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Regi, Mauro
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Preferred name
Regi, Mauro
Alternative Name
Regi, M.
Email
mauro.regi@ingv.it
ORCID
Researcher ID
N-7505-2016
28 results
Now showing 1 - 10 of 28
- PublicationOpen AccessThe location of the Earth's magnetic poles from circum‐terrestrial observations(2021)
; ; ; ; ; The magnetic poles or dip poles are the points on the Earth's surface and circum‐terrestrial area where the magnetic field is vertical, so the horizontal component vanishes. They are not coincident with geomagnetic poles, which are the points where the dipole axis, obtained by analytic models, intersects the Earth's surface, and their instrumental sampling determination from ad hoc ground surveys is difficult due to the harsh environmental conditions and remoteness of the areas where they are located. In this work, we use magnetic field measurements from ESA's Swarm satellites covering 5 years (2015‐2019), and determine the position of the magnetic poles by modelling the yearly average horizontal magnetic field component through analytic 2D Taylor polynomial fit and finding the locations where this component is minimum. The yearly dip poles positions at average satellites geocentric altitudes are also projected at ground level based on WGS84 geodetic reference system. Reliability of our method is evaluated by an optimized Monte Carlo test applied to combined IGRF model and Swarm data. The availability of several years of data allows us to investigate the long term variation and dynamics of the magnetic poles, also in comparison with the results provided by IGRF model (both IGRF12 and IGRF13). Our results agree with the model, in better accordance in the north hemisphere with IGRF13, indicating that both magnetic poles move in the north‐west direction, with a speed of ∼37‐72 km/y (lower in year 2016) for the north dip pole and of ∼5‐9 km/y for the south one.272 26 - PublicationOpen AccessSpace Weather Effects Observed in the Northern Hemisphere during November 2021 Geomagnetic Storm: The Impacts on Plasmasphere, Ionosphere and Thermosphere Systems(2022-11-15)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ;; ; ; ; ; ;; ; On 3 November 2021, an interplanetary coronal mass ejection impacted the Earth’s magnetosphere leading to a relevant geomagnetic storm (Kp = 8-), the most intense event that occurred so far during the rising phase of solar cycle 25. This work presents the state of the solar wind before and during the geomagnetic storm, as well as the response of the plasmasphere–ionosphere–thermosphere system in the European sector. To investigate the longitudinal differences, the ionosphere–thermosphere response of the American sector was also analyzed. The plasmasphere dynamics was investigated through field line resonances detected at the European quasi-Meridional Magnetometer Array, while the ionosphere was investigated through the combined use of ionospheric parameters (mainly the critical frequency of the F2 layer, foF2) from ionosondes and Total Electron Content (TEC) obtained from Global Navigation Satellite System receivers at four locations in the European sector, and at three locations in the American one. An original method was used to retrieve aeronomic parameters from observed electron concentration in the ionospheric F region. During the analyzed interval, the plasmasphere, originally in a state of saturation, was eroded up to two Earth’s radii, and only partially recovered after the main phase of the storm. The possible formation of a drainage plume is also observed. We observed variations in the ionospheric parameters with negative and positive phase and reported longitudinal and latitudinal dependence of storm features in the European sector. The relative behavior between foF2 and TEC data is also discussed in order to speculate about the possible role of the topside ionosphere and plasmasphere response at the investigated European site. The American sector analysis revealed negative storm signatures in electron concentration at the F2 region. Neutral composition and temperature changes are shown to be the main reason for the observed decrease of electron concentration in the American sector.659 57 - PublicationOpen AccessIonospheric Disturbances Over the Indian Sector During 8 September 2017 Geomagnetic Storm: Plasma Structuring and Propagation(2021)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The series of X and M class flares and associated coronal mass ejections that occurred on the first days of September 2017 induced significant perturbations on the low-latitude ionospheric electrodynamics. On 8 September in the Indian sector, the storm caused a severe modification of the equatorial electrojet (EEJ) with a consequent variation of the ionospheric structuring and dynamics. In our analysis, we propose an original method to isolate and identify EEJ variations from geomagnetic data and we detect the presence of equatorial plasma bubbles (EPB) from L-band total electron content (TEC) data in order to understand their movement. Our results provide evidence of independent EPBs appearance freshly generated and inherited