Aeronomy

This manuscript presents a method to identify the occurrence of Equatorial Plasma Bubbles (EPBs) with data gathered from receivers of Global Navigation Satellite System (GNSS). This method adapts a previously existing technique to detect Medium Scale Travelling Ionospheric Disturbances (MSTIDs), which focus on the 2nd time derivatives of total electron content estimated from GNSS signals (2DTEC). Results from this tool made possible to develop a comprehensive analysis of the characteristics of EPBs. Analyses of the probability of occurrence, effective time duration, depth of the depletion and total disturbance of the EPBs show their dependence on local time and season of the year at global scale within the latitude belt from 35°N to 35°S for the descending phase of solar cycle 23 and ascending phase of solar cycle 24, 2002–2014. These results made possible to build an EPBs model, bounded with the Solar Flux index, that simulates the probability of the number of EPBs and their charac...

The lower and middle atmosphere present long-term variations in temperature and other parameters linked to anthropogenic sources, such as the increase in greenhouse gases concentration since the start of the industrial era. Some examples are the well known temperature increase in the troposphere and stratosphere cooling. Upper atmosphere parameters also present long-term variations. While in the case of the middle and lower atmosphere it is debated whether the origin of the trends is primarily anthropogenic or solar, in the upper atmosphere other sources are also able to induce long-term changes, such as long-term variations in geomagnetic activity and secular variations of the Earth’s magnetic field. In this paper, trends of the F2 layer critical frequency, foF2, measured at three Southern Hemisphere stations (Brisbane, Canberra and Christchurch) are analyzed to determine the importance of increasing greenhouse gases concentration effect. According to our results for the period cov...

A correction method to remove proton contamination from the electron channels of the Polar‐orbiting Operational Environmental Satellites Medium Energy Proton/Electron Detector (MEPED) is described. Proton contamination estimates are based on measurements in five of the MEPED proton spectral channels. A constrained inversion of the MEPED proton channel response function matrix is used to calculate proton differential flux spectra. In this inversion, the proton energy distribution is described by a weighted combination of exponential, power law, and Maxwellian distributions. Proton contamination in the MEPED electron spectral channels is derived by applying the electron channel proton sensitivities to the proton fluxes from the best fit proton spectra. Once the electron channel measurements are corrected for proton contamination, an inversion of the electron channel response function matrix is used to calculate electron differential flux spectra. A side benefit of the method is that i...

The third workshop session of the National Science Foundation's Coupling Energetics, and Dynamics of Atmospheric Regions (CEDAR) initiative took place at the National Bureau of Standards and National Center for Atmospheric Research institutions in Boulder, Colo., June 6–10, and was attended by 155 participants, including about 40 graduate students.The CEDAR initiative represents the fruit of many years of efforts by the aeronomy community and NSF to modernize the techniques used to understand the many processes of the upper atmosphere both theoretically and experimentally. Since the beginning of this initiative (under the old name of Ground‐Based Optical Aeronomy) with a summer meeting in Logan, Utah, in 1983, there has been a workshop meeting every summer. The 1988 CEDAR meeting, in particular, reflected the growing maturity of the CEDAR initiative. The meeting was well attended, and, in general, we found fewer participants drawn to the meeting just by curiosity and more who ca...

Public attention has recently focused on high-impact extreme weather events in midlatitudes that originate in the sub-Arctic. We investigate movements of the stratospheric polar vortex (SPV) and related changes in lower atmospheric circulation during the February-March 2018 “Beast from the East” cold winter event that dramatically affected much of Europe and north-central North America. This study demonstrates that the movement of the SPV is a key linkage in late winter subarctic and northern midlatitude extreme weather events. February–March 2018 saw two types of subarctic-midlatitude weather connections. In the first type, the SPV was displaced from the pole to lower latitudes over North America in February and then was found over northern Siberia in March. Mid-February and mid-March are examples of persistent near vertically aligned geopotential height structures of the atmospheric circulation. These structures over North America and Eurasia advected cold Arctic air southward. Th...

