11-year Modulation Research Articles

A Perspective on the Solar Modulation of Cosmic Anti-Matter

Global modulation studies with comprehensive numerical models contribute meaningfully to the refinement of very local interstellar spectra (VLISs) for cosmic rays. Modulation of positrons and anti-protons are investigated to establish how the ratio of their intensity, and with respect to electrons and protons, are changing with solar activity. This includes the polarity reversal of the solar magnetic field which creates a 22-year modulation cycle. Modeling illustrates how they are modulated over time and the particle drift they experience which is significant at lower kinetic energy. The VLIS for anti-protons has a peculiar spectral shape in contrast to protons so that the total modulation of anti-protons is awkwardly different to that for protons. We find that the proton-to-anti-proton ratio between 1–2 GeV may change by a factor of 1.5 over a solar cycle and that the intensity for anti-protons may decrease by a factor of ~2 at 100 MeV during this cycle. A composition is presented of VLIS for protons, deuteron, helium isotopes, electrons, and particularly for positrons and anti-protons. Gaining knowledge of their respective 11 and 22 year modulation is useful to interpret observations of low-energy anti-nuclei at the Earth as tests of dark matter annihilation.

Responses and Periodic Variations of Cosmic Ray Intensity and Solar Wind Speed to Sunspot Numbers

To investigate the periodic behaviour and relationship of sunspot numbers with cosmic ray intensity and solar wind speed, we present analysis from daily data generated from 1995 January to 2018 December. Cross-correlation and wavelet transform tools were employed to carry out the investigation. The analyses confirmed that the cosmic ray intensity correlates negatively with the sunspot numbers, exhibiting an asynchronous phase relationship with a strong negative correlation. The trend in cosmic ray intensity indicates that it undergoes the 11-year modulation that mainly depends on the solar activity in the heliosphere. On the other hand, the solar wind speed neither shows a clear phase relationship nor correlates with the sunspot numbers but shows a wide range of periodicities that could possibly be connected to the pattern of coronal hole configuration. A number of short and midterm variations were also observed from the wavelet analysis, i.e., 64–128 and 128–256 days for the cosmic ray intensity, 4–8, 32–64, 128–256, and 256–512 days for the solar wind speed, and 16–32, 32–64, 128–256, and 256–512 days for the sunspot numbers.

Effects of solar activity and galactic cosmic ray cycles on the modulation of the annual average temperature at two sites in southern Brazil

Abstract. Quasi-periodic variations in solar activity and galactic cosmic rays (GCRs) on decadal and bidecadal timescales have been suggested as a climate forcing mechanism for many regions on Earth. One of these regions is southern Brazil, where the lowest values during the last century were observed for the total geomagnetic field intensity at the Earth's surface. These low values are due to the passage of the center of the South Atlantic Magnetic Anomaly (SAMA), which crosses the Brazilian territory from east to west following a latitude of ∼ 26∘. In areas with low geomagnetic intensity, such as the SAMA, the incidence of GCRs is increased. Consequently, possible climatic effects related to the GCRs tend to be maximized in this region. In this work, we investigate the relationship between the ∼ 11-year and ∼ 22-year cycles that are related to solar activity and GCRs and the annual average temperature recorded between 1936 and 2014 at two weather stations, both located near a latitude of 26∘ S but at different longitudes. The first of these stations (Torres – TOR) is located in the coastal region, and the other (Iraí – IRA) is located in the interior, around 450 km from the Atlantic Ocean. Sunspot data and the solar modulation potential for cosmic rays were used as proxies for the solar activity and the GCRs, respectively. Our investigation of the influence of decadal and bidecadal cycles in temperature data was carried out using the wavelet transform coherence (WTC) spectrum. The results indicate that periodicities of 11 years may have continuously modulated the climate at TOR via a nonlinear mechanism, while at IRA, the effects of this 11-year modulation period were intermittent. Four temperature maxima, separated by around 20 years, were detected in the same years at both weather stations. These temperature maxima are almost coincident with the maxima of the odd solar cycles. Furthermore, these maxima occur after transitions from even to odd solar cycles, that is, after some years of intense GCR flux. The obtained results offer indirect mathematical evidence that solar activity and GCR variations contributed to climatic changes in southern Brazil during the last century. A comparison of the results obtained for the two weather stations indicates that the SAMA also contributes indirectly to these temperature variations. The contribution of other mechanisms also related to solar activity cannot be excluded. Keywords. Meteorology and atmospheric dynamics (climatology)

