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  • 1
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    The response of high latitude ionosphere to the 2015 June 22 storm (2019)
    Details
    Publication Date: 2020-10-26
    Description: This work investigates physical mechanisms triggering phase scintillations on L-band signals under strong stormy conditions. Thanks to selected ground-based Global Navigation Satellite Systems (GNSS) receivers, located both in Antarctica and in the Arctic, an interhemispheric comparison between high latitude ionospheric observations in response to the peculiar solar wind conditions occurred on June 22, 2015 is here shown. To trace back the observed phase scintillations to the physical mechanisms driving it, we combine measurements from GNSS receivers with in-situ and ground-based observations. Our study highlights the ionospheric scenario in which irregularities causing scintillation form and move, leveraging on a multi-observation approach. Such approach allows deducing that scintillations are caused by the presence of fast-moving electron density gradients originated by particle precipitation induced by solar wind variations. In addition, we show how the numerous and fast oscillations of the north-south component of the interplanetary magnetic field (Bz,IMF) result to be less effective in producing moderate/intense scintillation events than during period of long lasting negative values. Finally, we also demonstrate how the in-situ electron density data can be used to reconstruct the evolution of the ionospheric dynamics, both locally and globally.
    Description: Published
    Description: GM454
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    The response of high latitude ionosphere to the 2015 St. Patrick’s day storm from in situ and ground based observations (2019)
    Details
    Publication Date: 2020-10-26
    Description: The storm onset of the so-called “St. Patrick’s day geomagnetic storm”, on March 17th, 2015 triggered several fluctuations of the electron density in the ionosphere causing severe scintillations at high latitudes of both hemispheres. Leveraging on ground-based Global Navigation Satellite Systems (GNSS) receivers we investigate the ionospheric response to the main phase of the most intense storm of the current solar cycle, in terms of phase scintillations on L-band signals recorded simultaneously in Antarctica and in the Arctic. In detail, we analyse phase scintillation index (σϕ) data from Eureka (79.99°N, 274.10°E), Concordia (75.10°S, 123.35°E), Resolute Bay (74.75°N, 265.00°E), Mario Zucchelli (74.41°S, 164.10°E), Ny-Ålesund (78.92°N, 11.98°E) and Zhongshan (69.37°S, 76.37°E) stations. Furthermore, by using ancillary data obtained from in-situ and ground-based observations, we investigate the origin and the evolution of the ionospheric irregularities causing scintillations, reconstructing the ionospheric background in which such irregularities formed and moved. The multi-instrumental approach used in this work allows identifying the Antarctic ionosphere as the most responsive to the solar perturbation driving the storm. Our study reveals how the in-situ electron density data can be used to reconstruct the picture of the ionospheric dynamics, both locally and globally. Finally, our results identify the important role played by particles precipitation in triggering the observed scintillations.
    Description: Published
    Description: 638-650
    Description: 2A. Fisica dell'alta atmosfera
    Description: 5A. Paleoclima e ricerche polari
    Description: JCR Journal
    Keywords: High-latitude ionosphere Ionospheric irregularities GNSS scintillations Multi-instrumental observations Ionospheric dynamics Interhemispheric study ; high latitude ionosphere
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Challenges to Equatorial Plasma Bubble and Ionospheric Scintillation Short-Term Forecasting and Future Aspects in East and Southeast Asia (2021)
    Springer
    Details
    Publication Date: 2023-11-21
    Description: Equatorial plasma bubbles (EPBs) can cause rapid fluctuations in amplitude and phase of radio signals traversing the ionosphere and in turn produce serious ionospheric scintillations and disrupt satellite-based communication links. Whereas numerous studies on the generation and evolution of EPBs have been performed, the prediction of EPB and ionospheric scintillation occurrences still remains unresolved. The generalized Rayleigh–Taylor (R–T) instability has been widely accepted as the physical mechanism responsible for the generation of EPBs. But how the factors, which seed the development of R–T instability and control the dynamics of EPBs and resultant ionospheric scintillations, change on a short-term basis are not clear. In the East and Southeast Asia, there exist significant differences in the generation rates of EPBs at