Publications

2022

• Enhancement of the Nonresonant Streaming Instability by Particle Collisions
  
  • Marret Alexis
  • Ciardi Andrea
  • Smets Roch
  • Fuchs Julien
  • Nicolas Loic
  Physical Review Letters, American Physical Society, 2022, 128 (11), pp.115101. Streaming cosmic rays can power the exponential growth of a seed magnetic field by exciting a nonresonant instability that feeds on their bulk kinetic energy. By generating the necessary turbulent magnetic field, it is thought to play a key role in the confinement and acceleration of cosmic rays at shocks. In this Letter we present hybrid-particle-in-cell simulations of the nonresonant mode including Monte Carlo collisions, and investigate the interplay between the pressure anisotropies produced by the instability and particle collisions in the background plasma. Simulations of poorly ionized plasmas confirm the rapid damping of the instability by proton-neutral collisions predicted by linear fluid theory calculations. In contrast we find that Coulomb collisions in fully ionized plasmas do not oppose the growth of the magnetic field, but under certain conditions suppress the pressure anisotropies and actually enhance the magnetic field amplification. (10.1103/PhysRevLett.128.115101)
  DOI : 10.1103/PhysRevLett.128.115101
• Scale-Dependent Kurtosis of Magnetic Field Fluctuations in the Solar Wind: A Multi-Scale Study With Cluster 2003-2015
  
  • Roberts O. W.
  • Alexandrova O.
  • Sorriso-Valvo L.
  • Vörös Z.
  • Nakamura R.
  • Fischer D.
  • Varsani A.
  • Escoubet C. Philippe
  • Volwerk M.
  • Canu Patrick
  • Lion S.
  • Yearby K.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2022, 127. During the lifetime of the Cluster mission, the inter-spacecraft distances in the solar wind have changed from the large, fluid, scales (∼10<SUP>4</SUP> km), down to the scales of protons (∼10<SUP>2</SUP> km). As part of the guest investigator campaign, the mission achieved a formation where a pair of spacecraft were separated by ∼7 km. The small distances and the exceptional sensitivity of the search coil magnetometer provide an excellent data set for studying solar wind turbulence at electron scales. In this study, we investigate the intermittency of the magnetic field fluctuations in the slow solar wind. Using 20 time intervals with different constellation orientations of Cluster we cover spatial scales between 7 and 10<SUP>4</SUP> km. We compare time-lagged increments from a single spacecraft with spatially lagged increments using multiple spacecraft. As the turbulent cascade proceeds to smaller scales in the inertial range, the deviation from Gaussian statistics is observed to increase in both temporal and spatial increments in the components transverse to the mean field direction. At ion scales, there is a maximum of kurtosis, and at sub-ion scales, the fluctuations are only weakly non-Gaussian. In the compressive component the deviation from Gaussian statistics is variable: it may increase throughout the inertial and sub-ion ranges, but also, it may have a maximum at magnetohydrodynamic scales associated with large scale magnetic holes. The observations show differences in kurtosis of time and space increments when the spacecraft pairs are transverse to the flow, indicating its spatial anisotropy. (10.1029/2021JA029483)
  DOI : 10.1029/2021JA029483
• Massive Multi‐Mission Statistical Study and Analytical Modeling of the Earth's Magnetopause: 4. On the Near‐Cusp Magnetopause Indentation
  
  • Nguyen G.
  • Aunai N.
  • Michotte de Welle Bayane
  • Jeandet A.
  • Lavraud B.
  • Fontaine D.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2022, 127 (1), pp.e2021JA029776. The shape and location of the magnetopause current sheet in the near-cusp region is still a debated question. Over time, several observations led to contradictory conclusions regarding the presence of an indentation of the magnetopause in that region. As a result several empirical models consider the surface is indented in that region, while some others do not. To tackle this issue, we fit a total of 17,230 magnetopause crossings to various indented and non-indented analytical models. The results show that while all models describe the magnetopause position and shape equivalently far from the cusp region, the non-indented version over-estimate the radial position of the near-cusp magnetopause. Among indented models, we show that the one designed from non-linearmagneto hydrodynamic simulations fits well the near-cusp magnetopause location, while the other underestimate its position probably because their design was possibly based on magnetopause crossing catalogs that contain cusp inner boundary crossings. (10.1029/2021JA029776)
  DOI : 10.1029/2021JA029776
• The Persistent Mystery of Collisionless Shocks
  
