K. Meziane - Academia.edu (original) (raw)

Papers by K. Meziane

Astronomy and Astrophysics, 1996

Space Weather, 2020

Global Positioning System (GPS) L1 amplitude data, obtained using the Canadian High Arctic Ionosp... more Global Positioning System (GPS) L1 amplitude data, obtained using the Canadian High Arctic Ionospheric Network (CHAIN) during the period 2008–2018, is used to study the seasonal and solar cycle dependence of high‐latitude amplitude scintillation. The occurrence of amplitude scintillation is predominantly confined to the 10–18 magnetic local time (MLT) and 72–87° Altitude‐Adjusted Corrected Geomagnetic (AACGM) sector and is a winter and equinoctial phenomenon. The occurrence of amplitude scintillation shows a clear seasonal and solar cycle dependence with a maximum value of ∼11% during the high solar activity early winter periods, and a secondary maximum in equinoctial months, and almost no occurrence during summer months. This pattern in occurrence suggests that amplitude scintillation is a phenomenon that is closely associated with the presence of patches and particle precipitation events.

Geophysical Research Letters, 2019

Electron velocity distributions in Mars's magnetosheath show a systematic erosion of the ener... more Electron velocity distributions in Mars's magnetosheath show a systematic erosion of the energy spectrum with distance downstream from the bow shock. Previous attempts to model this erosion invoked assumptions to promote electron ionization impact collisions with Mars's neutral hydrogen exosphere. We show that the near collision‐free magnetosheath requires a kinetic description; the population of electrons at any location is a convolution of electrons arriving from more distant regions that ultimately map directly to the solar wind. We construct a simple model that captures all the essential physics. The model demonstrates how the erosion of the electron distributions is the result of the trapping, escape, and replacement of electrons that traverse the global bow shock; some are temporarily confined to the expanding cavity formed by the cross‐shock electrostatic potential. The model also has implications for the ability of solar wind electrons to reach altitudes below the pi...

Geophysical Research Letters, 2018

Backstreaming electrons emanating from the bow shock of Mars reported from the Mars Atmosphere an... more Backstreaming electrons emanating from the bow shock of Mars reported from the Mars Atmosphere and Volatile EvolutioN/Solar Wind Electron Analyzer observations show a flux fall off with the distance from the shock. This feature is not observed at the terrestrial foreshock. The flux decay is observed only for electron energy E ≥ 29 eV. A reported recent study indicates that Mars foreshock electrons are produced at the shock in a mirror reflection of a portion of the solar wind electrons. In this context, and given that the electrons are sufficiently energetic to not be affected by the interplanetary magnetic field fluctuations, the observed flux decrease appears problematic. We investigate the possibility that the flux fall off with distance results from the impact of backstreaming electrons with Mars exospheric neutral hydrogen. We demonstrate that the flux fall off is consistent with the electron‐atomic hydrogen impact cross section for a large range of energy. A better agreement i...

AIP Conference Proceedings, 2007

Different types of backstreaming ion distributions have been reported in the region upstream from... more Different types of backstreaming ion distributions have been reported in the region upstream from the Earth's bow shock and magnetically connected to it (ion foreshock): field-aligned beams (FABs), gyrating ion and diffuse ion distributions. Contrary to the first type, the two others are always associated with ULF waves. Among them, gyrating ions with well-defined pitch-angle and gyrophase organization around the local magnetic field have been frequently observed in association with large amplitude quasi-monochromatic right-hand mode waves. These waves reveal the existence of coherent wave-particle interaction which is an efficient process to dissipate the energy of the particles reflected at the collisionless bow shock. It has been shown recently from a large data set from multi-spacecraft observations by Cluster that the gyrophase-bunched ion distributions are mainly produced by such a process from cyclotron-resonant FABs observed just both at the edge of the gyrating ions region and the boundary of ULF waves.

We report an observation by Cluster-CIS of an energetic (2--30~keV) upstream ion event presenting... more We report an observation by Cluster-CIS of an energetic (2--30~keV) upstream ion event presenting a clear double-peak spectrum. The lower-energy (E ˜~3.5~keV) peak is associated with an ion beam propagating along the magnetic field direction, while the higher-energy peak is associated with gyrating ions. Our analysis indicates that the gyrating ions had guiding centers on field lines downstream of the field-aligned component, but that both populations could be sampled simultaneously due to gyroradius effect. We find that downstream limit of the field-aligned beams is populated with protons having a speed 1.5 times the solar wind velocity, which is inconsistent with any known shock-related emission mechanisms. The spatial boundary separating the field-aligned beams from the gyrating ion guiding centers corresponds well with the ULF and intermediate ion foreshock boundary reported in previous studies. Like the field-aligned beams, the gyrating ions reported here have streaming speeds ...

