Annales Geophysicae (ANGEO)
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Open Access journal
ISSN (Print) 0992-7689 - ISSN (Online) 1432-0576
Published by European Geosciences Union [8 journals]
- Diurnal variations in integrated water vapor derived from a GPS ground
network in the Volga–Ural region of Russia
Abstract: Diurnal variations in integrated water vapor derived from a GPS ground network in the Volga–Ural region of Russia
Vladislav V. Kalinnikov and Olga G. Khutorova
Ann. Geophys., 35, 453-464, doi:10.5194/angeo-35-453-2017, 2017
Here, we present estimates of diurnal and semidiurnal harmonics of variations in integrated water vapor content (IWV) according to GPS data in the Volga–Ural region during 2013–2015. Comparison of diurnal cycle from GPS data and ERA-Interim reanalysis has revealed significant differences in the phase. It is found that, as a result of evaporation from underlying surface and convective lifting of moist air, the summer diurnal variations in IWV and surface density of water vapor are in antiphase.
- Comparisons between high-resolution profiles of squared refractive index
gradient M2 measured by the Middle and Upper Atmosphere Radar and unmanned
aerial vehicles (UAVs) during the Shigaraki UAV-Radar Experiment 2015
Abstract: Comparisons between high-resolution profiles of squared refractive index gradient M2 measured by the Middle and Upper Atmosphere Radar and unmanned aerial vehicles (UAVs) during the Shigaraki UAV-Radar Experiment 2015 campaign
Hubert Luce, Lakshmi Kantha, Hiroyuki Hashiguchi, Dale Lawrence, Masanori Yabuki, Toshitaka Tsuda, and Tyler Mixa
Ann. Geophys., 35, 423-441, doi:10.5194/angeo-35-423-2017, 2017
Results of comparisons between data collected from a VHF Doppler radar and small unmanned aerial vehicles (UAVs) are presented. The UAVs, equipped with meteorological sensors, flew nearby the radar up to an altitude of ~ 4.0 km. Both instruments detected the same clear-air refractive index gradients at a vertical scale of ~ 20 m when the vertical stratification was strong. A VHF radar can thus provide a faithful image of the vertical stratification of the atmosphere down to decimeter scales.
- THEMIS satellite observations of hot flow anomalies at Earth's bow shock
Abstract: THEMIS satellite observations of hot flow anomalies at Earth's bow shock
Christina Chu, Hui Zhang, David Sibeck, Antonius Otto, QiuGang Zong, Nick Omidi, James P. McFadden, Dennis Fruehauff, and Vassilis Angelopoulos
Ann. Geophys., 35, 443-451, doi:10.5194/angeo-35-443-2017, 2017
Hot flow anomalies (HFAs) at Earth's bow shock were identified in Time History of Events and Macroscale Interactions During Substorms (THEMIS) satellite data from 2007 to 2009. The events were classified as young or mature and regular or spontaneous hot flow anomalies (SHFAs). HFA–SHFA occurrence decreases with distance upstream from the bow shock. HFAs are more prevalent for radial interplanetary magnetic fields and solar wind speeds from 550 to 600 kms−1.
- Rocket in situ observation of equatorial plasma irregularities in the
region between E and F layers over Brazil
Abstract: Rocket in situ observation of equatorial plasma irregularities in the region between E and F layers over Brazil
Siomel Savio Odriozola, Francisco Carlos de Meneses Jr., Polinaya Muralikrishna, Alexandre Alvares Pimenta, and Esfhan Alam Kherani
Ann. Geophys., 35, 413-422, doi:10.5194/angeo-35-413-2017, 2017
In this paper we report several ionospheric plasma irregularities detected by an instrument (Langmuir probe) installed as a rocket payload that flew over the equatorial region of Brazil. The results of our measurements were compared with measurements made on a different date and by another instrument (radar) located under the magnetic equator in Peru. Our comparison suggests that the rocket intercepted the same type of irregularity previously detected in Peru.