  • Goodrich Katherine
  • Schwartz Steven
  • Wilson III Lynn
  • Cohen Ian
  • Caspi Amir
  • Smith Keith
  • Rose Randall
  • Whittlesey Phyllis
  • Plaschke Ferdinand
  • Halekas Jasper
  • Hospodarsky George
  • Burch James
  • Gingell Imogen
  • Chen Li-Jen
  • Retino Alessandro
  • Khotyaintev Yuri
  Bulletin of the American Astronomical Society, American Astronomical Society, 2022, 55 (3). Collisionless shock waves are one of the main forms of energy conversion in space plasmas. They can directly or indirectly drive other universal plasma processes such as magnetic reconnection, turbulence, particle acceleration and wave phenomena. Collisionless shocks employ a myriad of kinetic plasma mechanisms to convert the kinetic energy of supersonic flows in space to other forms of energy (e.g., thermal plasma, energetic particles, or Poynting flux) in order for the flow to pass an immovable obstacle. The partitioning of energy downstream of collisionless shocks is not well understood, nor are the processes which perform energy conversion. While we, as the heliophysics community, have collected an abundance of observations of the terrestrial bow shock, instrument and mission-level limitations have made it impossible to quantify this partition, to establish the physics within the shock layer responsible for it, and to understand its dependence on upstream conditions. This paper stresses the need for the first ever spacecraft mission specifically designed and dedicated to the observation of both the terrestrial bow shock as well as Interplanetary shocks in the solar wind. (10.3847/25c2cfeb.9053575b)
  DOI : 10.3847/25c2cfeb.9053575b
• Massive Multi-Mission Statistical Study and Analytical Modeling of the Earth's Magnetopause: 2. Shape and Location
  
  • Nguyen G.
  • Aunai N.
  • Michotte de Welle B.
  • Jeandet A.
  • Lavraud B.
  • Fontaine D.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2022, 127. The Earth magnetopause is the boundary between the magnetosphere and the shocked solar wind. Its location and shape are primarily determined by the properties of the solar wind and interplanetary magnetic field (IMF) but the nature of the control parameters and to what extent they impact the stand-off distance, the flaring, and the symmetries, on the dayside and night side, is still not well known. We present a large statistical study of the magnetopause location and shape based an extensive multi-mission magnetopause database, cumulating 17,230 crossings on 17 different spacecraft, from the dayside to lunar nightside distances. The results confirm the power-law dependency of the stand-off position on the solar wind pressure. The IMF clock angle itself (all amplitudes combined) does not impact the stand-off distance, nor does the cone angle. However, the magnetopause is found to move Earthward as the IMF gets stronger and more southward. All upstream conditions combined, it is found that the function used at the root of several analytical models still holds at lunar distances. We find that the equatorial flaring is larger than the meridional one. However, the meridional flaring is found to depend on the seasonal tilt conditions, being larger in the summer hemisphere. The flaring is also found to depend on the IMF clock angle. Meridional flaring increases as the IMF turns south and is then larger than the equatorial flaring. The equatorial flaring barely changes or weakly increases as the IMF turns northward, and is larger than the meridional flaring for northward conditions. The results of the study pave the way for the elaboration of a new analytical empirical expression of the magnetopause location and shape. (10.1029/2021JA029774)
  DOI : 10.1029/2021JA029774
• The RayGalGroupSims cosmological simulation suite for the study of relativistic effects: an application to lensing-matter clustering statistics
  
