Magnetosphere-Ionosphere Coupling

This study characterizes total electron content (TEC) measured by Global Positioning System (GPS) over African equatorial ioniza-tion anomaly (EIA) region for 2009–2016 period during both quiet geomagnetic conditions (Kp 1) and normal conditions (1 > Kp 4). GPS-TEC data from four equatorial/low-latitude stations, namely, Addis Ababa (ADIS: 9.04°N, 38.77°E, mag. lat: 0.2°N) [Ethiopia]; Yamoussoukro (YKRO: 6.87°N, 5.24°W, mag. lat: 2.6°S) [Ivory Coast]; Malindi (MAL2; 3.00°S, 40.19°E, mag. lat: 12.4°S) [Kenya] and Libreville (NKLG; 0.35°N, 9.67°W, mag. lat: 13.5°S) [Gabon] were used for this study. Interesting features like noontime TEC bite-out, winter anomaly during the ascending and maximum phases of solar cycle 24, diurnal and seasonal variations with solar activity have been observed and investigated in this study. The day-today variations exhibited ionospheric TEC asymmetry on an annual scale. TEC observed at equatorial stations (EIA-trough) and EIA-crest reach maximum values between $1300–1600 LT and $1300–1600 LT, respectively. About 76% of the high TEC values were recorded in equinoctial months while the June solstice predominantly exhibited low TEC values. Yearly, the estimated TEC values increases or decreases with solar activity, with 2014 having the highest TEC value. Solar activity dependence of TEC within the EIA zone reveals that both F10.7 cm index and EUV flux (24–36 nm) gives a stronger correlation with TEC than Sunspot Number (SSN). A slightly higher degree of dependence is on EUV flux with the mean highest correlation coefficient (R) value of 0.70, 0.83, 0.82 and 0.88 for quiet geomagnetic conditions (Kp 1) at stations ADIS, MAL2, NKLG, and YKRO, respectively. The correlation results for the entire period consequently reveals that SSN and solar flux F10.7 cm index might not be an ideal index as a proxy for EUV flux as well as to measure the variability of TEC strength within the EIA zone. The estimated TEC along the EIA crest (MAL2 and NKLG) exhibited double-hump maximum, as well as post-sunset peaks (night time enhancement of TEC) between $2100 and 2300 LT. EIA formation was prominent during evening/post-noon hours.

Storm time development of equatorial plasma bubbles (EPBs) around the meridian 120°E/60°W during early September 2017, when the Bz component of interplanetary magnetic field (IMF) experienced two large southward excursions, producing a strong geomagnetic storm that included two main phase decreases, was investigated. The observations from networks of Global Navigation Satellite Systems total electron content receivers, very high frequency radars, and ionosondes operated around the meridian reveal that in the American and Asian sectors, intense EPB irregularities developed and extended to dip latitudes of ~30°N and 46°N, respectively, following rapid sunset F layer height rises during two episodes of strong southward IMF Bz excursions. The storm-enhanced EPB irregularities, however, were not observed following the sunset terminator in the Pacific sector, where the sunset rise of F layer was not detected. More interestingly, the EPBs in the Asian sector were observed to drift toward the west, with velocity increasing from ~30 m/s at low latitude to ~95 m/s at middle latitude. The poleward increasing westward drifts drove the formation of west-titled structure of irregularities. For the EPBs in the American sector, no apparent west-tilted structure was detected. The results indicate that the prompt penetration undershielding electric fields (PPEF) of eastward polarity resulting from the two IMF Bz southward excursions dominated the generation of postsunset EPBs in the American and Asian sectors, respectively. The westward drifts of PPEF-induced EPBs in the Asian sector could be attributed dominantly to disturbance westward wind, with a possible contribution to it arising from the PPEF. Plain Language Summary The development and evolution of equatorial plasma bubbles (EPBs) exhibit complex global behavior during geomagnetic storms. In recent years, an international space weather meridian circle program, which aims to provide a global picture of unfolding space weather events by using diverse instruments along the approximate meridian 120°E/60°W, that is, the Asian and American longitude sectors, was launched. Considering the sunset interval (~12 hr) between the two longitudes, it is expected that the development of postsunset EPBs, if enhanced in one region by short-lived prompt penetration electric fields (PPEF), would be inhibited in the other region under the delayed and long duration effect of disturbance dynamo electric fields. Here we report a unique case of significantly enhanced postsunset EPBs developments by PPEF in both the American and Asian sectors, but their total absence by disturbance dynamo electric fields in the Pacific sector during the September 2017 geomagnetic storm sequence. Moreover, the PPEF-induced EPBs along the meridian show different characteristics, with apparent west-tilted structure in the Asian sector but not in the American sector. This sort of study based on the international space weather meridian circle program observations will strengthen our understanding on the generation and evolution characteristics of EPBs during geomagnetic storms.