from a migrating plasma structure. The EPB (or EPBs) occurring in the south of India is/are freshly generated just above the magnetic equator, and is/are likely triggered by the sudden increase of EEJ just before the local sunset, acting as a pre-reversal enhancement. The EPB appearing in the North-East Indian region is associated with a migrating structure, resulting in a northward movement with a velocity of about 650 m/s, possibly testifying the passage of a large-scale traveling ionospheric disturbance. The occurrence of severe post-sunset scintillations in the northeastern sector suggests a possible cascade process forming small-scale irregularities from the migrating EPB.891 43 - PublicationOpen AccessThe use of the empirical mode decomposition for the identification of mean field aligned reference frames(2016)
; ; ; ; ;The magnetic field satellite data are usually referred to geocentric coordinate reference frame. Conversely, the magnetohydrodynamic waves modes in magnetized plasma depend on the ambient magnetic field, and is then useful to rotate the magnetic field measurements into the mean field aligned (MFA) coordinate system. This reference frame is useful to study the ultra low frequency magnetic field variations along the direction of the mean field and perpendicularly to it. In order to identify the mean magnetic field the classical moving average (MAVG) approach is usually adopted but, under particular conditions, this procedure induces undesired features, such as spectral alteration in the rotated components. We discuss these aspects promoting an alternative and more efficient method for mean field aligned projection, based on the empirical mode decomposition (EMD).181 117 - PublicationOpen AccessSolar wind-driven Pc5 waves observed at a polar cap station and in the near cusp ionosphere(2016)
; ; ; ; ; ; ; ; ; ; ;We present the results of a comparative study conducted in Antarctica by using the ULF geomagnetic field measurements at Terra Nova Bay (Altitude Adjusted Corrected Geomagnetic Coordinates latitude 80°S) and simultaneous data from the Super Dual Auroral Radar Network radar at South Pole Station. Pc5 waves observed at Terra Nova Bay around local magnetic noon, when the station is close to the dayside cusp, can be interpreted as spatial integrated signals, produced by ionospheric currents associated to field line resonances at somewhat lower latitudes. The radar, providing the Doppler velocities of ionospheric plasma over a range of geomagnetic latitudes, allows to detect the occurrence of such field line resonances. In the reported case, our analysis shows evidence of resonant signals in the ionosphere at 75°S and 76°S that find correspondence in frequency and time with the geomagnetic signals observed at Terra Nova Bay around local noon. During the period of interest, oscillations of the solar wind dynamic pressure at the same frequency are detected by Geotail, just upstream of the morning flank of the bow shock. All the observations are consistent with the interpretation of the signals at Terra Nova Bay in terms of signatures of field line resonances occurring at lower latitudes, driven by solar wind oscillations transmitted into the magnetosphere. We discuss also the possibility of an additional contribution to the signals at Terra Nova Bay, due to the direct propagation of the solar wind waves along the local open field line.160 24 - PublicationOpen AccessSolar flare effect preceding Halloween storm (28 October 2003): Results of a worldwide analysis(2008)
; ; ;On 28 October 2003 an extreme solar flare with significant increases in the EUV and X-ray flux caused increased photoionization effects in the dayside ionosphere and determined a remarkable solar flare effect (SFE) manifestation that preceded Halloween storm. An analysis conducted at 53 stations revealed that the geomagnetic disturbance had greatest amplitude and longest duration at lowest latitudes in the dayside hemisphere, and its characteristics were basically controlled by the zenith angle of the observing stations. The aspects of the SFE onset and initial phase reveal a close correspondence with those of the EUV flux. At equatorial/electrojet latitudes, the SFE manifestation can be mostly interpreted in terms of a significant enhancement of the preflare current system during normal electrojet conditions, with some evidence for a highly confined counter electrojet in the dawn sector. Additional elements, at higher latitudes, might suggest in these regions a more significant role of the X-ray flux and the onset of additional currents below the normal dynamo current region.98 48 - PublicationOpen AccessULF geomagnetic activity effects on tropospheric temperature, specific humidity, and cloud cover in Antarctica, during 2003-2010(2017)