  • Rasera Y.
  • Breton M-A.
  • Corasaniti P-S.
  • Allingham J.
  • Roy F.
  • Reverdy V.
  • Pellegrin T.
  • Saga S.
  • Taruya A.
  • Agarwal S.
  • Anselmi S.
  Astronomy & Astrophysics - A&A, EDP Sciences, 2022, 661, pp.A90. General Relativistic effects on the clustering of matter in the universe provide a sensitive probe of cosmology and gravity theories that can be tested with the upcoming generation of galaxy surveys. Here, we present a suite of large volume high-resolution N-body simulations specifically designed to generate light-cone data for the study of relativistic effects on lensing-matter observables. RayGalGroupSims (or in short RayGal) consists of two N-body simulations of $(2625\,h^{-1}\,{\rm Mpc})^3$ volume with $4096^3$ particles of a standard flat $\Lambda$CDM model and a non-standard $w$CDM phantom dark energy model. Light-cone data from the simulations have been generated using a parallel ray-tracing algorithm that has accurately solved billion geodesic equations. Catalogues and maps with relativistic weak-lensing which include post-Born effects, magnification bias (MB) and redshift space distortions (RSD) due to gravitational redshift, Doppler, transverse Doppler, Integrated Sachs-Wolfe/Rees-Sciama effects, are publicly released. Using this dataset, we are able to reproduce the linear and quasi-linear predictions from the Class relativistic code for the 10 (cross-)power spectra (3$\times$2 points) of the matter density fluctuation field and the gravitational convergence at $z=0.7$ and $z=1.8$. We find 1-30% level contribution from both MB and RSD to the matter power spectrum, while the Fingers-of-God effect is visible at lower redshift in the non-linear regime. MB contributes at the $10-30\%$ level to the convergence power spectrum leading to a deviation between the shear power-spectrum and the convergence power-spectrum. MB also plays a significant role in the galaxy-galaxy lensing by decreasing the density-convergence spectra by $20\%$, while coupling non-trivial configurations (such as the one with the convergence at the same or even lower redshift than the density field). (10.1051/0004-6361/202141908)
  DOI : 10.1051/0004-6361/202141908
• Massive Multi-Mission Statistical Study and Analytical Modeling of the Earth's Magnetopause: 3. An Asymmetric Non Indented Magnetopause Analytical Model
  
  • Nguyen G.
  • Aunai Nicolas
  • Michotte de Welle Bayane
  • Jeandet A.
  • Lavraud B.
  • Fontaine D.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2022, 127. In a companion statistical study, we showed that the expression of the magnetopause surface as a power law of an elliptic function of the zenith angle θ holds at lunar distances, that the flaring of the magnetopause surface is influenced by the Interplanetary Magnetic Field (IMF) B<SUB>y</SUB> component and that the IMF B<SUB>x</SUB> component had no influence on the stand-off distance. As a follow-up to these statistical results, this paper presents a new empirical analytical asymmetric and non-indented model of the magnetopause location and shape. This model is obtained from fitting of 15,349 magnetopause crossings using 17 different spacecraft and is parametrized by the upstream solar wind dynamic and magnetic pressures, the IMF clock angle and the Earth dipole tilt angle. The constructed model provides a more accurate prediction of the magnetopause surface location than current Magnetopause surface models, especially on the night side of the magnetosphere. (10.1029/2021JA030112)
  DOI : 10.1029/2021JA030112
• Enceladus and Titan: emerging worlds of the Solar System
  
  • Sulaiman Ali H.
  • Achilleos Nicholas
  • Bertucci Cesar
  • Coates Andrew
  • Dougherty Michele
  • Hadid Lina
  • Holmberg Mika
  • Hsu Hsiang-Wen
  • Kimura Tomoki
  • Kurth William
  • Le Gall Alice
  • Mckevitt James
  • Morooka Michiko
  • Murakami Go
  • Regoli Leonardo
  • Roussos Elias
  • Saur Joachim
  • Shebanits Oleg
  • Solomonidou Anezina
  • Wahlund Jan-Erik
  • Waite J. Hunter
  Experimental Astronomy, Springer Link, 2022, 54, pp.849-876. Some of the major discoveries of the recent Cassini-Huygens mission have put Titan and Enceladus rmly on the Solar System map. The mission has revolutionised our view of Solar System satellites, arguably matching their scienti c importance with that of their host planet. While Cassini-Huygens has made big surprises in revealing Titan’s organically rich environment and Enceladus’ cryovolcanism, the mission’s success naturally leads us to further probe these ndings. We advocate the acknowl- edgement of Titan and Enceladus science as highly relevant to ESA’s long-term roadmap, as logical follow-on to Cassini-Huygens. In this White Paper, we will out- line important science questions regarding these satellites and identify the science themes we recommend ESA cover during the Voyage 2050 planning cycle. Address- ing these science themes would make major advancements to the present knowledge we have about the Solar System, its formation, evolution, and likelihood that other habitable environments exist outside the Earth’s biosphere. (10.1007/s10686-021-09810-z)
  DOI : 10.1007/s10686-021-09810-z
• Structure and Variability of Low-Energy Ions in Mercury's Magnetosphere: Initial Results from BepiColombo Mio MIA Observations
  