Modulation of Galactic Cosmic Rays in the Inner Heliosphere over Solar Cycles

Abstract The 11- and 22-year modulation of galactic cosmic rays (GCRs) in the inner heliosphere is studied using a numerical model developed by Qin and Shen in 2017. Based on the numerical solutions of Parker’s transport equations, the model incorporates a modified Parker heliospheric magnetic field, a locally static time-delayed heliosphere, and a time-dependent diffusion coefficients model in which an analytical expression of the variation of magnetic turbulence magnitude throughout the inner heliosphere is applied. Furthermore, during solar maximum, the solar magnetic polarity is determined randomly with the possibility of A > 0 decided by the percentage of the solar north polar magnetic field being outward and the solar south polar magnetic field being inward. The computed results are compared at various energies with several GCR observations, e.g., the Interplanetary Monitoring Platform 8 (IMP 8), EPHIN on board the Solar and Heliospheric Observatory (SOHO), Ulysses, and Voyager 1 and 2, and they show good agreement. We show that our model has successfully reproduced the 11- and 22-year modulation cycles.

Solar Variability, Galactic Cosmic Rays and Climate: A Review

Climate is among the most important natural resources for all living beings. The main external and internal driver for climate change is variability of the Sun. The Sun is the ultimate source of the energy on the Earth and play a key role in its climate change. What is still not known and needs to be found is the extent to which these variations in solar behavior affect the total energy that the Sun emits. The small variation in the solar irradiance and changes in its spectral distribution leads to a large variation in climate. An attempt has been made to report the present understanding of the solar variability and its consequences on the variability of solar irradiance which exhibits 11-year cyclic variation and modulation on higher time scale. Galactic Cosmic Rays (GCR) reaching the Earth’s atmosphere is modulated by the solar wind and geomagnetic field, which also exhibit 11-year cyclic variation. In the present paper, we have reviewed our current understanding on physics of solar variability, galactic cosmic rays and their effects on the Earth’s climate.

Solar Modulation of Cosmic Rays

This is an overview of the solar modulation of cosmic rays in the heliosphere. It is a broad topic with numerous intriguing aspects so that a research framework has to be chosen to concentrate on. The review focuses on the basic paradigms and departure points without presenting advanced theoretical or observational details for which there exists a large number of comprehensive reviews. Instead, emphasis is placed on numerical modeling which has played an increasingly significant role as computational resources have become more abundant. A main theme is the progress that has been made over the years. The emphasis is on the global features of CR modulation and on the causes of the observed 11-year and 22-year cycles and charge-sign dependent modulation. Illustrative examples of some of the theoretical and observational milestones are presented, without attempting to review all details or every contribution made in this field of research. Controversial aspects are discussed where appro- priate, with accompanying challenges and future prospects. The year 2012 was the centennial celebration of the discovery of cosmic rays so that several general reviews were dedicated to historical aspects so that such developments are brie y presented only in a few cases.

Modulation of the Arctic Oscillation and the East Asian winter climate relationships by the 11-year solar cycle

The modulation of the relationship between the Arctic Oscillation (AO) and the East Asian winter climate by the 11-year solar cycle was investigated. During winters with high solar activity (HS), robust warming appeared in northern Asia in a positive AO phase. This result corresponded to an enhanced anticyclonic flow at 850 hPa over northeastern Asia and a weakened East Asian trough (EAT) at 500 hPa. However, during winters with low solar activity (LS), both the surface warming and the intensities of the anticyclonic flow and the EAT were much less in the presence of a positive AO phase. The possible atmospheric processes for this 11-year solar-cycle modulation may be attributed to the indirect influence that solar activity induces in the structural changes of AO. During HS winters, the sea level pressure oscillation associated with the AO became stronger, with the significant influence of AO extending to East Asia. In the meantime, the AO-related zonal-mean zonal winds tended to extend more into the stratosphere during HS winters, which implies a stronger coupling to the stratosphere. These trends may have led to an enhanced AO phase difference; thus the associated East Asian climate anomalies became larger and more significant. The situation tended to reverse during LS winters. Further analyses revealed that the relationship between the winter AO and surface-climate anomalies in the following spring is also modulated by the 11-year solar cycle, with significant signals appearing only during HS phases. Solar-cycle variation should be taken into consideration when the AO is used to predict winter and spring climate anomalies over East Asia.

