scholarly journals RESPONSE OF F2- REGION MAXIMUM ELECTRON DENSITY (NmF2/foF2) TO SOLAR ACTIVITY USING PEARSON PRODUCT MOMENT CORRELATION

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Eugene Onori
Keyword(s):  
Puerto Rico ◽  
Solar Activity ◽  
Correlation Analysis ◽  
Electron Density ◽  
Upper Atmosphere ◽  
High Solar Activity ◽  
The Sun ◽  
Pearson Product Moment Correlation ◽  
Maximum Electron Density ◽  
Temporal And Spatial

Introduction: The ionosphere owes its origin primarily to ultraviolet radiation from the Sun. The ionosphere is an essential part of the Earth’s upper atmosphere. It is ionized by solar radiation and influences transionospheric radio wave propagation. Maximum electron density of the F2- layer (NmF2) is an important parameter for studying the ionosphere. The ionospheric F2-region maximum electron density (NmF2) depends strongly on solar activity, it also suffers temporal and spatial variations. Aim: The aim of this paper is to investigate the response of NmF2 to solar activity during high solar activity (HSA), moderate solar activity (MSA) and low solar activity (LSA) years using correlation analysis. Materials and Methods: The data used in this work are the hourly NmF2 values derived from foF2 data observed at Jicamarca (Lat.11.9 oS, Long.76.8 oW) and Puerto Rico (Lat.18.5 oN, Long.67.2 oW) during high solar activity HSA (2002), moderate solar activity MSA (2011) and low solar activity LSA (2006) years. The NmF2 data were evaluated using the relation in equation 1 NmF2 = 1.24 x 1010 (foF2)2 (1) Where NmF2 is in el/m3 and foF2 is in MHz. Pearson Product Moment Correlation (PPMC) was used to further analyse the NmF2 data. Results: Our results revealed two unequal NmF2 peaks. The NmF2 peaks values at Jicamarca (60 - 240; 63– 204) x 1010 el/m3 are observed to be higher in values than those at Puerto Rico (63 – 187; 57 – 164) x 1010 el/m3. The highest NmF2 peak values of 240 and 187x 1010 el/m3 occurred during March equinox at 09:00 and 14:00 hours at Jicamarca and Puerto Rico respectively during HSA year. Conclusion: Correlation analysis for the three epochs of solar activity revealed that NmF2 showed positive correlation with sunspot number with highest correlation values of 0.904 and 0.976 at Jicamarca and Puerto Rico stations respectively during MSA year.

scholarly journals Cosmic-ray propagation around the Sun: investigating the influence of the solar magnetic field on the cosmic-ray Sun shadow

2020 ◽  
Vol 633 ◽  
pp. A83
Author(s):  
J. Becker Tjus ◽  
P. Desiati ◽  
N. Döpper ◽  
H. Fichtner ◽  
J. Kleimann ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Solar Cycle ◽  
Cosmic Rays ◽  
Solar Magnetic Field ◽  
Cosmic Ray ◽  
High Energy ◽  
High Solar Activity ◽  
The Sun ◽  
Theoretical Understanding

The cosmic-ray Sun shadow, which is caused by high-energy charged cosmic rays being blocked and deflected by the Sun and its magnetic field, has been observed by various experiments, such as Argo-YBJ, Tibet, HAWC, and IceCube. Most notably, the shadow’s size and depth was recently shown to correlate with the 11-year solar cycle. The interpretation of such measurements, which help to bridge the gap between solar physics and high-energy particle astrophysics, requires a solid theoretical understanding of cosmic-ray propagation in the coronal magnetic field. It is the aim of this paper to establish theoretical predictions for the cosmic-ray Sun shadow in order to identify observables that can be used to study this link in more detail. To determine the cosmic-ray Sun shadow, we numerically compute trajectories of charged cosmic rays in the energy range of 5−316 TeV for five different mass numbers. We present and analyze the resulting shadow images for protons and iron, as well as for typically measured cosmic-ray compositions. We confirm the observationally established correlation between the magnitude of the shadowing effect and both the mean sunspot number and the polarity of the magnetic field during the solar cycle. We also show that during low solar activity, the Sun’s shadow behaves similarly to that of a dipole, for which we find a non-monotonous dependence on energy. In particular, the shadow can become significantly more pronounced than the geometrical disk expected for a totally unmagnetized Sun. For times of high solar activity, we instead predict the shadow to depend monotonously on energy and to be generally weaker than the geometrical shadow for all tested energies. These effects should become visible in energy-resolved measurements of the Sun shadow, and may in the future become an independent measure for the level of disorder in the solar magnetic field.

scholarly journals Could periodic patterns in human mortality be sensitive to solar activity?