Le GPS (Global Positioning System) qui est l'un des systèmes de géolocalisation et de radionavigation globale, permet un positionnement tridimensionnel dans un référentiel global (WGS84) pour les diverses applications potentielles. Cependant, le trajet du signal radioélectrique émis par un satellite GPS est soumis à des contraintes et des perturbations causées par l'atmosphère terrestre qui influe sur le rayonnement électromagnétique et qui est constituée de plusieurs couches distinctes dont principalement la troposphère et l'ionosphère. Pour des études approfondies du milieu atmosphérique, le GPS est devenu un outil précieux et incontournable. Pour les couches ionosphériques, milieu considéré comme dispersif, cette perturbation est exprimée à l'aide du paramètre physique donnant le contenu total en électrons (TEC, Total Electron Content) libres de la zone traversée. Dans un premier temps, il a été procédé à l'élaboration des cartes ionosphériques bidimensionnelles du TEC sur les deux échelles globales et locales à différentes altitudes ionosphériques. Ces cartes sont dérivées des modèles 2D basés sur les développements en harmoniques sphériques et utilisant des données d'observations (O-files aux formats RINEX) de 140 stations GPS fournis par l'IGS (International GNSS Service). Les résultats obtenus ont montré que le milieu ionosphérique actif se concentre dans une seule couche mince située à 350 km d'altitude. Le problème majeur rencontré dans cette modélisation est que ces modèles 2D sont insuffisants pour estimer les variations ionosphériques à des différentes couches (erreurs jusqu'à plusieurs TECU). La tomographie ionosphérique (modèle 3D) qui est la détermination de la densité électronique de l'ionosphère le long du trajet du signal radioélectrique à différentes altitudes, est basée sur les Fonctions Harmoniques Sphériques (F.H.S : modélisation du profil horizontal de l'ionosphère) et les Fonctions Empiriques Orthogonales (F.E.O : modélisation du profil vertical). Le problème d'inversion du TEC mesuré par les récepteurs GPS reste la grande entrave dans la modélisation en 3D. Pour la validation des résultats obtenus dans le calcul du TEC au-dessus de la ville d'Arzew, une étude comparative de notre modèle ionosphérique bidimensionnel avec les modèles publiés par le GIMs (Global Ionospheric Models), fournis par Bernese 5.0 ou par le modèle IRI-2007, a donné des différences peu significatives (<6 TECU). Pour le modèle ionosphérique 3D), les résultats fournis par la technique de tomographie basés sur les fonctions FHS et FEO, sont similaires (différence < 2 TECU) à ceux publiés par le système MIDAS (Multi Instrument Data Analysis System).

Accurate evaluation of the physical processes during the substorm growth phase, including formation of field-aligned currents (FACs), isotropization by current sheet scattering, instabilities, and ionosphere-magnetosphere connection, relies on knowing the realistic three-dimensional (3-D) magnetic field configuration, which cannot be reliably provided by current available empirical models. We have established a 3-D substorm growth phase magnetic field model, which is uniquely constructed from empirical plasma sheet pressures under the constraint of force balance. We investigated the evolution of model pressure and magnetic field responding to increasing energy loading and their configurations under different solar wind dynamic pressure (PSW) and sunspot number. Our model reproduces the typical growth phase evolution signatures: plasma pressure increases, magnetic field lines become more stretched, current sheet becomes thinner, and the Region 2 FACs are enhanced. The model magnetic fields agree quantitatively well with observed fields. The magnetic field is substantially more stretched under higher PSW, while the dependence on sunspot number is nonlinear and less substantial. By applying our modeling to a substorm event, we found that (1) the equatorward movement of proton aurora during the growth phase is mainly due to continuous stretching of magnetic field lines, (2) the ballooning instability is more favorable during late growth phase around midnight tail where there is a localized plasma beta peak, and (3) the equatorial mapping of the breakup auroral arc is at X~
14 RE near midnight, coinciding with the location of the maximum growth rate for the ballooning instability.

