time series at 26 BDS stations over the Asia-Pacific area is then analyzed. Results acquired from the vertical TEC (VTEC) observations in 2017 indicate obvious periodic variations and spatial variations with a semi-annual anomaly. Through an analysis of the VTEC series over a span of five years, it is revealed that the long-term TEC variations are quite dependent on the solar activity intensity in terms of the F10.7 index. Besides, the BDS GEO-derived VTEC variation trend is consistent with those acquired from the global ionospheric map (GIM) and the NeQuick model. However, significant biases exist at some stations due to uneven accuracy of the two global ionospheric models. The maximum RMS discrepancies reach 4.3 TECU and 9.9 TECU for the GIM and NeQuick, respectively.

Multiresolution Analysis of the Relationship of Solar Activity, Global Temperatures, and Global Warming

Sunspot number is an important parameter for presenting the intensity of solar activity. Based on the sunspot number series, which has been replaced by a new improved version since 2015, we confirm that the sunspot number has significant variations at 11-year and 112-year periods. The sunspot number has also increased from 1700 to 2016 with 0.08 annual increments on the basis of wavelet analysis and least-square fitting. We further confirm that global temperatures are remarkable in 22-year and 64-year cycles. The result of wavelet transform coherence (WTC) analysis suggests that solar activity has a positive lag effect on global temperatures in the period band of 22 years with a 3-year lag. However, the linearly increasing global temperature has hampered WTC analysis since 1960. Aiming to solve this problem, we apply wavelet decomposition and cross correlation to determine whether the aforementioned lag effect in the period band of 22 years has a 2-year lag rather than a 3-year lag. We find that the 22-year magnetic field solar cycle plays a greater role in global climate change than the 11-year sunspot cycle. In addition, we notice that the solar activity is not a representation of the driving force of the upward trend of global temperature after the industrial age. The Granger causality test results demonstrate that the phenomenon of the global warming is caused by excessive CO2 emissions.

Sensing the upper and lower levels of the atmosphere during the 2009 equinoxes using GPS measurements

<p>This short-term work characterized the upper and lower levels of the atmosphere through Global Positioning System (GPS) measurements. The observations were conducted during the 2009 equinoxes from two pairs of conjugate polar observing stations: Husafell, Iceland (HUSA) and Resolute in Nunavut, Canada (RESO) and their conjugate pairs at Scott Base (SBA) and Syowa (SYOG) in Antarctica, respectively. The total electron content (TEC), an indicator of the upper atmosphere, and the precipitable water vapor (PWV), which served as the lower atmospheric response, were retrieved and analyzed. The results reveal a good relationship between TEC and PWV at each station during the onset day of the equinoxes, whereas an asymmetrical response was observed in the beginning of and after the equinoxes. In addition, the conjugate pairs were only consistent during the autumnal equinox. Thus, the high correlation was observed following the seasonal pattern for the onset day, while strong and moderate correlations were found only for the vernal equinox in Antarctica and the Arctic, respectively. This relationship reflects the fact that the intensity of solar activity during the solar minimum incident on the lower atmosphere through the conjugate points is associated with the variation of the Sun’s seasonal cycle, whereas the TEC and PWV showed an opposite relationship.</p>

Viewing the “rush to the poles” through phase analysis

Abstract At mid and low heliographic latitudes, filament activity shifts equatorward starting from the beginning of the solar cycle. At high latitudes, it migrates poleward. Solar filaments exhibit the “rush to the poles” close to solar maximum, when the solar polar magnetic field reverses polarity. In order to better understand the behavior of the “rush to the poles,” we used cross-correlation analysis and wavelet transform methods for investigating the periodic characteristics and the phase relationship between two groups of the solar filaments at high latitudes observed during the period from 1919 March to 1989 December. The length of the solar cycle derived from the continuous wavelet transform is a function of latitude, but still shows a significant 11-yr cycle. The most significant periods of the solar filaments, respectively at higher latitudes than 50° and 60°, are 10.77 and 10.62 yr, using the wavelet transform method. From the cross-correlation analysis, the solar filaments at higher latitudes than 50° have a lead of six months with respect to those at higher latitudes than 60°. Different solar cycles exhibited different phase relationships between the two groups of solar filaments. The analysis of the cross-wavelet transform also indicates that the solar filaments at higher latitudes than 50° lead those at higher latitudes than 60° in the entire time interval. The relationship between the phase difference of the two groups of solar filaments and the intensity of solar activity is also discussed. What is more, the poleward shifting speeds are estimated.

