166 research outputs found
Ionospheric response during Tropical Cyclones-a brief review on Amphan and Nisarga
Here, we explore the different characteristics of a possible coupling between
tropospheric and ionospheric activities during the impact of tropical cyclones
(TC) like Amphan and Nisarga in the Indian subcontinent. We have analyzed the
effect of TCs Amphan and Nisarga on the low latitude ionosphere using the
measurements from several IGS stations around India and a GPS+ NavIC station in
Indore, India. For the first time, this study assesses the impact of tropical
cyclones on the equatorial ionosphere using both GPS and NavIC. After the
landfall of TC Amphan, the VTEC analysis shows a significant drop from nominal
values in both NavIC as well in GPS by TECU and TECU, respectively.
In contrast to TC Amphan, Nisarga showed a rise in VTEC which ranged from
TECU in GPS to - TECU in NavIC satellites except for PRN6. The paper
examines Outgoing Longwave Radiation as a proxy to the convective activity
which may be responsible for the ionospheric variation through the generation
of gravity waves. In addition, the horizontal neutral wind observations at the
location of TC landfall confirm the presence of ionospheric disturbances. VTEC
perturbation analysis using a band-pass filter reveals a variation in
differential TEC values between and based on the IGS station
measurements. This indicates that the gravity wave is one of the responsible
mechanisms for the lower-upper atmospheric coupling during both cyclones
The First Comparison Between Swarm-C Accelerometer-Derived Thermospheric Densities and Physical and Empirical Model Estimates
The first systematic comparison between Swarm-C accelerometer-derived
thermospheric density and both empirical and physics-based model results using
multiple model performance metrics is presented. This comparison is performed
at the satellite's high temporal 10-s resolution, which provides a meaningful
evaluation of the models' fidelity for orbit prediction and other space weather
forecasting applications. The comparison against the physical model is
influenced by the specification of the lower atmospheric forcing, the
high-latitude ionospheric plasma convection, and solar activity. Some insights
into the model response to thermosphere-driving mechanisms are obtained through
a machine learning exercise. The results of this analysis show that the
short-timescale variations observed by Swarm-C during periods of high solar and
geomagnetic activity were better captured by the physics-based model than the
empirical models. It is concluded that Swarm-C data agree well with the
climatologies inherent within the models and are, therefore, a useful data set
for further model validation and scientific research.Comment: https://goo.gl/n4QvU
Ionospheric Response at Conjugate Locations During the 7–8 September 2017 Geomagnetic Storm Over the Europe-African Longitude Sector
This paper focuses on unique aspects of the ionospheric response at conjugate locations over Europe and South Africa during the 7–8 September 2017 geomagnetic storm including the role of the bottomside and topside ionosphere and plasmasphere in influencing electron density changes. Analysis of total electron content (TEC) on 7 September 2017 shows that for a pair of geomagnetically conjugate locations, positive storm effect was observed reaching about 65% when benchmarked on the monthly median TEC variability in the Northern Hemisphere, while the Southern Hemisphere remained within the quiet time variability threshold of ±40%. Over the investigated locations, the Southern Hemisphere midlatitudes showed positive TEC deviations that were in most cases twice the comparative response level in the Northern Hemisphere on the 8 September 2017. During the storm main phase on 8 September 2017, we have obtained an interesting result of ionosonde maximum electron density of the F2 layer and TEC derived from Global Navigation Satellite System (GNSS) observations showing different ionospheric responses over the same midlatitude location in the Northern Hemisphere. In situ electron density measurements from SWARM satellite aided by bottomside ionosonde-derived TEC up to the maximum height of the F2 layer (hmF2) revealed that the bottomside and topside ionosphere as well as plasmasphere electron content contributions to overall GNSS-derived TEC were different in both hemispheres especially for 8 September 2017 during the storm main phase. The differences in hemispheric response at conjugate locations and on a regional scale have been explained in terms of seasonal influence on the background electron density coupled with the presence of large-scale traveling ionospheric disturbances and low-latitude-associated processes. The major highlight of this study is the simultaneous confirmation of most of the previously observed features and their underlying physical mechanisms during geomagnetic storms through a multi–data set examination of hemispheric differences. © 2020. American Geophysical Union. All Rights Reserved
Ionosphere Monitoring with Remote Sensing
This book focuses on the characterization of the physical properties of the Earth’s ionosphere, contributing to unveiling the nature of several processes responsible for a plethora of space weather-related phenomena taking place in a wide range of spatial and temporal scales. This is made possible by the exploitation of a huge amount of high-quality data derived from both remote sensing and in situ facilities such as ionosondes, radars, satellites and Global Navigation Satellite Systems receivers
Fusion of wildlife tracking and satellite geomagnetic data for the study of animal migration
This work was supported by the Leverhulme Trust [Research Project Grant RPG-2018-258].Background: Migratory animals use information from the Earth’s magnetic field on their journeys. Geomagnetic navigation has been observed across many taxa, but how animals use geomagnetic information to find their way is still relatively unknown. Most migration studies use a static representation of geomagnetic field and do not consider its temporal variation. However, short-term temporal perturbations may affect how animals respond - to understand this phenomenon, we need to obtain fine resolution accurate geomagnetic measurements at the location and time of the animal. Satellite geomagnetic measurements provide a potential to create such accurate measurements, yet have not been used yet for exploration of animal migration. Methods: We develop a new tool for data fusion of satellite geomagnetic data (from the European Space Agency’s Swarm constellation) with animal tracking data using a spatio-temporal interpolation approach. We assess accuracy of the fusion through a comparison with calibrated terrestrial measurements from the International Real-time Magnetic Observatory Network (INTERMAGNET). We fit a generalized linear model (GLM) to assess how the absolute