VERY MUCH A PRECURSOR TO THE 3 DAYS OF DARKNESS EVENT – LETTING US KNOW THAT IT IS A GOOD THING THAT WE DESIGNED FOR THIS TIME.  A CLEANSING PULSE – THE EVENT IS MEANT TO CLEAR ALL OF THE PLASTIC OUT OF THE OCEANS, RETURN THE ENTIRE PLANET TO PRISTINE, RETURN ALL PEOPLE TO THEIR 20 YEAR OLD PRISTINE BODIES AND CAUSE MOST FEARFUL BEINGS TO PERISH OF THEIR OWN ACCORD, WHICH HAPPENS AROUND THE ORGANMIC BUBBLE NOW.

1] The contribution of ionospheric plasma to the Earth's magnetosphere has been recognized for more than 3 decades. The magnitude of this contribution has become more evident over that same time period with the observed magnitude of the low-energy ionospheric supply increasing as the measurement techniques improved. Estimates based on Dynamics Explorer measurements in the mid-1980s suggested that the ionospheric plasma supply is sufficient to populate the plasmasphere, plasma trough, plasma sheet, and magnetotail lobes. Recent measurements from the Thermal Ion Dynamics Experiment on the Polar spacecraft have been used in conjunction with an ion trajectory model to reexamine the process and magnitude of the ionospheric supply of magnetospheric plasma. These measurements reveal the energy, pitch angle, and flux characteristics of the upward flowing polar wind over broad regions of the high-latitude ionosphere. Onboard measurement of spacecraft potential is found to be a fundamental element in interpreting the measured ion outflow. Newly derived polar wind fluxes are determined to be near 6.0 Â 10 7 ions cm À2 s À1 at 5000 km altitude during local winter and magnetically quiet conditions. Using the measured ionospheric source characteristics in combination with the trajectory code reveals the nature of the ionospheric/magnetosphere filling process and shows that the ionospheric source is sufficient to supply the observed densities and energies of the plasma sheet and magnetotail lobes. Many of the ionospheric particles are further transformed to ring current energies and locations after circulation through the plasma sheet. This measurement/calculation approach is able to show which regions of the high-latitude ionosphere are important for plasma sheet/ring current filling. The ionospheric sources used in the calculations include the dominant polar wind, the cleft ion fountain, and the auroral zone. Citation: Huddleston, M. M., C. R. Chappell, D. C. Delcourt, T. E. Moore, B. L. Giles, and M. O. Chandler (2005), An examination of the process and magnitude of ionospheric plasma supply to the magnetosphere,

Previous studies of the magnetospheric plasma populations have concentrated on the low energy (1eV) plasma of the plasmasphere, the more energetic (1-100 keV) plasma of the plasma sheet and ring current, and the high energy (~ MeV) plasma of the radiation belts. A compilation of satellite measurements over the past thirty years augmented by recent observations from the Polar/TIDE instrument has revealed a new perspective on a plasma population in the middle magnetosphere. This population consists of ions with energies of a few eV to greater than several hundred eV which display a characteristic bidirectional field-aligned pitch angle distribution. Measurements from the ATS, ISEE, SCATHA, DE, and POLAR satellites establish the characteristics of this "warm plasma cloak" of particles that is draped over the nightside region of the plasmasphere and is blown into the morning and early afternoon dayside sector by the sunward convective wind in the magnetosphere. The satellite observations combined with the predictions of an ion trajectory model are used to describe the formation and dynamics of the warm plasma cloak.