  • Harada Yuki
  • Saito Yoshifumi
  • Aizawa Sae
  • Hadid L. Z.
  • André Nicolas
  • Persson Moa
  • Delcourt Dominique
  • Fraenz Markus
  • Yokota Shoichiro
  • Murakami Go
  • Fedorov Andrei
  • Miyake Wataru
  • Penou Emmanuel
  • Barthe Alain
  • Savaud Jean-André
  • Katra Bruno
  • Matsuda Shoya
  , 2022, 2022. We present initial results from low-energy ion measurements by the Mercury Ion Analyzer (MIA) on board BepiColombo Mio during the first and second Mercury flybys. The orbital configurations of the two flybys were very similar, but the ion properties observed by MIA are significantly different presumably because of different upstream solar wind conditions. Specifically, the ion energies are generally lower during the first flyby than the second flyby, suggesting slower solar wind conditions in the former case. The ion energy spectra obtained during the first flyby suggest the presence of a relatively cold dense ion component in the midnight magnetotail, sources and transport mechanisms of which remain elusive. Additionally, by utilizing an MIA data product that is originally designed to separate ion directions according to the spacecraft spin phase, we derive bonus data of high-time resolution (>~1 s) ion flux measurements from non-spinning observations during the cruise phase. Such high-time resolution measurements could be useful to investigate boundary dynamics, ion kinetics, etc. These flyby observations with limited capabilities suggest rich dynamics of low-energy ions in Mercury's magnetosphere, more complete views of which will be derived from future in-orbit observations of full 3-dimensional ion velocity distribution functions by MIA, along with ion composition and magnetic field measurements by other instruments on Mio.
• Massive Multi‐Mission Statistical Study and Analytical Modeling of the Earth's Magnetopause: 1. A Gradient Boosting Based Automatic Detection of Near‐Earth Regions
  
  • Nguyen G.
  • Aunai N.
  • Michotte de Welle B.
  • Jeandet Alexis
  • Lavraud B.
  • Fontaine D.
  Journal of Geophysical Research Space Physics, American Geophysical Union/Wiley, 2022, 127 (1), pp.e2021JA029773. We present an automatic classification method of the three near-Earth regions, the magnetosphere, the magnetosheath and the solar wind from their in situ data measurement by multiple spacecraft. Based on gradient boosting classifier, this very simple and very fast method outperforms the detection routines based on manually set thresholds. The method is used to identify 15,062 magnetopause crossings and 17,227 bow shock crossings in the data of 11 different spacecraft of the THEMIS, ARTEMIS, Cluster, MMS, and Double Star missions and for a total of 83 cumulated years. These multi-mission catalogs are easily reproducible, can be automatically enlarged with additional data and their elaboration paves the way for future massive statistical analysis of near-Earth boundaries. (10.1029/2021JA029773)
  DOI : 10.1029/2021JA029773
• Transport barrier in 5D gyrokinetic flux-driven simulations
  
  • Lo-Cascio G.
  • Gravier Etienne
  • Réveillé T.
  • Lesur M.
  • Sarazin Y.
  • Garbet X.
  • Vermare L.
  • Lim K.
  • Guillevic A.
  • Grandgirard V.
  Nuclear Fusion, IOP Publishing, 2022, 62 (12), pp.126026. Abstract Two ways for producing a transport barrier through strong shear of the E × B poloidal flow have been investigated using GYSELA gyrokinetic simulations in a flux-driven regime. The first one uses an external poloidal momentum (i.e. vorticity) source that locally polarizes the plasma, and the second one enforces a locally steep density profile that also stabilizes the ion temperature gradient (ITG) instability modes linearly. Both cases show a very low local turbulent heat diffusivity coefficient χ T turb and a slight increase in core pressure when a threshold of ω E × B ≈ γ ¯ lin (respectively the E × B shear rate and average linear growth rate of ITG) is reached, validating previous numerical results. This pressure increase and χ T turb quench are the signs of a transport barrier formation. This behaviour is the result of a reduced turbulence intensity which strongly correlates with the shearing of turbulent structures as evidenced by a reduction of the auto-correlation length of potential fluctuations as well as an intensity reduction of the k θ spectrum. Moreover, a small shift towards smaller poloidal wavenumber is observed in the vorticity source region which could be linked to a tilt of the turbulent structures in the poloidal direction. (10.1088/1741-4326/ac945d)
  DOI : 10.1088/1741-4326/ac945d
• Cyto- and bio-compatibility assessment of plasma-treated polyvinylidene fluoride scaffolds for cardiac tissue engineering
  
