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  • 1
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    Are there new findings in the search for ULF magnetic precursors to earthquakes? (2016)
    American Geophysical Union
    Details
    Publikationsdatum: 2021-02-10
    Beschreibung: Moore (1964) in a letter published in Nature reported disturbances in geomagnetic field data prior to the 27 March 1964 Alaska earthquake. After the publication of this report, many papers have shown magnetic changes preceding earthquakes. However, a causal relationship between preearthquake magnetic changes and impending earthquakes has never been demonstrated. As a consequence, after 50 years, magnetic disturbances in the geomagnetic field are still candidate precursory phenomena. Some researchers consider the investigation of ultra low frequency (ULF: 0.001–10 Hz) magnetic data the correct approach for identifying precursory signatures of earthquakes. Other researchers, instead, have recently reviewed many published ULF magnetic changes that preceded earthquakes and have shown that these are not actual precursors. The recent studies by Currie and Waters (2014) and Han et al. (2014) aim to provide relevant new findings in the search for ULF magnetic precursory signals. However, in order to contribute to science, alleged precursors must be shown to be valid and reproducible by objective testing. Here we will briefly discuss the state of the art in the search for ULF magnetic precursors, paying special attention to the recent findings of Currie and Waters (2014) and Han et al. (2014). We do not see in these two reports significant evidence that may support the observation of precursory signatures of earthquakes in ULF magnetic records.
    Beschreibung: Published
    Beschreibung: 10289–10304
    Beschreibung: 1A. Geomagnetismo e Paleomagnetismo
    Beschreibung: JCR Journal
    Beschreibung: restricted
    Schlagwort(e): Geomagnetic field ; Magnetic anomalies ; Earthquake precursors ; 01. Atmosphere::01.03. Magnetosphere::01.03.03. Magnetospheric physics ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 2
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    A statistical analysis of low-frequency magnetic pulsations at cusp and cap latitudes in Antarctica (2015)
    American Geophysical Union
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: We report a statistical analysis of low-frequency magnetic variations (magnetic pulsations, 0.8–7 mHz) at South Pole (74 S corrected geomagnetic latitude) and Terra Nova Bay (80 S) during 1996. The results show that at South Pole (at cusp latitudes) the pulsation power exhibits two maxima during the day, one in the local premidnight and the other in the morning. The first maximum disappears when the analysis is restricted to northward interplanetary magnetic field conditions (Bz 〉 1 nT), suggesting that it might be associated to substorm phenomena. During closed magnetospheric conditions, when the cusp is expected to be located poleward with respect to the station, the spectral and polarization characteristics of pulsations between 1 and 3 mHz suggest that resonant oscillations of the outermost closed field lines commonly occur at South Pole in the local morning. At Terra Nova Bay, in the polar cap, the pulsation power is much lower and its diurnal variation is characterized by a single maximum, which occurs around local noon, when the station approaches the cusp. The corresponding polarization pattern indicates that Terra Nova Bay is always located poleward with respect to resonant field lines.
    Beschreibung: Published
    Beschreibung: A02205
    Beschreibung: 1A. Geomagnetismo e Paleomagnetismo
    Beschreibung: JCR Journal
    Beschreibung: restricted
    Schlagwort(e): geomagnetic pulsations ; magnetospheric dynamics ; 01. Atmosphere::01.03. Magnetosphere::01.03.03. Magnetospheric physics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 3
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    Propagation characteristics of ULF waves in the Earth’s magnetosphere as inferred by an analysis of polarization parameters of geomagnetic pulsations at a low latitude station (2015)
    ESA
    Details
    Publikationsdatum: 2020-02-24
    Beschreibung: We have conducted an extensive statistical analysis of the polarization characteristics of geomagnetic pulsations (10-100 mHz) recorded at L’Aquila (Italy, L = 1.6) during 15 years (1985-1999). The dependence on frequency, local time, season, solar cycle and interplanetary magnetic field orientation has been investigated. The diurnal pattern of the dominant sense of polarization suggests the presence of two distinct sources of ULF waves, one located 1-2 hours before noon and the other one around midnight. Significant variations of the ellipticity occur at sunrise and sunset with clear seasonal dependence. The results are discussed in terms of combined effects of exogenic wave sources, field line resonant mechanism and ionospheric influence.