2011 ◽  
Vol 29 (6) ◽  
pp. 1113-1120 ◽  
Author(s):  
R. Díaz-Sandoval ◽  
R. Erdélyi ◽  
R. Maheswaran
Keyword(s):  
Solar Activity ◽  
Winter Season ◽  
Maximum Activity ◽  
Wavelet Coherence ◽  
High Solar Activity ◽  
The Sun ◽  
Periodic Patterns ◽  
Origin And Evolution ◽  
Life On Earth ◽  
Wavelet Coherence Analysis

Abstract. Seasonal behaviour of human diseases have been observed and reported in the literature for years. Although the Sun plays an essential role in the origin and evolution of life on Earth, it is barely taken into account in biological processes for the development of a specific disease. Higher mortality rates occur during the winter season in the Northern Hemisphere for several diseases, particularly diseases of the cardiovascular and respiratory systems. This increment has been associated with seasonal and social causes. However, is there more behind these correlations, in particular in terms of solar variability? In this paper we attempt to make a first step towards answering this question. A detailed wavelet analysis of periodicities for diseases from England and Wales seem to reveal that mortality periodicities (3 days to half a year) could be due to the Earth's position around the Sun. Moreover, crosswavelet and wavelet coherence analysis show common features between medical diseases and solar proxies around solar maximum activity suggesting that this relation, if any, has to be searched in times of high solar activity.

scholarly journals THE STRUCTURE OF THE SOLAR WIND IN THE HELIOSPHERE DEPENDING ON THE PHASE OF THE SOLAR CYCLE: LARGE-SCALE DYNAMICS OF THE HELIOSPHERIC CURRENT SHEET

2019 ◽  
Vol 47 (1) ◽  
pp. 85-87
Author(s):  
E.V. Maiewski ◽  
R.A. Kislov ◽  
H.V. Malova ◽  
O.V. Khabarova ◽  
V.Yu. Popov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Activity ◽  
Solar Cycle ◽  
Current Sheet ◽  
Heliospheric Current Sheet ◽  
High Solar Activity ◽  
The Sun ◽  
High Latitudes ◽  
The Magnetic Field

A stationary axisymmetric MHD model of the solar wind has been constructed, which allows us to study the spatial distribution of the magnetic field and plasma characteristics at radial distances from 20 to 400 radii of the Sun at almost all heliolatitudes. The model takes into account the changes in the magnetic field of the Sun during a quarter of the solar cycle, when the dominant dipole magnetic field is replaced by a quadrupole. Selfconsistent solutions for the magnetic and velocity fields, plasma concentration and current density of the solar wind depending on the phase of the solar cycle are obtained. It is shown that during the domination of the dipole magnetic component in the solar wind heliospheric current sheet (HCS) is located in the equatorial plane, which is a part of the system of radial and transverse currents, symmetrical in the northern and southern hemispheres. As the relative contribution of the quadrupole component to the total magnetic field increases, the shape of the HCS becomes conical; the angle of the cone gradually decreases, so that the current sheet moves entirely to one of the hemispheres. At the same time, at high latitudes of the opposite hemisphere, a second conical HCS arises, the angle of which increases. When the quadrupole field becomes dominant (at maximum solar activity), both HCS lie on conical surfaces inclined at an angle of 35 degrees to the equator. The model describes the transition from the fast solar wind at high latitudes to the slow solar wind at low latitudes: a relatively gentle transition in the period of low solar activity gives way to more drastic when high solar activity. The model also predicts an increase in the steepness of the profiles of the main characteristics of the solar wind with an increase in the radial distance from the Sun. Comparison of the obtained dependences with the available observational data is discussed.

scholarly journals Impact of Solar Activity on Global Atmospheric Circulation Based on SD-WACCM-X Simulations from 2002 to 2019

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1526
Author(s):  
Chen-Ke-Min Teng ◽  
Sheng-Yang Gu ◽  
Yusong Qin ◽  
Xiankang Dou
Keyword(s):  
Solar Activity ◽  
Atmospheric Circulation ◽  
Southern Oscillation ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
High Solar Activity ◽  
Low Latitude ◽  
Quasi Biennial Oscillation ◽  
Global Atmospheric Circulation ◽  
The Impact