In this work we attempt to quantify and investigate the causes of earthquakes using the magnetic signal and hence
to predict. We proceed several trails to quantify forces using Sq-variation currents in the Earth’s lithosphere and
the electromagnetic induction prevailed in the ionosphere at the time of earthquakes. The deep sources of magnetic
field prevailed in the Lithosphere has been investigated using the magnetic jerks. Also, the relationship between
the applied stress and the corresponding variation in the remanent magnetization has been investigated for rock
samples collected along active tectonic zones, while the electromagnetic variations prevailed in the ionosphere
were studied using Kp index with respect to the earthquake occurrences.
The results show that correlation between the variations in the magnetic field and the tectonic activities has been
approved along the diurnal and long term variations. The cross-correlation coefficients (PCC) factors between the
correlated data sets are ranging between 0.813 and 0.94 indicating strong linear relationship. We concluded that
we can trace a noticeable magnetic signal during the 24 before earthquake events. We determine the occurrence
times of geomagnetic impulses (jerks) at the time of earthquakes. We show a direct relation between the stress and
the remanent magnetization confirming the additional magnetic values (
H) that is added to the main magnetic
field. Also analysis of the Kp and the variations of geomagnetic background (perturbations) shows the possibility
of the coupling interaction process between the magnetosphere-ionosphere during the time of earthquake. In fact,
by analyzing the modulation of solar activity taking as reference the change in density of the solar wind, was
verified that M6+ global seismic activity is influenced by the variations of the density of the solar wind.

In this work we attempt to quantify and investigate the causes of earthquakes using the magnetic signal and hence to predict. We proceed several trails to quantify forces using Sq-variation currents in the Earth’s lithosphere and the electromagnetic induction prevailed in the ionosphere at the time of earthquakes. The deep sources of magnetic field prevailed in the Lithosphere has been investigated using the magnetic jerks. Also, the relationship between the applied stress and the corresponding variation in the remanent magnetization has been investigated for rock samples collected along active tectonic zones, while the electromagnetic variations prevailed in the ionosphere were studied using Kp index with respect to the earthquake occurrences. The results show that correlation between the variations in the magnetic field and the tectonic activities has been approved along the diurnal and long term variations.

1] The open-closed magnetic field line boundary (OCB) is an important indicator of magnetospheric dynamics and can be used to identify locations of particle precipitation at the edge of the magnetosphere. The OCB can fluctuate during geomagnetic events, and the extent of this variability is a vital component of space weather research and modeling. There was a unique opportunity to identify and study the synoptic variability of the OCB during the extended 2007-2009 solar quiet period through use of the Polar Experiment Network for Geophysical Upper-atmosphere Investigations-Automatic Geophysical Observatory (PENGUIn-AGO) network of ground-based fluxgate magnetometers on the Antarctic continent. The fluxgates, which measured the occurrence of standing Pc5 modes on closed field magnetic field lines, allowed for identification of the OCB structure and study of the synoptic behavior of the OCB before and during a corotating interaction region (CIR)-driven magnetic storm. Observations were compared with results from the BATSRUS space weather model and show 83% agreement for over ∼2 days before the CIR event. It is shown that such synoptic magnetometer data sets of the OCB during these storms allow for a careful test of current space weather models. The current study investigates the pre-storm time period, while a future paper will address the storm time evolution of the OCB.

It is considered that a part of the polar cap, adjacent to the aurora1 oval, lies on closed magnetic field lines. This has found a reasonable explanation in the framework of a model of the plasma sheet as a collisionless shock wave (Fridman and Voronov, 1993, J. geophys. Res. A98, 143-151). According to the model, the polar cap can exist even if all of its magnetic field lines intersect the plasma sheet. The global magnetospheric electric field controls the dynamics of the aurora1 oval polar boundary. An abrupt enhancement of the global magnetospheric convection electric field is followed immediately by a thinning of the plasma sheet and by an equatorward displacement of the boundary. With a decrease of the magnetospheric electric field, the boundary moves toward the cusp. Whether the electric field increases or decreases, the local aurora1 formations inside the aurora1 oval move equatorward with respect to the Earth.