We illustrate a semi−automated procedure to detect the field line resonance (FLR) frequencies and the derived equatorial plasma mass den− sities in the inner magnetosphere from ULF measurements recorded at the European quasi−Meridional Magnetometer Array (EMMA). FLR frequencies are detected using the standard technique based on cross−phase and amplitude ratio spectra from pairs of stations latitudi− nally separated. Equatorial plasma mass densities are then inferred by solving the toroidal MHD wave equation using the TS05 Tsyga− nenko magnetic field model and assuming a 1/r dependence of the mass density along the field line. We also present a statistical analysis of the results obtained from 165 non−consecutive days of observations at 8 station pairs covering the range of magnetic L−shells 2.4−5.5 and encompassing a wide range of geomagnetic conditions. The rate of FLR detection maximizes around local noon at each pair of sta− tions, reaching the highest values (~95%) around L = 3. A clear diurnal modulation of the FLR frequency is observed at all L values. At the lowest latitudes, the variation is characterized by a rapid decrease in the early morning hours, a stagnation in the middle of the day, and an increase in the evening hours. At higher latitudes, a continuous and more pronounced decrease of the FLR frequency is observed during all daytime hours reflecting a permanent state of recovery of flux tubes depleted by events of enhanced magnetospheric convec− tion. Consistently, the radial profiles of the inferred equatorial mass density show a density increase from morning to afternoon which gets more pronounced with increasing distance and with the level of the preceding geomagnetic activity. The results also confirm the forma− tion of the plasmapause at geocentric distances that decrease as the disturbance level increases. Mean mass density distributions in the equatorial plane are also shown in 2−D maps for different geomagnetic conditions, as well as for a representative stormy day.

A full-halo coronal mass ejection left the sun on June 21, 2015 from the active region NOAA 12371 encountering Earth on June 22, 2015, generating a G3 strong geomagnetic storm. The CME was associated with an M2 class flare observed at 01:42 UT, located near the center disk (N12E16). Using satellite data from solar, heliospheric, magnetospheric missions and ground-based instruments, we performed a comprehensive Sun-to-Earth analysis. In particular, we analyzed the active region evolution using ground-based and satellite instruments (BBSO, IRIS, HINODE, SDO/AIA, RHESSI --Halpha, EUV, UV, X), the AR magnetograms, using data from SDO HMI, the relative particle data, using PAMELA instruments and the effects of interplanetary perturbation on cosmic ray intensity. We also evaluated the

A local time dependent empirical model of the equatorial plasma mass density in the inner magnetosphere is derived from field line resonance (FLR) observations at the European quasi‐Meridional Magnetometer Array (EMMA). Models of the plasmasphere, plasmatrough, and plasmapause are derived separately and then combined. The whole model is limited to the local time (LT) sector 06:00‐18:00 and to the range of equatorial distances 2.33.0235ptRE

This paper presents how the magnetosphere–plasmasphere–ionosphere system was affected as a whole during the geomagnetic storm peaking on 27 May 2017. The interplanetary conditions, the magnetospheric response in terms of the magnetopause motion, and the ionospheric current flow pattern were investigated using data, respectively, from the WIND spacecraft, from GOES15, GOES13, THEMIS E, THEMIS D and THEMIS A satellites and from the INTERMAGNET magnetometer array. The main objective of the work is to investigate the plasmaspheric dynamics under disturbed conditions and its possible relation to the ionospheric one; to reach this goal, the equatorial plasma mass densities derived from geomagnetic field line resonance observations at the European quasi-Meridional Magnetometer Array (EMMA) and total electron content values obtained through three GPS receivers close to EMMA were jointly considered. Despite the complexity of physical mechanisms behind them, we found a similarity between the ionospheric and plasmaspheric characteristic recovery times. Specifically, the ionospheric characteristic time turned out to be ~ 1.5 days, ~ 2 days and ~ 3.1 days, respectively, at L ~ 3, L ~ 4 and L ~ 5, while the plasmaspheric one, for similar L values, ranged from ~ 1 day to more than 4 days.

Multiharmonic toroidal standing Alfvén waves were detected in the midnight sector of the plasmasphere.• The source of the waves are considered to be ultralow frequency waves generated in the ion foreshock.• The toroidal waves were not detected on the ground at stations located in the midnight sector.