- High-order ionospheric effects on electron density estimation from
Fengyun-3C GPS radio occultation
Abstract: High-order ionospheric effects on electron density estimation from Fengyun-3C GPS radio occultation
Junhai Li and Shuanggen Jin
Ann. Geophys., 35, 403-411, doi:10.5194/angeo-35-403-2017, 2017
In this paper, we discuss the higher-order ionospheric effects on electron density estimation. We estimate the higher-order ionospheric effect carefully and obtain some conclusions. The results show that the second-order ionospheric effects cannot be ignored in precise ionospheric electron density estimation. The azimuth, the solar activity, and the occultation time and position are the main effect factors of the high-order ionospheric delay which we should consider.
- High-resolution coherent backscatter interferometric radar images of
equatorial spread F using Capon's method
Abstract: High-resolution coherent backscatter interferometric radar images of equatorial spread F using Capon's method
Fabiano S. Rodrigues, Eurico R. de Paula, and Gebreab K. Zewdie
Ann. Geophys., 35, 393-402, doi:10.5194/angeo-35-393-2017, 2017
We present results of Capon's method for the estimation of in-beam images of equatorial spread F (ESF) irregularities observed by the São Luís radar interferometer. Results of numerical simulations show that, despite the short baselines of the system, the method is capable of distinguishing localized features with kilometric scale sizes (zonal direction). Results from the application of Capon’s method to actual measurements show that it is able to resolve features expected to occur in ESF.
- MONITOR Ionospheric Network: two case studies on scintillation and
electron content variability
Abstract: MONITOR Ionospheric Network: two case studies on scintillation and electron content variability
Yannick Béniguel, Iurii Cherniak, Alberto Garcia-Rigo, Pierrick Hamel, Manuel Hernández-Pajares, Roland Kameni, Anton Kashcheyev, Andrzej Krankowski, Michel Monnerat, Bruno Nava, Herbert Ngaya, Raül Orus-Perez, Hughes Secrétan, Damien Sérant, Stefan Schlüter, and Volker Wilken
Ann. Geophys., 35, 377-391, doi:10.5194/angeo-35-377-2017, 2017
The work presented in this paper was done in the frame of an ESA activity. The aim of this project was to study ionosphere disturbances liable to impact navigation systems. This project has been running over several years, allowing enough data acquisition to gain sufficient knowledge of ionosphere variability. It was launched to support the European Satellite-Based Augmented System (EGNOS), also considering a possible extension of the system over Africa.
- Non-triggered auroral substorms and long-period (1–4 mHz) geomagnetic
and auroral luminosity pulsations in the polar cap
Abstract: Non-triggered auroral substorms and long-period (1–4 mHz) geomagnetic and auroral luminosity pulsations in the polar cap
Nadezda Yagova, Natalia Nosikova, Lisa Baddeley, Olga Kozyreva, Dag A. Lorentzen, Vyacheslav Pilipenko, and Magnar G. Johnsen
Ann. Geophys., 35, 365-376, doi:10.5194/angeo-35-365-2017, 2017
A substorm is a dramatic phenomenon in the near-Earth space that is visualized as an aurora. Mostly substorms are caused by changes in the solar wind, but some of them can develop without any evident trigger. Such substorms together with undisturbed days were investigated using magnetometer and photometer data from Svalbard. Substorm precursors, i.e., specific features in 1–4 mHz geomagnetic and auroral luminosity pulsations, have been found at high geomagnetic latitudes.
- Ionospheric response to magnetar flare: signature of SGR J1550–5418 on
coherent ionospheric Doppler radar
Abstract: Ionospheric response to magnetar flare: signature of SGR J1550–5418 on coherent ionospheric Doppler radar
Ann. Geophys., 35, 345-351, doi:10.5194/angeo-35-345-2017, 2017
This is the first time a traveling ionospheric disturbance caused by an extraterrestrial source like a magnetar has been detected. The source entered an active phase on 22 January 2009, during which a large number of bursts were observed by several satellites. We detected its ionospheric signature using the coherent ionospheric Doppler radar system. In general, the Earth's ionosphere is a gigantic detector that responds to the ionizing radiation emitted through high-energy astrophysical objects.