closely located stations, for example, Kototabang (0.2°S, 100.3°E) and Sanya (18.3°N, 109.6°E), indicating that the decorrelation distance of EPB generation is small (hundreds of kilometers) in longitude. In contrast, after the initial generation of EPBs at one longitude, they can drift zonally more than 2000 km and extend from the magnetic equator to middle latitudes of 40° or higher under some conditions. These features make it difficult to identify the possible seeding sources for the EPBs and to accurately predict their occurrence, especially when the onset locations of EPBs are far outside the observation sector. This paper presents a review on the current knowledge of EPBs and ionospheric scintillations in the East and Southeast Asia, including their generation mechanism and occurrence morphology, and discusses some unresolved issues related to their short-term forecasting, including (1) what factors control the generation of EPBs, its day-to-day variability and storm-time behavior, (2) what factors control the evolution and lifetime of EPBs, and (3) how to accurately determine ionospheric scintillation from EPB measurements. Special focus is given to the whole process of the EPB generation, development and disruption. The current observing capabilities, future new facilities and campaign observations in the East and Southeast Asia in helping to better understand the short-term variability of EPBs and ionospheric scintillations are outlined.
    Description: Published
    Description: 201–238
    Description: 2A. Fisica dell'alta atmosfera
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Nighttime ionospheric enhancements induced by the occurrence of an evening solar eclipse (2013)
    Wiley
    Details
    Publication Date: 2013-09-10
    Description: [1]  The solar eclipse on 15 January 2010 traversed Asia and completed its travel on the Shandong Peninsula in China at sunset. Two vertical-incidence ionosondes at Wuhan and Beijing and the oblique-incidence ionosonde network in North China were implemented to record the ionospheric response to the solar eclipse. Following the initial electron density decrease caused by the eclipse, the ionosphere was characterized by a strong pre-midnight enhancement, and a subsequent ionospheric decay, and a ~10 hour later post-midnight enhancement. Neither geomagnetic disturbance occurred during the eclipse day, nor did obvious nighttime peak appear for the ten-day mean of the F2-layer critical frequency ( fo F2). The electron density profilogram of the Beijing ionosonde indicates that the two enhancements were the result of the plasma flux downward from the top ionosphere, possibly due to the steep decrease of the ionospheric electron density and plasma temperature during the solar eclipse. The two-dimensional differential fo F2 maps present the regional variations of the nighttime electron density peaks and decay. Both the pre- and post-midnight enhancements initially appeared in a belt almost in parallel with the eclipse track and then drifted southward. The different magnitudes of greatest eclipse in the umbra and outside tend to account for the different occurrence times of the plasma flux. The ionospheric decay following the pre-midnight enhancement is also considered as a consequence of the eclipse shade.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Longitudinal characteristics of spread F backscatter plumes observed with the EAR and Sanya VHF radar in Southeast Asia (2013)
    Wiley
    Details
    Publication Date: 2013-09-22
    Description: [1]  The development of equatorial plasma irregularity plumes can be well recorded by steerable backscatter radars operated at and off the magnetic equator due to the fact that the vertically extended plume structures are tracers of magnetically north-south aligned larger scale structures. From observations during March 2012, using two low latitude steerable backscatter radars in Southeast Asia, the Equatorial Atmosphere Radar (EAR) (0.2ºS, 100.3ºE; dip lat 10.4ºS) and the Sanya VHF radar (18.4ºN, 109.6ºE; dip lat 12.8ºN), the characteristics of backscatter plumes over the two sites separated in longitude by ~1000 km were simultaneously investigated. The beam steering measurements reveal frequent occurrences of multiple plumes over both radar sites, of which two cases are analyzed here. The observations on 30 March 2012 show plume structures initiated within the radar scanned area, followed by others drifting from the west of the radar beam over both stations. A tracing analysis on the onset locations of plasma plumes reveals spatially well-separated backscatter plumes, with a maximum east-west wavelength of about 1000 km, periodically generated in longitudes between 85ºE and 110ºE. The post-sunset backscatter plumes seen by the Sanya VHF radar are found to be due to the passage of sunset plumes initiated around the longitude of EAR. Most interestingly, the EAR measurements on the night of 21 March 2012 show multiple plume structures that developed successively in the radar scanned area with east-west separation of ~50 km, with however, no sunset plasma plume over Sanya. Co-located ionogram measurements show that spread F irregularities occurred mainly in the bottomside F-region at Sanya, whereas satellite traces in ionograms that are indications of large-scale wave structures, were observed on that night at both stations. Possible causes for the longitudinal difference in the characteristics of radar backscatter plumes are discussed.