A5078845211- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Solar Radiation and Photovoltaics
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Atomic and Molecular Physics
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Calibration and Measurement Techniques
- Historical Astronomy and Related Studies
- Global Energy and Sustainability Research
- Laser-induced spectroscopy and plasma
- Mass Spectrometry Techniques and Applications
- Atmospheric Ozone and Climate
- Impact of Light on Environment and Health
- X-ray Spectroscopy and Fluorescence Analysis
- Chemical Thermodynamics and Molecular Structure
- Photovoltaic System Optimization Techniques
- Optical Systems and Laser Technology
- Advanced Chemical Physics Studies
- Cosmology and Gravitation Theories
- Historical and Architectural Studies
Université Côte d'Azur
2008-2025
Observatoire de la Côte d’Azur
2008-2025
Centre National de la Recherche Scientifique
2008-2018
Beef Farmers of Ontario
2012
University of California, Los Angeles
2006
Instituto Superior Técnico
2005
Instituto Politécnico de Lisboa
2005
Laboratoire d’Études en Géophysique et Océanographie Spatiales
1984
United States Naval Research Laboratory
1983
Astronomical Institute of the Slovak Academy of Sciences
1983
Here we analyze solar activity by focusing on time variations of the number sunspot groups (SGs) as a function their modified Zurich class. We analyzed data for cycles 20–23 using Rome (cycles 20 and 21) Learmonth Solar Observatory 22 23) SG numbers. All SGs recorded during these intervals were separated into two groups. The first group includes small (A, B, C, H, J classes classification), second consists large (D, E, F, G classes). then calculated numbers from daily mean observed disk...
In this study, we performed periodicity analyses of selected daily solar (flare index, coronal number mass ejections), geomagnetic (planetary equivalent range disturbance storm time interplanetary magnetic field) and cosmic ray indices for the last Solar Cycle 24 (from December 2008 to 2019). To study periodic variation above-listed datasets, following analysis methods were applied; multi-taper method, Morlet wavelet, cross-wavelet transform wavelet coherence analysis. The outcome our...
The discovery of the solar activity cycle was linked from outset to observation temporal variability sunspots, which we know be result complex processes associated with dynamics inner layers. Numerous recent studies have highlighted changes in Sun's Near-Surface Shear Layer (NSSL), pointing role leptocline, a shallow and sharp rotational shear layer top around 8 Mm. mainly characterized by strong radial gradient at middle latitudes self-organized meridional flows, is cradle numerous...
The discovery of the solar activity cycle was linked from outset to observation temporal variability sunspots, which we know be result complex processes associated with dynamics inner layers. Numerous recent studies have highlighted changes in Sun’s Near-Surface Shear Layer (NSSL), pointing role leptocline, a shallow and sharp rotational shear layer top \(\sim 8\) Mm. mainly characterized by strong radial gradient at middle latitudes self-organized meridional flows, is cradle numerous...
We investigate the relationship between monthly averaged maximal speeds of coronal mass ejections (CMEs), international sunspot number (ISSN), and geomagnetic Dst Ap indices covering 1996–2008 time interval (solar cycle 23). Our new findings are as follows. (1) There is a noteworthy maximum CME numbers, indices. Various peculiarities in index correlated better with fine structures speed profile than that ISSN data. (2) Unlike does not exhibit double peak maximum. Instead, peaks during...
Here, we analyze different sunspot group (SG) behaviors from the points of view both counts (SSCs) and number SGs, in four categories, for time period 1982 January–2014 May. These categories include data simple (A B), medium (C), large (D, E, F), decaying (H) SGs. We investigate temporal variations all sets used this study find following results. (1) There is a very significant decrease groups' SSCs SGs solar cycle 24 (cycle 24) compared to cycles 21–23. (2) no strong variation entire...
Polar brightening of the Sun at radio frequencies has been studied for almost fifty years and yet a disagreement persists between solar atmospheric models observations. Some observations reported values much smaller than expected obtained from models, with discrepancies being particularly large millimeter wavelengths. New clues to calibrate can be advent Atacama Large Millimeter/submillimeter Array (ALMA) interferometer. In this work, we analyzed lower limit polar observed 100 230 GHz by...
Recent models of variations the Sun's structure with 11 year activity cycle by Sofia et al. predict strong nonhomologous changes radius subsurface layers, due to magnetic fields and field-modulated turbulence. According their best model, surface may be 1000 times larger than those at depth 5 Mm. We use f-mode oscillation frequency data from SOHO MDI measurements solar ground-based observatories during 23 (1996-2005) put constraints on changes. The results show that above model overestimates...
Based on historical records, the Sun's dimensions are temporally dependent. Until recent past, varying were keenly disputed. Recent accurate observations have removed doubt, whether from direct limb or helioseismology f-modes analysis. A shrinking an expanding shape is ultimately linked to solar activity, as even a small variation in radius causes variations gravitational energy. space- and ground-based observations, we will argue that oblateness of Sun time Indeed, considering first two...
We use Singular Spectrum Analysis (SSA) to analyze total solar irradiance variations and CERGA radius measurements. Total has been monitored from space for more than two decades, whilst ground-based measurements are available as a coherent time series 1975. compare these indicators try understand the origin of energy production inside Sun. One main objectives was assess reality observed Sun's by distinguishing signal noise. Two approaches were used: one using SSA on data averaged over 90...
Recent solar radius determinations from space observations of Mercury and Venus transits have been made by different teams in 2003, 2006, 2012, 2014. Seemingly the results are not consistent: authors interpreted discrepancies as caused methods analysis. However, looking at wavelength dependence adding other available X-EUV up to radio, a typical can be found, reflecting heights which lines formed. Measurements obtained during periods time would, principle, allow us detect signature temporal...
Regular measurements of the Sun's diameter have been obtained by means solar astrolabes for several decades. However, variations found from those are still very controversial, and results implying changes in radius not conclusive. Since quality cannot be doubted, it is necessary to wonder what they actually observing. We show here that some refraction effects, neglected so far, must taken into account. Then, if lower atmospheric layers merely add high-frequency noise (validated measured...
Abstract The questions asking whether the Sun shrinks with solar activity and what causes this have been a subject of debate. Helioseismology provides means to measure high precision radial displacement subsurface layers, so-called “seismic radius,” through analysis oscillation frequencies surface gravity ( f ) modes. Here, we present results new 21 years helioseismology data from two space missions, Solar Heliospheric Observatory Dynamics , which allow us resolve previous uncertainties...
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Solar diameters have been measured from different ground-based instruments on sites all around the world. There are values dating back to three centuries ago, but revival of interest began in 1970s when it was claimed that a temporal periodic modulation had found. The such measurements, pinpointed only two decades, may not lie these variations, fact latitudinal heliographic dependence exist. Such solar shape distortion has deduced analysis astrolabe data sorted by latitudes, observational...