error of annotated geomagnetic intensity varies with interpolation parameters and with the local geomagnetic disturbance. Results: We find that the average absolute error of intensity is − 21.6 nT (95% CI [− 22.26555, − 20.96664]), which is at the lower range of the intensity that animals can sense. The main predictor of error is the level of geomagnetic disturbance, given by the Kp index (indicating the presence of a geomagnetic storm). Since storm level disturbances are rare, this means that our tool is suitable for studies of animal geomagnetic navigation. Caution should be taken with data obtained during geomagnetically disturbed days due to rapid and localised changes of the field which may not be adequately captured. Conclusions: By using our new tool, ecologists will be able to, for the first time, access accurate real-time satellite geomagnetic data at the location and time of each tracked animal, without having to start new tracking studies with specialised magnetic sensors. This opens a new and exciting possibility for large multi-species studies that will search for general migratory responses to geomagnetic cues. The tool therefore has a potential to uncover new knowledge about geomagnetic navigation and help resolve long-standing debates.Publisher PDFPeer reviewe
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Review of Environmental Monitoring by Means of Radio Waves in the Polar Regions: From Atmosphere to Geospace
The Antarctic and Arctic regions are Earth's open windows to outer space. They provide unique opportunities for investigating the troposphere–thermosphere–ionosphere–plasmasphere system at high latitudes, which is not as well understood as the mid- and low-latitude regions mainly due to the paucity of experimental observations. In addition, different neutral and ionised atmospheric layers at high latitudes are much more variable compared to lower latitudes, and their variability is due to mechanisms not yet fully understood. Fortunately, in this new millennium the observing infrastructure in Antarctica and the Arctic has been growing, thus providing scientists with new opportunities to advance our knowledge on the polar atmosphere and geospace. This review shows that it is of paramount importance to perform integrated, multi-disciplinary research, making use of long-term multi-instrument observations combined with ad hoc measurement campaigns to improve our capability of investigating atmospheric dynamics in the polar regions from the troposphere up to the plasmasphere, as well as the coupling between atmospheric layers. Starting from the state of the art of understanding the polar atmosphere, our survey outlines the roadmap for enhancing scientific investigation of its physical mechanisms and dynamics through the full exploitation of the available infrastructures for radio-based environmental monitoring
Challenges in Arctic Navigation and Geospatial Data : User Perspective and Solutions Roadmap
Navigation and location-based applications, including business such as transport, tourism, and mining, in Arctic areas face a variety of specific challenges. In fact, these challenges concern not only the Arctic Circle but certain other areas as well, such as the Gulf of Bothnia. This report provides a review on these challengs which concern a variety of technologies ranging from satellite navigation to telecommunications and mapping.
In order to find out end-users' views on the significance of Arctic challenges, an online survey was conducted. The 77 respondents representing all Arctic countries, the majority being from Finland, highlighted the challenges in telecommunications as well as accuracy concerns for emerging applications dealing with precise navigation.
This report provides a review of possible technologies for addressing the Arctic challenges, based on which a road map for solving them is developed. The road map also uses the results of expert working groups from the Challenges in Arctic Navigation workshop arranged in April 2018 in Olos, Muonio, Finland.
This report was produced within the ARKKI project. It was funded by the Finnish Ministry of Foreign Affairs under the Baltic Sea, Barents and Arctic cooperation programme, and implemented by the Finnish Geospatial Research Institute in collaboration with the Finnish Ministry of Transport and Communications
Lower-thermosphere–ionosphere (LTI) quantities: current status of measuring techniques and models
The lower-thermosphere-ionosphere (LTI) system consists of the upper atmosphere and the lower part of the ionosphere and as such comprises a complex system coupled to both the atmosphere below and space above. The atmospheric part of the LTI is dominated by laws of continuum fluid dynamics and chemistry, while the ionosphere is a plasma system controlled by electromagnetic forces driven by the magnetosphere, the solar wind, as well as the wind dynamo. The LTI is hence a domain controlled by many different physical processes. However, systematic in situ measurements within this region are severely lacking, although the LTI is located only 80 to 200 km above the surface of our planet. This paper reviews the current state of the art in measuring the LTI, either in situ or by several different remote-sensing methods. We begin by outlining the open questions within the LTI requiring high-quality in situ measurements, before reviewing directly observable parameters and their most important derivatives. The motivation for this review has arisen from the recent retention of the Daedalus mission as one among three competing mission candidates within the European Space Agency (ESA) Earth Explorer 10 Programme. However, this paper intends to cover the LTI parameters such that it can be used as a background scientific reference for any mission targeting in situ observations of the LTI.Peer reviewe
Imaging ionospheric irregularities by earth observation radar satellite
The sensitivity of Synthetic Aperture Radar (SAR) satellite signal in the L-band to
ionospheric plasma density is used to obtain two-dimensional imaging of
ionospheric density irregularities. As an application for equatorial ionosphere, we have
recently reported first simultaneous observation of equatorial plasma bubble by the
ALOS-2/PALSAR-2 satellite and a ground 630-nm airglow imager in northern Brazil.
In this case, SAR ionospheric scintillation are represented as stripe-like signature of
radar image over the terrain along the local magnetic field lines near an airglow
depletion region. This so-called SAR scintillation stripes are discussed to be the
signature of existing small-scale plasma irregularities with the scale size of hundreds of
meters associated with equatorial plasma bubbles. We present the observational setup
and the interpretation of SAR signal parameters to characterize the two-dimensional
ionospheric density structures, and discuss future studies
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