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]
- Determination of errors in derived magnetic field directions
in geosynchronous orbit: results from a statistical approach
Abstract: Determination of errors in derived magnetic field directions in geosynchronous orbit: results from a statistical approach
Yue Chen, Gregory Cunningham, and Michael Henderson
Ann. Geophys., 34, 831-843, doi:10.5194/angeo-34-831-2016, 2016
This study statistically quantifies the errors in local magnetic field directions that are derived from electron directional distributions measured by Los Alamos National Laboratory geosynchronous (LANL GEO) satellites. We demonstrate for the first time that derived magnetic field directions in GEO orbit should statistically match the real magnetic directions ~2 times better than those from a list of empirical models and have no significant dependence on magnetospheric activities.
- Numerical study of the generation and propagation of ultralow-frequency
waves by artificial ionospheric F region modulation at different latitudes
Abstract: Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes
Xiang Xu, Chen Zhou, Run Shi, Binbin Ni, Zhengyu Zhao, and Yuannong Zhang
Ann. Geophys., 34, 815-829, doi:10.5194/angeo-34-815-2016, 2016
ULF waves can be generated by modulated HF heating in the ionospheric F region, which has long been considered for secure communication with submarines. In this paper we study the effects of background parameters on the process of ULF wave generation and propagation by using a numerical simulation. We find that wave radiation efficiency is higher in the daytime ionosphere at lower latitudes, while ground wave intensity is larger in the nighttime ionosphere with lower modulation frequency.
- Ozone and temperature decadal responses to solar variability in
the stratosphere and lower mesosphere, based on measurements from SABER
Abstract: Ozone and temperature decadal responses to solar variability in the stratosphere and lower mesosphere, based on measurements from SABER on TIMED
Frank T. Huang, Hans G. Mayr, James M. Russell III, and Martin G. Mlynczak
Ann. Geophys., 34, 801-813, doi:10.5194/angeo-34-801-2016, 2016
We have derived ozone and temperature responses to solar variability over a solar cycle, from 2002 to 2014 at 20–60 km and 48°S–48°N, based on a new dataset (SABER). These global results can be directly compared with 3-D models and will help in understanding not only the physical processes but also how they affect the Earth's climate. The simultaneous measurements of ozone and temperature will give added insight into the dynamics and photochemistry of the middle and upper atmosphere.
- Optimization of GPS water vapor tomography technique with radiosonde
and COSMIC historical data
Abstract: Optimization of GPS water vapor tomography technique with radiosonde and COSMIC historical data
Shirong Ye, Pengfei Xia, and Changsheng Cai
Ann. Geophys., 34, 789-799, doi:10.5194/angeo-34-789-2016, 2016
The near-real-time high spatial resolution of atmospheric water vapor distribution is vital in numerical weather prediction. GPS tomography technique has been proved effectively for three-dimensional water vapor reconstruction. In this study, the tomography processing is optimized in a few aspects by the aid of radiosonde and COSMIC historical data, including the accuracy improvement of tropospheric zenith hydrostatic delay and precipitable water vapor conversion factor.
- Atmospheric inertia-gravity waves retrieved from level-2 data of the
satellite microwave limb sounder Aura/MLS
Abstract: Atmospheric inertia-gravity waves retrieved from level-2 data of the satellite microwave limb sounder Aura/MLS
Klemens Hocke, Martin Lainer, Lorena Moreira, Jonas Hagen, Susana Fernandez Vidal, and Franziska Schranz
Ann. Geophys., 34, 781-788, doi:10.5194/angeo-34-781-2016, 2016
The dense horizontal sampling of atmospheric temperature profiles by the microwave limb sounder MLS on the NASA satellite AURA permit the estimation of global distributions of inertia-gravity waves (IGWs) in the middle atmosphere. We present and discuss the estimated global distributions of IGWs for July 2015 and January 2016. A dependence on the zonal wind distribution is obvious. The distributions of IGWs are a bit similar to the global distributions of small-scale gravity waves.
- Simultaneous observations of structure function parameter of refractive
index using a high-resolution radar and the DataHawk small airborne
Abstract: Simultaneous observations of structure function parameter of refractive index using a high-resolution radar and the DataHawk small airborne measurement system
Danny E. Scipión, Dale A. Lawrence, Marco A. Milla, Ronald F. Woodman, Diego A. Lume, and Ben B. Balsley
Ann. Geophys., 34, 767-780, doi:10.5194/angeo-34-767-2016, 2016
The paper presents simultaneous observations made with a radar (SOUSY) and an unmanned aerial system (DataHawk) with the propose of studying the lower troposphere with high resolution. Through the comparison of both measurements, it was possible to compute the radar calibration constant, which will help to obtain calibrated measurements of turbulent parameters of the atmosphere.
- On determining fluxgate magnetometer spin axis offsets from mirror mode
Abstract: On determining fluxgate magnetometer spin axis offsets from mirror mode observations
Ferdinand Plaschke and Yasuhito Narita
Ann. Geophys., 34, 759-766, doi:10.5194/angeo-34-759-2016, 2016
Spacecraft-mounted magnetic field instruments (magnetometers) need to be routinely calibrated. This involves determining the magnetometer outputs in vanishing ambient magnetic fields, the so-called offsets. We introduce and test a new method to determine these offsets with high accuracy, the mirror mode method, which is complementary to existing methods. The mirror mode method should be highly beneficial to current and future magnetic field observations near Earth, other planets, and comets.