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    An interhemispheric comparison of GPS phase scintillation with auroral emission observed at the South Pole and from the DMSP satellite (2013)
    Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Details
    Publication Date: 2013-06-12
    Description: The global positioning system (GPS) phase scintillation caused by high-latitude ionospheric irregularities during an intense high-speed stream (HSS) of the solar wind from April 29 to May 5, 2011, was observed using arrays of GPS ionospheric scintillation and total electron content monitors in the Arctic and Antarctica. The one-minute phase-scintillation index derived from the data sampled at 50 Hz was complemented by a proxy index (delta phase rate) obtained from 1-Hz GPS data. The scintillation occurrence coincided with the aurora borealis and aurora australis observed by an all-sky imager at the South Pole, and by special sensor ultraviolet scanning imagers on board satellites of the Defense Meteorological Satellites Program. The South Pole (SP) station is approximately conjugate with two Canadian High Arctic Ionospheric Network stations on Baffin Island, Canada, which provided the opportunity to study magnetic conjugacy of scintillation with support of riometers and magnetometers. The GPS ionospheric pierce points were mapped at their actual or conjugate locations, along with the auroral emission over the South Pole, assuming an altitude of 120 km. As the aurora brightened and/or drifted across the field of view of the all-sky imager, sequences of scintillation events were observed that indicated conjugate auroras as a locator of simultaneous or delayed bipolar scintillation events. In spite of the greater scintillation intensity in the auroral oval, where phase scintillation sometimes exceeded 1 radian during the auroral break-up and substorms, the percentage occurrence of moderate scintillation was highest in the cusp. Interhemispheric comparisons of bipolar scintillation maps show that the scintillation occurrence is significantly higher in the southern cusp and polar cap.
    Print ISSN: 1593-5213
    Topics: Geosciences
    Published by Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Mid-latitude ionospheric responses to the 2013 SSW under high solar activity (2015)
    Wiley
    Details
    Publication Date: 2015-12-30
    Description: Ionospheric responses to sudden stratospheric warming (SSW) are not well understood, particularly in the mid-latitudes and under high solar conditions. During the 2013 SSW, ionospheric disturbances were observed in eight locations on the meridional chain from 30.5°N to 42.8°N in northern China. The mid-latitude ionosphere responded strongly to the SSW despite being under high solar flux. The F2-layer maximum electric density increased by more than 80%, and the peak height was elevated more than 60 km. Well-set and organized semidiurnal variations were recorded in early and middle January during the SSW in eight observation locations. The expected f o F 2 decrease in the afternoon hours was not clearly discernible; however, nighttime enhancements occurred frequently. The time-period spectra of the average f o F 2 and zonal winds and meridional winds at altitudes of 86-95 km presented quasi-16-day planetary wave-like oscillations during the warming event. The coupling between the atmosphere and ionosphere may be strengthened by the quasi-16-day waves. The amplified diurnal, semidiurnal and ter-diurnal tides in f o F 2 were also recorded during the warming, in good agreement with earlier observations. Importantly, the variations in the semidiurnal tides included a 16-day periodic component, indicating that the modulated semidiurnal tides may transmit this 16-day planetary wave-like oscillations to the F-region through wind dynamo. Although the PW-tide interaction theory is not novel, it is of significance in the mid-latitude ionospheric response to SSW.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Seasonal variations of MLT tides revealed by a meteor radar chain based on Hough mode decomposition (2015)
    Wiley
    Details
    Publication Date: 2015-07-30