Galactic cosmic ray modulation for sunspot cycle 23

We present a study of the galactic cosmic ray modulation for sunspot cycle 23. We use the monthly and the annual mean hourly, pressure corrected, data from neutron monitors of the global network (monthly rate is calculated as the average of the hourly pressure corrected values). We draw attention to an asymmetry in the galactic cosmic ray (GCR) recovery during odd and even cycles for the monthly mean hourly rate data. For over half a century of observations, we find that the recovery for the odd cycles is to a higher level than for the even cycles. Qualitatively the effect is ascribed to charged particle drifts in inhomogeneous interplanetary magnetic field. Even so it has not been possible to arrive at a quantitative, self-consistent, explanation in terms of drifts at higher and lower GCR rigidities. We also study the rigidity dependence of the amplitude of 11-year modulation over a wide range (1–200 GV) of GCR spectrum; it is a power law in rigidity with an exponent −1.22. We discuss the implication of these findings on quasi-linear diffusion theories of modulation. We reflect on GCR recovery pattern for 2006–2009.

Geoelectromagnetism and the changing Earth

The paper describes research in geomagnetism and aeronomy carried out in the framework of a project organized by the Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences. It includes the development of the instrumentation of the Nagycenk Geophysical Observatory (geomagnetic measuring systems, ionosonde), moreover other instrumental and methodological developments, too. Observatory data are available in a database. Based on results of the Nagycenk and Tihany observatories and on data of permanent and temporal networks, long-term trends of different electromagnetic parameters were investigated. Thus geomagnetic activity was found secularly increasing, a decrease of the atmospheric electric potential gradient and a 11-year modulation of the winter/December attenuation of the geomagnetic pulsation activity were confirmed. Several possibilities (pulsations, whistlers, modelling) were used to improve knowledge about structure and parameters of the magnetosphere. Electromagnetic precursors of earthquakes were looked for. A significant increase of understanding was obtained in connection with Schumann resonances and electromagnetic transients caused by lightning. It was shown that see-coasts influence characteristically changes in ionospheric trends (hmF2). When looking for the effect of the global climate changes in the subsurface electric resistivity, an example was discovered for the decrease of the resistivity due to infiltrating water from precipitation. Electromagnetic exploration of tectonically conditioned weak zones was continued, too.

Solar cycle signatures in the NCEP equatorial annual oscillation

Abstract. Our analysis of temperature and zonal wind data (1958 to 2006) from the National Center for Atmospheric Research (NCAR) reanalysis (Re-1), supplied by the National Centers for Environmental Prediction (NCEP), shows that the hemispherically symmetric 12-month equatorial annual oscillation (EAO) contains spectral signatures with periods around 11 years. Moving windows of 44 years show that, below 20 km, the 11-year modulation of the EAO is phase locked to the solar cycle (SC). The spectral features from the 48-year data record reveal modulation signatures of 9.6 and 12 years, which produce EAO variations that mimic in limited altitude regimes the varying maxima and minima of the 10.7 cm flux solar index. Above 20 km, the spectra also contain modulation signatures with periods around 11 years, but the filtered variations are too irregular to suggest that systematic SC forcing is the principal agent.

Solar-terrestrial energy transfer during sunspot cycles and mechanism of Earth rotation excitation

AbstractThe solar-terrestrial energy transfer, due to the total solar irradiance (TSI), solar wind and interplanetary magnetic field, has 11-year modulation during the sunspot cycles. Other oscillations of solar-terrestrial energy transfer are with periods of 22 and 45 year due to the magnetic reversal and equatorial solar asymmetry, which cause corresponding oscillations of all Earth systems, including climate and weather, atmosphere and ocean circulations, geomagnetic field and core processes. A part of this energy variation is transformed to oscillations of the Earth rotation. A model of indirect mechanism of Earth rotation excitation during sunspot cycles is proposed, which is based on global water circulation and periodical mass transfer between oceans and polar ice caps. The oscillations of the mean sea level (MSL) with periods 11, 22 and 45 years are determined by sea level data for the last two centuries from 13 maregraph stations. The necessary energy of water evaporation, corresponding to the observed MSL variations is provided by TSI oscillations with amplitudes between 0.2-0.5W/m2, determined by means of reconstructed time series of the TSI since 1610. The determined mean Universal Time (UT1) amplitudes, corresponding to the 22-year and 45-year cycles of the solar activity are 185ms and 310ms.