  • Kitsara Maria
  • Revet Gaëlle
  • Vartanian-Grimaldi Jean-Sébastien
  • Simon Alexandre
  • Minguy Mathilde
  • Miche Antoine
  • Humblot Vincent
  • Dufour Thierry
  • Agbulut Onnik
  Frontiers in Bioengineering and Biotechnology, Frontiers, 2022, 10, pp.1008436. As part of applications dealing with cardiovascular tissue engineering, drop-cast polyvinylidene fluoride (PVDF) scaffolds have been treated by cold plasma to enhance their adherence to cardiac cells. The scaffolds were treated in a dielectric barrier device where cold plasma was generated in a gaseous environment combining a carrier gas (helium or argon) with/without a reactive gas (molecular nitrogen). We show that an Ar-N2 plasma treatment of 10 min results in significant hydrophilization of the scaffolds, with contact angles as low as 52.4° instead of 132.2° for native PVDF scaffolds. Correlation between optical emission spectroscopy and X-ray photoelectron spectroscopy shows that OH radicals from the plasma phase can functionalize the surface scaffolds, resulting in improved wettability. For all plasma-treated PVDF scaffolds, the adhesion and maturation of primary cardiomyocytes is increased, showing a well-organized sarcomeric structure (α-actinin immunostaining). The efficacy of plasma treatment was also supported by real-time PCR analysis to demonstrate an increased expression of the genes related to adhesion and cardiomyocyte function. Finally, the biocompatibility of the PVDF scaffolds was studied in a cardiac environment, after implantation of acellular scaffolds on the surface of the heart of healthy mice. Seven and 28 days after implantation, no exuberant fibrosis and no multinucleated giant cells were visible in the grafted area, hence demonstrating the absence of foreign body reaction and the biocompatibility of these scaffolds. (10.3389/fbioe.2022.1008436)
  DOI : 10.3389/fbioe.2022.1008436
• Science goals and new mission concepts for futureexploration of Titan’s atmosphere, geologyand habitability: titan POlar scout/orbitEr and in situ lakelander and DrONe explorer (POSEIDON)
  
  • Rodriguez Sébastien
  • Vinatier Sandrine
  • Cordier Daniel
  • Tobie G.
  • Achterberg Richard K.
  • Anderson Carrie M.
  • Badman Sarah V.
  • Barnes Jason W.
  • Barth Erika L.
  • Bézard Bruno
  • Carrasco Nathalie
  • Charnay Benjamin
  • Clark Roger N.
  • Coll Patrice
  • Cornet Thomas
  • Coustenis Athena
  • Couturier-Tamburelli Isabelle
  • Dobrijevic Michel
  • Flasar F. Michael
  • de Kok Remco
  • Freissinet Caroline
  • Galand Marina
  • Gautier Thomas
  • Geppert Wolf D.
  • Griffith Caitlin A.
  • Gudipati Murthy S.
  • Hadid Lina Z.
  • Hayes Alexander G.
  • Hendrix Amanda R.
  • Jauman Ralf
  • Jennings Donald E.
  • Jolly Antoine
  • Kalousova Klara
  • Koskinen Tommi T.
  • Lavvas Panayotis
  • Lebonnois Sébastien
  • Lebreton Jean-Pierre
  • Le Gall Alice
  • Lellouch Emmanuel
  • Le Mouélic Stéphane
  • Lopes Rosaly M. C.
  • Lora Juan M.
  • Lorenz Ralph D.
  • Lucas Antoine
  • Mackenzie Shannon
  • Malaska Michael J.
  • Mandt Kathleen
  • Mastrogiuseppe Marco
  • Newman Claire E.
  • Nixon Conor A.
  • Radebaugh Jani
  • Rafkin Scot C.
  • Rannou Pascal
  • Sciamma-O-Brien Ella M.
  • Soderblom Jason M.
  • Solomonidou Anezina
  • Sotin Christophe
  • Stephan Katrin
  • Strobel Darrell
  • Szopa Cyril
  • Teanby Nicholas A.
  • Turtle Elizabeth P.
  • Vuitton Véronique
  • West Robert A.
  Experimental Astronomy, Springer Link, 2022, 54, pp.911-973. In response to ESA Voyage 2050 announcement of opportunity, we propose an ambitious L-class mission to explore one of the most exciting bodies in the Solar System, Saturn largest moon Titan. Titan, a "world with two oceans", is an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. Titan is also one of the few places in the Solar System with habitability potential. Titan remarkable nature was only partly revealed by the Cassini-Huygens mission and still holds mysteries requiring a complete exploration using a variety of vehicles and instruments. The proposed mission concept POSEIDON (Titan POlar Scout/orbitEr and In situ lake lander DrONe explorer) would perform joint orbital and in situ investigations of Titan. It is designed to build on and exceed the scope and scientific/technological accomplishments of Cassini-Huygens, exploring Titan in ways that were not previously possible, in particular through full close-up and in situ coverage over long periods of time. In the proposed mission architecture, POSEIDON consists of two major elements: a spacecraft with a large set of instruments that would orbit Titan, preferably in a low-eccentricity polar orbit, and a suite of in situ investigation components, i.e. a lake lander, a "heavy" drone (possibly amphibious) and/or a fleet of mini-drones, dedicated to the exploration of the polar regions. The ideal arrival time at Titan would be slightly before the next northern Spring equinox (2039), as equinoxes are the most active periods to monitor still largely unknown atmospheric and surface seasonal changes. The exploration of Titan northern latitudes with an orbiter and in situ element(s) would be highly complementary with the upcoming NASA New Frontiers Dragonfly mission that will provide in situ exploration of Titan equatorial regions in the mid-2030s. (10.1007/s10686-021-09815-8)
  DOI : 10.1007/s10686-021-09815-8
• Fast gas heating and kinetics of electronically excited states in a nanosecond capillary discharge in CO2
  