    Description: Seasonal variations of different tides in the mesosphere and lower thermosphere are investigated from wind observations of a meteor radar chain on the basis of Hough mode decomposition. Firstly, the observed winds are decomposed into different (diurnal, semidiurnal and terdiurnal) tidal components. Different seasonal patterns are revealed for each component. Pronounced semiannual oscillation (SAO) is presented in the diurnal component. While latitude-depended seasonal variation is found in the semidiurnal and terdiurnal components. At the low/mid- latitude stations, the semiannual/annual oscillation is relatively stronger. Then, Hough mode decomposition is utilized to extract the dominant tidal modes of each decomposed component. It is found that each component is dominated by one of its symmetric tidal modes with strong seasonal dependency. Apparent SAO is observed in the dominant (1, 1) mode; (2, 4) mode is strong in the autumn and winter months (after the Sep. equinox). Based on the extracted results we further map the three-dimensional distribution (latitude × altitude × season) of each tidal component. The mapped results are finally compared with the corresponding values observed by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) Doppler Interferometer (TIDI) and modeled from the Global Scale Wave Model (GSWM). Each mapped tidal component agrees well with corresponding TIDI observation in the seasonal variation. Meanwhile, coincidences are found in the seasonal dependency of the diurnal component between the mapped values and the modeled results from GSWM, while difference between them exists in that of the semidiurnal one.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    Concentric gravity waves over Northern China observed by an airglow imager network and satellites (2015)
    Wiley
    Details
    Publication Date: 2015-10-13
    Description: The first no-gap OH airglow all-sky imager network was established in northern China in February 2012. The network is composed of 6 all-sky airglow imagers that make observations of OH airglow gravity waves and cover an area of about 2000 km east and west and about 1400 km south and north. An unusual outbreak of Concentric Gravity Wave (CGW) events were observed by the network nearly every night during the first half of August 2013. These events were coincidentally observed by satellite sensors from FY-2, AIRS/Aqua, and VIIRS/Suomi NPP. Combination of the ground imager network with satellites provides multi-level observations of the CGWs from the stratosphere to the mesopause region. In this paper, two representative CGW events in August 2013 are studied in detail. First, is the CGW on the night of 13 August 2013, likely launched by a single thunderstorm. The temporal and spatial analyses indicate that the CGW horizontal wavelengths follow freely propagating waves based on a GW dispersion relation within 300 km from the storm center. In contrast, the more distant observed gravity wave field exhibits a smaller horizontal wavelength of ~20 km and our analysis strongly suggest this wave field represents a ducted wave. A second event, exhibiting multiple CGWs, was induced by two very strong thunderstorms on 09 August 2013. Multi-scale waves with horizontal wavelengths ranging from less than 10 km to 200 km were observed.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Evidence for lightning-associated enhancement of the ionospheric sporadic E layer dependent on lightning stroke energy (2015)
    Wiley
    Details
    Publication Date: 2015-10-14
    Description: In this study we analyze the lightning data obtained by the World-Wide Lightning Location Network (WWLLN) and hourly ionospheric data observed by ionosondes located at Sanya and Beijing, to examine the changes in ionospheric electron density in response to the underlying thunderstorms, to investigate the possible connection between lightning discharges and the enhancement of the ionospheric sporadic-E (Es) layer. We identify a statistically significant enhancement and a decrease in altitude of the Es layer at Sanya station, in agreement with the results found at Chilton, United Kingdom [ Davis and Johnson , 2005]. However, the lightning-associated modification of the Es layer investigated using the same approach is not evident at Beijing station. Furthermore, we compare the responses to weak and strong lightning strokes using WWLLN-determined energies at Sanya in 2012. The lightning-associated enhancement of the Es layer is predominantly attributed to powerful strokes with high stroke energy. A statistically significant intensification of the Es layer with higher energy strokes at Sanya, along with the statistical dependence of lightning-associated enhancement of the Es layer on stroke energy, leads us to conclude that the magnitude of the enhancement is likely associated with lightning stroke energy.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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