Proceedings of ISSS, 2005

The foreshock region is the first signature of the interaction of the solar wind with a planet's ... more The foreshock region is the first signature of the interaction of the solar wind with a planet's plasma environment when approaching its collisionless bow shock. Part of its structure and dynamic is determined by instabilities, which are created by the interaction of the solar wind with backstreaming ion populations. Large amplitude quasimonochromatic low-frequency waves are often observed in the Earth's foreshock. Associated backstreaming ion distributions often reveal the existence of gyrating ions with well-defined pitch-angle and gyrophase organization around the local magnetic field. Field-aligned ion beams observed in the region close to the gyrating ions region are quantitatively shown to be good candidate to generate the waves via the ion/ion resonant right-hand mode instability. Different mechanisms have been put forward to explain the existence of the gyrophase-bunched ions. The possibility of local nonlinear wave-particle interaction involving initially field-aligned beam ions have been quantitatively shown by analytical test particle calculations for some case studies from multi-spacecraft observations by Cluster. Such wave trapping mechanism would need now to be studied by using a kinetic hybrid or particle simulation approach.

New features of Earth's bow shock structure have been observed by the HIA ion experiment on ... more New features of Earth's bow shock structure have been observed by the HIA ion experiment on the first Chinese scientific satellite, Double Star. At times of coincident apogee, the Cluster spacecraft served as monitors of the upstream condition providing information from nearly identical instruments. The combination of the orbit with an apogee approximately at 13.5 Re and data obtained in high time resolution (4s) has permitted observations of the shock structure with unprecendented detail. We present examples of laminar and turbulent shocks observed in late February and early March (2004) when the Double Star apogee was located on the sunward side skimming the shock boundary. This talk will discuss (1) evolutionary features of ion distributions of the solar wind slowdown converting almost the entire flow energy into thermal energy, (2) microscopic features that could be signifying kinetic processes at work and (3) ordering of density, bulk velocity and temperature to show the d...

Journal of Geophysical Research: Space Physics, 2009

Journal of Geophysical Research, 2004

We examine an energetic (2-30 keV) upstream ion event presenting a clear doublepeak spectrum obse... more We examine an energetic (2-30 keV) upstream ion event presenting a clear doublepeak spectrum observed 1REupstreamfromthebowshock.Thelower−energy(E1 R E upstream from the bow shock. The lower-energy (E 1REupstreamfromthebowshock.Thelower−energy(E 3.5 keV) peak is associated with an ion beam propagating along the magnetic field direction, while the higher-energy (E $ 13 keV) peak is associated with gyrating ions having pitch angles $30°. The latter population progressively extends to lower energies over the span of the event. During times when the field-aligned beams were observed, the interplanetary magnetic field was remarkably steady, while the appearance of the 30°p itch angle gyrating ions was accompanied by the onset of large-amplitude ultralow frequency fluctuations of the magnetic field. Our analysis indicates that the gyrating ions had guiding centers on field lines downstream of the field-aligned component but that both populations could be sampled simultaneously because of the orbits of the former. We find that the downstream limit of the field-aligned beams is populated with protons having a speed 1.68 times the solar wind velocity, which is inconsistent with any known shockrelated emission mechanisms. This boundary makes an angle of 77°with respect to the Sun-Earth line in agreement with theoretical predictions. Just downstream of this rapid transition, gyrating ions having a flow speed of 1.52 times the solar wind speed are observed in association with ULF waves. Like the field-aligned beams, the gyrating ions reported here have streaming speeds inconsistent with any known shock emission mechanisms. While the simultaneous observation of field-aligned and gyrating components is possible because of the large gyration orbits of the latter, the observational sequence is consistent with a very sharp (]1 gyroradius) boundary separating the guiding centers of each. Explicit observations of such a sharp demarcation between these populations have not been reported before, and they place a significant constraint on the production mechanisms of the two populations. Our interpretation of these observations provides a refinement of the usual framework for foreshock morphology.

Geophysical Research Letters, 1999

... The solar wind velocity was ~ 620 km/s. A CIR event which began at 06:35 UT [Mason et al., 19... more ... The solar wind velocity was ~ 620 km/s. A CIR event which began at 06:35 UT [Mason et al., 1997], had filled the interplanetary medium at ~1 AU ... T| -T|u.) where T| is the ratio of the shock velocity Vs to particle velocity V, and p. the cosine of the particle pitch-angle [Decker, 1983 ...

Geophysical Research Letters, 2003

We report on gyrophase‐restricted ion beams with energies extending from ∼100 keV up to ∼2 MeV, o... more We report on gyrophase‐restricted ion beams with energies extending from ∼100 keV up to ∼2 MeV, observed by Wind in the Earth's distant (∼65 RE) foreshock. The ion gyrophases seen were nearly constant during periods when the distance to the shock contact point could be expected to vary by several RE, when there was no significant wave activity. At times the distributions had two peaks ∼180° apart in gyrophase. These were consistent with a remotely‐sensed energetic ion foreshock region having a thickness <2 gyroradii (∼1.5 RE for 0.5 MeV protons with pitch‐angle α = 30°). In this picture, gaps in phase space would correspond to particles with guiding centers outside of the energetic foreshock region. Similar observations over a decade of energies (100 keV–2 MeV) suggest that the region thickness scales with gyroradius. According to this interpretation, we have determined a rough range of geometries for which energetic particle production is favored. (Eg., θBn ∼70–80° for 500 k...