  • Pokrovskiy G V
  • Popov N A
  • Starikovskaia S M
  Plasma Sources Science and Technology, IOP Publishing, 2022, 31 (3), pp.035010. Fast gas heating in a pulsed nanosecond capillary discharge in pure CO_2 under the conditions of high specific deposited energy (around 1.2 eV/molecule) and high reduced electric fields (150–250 Td) has been studied experimentally and numerically. Specific deposited energy, reduced electric field and gas temperature have been measured as functions of time. The radial distribution of the electron density has been analyzed experimentally. The role of quenching of O( ^1D), O(^1S) and CO(a^3Π) excited atoms and molecules leading to heat release at sub-microsecond time scale have been analyzed by numerical modeling in the framework of 1D axial approximation. (10.1088/1361-6595/ac5102)
  DOI : 10.1088/1361-6595/ac5102
• A Study of Solar Flare Effects on the Geomagnetic Field Components during Solar Cycles 23 and 24
  
  • Grodji Oswald Didier Franck
  • Doumbia Vafi
  • Amaechi Paul Obiakara
  • Diaby Kassamba Abdel Aziz
  • Amaechi Paul Obiakara
  • Amory-Mazaudier Christine
  • N’guessan Kouassi
  • Diaby Kassamba Abdel Aziz
  • Zie Tuo
  • Boka Kouadio
  Atmosphere, MDPI, 2022, 13 (1), pp.69. In this paper, we investigated the impact of solar flares on the horizontal (H), eastward (Y) and vertical (Z) components of the geomagnetic field during solar cycles 23 and 24 (SC23/24) using data of magnetometer measurements on the sunlit side of the Earth. We examined the relation between sunspot number and solar flare occurrence of various classes during both cycles. During SC23/24, we obtained correlation coefficient of 0.93/0.97, 0.96/0.96 and 0.60/0.56 for C-class, M-class and X-class flare, respectively. The three components of the geomagnetic field reached a peak a few minutes after the solar flare occurrence. Generally, the magnetic crochet of the H component was negative between the mid-latitudes and Low-latitudes in both hemispheres and positive at low latitudes. By contrast, the analysis of the latitudinal variation of the Y and Z components showed that unlike the H component, their patterns of variations were not coherent in latitude. The peak amplitude of solar flare effect (sfe) on the various geomagnetic components depended on many factors including the local time at the observing station, the solar zenith angle, the position of the station with respect to the magnetic equator, the position of solar flare on the sun and the intensity of the flare. Thus, these peaks were stronger for the stations around the magnetic equator and very low when the geomagnetic field components were close to their nighttime values. Both cycles presented similar monthly variations with the highest sfe value (ΔHsfe = 48.82 nT for cycle 23 and ΔHsfe = 24.68 nT for cycle 24) registered in September and lowest in June for cycle 23 (ΔHsfe = 8.69 nT) and July for cycle 24 (ΔHsfe = 10.69 nT). Furthermore, the sfe was generally higher in cycle 23 than in cycle 24. (10.3390/atmos13010069)
  DOI : 10.3390/atmos13010069