    Beschreibung: Published
    Beschreibung: Vico Equense, Italy
    Beschreibung: 1A. Geomagnetismo e Paleomagnetismo
    Beschreibung: open
    Schlagwort(e): Geomagnetic pulsation- ULF waves-polarization analysis ; 01. Atmosphere::01.03. Magnetosphere::01.03.03. Magnetospheric physics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: Conference paper
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  • 4
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    Two-dimensional structure of long-period pulsations at polar latitudes in Antarctica (2015)
    American Geophysical Union
    Details
    Publikationsdatum: 2017-04-04
    Beschreibung: Two-dimensional (2-D) statistical distributions of spectral power and coherence of polar geomagnetic variations with quasi-periods about 10 min are analyzed using data from magnetometer arrays in Antarctica. Examination of the 2-D patterns of spectral power and coherence shows the occurrence of significant variations in geomagnetic power levels but with low spatial coherence near the cusp projection and in the auroral region. At the same time, low-amplitude pulsations, which we coin Picap3 pulsations, are very coherent throughout the polar cap. The region occupied by coherent Picap3 pulsations is shifted toward local MLT night from the geomagnetic pole and is decoupled from the regions of auroral and cusp ULF activity. The spectral power varies with time at polar latitudes in a manner different from that at auroral latitudes. Diurnal variations of power at different stations at the same geomagnetic latitude exhibit different behavior depending on the station’s position relative to geomagnetic and geographic poles. This asymmetry is shown to be partly attributed to the variations of the ionospheric conductance. The primary source of polar pulsations is probably related to intermittent magnetosheath turbulence and tail lobe oscillations, though a particular propagation mechanism has not as yet been identified
    Beschreibung: Published
    Beschreibung: A03222
    Beschreibung: 1A. Geomagnetismo e Paleomagnetismo
    Beschreibung: JCR Journal
    Beschreibung: restricted
    Schlagwort(e): geomagnetic pulsations, polar cap ; 01. Atmosphere::01.03. Magnetosphere::01.03.03. Magnetospheric physics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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  • 5
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    Formation of ionospheric irregularities over Southeast Asia during the 2015 St. Patrickˈs Day storm (2017)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-11-23
    Beschreibung: We investigate the geospace response to the 2015 St. Patrickˈs Day storm leveraging on instruments spread over Southeast Asia (SEA), covering a wide longitudinal sector of the low-latitude ionosphere. A regional characterization of the storm is provided, identifying the peculiarities of ionospheric irregularity formation. The novelties of this work are the characterization in a broad longitudinal range and the methodology relying on the integration of data acquired by Global Navigation Satellite System (GNSS) receivers, magnetometers, ionosondes, and Swarm satellites. This work is a legacy of the project EquatoRial Ionosphere Characterization in Asia (ERICA). ERICA aimed to capture the features of both crests of the equatorial ionospheric anomaly (EIA) and trough (EIT) by means of a dedicated measurement campaign. The campaign lasted from March to October 2015 and was able to observe the ionospheric variability causing effects on radio systems, GNSS in particular. The multiinstrumental and multiparametric observations of the region enabled an in-depth investigation of the response to the largest geomagnetic storm of the current solar cycle in a region scarcely reported in literature. Our work discusses the comparison between northern and southern crests of the EIA in the SEA region. The observations recorded positive and negative ionospheric storms, spread F conditions, scintillation enhancement and inhibition, and total electron content variability. The ancillary information on the local magnetic field highlights the variety of ionospheric perturbations during the different storm phases. The combined use of ionospheric bottomside, topside, and integrated information points out how the storm affects the F layer altitude and the consequent enhancement/suppression of scintillations.
    Beschreibung: Published
    Beschreibung: 12211–12233
    Beschreibung: 1A. Geomagnetismo e Paleomagnetismo
    Beschreibung: 2A. Fisica dell'alta atmosfera
    Beschreibung: 1IT. Reti di monitoraggio e Osservazioni
    Beschreibung: 5IT. Osservazioni satellitari
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): Saint Patrickˈs Day storm ; scintillation enhancement/suppression ; equatorial ionospheric anomaly ; positive and negative ionospheric storms ; spread F ; total electron content variability ; 01. Atmosphere::01.02. Ionosphere::01.02.99. General or miscellaneous ; 01. Atmosphere::01.02. Ionosphere::01.02.02. Dynamics ; 01. Atmosphere::01.02. Ionosphere::01.02.04. Plasma Physics ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 01. Atmosphere::01.02. Ionosphere::01.02.06. Instruments and techniques ; 01. Atmosphere::01.02. Ionosphere::01.02.07. Scintillations ; 01. Atmosphere::01.03. Magnetosphere::01.03.99. General or miscellaneous ; 01. Atmosphere::01.03. Magnetosphere::01.03.02. Magnetic storms ; 01. Atmosphere::01.03. Magnetosphere::01.03.03. Magnetospheric physics
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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