- A comparison of ground-based hydroxyl airglow temperatures with
SABER/TIMED measurements over 23° N, India
Abstract: A comparison of ground-based hydroxyl airglow temperatures with SABER/TIMED measurements over 23° N, India
Navin Parihar, Dupinder Singh, and Subramanian Gurubaran
Ann. Geophys., 35, 353-363, doi:10.5194/angeo-35-353-2017, 2017
Using an all-sky imager, near-mesopause OH temperatures were derived from OH(6, 2) Meinel band intensity measurements. A limited comparison of OH temperatures with SABER/TIMED measurements performed by defining almost-coincident criteria of ±1.5° latitude–longitude and ±3 min indicated fair agreement between ground-based and SABER measurements in general. The difference of two measurements increased when the peak of the OH emission layer lay in the vicinity of large temperature inversions.
- New results on equatorial thermospheric winds and temperatures from
Abstract: New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa
Fasil Tesema, Rafael Mesquita, John Meriwether, Baylie Damtie, Melessew Nigussie, Jonathan Makela, Daniel Fisher, Brian Harding, Endawoke Yizengaw, and Samuel Sanders
Ann. Geophys., 35, 333-344, doi:10.5194/angeo-35-333-2017, 2017
Measurements of equatorial thermospheric winds obtained from an optical instrument called a Fabry–Perot interferometer in Ethiopia show a significance difference as compared with other longitudinal sectors. The zonal wind in this sector is small and shows a gradual decrease through out the night. Application of climatological wind and temperature models shows good agreement with the observations over Ethiopia.
- Error estimate of Taylor's frozen-in flow hypothesis in the spectral
Abstract: Error estimate of Taylor's frozen-in flow hypothesis in the spectral domain
Ann. Geophys., 35, 325-331, doi:10.5194/angeo-35-325-2017, 2017
In situ spacecraft data in space plasma are obtained often as time series data. Using Taylor's frozen-in flow hypothesis, one can interpret the time series data as spatial variations swept by the slow and passing by the spacecraft. A quantitative method for estimating the error for Taylor's hypothesis is developed here.
- Double-layer structure in polar mesospheric clouds observed from SOFIE/AIM
Abstract: Double-layer structure in polar mesospheric clouds observed from SOFIE/AIM
Haiyang Gao, Gordon G. Shepherd, Yuanhe Tang, Lingbing Bu, and Zhen Wang
Ann. Geophys., 35, 295-309, doi:10.5194/angeo-35-295-2017, 2017
We find double-layer structure events with percentages of 10.32 and 7.25 % compared to total PMCs events, and the mean distances between two peaks are 3.06 and 2.73 km for the NH and SH respectively using SOFIE data from 2007 to 2014. By analysis of the background temperature and water vapour residual profiles, we conclude that the lower layer is a reproduced one formed at the bottom of the upper layer. These structures have close relationships with temperature enhancements and GWs.
- New parameterized model for GPS water vapor tomography
Abstract: New parameterized model for GPS water vapor tomography
Nan Ding, Shubi Zhang, and Qiuzhao Zhang
Ann. Geophys., 35, 311-323, doi:10.5194/angeo-35-311-2017, 2017
We propose a new GPS tomographic parameterization approach based on inverse distance weighted (IDW) interpolation. This approach can reconstruct a humidity field. In the future, the fusion of GNSS and external measurements from other sensors in the GPS tomography system will be a potential means to enhance the stability and reliability of water vapor tomography and to decrease tomography intervals.