; ; ; ; ; ; ;In the present study we investigated the possible relationship between the ULF geomagnetic activity and the variations of several atmospheric parameters. In particular, we compared the ULF activity in the Pc1-2 frequency band (100 mHz–5 Hz), computed from geomagnetic field measurements at Terra Nova Bay in Antarctica, with the tropospheric temperature T, specific humidity Q, and cloud cover (high cloud cover, medium cloud cover, and low cloud cover) obtained from reanalysis data set. The statistical analysis was conducted during the years 2003–2010, using correlation and Superposed Epoch Analysis approaches. The results show that the atmospheric parameters significantly change following the increase of geomagnetic activity within 2 days. These changes are evident in particular when the interplanetary magnetic field Bz component is oriented southward (Bz <0) and the By component duskward (By > 0). We suggest that both the precipitation of electrons induced by Pc1-2 activity and the intensification of the polar cap potential difference, modulating the microphysical processes in the clouds, can affect the atmosphere conditions.144 36 - PublicationOpen AccessThe geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF rangeWe examined the coast effect in Antarctica along the 80 S magnetic parallel. We used the geomagnetic field measurements at the two coastal stations of Mario Zucchelli Station and Scott Base, and, as a reference, at the inland temporary station Talos Dome, during 18 January– 14 March 2008. Spectral analysis in the Pc5 frequency range (1–7 mHz) revealed large differences between coastal and inland stations, such as higher spectral power levels in the vertical component and higher coherence between horizontal and vertical components at coastal stations. Using the interstation method on selected active time intervals, with Talos Dome as a remote reference station, we found that remote reference induction arrows are directed almost perpendicularly with respect to their respective coastlines. Moreover, the singlestation analysis shows that at Talos Dome the amplitude of the induction arrows is much smaller than at coastal stations. These results clearly indicate that coast effect at a few hundred kilometers from the coastline is relatively small. The coast effect on polarization parameters was examined, for a Pc5 event that occurred on 11 March 2008. The results evidenced that the azimuthal angle of polarized signals at one of the coastal stations is largely different with respect to the inland station (by 110 ), while the polarization ratio and ellipticity attain comparable values. We proposed a correction method of the polarization parameters, which operates directly in the frequency domain, obtaining comparable azimuthal angles at coastal and inland stations.
338 120 - PublicationRestrictedA case study of upstream wave transmission to the ground at polar and low latitudes(2012)
; ; ; ; ; ; ; ; ;In this study we analyzed a long-duration ULF wave event detected on 18–19 February 2005 by Cluster satellites, upstream of the nose of the bow shock. The availability of simultaneous data from Geotail satellite, located in the foreshock region close to the dawn flank of the bow shock, allowed us to make a comparison between the observations at the two different sites. The results can be explained in terms of local wave generation, depending on the orientation of the interplanetary magnetic field with respect to the local bow shock normal. In addition, simultaneous data from Polar satellite in the inner magnetosphere and from ground stations in the southern polar cap and at low latitude allowed us to investigate the transmission of the external waves through the magnetosphere up to the ground. The observations suggest different paths of transmission. Waves generated upstream of the bow shock nose directly transmit near the subsolar point, progressively propagate into the magnetosphere and, after conversion into field-guided Alfven modes, reach the ground at high and low latitudes; waves generated on the flanks of the bow shock do not affect the subsolar magnetosphere, and consequently, there is no propagation along the closed field lines at both high and low latitudes. On the other hand, near the geomagnetic pole, the occurrence of pulsations can be related to the transmission across the magnetopause flanks of upstream waves, anywhere generated, as they are convected downstream by the solar wind; the compressional waves do not propagate deeply into the tail lobes but can couple to Alfven-guided waves along the outermost field lines.143 5 - PublicationOpen AccessThe propagation of ULF waves from the Earth's foreshock region to ground: The case study of 15 February 2009(2014)
; ; ; ; ; ; ;A long-duration upstream ultralow frequency (ULF) wave event was detected on 15 February 2009 by Cluster satellites, close to the bow shock nose. A clear wave activity was identified when the interplanetary magnetic field orientation was favorable to the local generation. We examined the wave properties in both the solar wind and the spacecraft frame during a selected time interval and found that foreshock waves were ssentially Alfven waves propagating at a small angle with respect to the interplanetary magnetic field. A comparison of Cluster observations with those on the ground, in the polar cap and at low-latitude stations, confirms the results of previous studies, indicating that upstream waves can reach different ground regions along different paths.131 19
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