In this study, a global atmospheric model, Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (SD-WACCM-X), and the residual circulation principle were used to study the global atmospheric circulation from the lower to upper atmosphere (~500 km) from 2002 to 2019. Our analysis shows that the atmospheric circulation is clearly influenced by solar activity, especially in the upper atmosphere, which is mainly characterized by an enhanced atmospheric circulation in years with high solar activity. The atmospheric circulation in the upper atmosphere also exhibits an ~11 year period, and its variation is highly correlated with the temporal variation in the F10.7 solar index during the same time series, with a maximum correlation coefficient of up to more than 0.9. In the middle and lower atmosphere, the impact of solar activity on the atmospheric circulation is not as obvious as in the upper atmosphere due to some atmospheric activities such as the Quasi-Biennial Oscillation (QBO), El Niño–Southern Oscillation (ENSO), sudden stratospheric warming (SSW), volcanic forcing, and so on. By comparing the atmospheric circulation in different latitudinal regions between years with high and low solar activity, we found the atmospheric circulation in mid- and high-latitude regions is more affected by solar activity than in low-latitude and equatorial regions. In addition, clear seasonal variation in atmospheric circulation was detected in the global atmosphere, excluding the regions near 10−4 hPa and the lower atmosphere, which is mainly characterized by a flow from the summer hemisphere to the winter hemisphere. In the middle and low atmosphere, the atmospheric circulation shows a quasi-biennial oscillatory variation in the low-latitude and equatorial regions. This work provides a referable study of global atmospheric circulation and demonstrates the impacts of solar activity on global atmospheric circulation.

scholarly journals Inflection point in the power spectrum of stellar brightness variations

2020 ◽  
Vol 636 ◽  
pp. A69 ◽  
Author(s):  
E. M. Amazo-Gómez ◽  
A. I. Shapiro ◽  
S. K. Solanki ◽  
N. A. Krivova ◽  
G. Kopp ◽  
...  
Keyword(s):  
Solar Activity ◽  
Power Spectrum ◽  
Solar Irradiance ◽  
Inflection Point ◽  
Solar Rotation ◽  
Light Curves ◽  
High Solar Activity ◽  
The Sun ◽  
Rotation Periods ◽  
Active Stars

Context. Young and active stars generally have regular, almost sinusoidal, patterns of variability attributed to their rotation, while the majority of older and less active stars, including the Sun, have more complex and non-regular light curves, which do not have clear rotational-modulation signals. Consequently, the rotation periods have been successfully determined only for a small fraction of the Sun-like stars (mainly the active ones) observed by transit-based planet-hunting missions, such as CoRoT, Kepler, and TESS. This suggests that only a small fraction of such systems have been properly identified as solar-like analogues. Aims. We aim to apply a new method of determining rotation periods of low-activity stars, such as the Sun. The method is based on calculating the gradient of the power spectrum (GPS) of stellar brightness variations and identifying a tell-tale inflection point in the spectrum. The rotation frequency is then proportional to the frequency of that inflection point. In this paper, we compare this GPS method to already-available photometric records of the Sun. Methods. We applied GPS, auto-correlation functions, Lomb-Scargle periodograms, and wavelet analyses to the total solar irradiance (TSI) time series obtained from the Total Irradiance Monitor on the Solar Radiation and Climate Experiment and the Variability of solar IRradiance and Gravity Oscillations experiment on the SOlar and Heliospheric Observatory missions. We analysed the performance of all methods at various levels of solar activity. Results. We show that the GPS method returns accurate values of solar rotation independently of the level of solar activity. In particular, it performs well during periods of high solar activity, when TSI variability displays an irregular pattern, and other methods fail. Furthermore, we show that the GPS and light curve skewness can give constraints on facular and spot contributions to brightness variability. Conclusions. Our results suggest that the GPS method can successfully determine the rotational periods of stars with both regular and non-regular light curves.

scholarly journals Changes in solar activity based on radiocarbon data and climate variations in the interval 8000 - 1000 BC

2021 ◽  
Vol 2103 (1) ◽  
pp. 012025
Author(s):  
V A Dergachev ◽  
I V Kudryavtsev
Keyword(s):  
Solar Activity ◽  
Surface Temperature ◽  
High Solar Activity ◽  
Time Interval ◽  
The Sun ◽  
Climate Variations ◽  
Radiocarbon Data ◽  
Earth’S Climate ◽  
Global Surface ◽  
Recorded Temperature