- Near real-time estimation of ionosphere vertical total electron content
from GNSS satellites using B-splines in a Kalman filter
Abstract: Near real-time estimation of ionosphere vertical total electron content from GNSS satellites using B-splines in a Kalman filter
Eren Erdogan, Michael Schmidt, Florian Seitz, and Murat Durmaz
Ann. Geophys., 35, 263-277, doi:10.5194/angeo-35-263-2017, 2017
Although the number of terrestrial GNSS receivers is rapidly growing, the rather unevenly distributed observations do not allow the generation of high-resolution global ionosphere products. With the regionally enormous increase in GNSS data, the demands on near real-time products are growing very fast. Thus, a procedure for estimating the vertical total electron content based on B-spline representations and Kalman filtering was developed and validated by self-consistency check and altimetry.
- Comparison of the long-term trends in stratospheric dynamics of four
Abstract: Comparison of the long-term trends in stratospheric dynamics of four reanalyses
Michal Kozubek, Peter Krizan, and Jan Lastovicka
Ann. Geophys., 35, 279-294, doi:10.5194/angeo-35-279-2017, 2017
A study of trends in the middle stratosphere using comparisons of four main reanalyses (ERA-Interim, JRA-55, MERRA and NCEP/NCAR). We identified that all four reanalyses show very similar trends on a season or monthly basis. We also compute trends for each grid point not as a zonal mean. This approach shows detailed features in the trend studies in both hemispheres.
- Average plasma sheet polytropic index as observed by THEMIS
Abstract: Average plasma sheet polytropic index as observed by THEMIS
Dennis Frühauff, Johannes Z. D. Mieth, and Karl-Heinz Glassmeier
Ann. Geophys., 35, 253-262, doi:10.5194/angeo-35-253-2017, 2017
The determination of the polytropic index the plasma sheet of Earth's magnetosphere using THEMIS data. The data set reveals that the active magnetotail density and pressure data are well correlated. Yet, considering broad distributions of specific entropies, the evaluation is best performed on shorter timescales.
- The generation of Ganymede's diffuse aurora through pitch angle scattering
Abstract: The generation of Ganymede's diffuse aurora through pitch angle scattering
Arvind K. Tripathi, Rajendra P. Singhal, and Onkar N. Singh II
Ann. Geophys., 35, 239-252, doi:10.5194/angeo-35-239-2017, 2017
In the present paper diffuse auroral intensities of OI λ1356 Å emission have been calculated, resulting from pitch angle diffusion of magnetospheric electrons by whistler-mode waves. Three cases are considered for estimating precipitation flux into the atmospheric loss cone. An analytical yield spectrum (AYS) approach is used to calculate energy deposition of electrons in the atmosphere of Ganymede. It is found that the intensities are inadequate to account for the observational intensities.
- Large- and small-scale periodicities in the mesosphere as obtained from
variations in O2 and OH nightglow emissions
Abstract: Large- and small-scale periodicities in the mesosphere as obtained from variations in O2 and OH nightglow emissions
Ravindra P. Singh and Duggirala Pallamraju
Ann. Geophys., 35, 227-237, doi:10.5194/angeo-35-227-2017, 2017
A near-infrared imaging spectrograph (NIRIS) has been developed in-house and is being operated from a low-latitude location, Gurushikhar, Mount Abu (24.6° N, 72.8° E), in India. The results presented in this study provide us with a comprehensive picture of mesospheric wave dynamics in terms of characterizing their response to various sources (solar and atmospheric) that give rise to the variability in the mesospheric intensities and temperatures.
- A statistical study of the motion of pulsating aurora patches: using the
THEMIS All-Sky Imager
Abstract: A statistical study of the motion of pulsating aurora patches: using the THEMIS All-Sky Imager
Bing Yang, Eric Donovan, Jun Liang, and Emma Spanswick
Ann. Geophys., 35, 217-225, doi:10.5194/angeo-35-217-2017, 2017
This is the first statistical study of the motion of patchy pulsating aurora (PPA). Our results show that PPA patches mainly drift eastward after midnight and westward before midnight, which suggests that the drifts of auroral patches could be a proxy for the ionospheric convection and provide a convenient and accurate method to remotely sense the magnetospheric convection. We also found that patch velocities do not seem to depend on AE index.