The eddy-driven jet is located in the midlatitudes, bounded on one side by the pole and often bounded on the opposite side by a strong Hadley-driven jet. This work explores how the eddy-driven jet and its variability persist within these limits. It is demonstrated in a barotropic model that as the jet is located at higher latitudes, the leading mode of variability of the jet changes from a meridional shift to a pulse, and the eddy-length scale increases, consistent with the Rhines-scale prediction. Looking equatorward, a similar change in eddy-driven jet variability is observed when a constant subtropical jet is moved toward the eddy-driven jet in midlatitudes. In both the poleward and equatorward limits, the change in variability from a shift to a pulse is due to the modulation of eddy propagation and momentum flux. Near the pole, the small value of beta and subsequent lack of wavebreaking near the pole accounts for the change in variability, whereas on the equatorward side of the ...

COMPARING MANUAL AND SEMI-AUTOMATIC UNDERWATER IMAGERY ANALYSIS 1 APPROACHES FOR HARD BOTTOM BENTHIC MACROFAUNA MONITORING AT OFFSHORE 2 RENEWABLE ENERGY INSTALLATIONS 3 4 Aleksej Šaškov, Thomas G. Dahlgren, Yuri Rzhanov, Marie-Lise Schläppy 5 1 Marine Science and Technology Center, Klaipėda University, Lithuania 6 2 Uni Research, Bergen, Norway 7 Center for Coastal and Ocean Mapping/Joint Hydrographic Center, University of New Hampshire, USA 8 4 Environmental research institute, University of Highlands and Island, Thurso, UK (current affiliation) 9

As posted by the Working Group V of the International Association of Geomagnetism and Aeronomy (IAGA), the 13th generation of the International Geomagnetic Reference Field (IGRF) has been released at the end of 2019. Following IAGA recommendations, in this work we present a candidate model for the IGRF-13, for which we have used the available Swarm satellite and geomagnetic observatory ground data for the last year. In order to provide the IGRF-13 candidate, we have extrapolated the Gauss coefficients of the main field and its secular variation to January 1st, 2020. In addition, we have generated a Definitive Geomagnetic Reference Field model for 2015.0 using the same modelling approach, but focussed on a 1-year time window of data centred on 2015.0. To jointly model both satellite and ground data, we have followed the classical protocols and data filters applied in geomagnetic field modelling. Novelty arrives from the application of bootstrap analysis to solve issues related to the...

Inversion techniques applied to GPS‐LEO radio occultation data allow the retrieval of accurate and worldwide‐distributed refractivity profiles, which, in the case of the ionosphere, can be converted into electron densities providing information regarding the electron content distribution in this atmospheric region. In order to guarantee the accuracy of the electron density retrievals, two key points should be taken into account: the horizontal gradients of the electronic distribution and the topside electron content above the LEO orbit. The deployment in April 2006 of the satellite Constellation Observing System for Meteorology Ionosphere and Climate (FORMOSAT‐3/COSMIC), carrying GPS receivers on board, provides valuable radio occultation data with global and almost uniform coverage overcoming the sparsity of data from previous LEO missions (for instance, GPS/MET, CHAMP, and SAC‐C). This is also one of the main limitations of other sources providing direct observations, such as iono...

METRO is the acronym for MEteor TRajectories and Origins. It is an interdisciplinary project with a collaboration between several scientific institutes and also with radio amateurs. The METRO project focuses on radio meteor observations and what we can learned from them. For that purposes, the dataset from the BRAMS network are used. BRAMS (Belgian RAdio Meteor Stations) relies on forward scattering of radio waves emitted by a beacon in Dourbes off meteor ionization trails and received at 30 stations across Belgium. One of the main goal of METRO is to determine the trajectories of meteors in the sky. For some meteors, it is possible to retrieve meteor speed. Adding these two informations, we can trace back the orbit of the meteoroids. We present here the results of a method developed by Jones et al (1998) applied on the interferometric system based in Humain (Belgium). It consists in a 5 antennas configuration (two orthogonal sets of three aligned antennas with one central antenna c...

Jurnal Sains Dirgantara (JSD) berisi hasil penelitian, pengembangan, dan/atau pemikirian di sains atmosfer dan antariksa. Jurnal Sains Dirgantara (JSD) berisi hasil penelitian, pengembangan, dan/atau pemikiran di bidang sains atmosfer dan antariksa. Jurnal ini terbit sejak tahun 2004 dan dipublikasikan dua kali dalam setahun (Juni dan Desember) SUSUNAN DEWAN PENYUNTING JURNAL SAINS DIRGANTARA Penyunting  Ketua