Geophysical Research Letters, 2011

The Earth's ionosphere is embedded in the "magnetosphere"; a cavity carved by the interaction of ... more The Earth's ionosphere is embedded in the "magnetosphere"; a cavity carved by the interaction of the high-speed solar wind and its "frozen-in" magnetic field with the terrestrial magnetic field. The solar wind is inherently non-steady, with its magnetic field, density, and flow speed varying on a range of time and amplitude scales. Variations in the solar wind and its magnetic field are known to be the major driver of variations in the high-latitude ionosphere. Using ionospheric total electron content (TEC) measured by Global Positioning System (GPS) receivers of the Canadian High Arctic Network (CHAIN), we provide clear evidence for a systematic and propagating TEC enhancement produced by the compression of the magnetosphere due to a sudden increase in the solar wind dynamic pressure. The magnetospheric compression is evident in the THEMIS/GOES data. Application of a GPS triangulation technique revealed that the TEC chnages propagated with a speed of ~ 6 km/s in the antisunward direction near noon and ~ 7 km/s in the sunward direction in the pre-noon sector. This is consistent with the scenario of increased ionospheric convection due to the magnetospheric compression. The characteristics of the TEC changes seems to indicate that they are due to the particle precipitation associated with the sudden magnetospheric compression.

Annales Geophysicae, 2004

An energetic ion (E≤40 keV) event observed by the CLUSTER/CIS experiment upstream of the Earth's ... more An energetic ion (E≤40 keV) event observed by the CLUSTER/CIS experiment upstream of the Earth's bow shock is studied in detail. The ion event is observed in association with quasi-monochromatic ULF MHD-like waves, which we show modulate the ion fluxes. According to three statistical bow shock position models, the Cluster spacecrafts are located at ∼0.5 R E from the shock and the averaged bow shock θ Bn0 is about ∼30 •. The analysis of the threedimensional angular distribution indicates that ions propagating roughly along the magnetic field direction are observed at the onset of the event. Later on, the angular distribution is gyrophase-bunched and the pitch-angle distribution is peaked at α 0 ∼θ Bn0 , consistent with the specular reflection production mechanism. The analysis of the waves shows that they are left-handed in the spacecraft frame of reference (right-handed in the solar wind frame) and propagate roughly along the ambient magnetic field; we have found that they are in cyclotron-resonance with the field-aligned beam observed just upstream. Using properties of the waves and particles, we explain the observed particle flux-modulation in the context of θ Bn changes at the shock caused by the convected ULF waves. We have found that the high count rates coincide with particles leaving the shock when θ Bn angles are less than ∼40 • , consistent with the specular reflection hypothesis as the production mechanism of ions.

Annales Geophysicae, 1998

A statistical investigation of the location of onset of intermediate and gyrating ion populations... more A statistical investigation of the location of onset of intermediate and gyrating ion populations in the Earth's foreshock is presented based on Fixed Voltage Analyzer data from ISEE 1. This study reveals the existence of a spatial boundary for intermediate and gyrating ion populations that coincides with the reported ULF wave boundary. This boundary position in the Earth's foreshock depends strongly upon the magnetic cone angle h f and appears well de®ned for relatively large cone angles, though not for small cone angles. As reported in a previous study of the ULF wave boundary, the position of the intermediate-gyrating ion boundary is not compatible with a ®xed growth rate of the waves resulting from the interaction between a uniform beam and the ambient plasma. The present work examines the momentum associated with protons which travel along this boundary, and we show that the variation of the boundary position (or equivalently, the associated particle momentum) with the cone angle is related to classical acceleration mechanisms at the bow shock surface. The same functional behavior as a function of the cone angle is obtained for the momentum predicted by an acceleration model and for the particle momentum associated with the boundary. However, the model predicts systematically larger values of the momentum than the observation related values by a constant amount; we suggest that this dierence may be due to some momentum exchange between the incident solarwind population and the backstreaming particles through a wave-particle interaction resulting from a beam plasma instability.

Advances in Space Research, 1997

Several upstream ion distributions having a gyrating signature have been identified with the 3DP/... more Several upstream ion distributions having a gyrating signature have been identified with the 3DP/PESA-High analyser on board the WIND spacecraft. These distributions are observed at distances greater than 20 R, from the Earth's bow shock. The distributions are observed in association with low frequency waves propagating quasi-parallel to the background magnetic field. By estimating the bulk velocity of the gyrating ions, we have found that the waves resonate with the particles. The observation of gyrating ions at large distances from the shock suggests their local production, probably from field-aligned beam disruption.