Study of solar activity by measuring cosmic rays with a water Cherenkov detector

We report on an indirect study of solar activity by using the Forbush effect which consists on the anti-correlation between the intensity of solar activity and the intensity of secondary cosmic radiation detected at ground level at the Earth. We have used a cylindrical water Cherenkov detector to measure the rate of arrival of secondary cosmic rays in Morelia Mich., Mexico, at 1950 m.a.s.l. We describe the analysis required to unfold the effect of atmospheric pressure and the search for Forbush decreases in our data, the latter correspond to more than one year of continuous data collection.

A New Way that Planets Can Affect the Sun

As planets orbit the Sun, the Sun also has to move to keep the total momentum of the solar system constant. The Sun's small orbital motion plus its 25 day rotation about its axis combine to invigorate some solar instabilities. Occasional convection cells at the proper phase in their short life can be strengthened by factors of two or more. This local burst of extra kinetic energy eventually reaches the surface where it can increase the intensity of solar activity. It might explain some reports in the last century of how planetary positions correlate with solar activity. This is the first effect of planets that is large enough to cause a significant response on the Sun.

Dynamics of blood values in experimental geomagnetic deprivation (in vitro) reflects biotropic effects of natural physical factors during early human ontogeny

Heliogeophysical situation during prenatal development of humans is essential for blood rheology, hemostasis, and spectral and frequency parameters of the blood. The relationship between these parameters and natural physical factors is determined by the intensity of solar activity and geomagnetic induction during postnatal ontogeny. Analysis of changes in the functional relationship between hematological values and heliogeophysical factors under conditions of simulated hypogeomagnetic space included evaluation of possible consequences of distortions of the heliobiospheric relationships in large cities, particularly pronounced for cardiovascular patients.

Predictions of Intense Solar Activity Needed

Many of the sophisticated modeling efforts of the Sun-to-Earth system currently underway do not address some very important impacts of the Sun on terrestrial technologies. Thus, there is a serious need for more detailed models and improved predictions of intense solar activity. This gap in current capabilities of predicting the intensity of solar activity–especially the intensities of solar X-ray and radio bursts–was spectacularly illustrated in December 2006 during the passage of solar active region 0930 across the Sun. The solar radio burst at about 1900 UT on 6 December lasted for more than an hour, is reported to have been one of the largest (if not the largest) bursts ever recorded at gigahertz frequencies, and caused havoc for GPS measurements on Earth. Accompanying the solar burst was one of the largest increases in solar electron fluxes observed at the L1 ACE spacecraft in the past decade or more. If the active region at the time of the solar burst was more centered in the direction of the Earth, a coronal mass ejection with a resulting huge magnetic disturbance with resulting technology impacts might have been expected at Earth. As it was, the technologies largely affected were GPS receivers and other receiving systems such as radars oriented slightly towards the Sun (including possibly some cellular phone cell sites, a situation still under investigation by researchers). None of these effects are addressed by most current modeling of the Sun-Earth system. Just because the effects from this event were limited to certain technologies and did not generate a large magnetic storm (which is what most space weather modeling is currently directed toward) does not make this solar event less important for space weather researchers, modelers, and system operators. Rather, it clearly points out that considerably more research and understanding are needed to predict the types of solar activity that can produce so unexpectedly the intense electromagnetic emissions observed on 6 December. Like large magnetic storms, we now know first hand that these types of events can also affect important navigation and communications technologies at essentially the same moment (just the light travel time) when the solar event is first observed at Earth. Louis J. Lanzerotti is editor of Space Weather, a distinguished research professor at the New Jersey Institute of Technology, and a consultant at Alcatel-Lucent Technologies’ Bell Laboratories.

Accumulation in Dasuopu ice core in Qinghai-Tibet Plateau and solar activity

The time series of accumulation in recent 300 years correlated well with solar activity in Dasuopu ice core. Results of spectrum analysis on the accumulation time series of the Dasuopu ice core shows that there are some periods that coincide with the periods of solar activity. By comparing the long-time change trend of the accumulation in the Dasuopu ice core with various kinds of indexes of solar activity intensity, a negative correlation is found between the trend and solar activity.

Prediction of maximum sunspot number in solar cycle 23

Instantaneous predictions of the maximum monthly smoothed sunspot number in solar cycle 23 have been made with a linear regressive model, which gives the predicted maximum value as a function of the smoothed sunspot numbers corresponding to a given month from the minimum in all preceding cycles. These predictions indicate that the intensity of solar activity in the current cycle will be at an average level.

Frequency of ball lightning reports

The frequency distribution by publication date of ball lightning reports and papers from 1651 to 1978 does not reflect a positive correlation with the intensity of solar activity nor indicate a cyclic characteristic. It is recognized that skewing of the distribution may have occurred because of human factors, such as publication bias, possible quasi‐periodic public interest, misinterpretation and misidentification of the actual event, and hesitancy of reporting by the observer. A natural dependence is not apparent.