Extrapolating cosmic ray variations and impacts on life: Morlet wavelet analysis

AbstractExposure to cosmic rays may have both a direct and indirect effect on Earth's organisms. The radiation may lead to higher rates of genetic mutations in organisms, or interfere with their ability to repair DNA damage, potentially leading to diseases such as cancer. Increased cloud cover, which may cool the planet by blocking out more of the Sun's rays, is also associated with cosmic rays. They also interact with molecules in the atmosphere to create nitrogen oxide, a gas that eats away at our planet's ozone layer, which protects us from the Sun's harmful ultraviolet rays. On the ground, humans are protected from cosmic particles by the planet's atmosphere.In this paper we give estimated results of wavelet analysis from solar modulation and cosmic ray data incorporated in time-dependent cosmic ray variation. Since solar activity can be described as a non-linear chaotic dynamic system, methods such as neural networks and wavelet methods should be very suitable analytical tools. Thus we have computed our results using Morlet wavelets. Many have used wavelet techniques for studying solar activity. Here we have analysed and reconstructed cosmic ray variation, and we have better depicted periods or harmonics other than the 11-year solar modulation cycles.

Galactic cosmic ray H and He nuclei energy spectra measured by Voyagers 1 and 2 near the heliospheric termination shock in positive and negative solar magnetic polarity cycles

Using data from the Voyager 1 and 2 spacecraft, we have followed the intensity variations of H, He and C + O nuclei between 1998 and 2008 and determined the spectra for H and He at the time of minimum modulation in 1998, when the solar magnetic polarity was positive and again in 2008 when the solar magnetic polarity was negative. At these times these data are representative of conditions near a heliospheric termination shock assumed to be located at ∼90 AU. Above ∼400 MeV/nuc for He nuclei the 11‐year solar modulation cycle observed at the Earth is not seen; instead there is a 22‐year variation. The negative polarity cycle intensities above ∼150 MeV/nuc are higher than those in the positive polarity cycle by a factor of 1.4–1.7 times for both H and He nuclei. Below ∼100 MeV/nuc the C nuclei intensities are similar in the two cycles to within ±10%. These observations are compared with theoretical calculations which also show a negative to positive polarity cycle intensity difference at higher energies, most likely associated with energy changes due to drifts near the termination shock, but the comparison suggests that improved estimates of the local interstellar spectra are required.

11-year and 22-year variations in the anisotropy of galactic cosmic rays

An 11-year modulation of the electric drift anisotropy directed across the force lines of the interplanetary magnetic field and a 22-year modulation of the magnetic drift anisotropy along the interplanetary magnetic field have been found on the basis of the data of the Yakutsk underground complex of muon telescopes. Some specific features of the anisotropy during the pole reversal of the total solar magnetic field are discussed.

Effect of QBO and ENSO on the Solar Cycle Modulation of Winter North Atlantic Oscillation

The effect of the Quasi-Biennial Oscillation (QBO) and the El Nino Southern Oscillation (ENSO) on the 11-year solar cycle modulation of the winter-mean North Atlantic Oscillation (NAO) is examined through analysis of observational data from 1958 to 2000. It is found that the solar cycle modulation of the NAO is more strongly enhanced in the westerly phase of the 50-hPa QBO wind and the cold phase of ENSO, although separation of these effects is statistically difficult. On these phases, the signal of the winter-mean NAO extends more to the upper stratosphere and summer-AO reappears more strongly in high solar years, whereas the signal is weaker throughout in low solar years.

Solar proton events in cosmogenic isotope data

A possible contribution of solar energetic particle events to the production of cosmogenic 10Be and 14C in the atmosphere is studied. The solar particle effect is negligible in the 14C data, but extreme events may be detectable in high‐resolution 14C data. Although the overall effect is small in the 10Be data, strong events may contribute notably on the inter‐annual time scale. In combination with the 11‐year solar modulation of galactic cosmic rays, it may lead to an intermittent 5.5‐year periodicity, which is seen in high resolution 10Be data. We have identified ten episodes during 1750–1950 when 10Be may hold signatures of strong solar proton events. This opens a new possibility to study extreme solar particle events in the past using high resolution cosmogenic isotope data.