Abstract This work examines the change in the activity of the Sun based on the reconstruction of the heliospheric modulation potential in the time interval 8000 - 1000 BC. Reconstructions of this potential were obtained using radiocarbon data, taking into account the influence of changes in the Earth’s climate. A comparison is made of the variations in the activity of the Sun with the global surface temperature. It is shown that variations in global temperature during this period could be the result of changes in solar activity. So high solar activity could lead to recorded temperature maximums around 7000 and 5300 BC. The drop in temperature in the range 3000-1000BC could be the result of low solar activity.

scholarly journals Equinoctial asymmetry in solar activity variations of <I>Nm</I>F2 and TEC

2012 ◽  
Vol 30 (3) ◽  
pp. 613-622 ◽  
Author(s):  
Y. Chen ◽  
L. Liu ◽  
W. Wan ◽  
Z. Ren
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
High Solar Activity ◽  
Solar Cycles ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Increase Rate ◽  
Dip Equator ◽  
The Difference

Abstract. The ionosonde NmF2 data (covering several solar cycles) and the JPL TEC maps (from 1998 through 2009) were collected to investigate the equinoctial asymmetries in ionospheric electron density and its variation with solar activity. With solar activity increasing, the equinoctial asymmetry of noontime NmF2 increases at middle latitudes but decreases or changes little at low latitudes, while the equinoctial asymmetry of TEC increases at all latitudes. The latitudinal feature of the equinoctial asymmetry at high solar activity is different from that at low solar activity. The increases of NmF2 and TEC with the solar proxy P = (F10.7+F10.7A)/2 also show equinoctial asymmetries that depend on latitudes. The increase rate of NmF2 with P at March equinox (ME) is higher than that at September equinox (SE) at middle latitudes, but the latter is higher than the former at the EIA crest latitudes, and the difference between them is small at the EIA trough latitudes. The phenomenon of higher increase rate at SE than at ME does not appear in TEC. The increase rate of noontime TEC with P at ME is higher than that at SE at all latitudes, and the difference between them peaks at both sides of dip equator. It is mentionable that the equinoctial asymmetries of NmF2 and TEC increase rates present some longitudinal dependence at low latitude. The influences of equinoctial differences in the thermosphere and ionospheric dynamics processes on the equinoctial asymmetry of the electron density were briefly discussed.

scholarly journals Anomalous variations of <I>Nm</I>F2 over the Argentine Islands: a statistical study

2009 ◽  
Vol 27 (4) ◽  
pp. 1363-1375 ◽  
Author(s):  
A. V. Pavlov ◽  
N. M. Pavlova
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Conditional Probability ◽  
Statistical Study ◽  
Expected Value ◽  
Diurnal Variations ◽  
High Solar Activity ◽  
Winter Anomaly ◽  
Anomalous Feature ◽  
The Mean

Abstract. We present a statistical study of variations in the F2-layer peak electron density, NmF2, and altitude, hmF2, over the Argentine Islands ionosonde. The critical frequencies, foF2, and, foE, of the F2 and E-layers, and the propagation factor, M(3000)F2, measured by the ionosonde during the 1957–1959 and 1962–1995 time periods were used in the statistical analysis to determine the values of NmF2 and hmF2. The probabilities to observe maximum and minimum values of NmF2 and hmF2 in a diurnal variation of the electron density are calculated. Our study shows that the main part of the maximum diurnal values of NmF2 is observed in a time sector close to midnight in November, December, January, and February exhibiting the anomalous diurnal variations of NmF2. Another anomalous feature of the diurnal variations of NmF2 exhibited during November, December, and January when the minimum diurnal value of NmF2 is mainly located close to the noon sector. These anomalous diurnal variations of NmF2 are found to be during both geomagnetically quiet and disturbed conditions. Anomalous features are not found in the diurnal variations of hmF2. The statistical study of the NmF2 winter anomaly phenomena over the Argentine Islands ionosonde was carried out. The variations in a maximum daytime value, R, of a ratio of a geomagnetically quiet daytime winter NmF2 to a geomagnetically quiet daytime summer NmF2 taken at a given UT and for approximately the same level of solar activity were studied. The conditional probability of the occurrence of R in an interval of R, the most frequent value of R, the mean expected value of R, and the conditional probability to observe the F2-region winter anomaly during a daytime period were calculated for low, moderate, and high solar activity. The calculations show that the mean expected value of R and the occurrence frequency of the F2-region winter anomaly increase with increasing solar activity.

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