THEORETICAL AND EXPERIMENTAL STUDIES OF THE 11-YEAR AND 27-DAY VARIATIONS OF THE GALACTIC COSMIC RAYS INTENSITY AND ANISOTROPY

The changes of the structure in the energy range of the interplanetary magnetic field (IMF) turbulence versus solar activity can be considered as one of the important reasons of the long period (11-year) modulation of galactic cosmic ray (GCR) intensity; the amplitude of the 27-day variation of GCR anisotropy is greater in the qA > 0 periods than in the qA < 0 periods of the solar magnetic cycles in a good correlation with the similar changes of the 27-day variation of GCR intensity.

The 11-year solar-cycle effects on the temperature in the upper-stratosphere and mesosphere: Part I—Assessment of observations

Three independent temperature datasets have been analyzed for quantifying the influence of the 11-year solar cycle modulation of the UV radiation. The datasets used include: US rocketsondes, the OHP lidar, and the global temperature database made by the successive SSU on the NOAA satellites, adjusted and provided by the UK Meteorological Office. These measurements cover the upper stratosphere and the mesosphere, where the direct photochemical effect is expected. The improvement of the analysis compared to previous ones was possible because the overall quality and the continuity of many data series have been checked more carefully during the last decade in order to look for anthropogenic fingerprints and the one used here have been recognized as the best series according to their temporal continuity. The analysis of the different data set is based on the same regression linear model. The 11-year solar temperature response observed presents a variable behavior, depending on the location. However, an overall adequate agreement among the results has been obtained, and thus the global picture of the solar impact in the upper stratosphere and lower mesosphere has been obtained and is presented here. In the tropics, a 1–2 K positive response in the mid and upper stratophere has been found, in agreement with photochemical theory and previous analyses. On the opposite, at mid-latitudes, negative responses of several Kelvin have been observed, during winters, in the analyses of the datasets analyzed here. In the mesosphere, at sub-tropic and mid-latitude regions, we observe a positive response all the year round increasing by a factor of two during winter.

Solar cycle modulation of the Southern Annular Mode

The effect of the 11‐year solar cycle modulation on the Southern Annular Mode (SAM) in the Southern Hemisphere is examined through analysis of observational data from 1968 to 2001. It is found that the year‐to‐year variability of the October–November mean SAM differs significantly according to the solar activity. In high solar activity years, the SAM signal extends to the upper stratosphere during October to December and activity in the troposphere lasts until autumn, whereas in low solar activity years, the SAM signal is confined almost inside the troposphere from October to December and it disappears by January. This situation is very similar to that observed for the modulation of the winter mean North Atlantic Oscillation in the Northern Hemisphere. A possible mechanism of solar cycle modulation of the SAM is also discussed.

Intensities of galactic cosmic rays of ∼1.5 GV rigidity at Earth versus the heliospheric current sheet tilt

In this paper we have compared the cosmic ray intensity variations at ∼1.5 GV rigidity with the corresponding time variations of the heliospheric current sheet tilt (HCST). These studies extend earlier work comparing neutron monitor variations with the HCST. In addition to the results of this earlier work we have found that (1) the delay of the cosmic ray intensity changes relative to the HCST changes is much less in 11‐year cycles starting in a negative solar magnetic cycles. (2) During the specific periods of actual changeover of the solar magnetic field from positive to negative polarity, the cosmic ray intensity decrease is ∼50% of the total 11‐year cycle intensity decrease. During the changeover from negative to positive polarity, the entire cosmic ray 11‐year decrease has almost fully occurred before the polarity changeover. (3) In 11‐year modulation cycles starting in a negative polarity period, the regression coefficient between the cosmic ray intensity and tilt is ∼0.9% per degree of tilt during both the decreasing and increasing phases. In the 11‐year modulation cycles starting in a positive polarity cycle, the regression coefficient is much smaller, only ∼0.4% per degree during much of the cycle; then it becomes much steeper toward the end of the cycle. These features are discussed in terms of current models for cosmic ray modulation that include diffusion, convection, drifts, and the wavy current sheet.