- An evaluation of International Reference Ionosphere electron density in
the polar cap and cusp using EISCAT Svalbard radar measurements
Abstract: An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements
Lindis Merete Bjoland, Vasyl Belyey, Unni Pia Løvhaug, and Cesar La Hoz
Ann. Geophys., 34, 751-758, doi:10.5194/angeo-34-751-2016, 2016
The international reference ionosphere (IRI) model is a widely used model of the ionosphere. We compared this model with 16 years of radar measurements of electron density from Svalbard at altitudes between 200 and 500 km. Our results show that the model is biased towards an underestimation of the electron density in the high-latitude ionosphere and that this underestimation is most severe at nighttime. The model performs best at altitudes around the peak height of the electron density.
- Current sheet flapping in the near-Earth magnetotail: peculiarities of
propagation and parallel currents
Abstract: Current sheet flapping in the near-Earth magnetotail: peculiarities of propagation and parallel currents
Egor V. Yushkov, Anton V. Artemyev, Anatoly A. Petrukovich, and Rumi Nakamura
Ann. Geophys., 34, 739-750, doi:10.5194/angeo-34-739-2016, 2016
In the paper we study flapping wave structures, generated in the neutral plane of the Earth magnetotail. Investigated flapping is an important process of magnetosphere dynamics, connected with magnetic energy transformation and magnetic storm formation. Large separation of Cluster spacecraft allows us to estimate both local and global properties of flapping current sheets, the typical flapping times and propagation directions.
- Anisotropic Jüttner (relativistic Boltzmann) distribution
Abstract: Anisotropic Jüttner (relativistic Boltzmann) distribution
Rudolf A. Treumann and Wolfgang Baumjohann
Ann. Geophys., 34, 737-738, doi:10.5194/angeo-34-737-2016, 2016
The rigorous derivation of the Jüttner (covariant Boltzmann) distribution is provided for anisotropic pressure (or temperature) tensors. It was in similar form anticipated first by Gladd (1983). Its manifestly covariant version follows straightforwardly from its scalar property.
- Effect of the solar activity variation on the Global Ionosphere
Thermosphere Model (GITM)
Abstract: Effect of the solar activity variation on the Global Ionosphere Thermosphere Model (GITM)
Davide Masutti, Günther March, Aaron J. Ridley, and Jan Thoemel
Ann. Geophys., 34, 725-736, doi:10.5194/angeo-34-725-2016, 2016
The Global Ionosphere Thermosphere Model has been validated against flight data. The validation shows a linear dependency of the neutral density values with respect to the solar activity. In particular, the thermosphere model shows an over-predicting or under-predicting behaviour under high or low solar activity respectively. The reasons for such behaviour can be attributed to an erroneous implementation of the chemical processes or the gas transport properties in the model.
- A modeling study of asymmetries in plasma irregularity characteristics
near gradient reversals
Abstract: A modeling study of asymmetries in plasma irregularity characteristics near gradient reversals
Leslie J. Lamarche and Roman A. Makarevich
Ann. Geophys., 34, 709-723, doi:10.5194/angeo-34-709-2016, 2016
The asymmetries between the leading and trailing edges of large-scale plasma density structures in the ionosphere are examined using a general formalism for the gradient-drift instability for arbitrary altitude and propagation direction. The asymmetry changes dramatically with propagation direction and is most likely to be observed by a ground-based radar when the radar’s boresight is parallel to the structure’s elongation direction and perpendicular to its direction of motion.
- Modified ion-Weibel instability as a possible source of wave activity at
Abstract: Modified ion-Weibel instability as a possible source of wave activity at Comet 67P/Churyumov-Gerasimenko
Patrick Meier, Karl-Heinz Glassmeier, and Uwe Motschmann
Ann. Geophys., 34, 691-707, doi:10.5194/angeo-34-691-2016, 2016
A new type of wave has been detected by the magnetometer of the Rosetta spacecraft close to comet P67/Churyumov-Gerasimenko. We provide the analytical model of this wave excitation from linear perturbation theory. A modified ion-Weibel instability is identified as source of this wave excited by a cometary current. The waves predominantly grow perpendicular to this current. A fan-like phase structure results from superposing the strongest growing waves in a cometary rest frame.
- Inverse scattering problem in turbulent magnetic fluctuations
Abstract: Inverse scattering problem in turbulent magnetic fluctuations
Rudolf A. Treumann, Wolfgang Baumjohann, and Yasuhito Narita
Ann. Geophys., 34, 673-689, doi:10.5194/angeo-34-673-2016, 2016
In support of low-frequency electromagnetic turbulence we formulate the inverse scattering theory of electromagnetic fluctuations in plasma. Its solution provides the turbulent response function which contains all information of the dynamical causes of the electromagnetic fluctuations. This is of basic interest in any electromagnetic turbulence. It requires measurement of magnetic and electric fluctuations but makes no direct use of the turbulent power spectral density.
- Quantitative assessment of AOD from 17 CMIP5 models based on
satellite-derived AOD over India
Abstract: Quantitative assessment of AOD from 17 CMIP5 models based on satellite-derived AOD over India
Amit Misra, Vijay P. Kanawade, and Sachchida Nand Tripathi
Ann. Geophys., 34, 657-671, doi:10.5194/angeo-34-657-2016, 2016
For an accurate understanding of earth climate system, it is necessary to evaluate the performance of the climate models used to perform these simulations. In this work we have examined aerosol optical depths simulated by 17 models by comparing them with satellite-derived aerosol optical depth. Our results indicate the role of dust aerosols and biogeochemistry in the simulation of aerosols by models.
- Optimization of Saturn paraboloid magnetospheric field model
parameters using Cassini equatorial magnetic field data
Abstract: Optimization of Saturn paraboloid magnetospheric field model parameters using Cassini equatorial magnetic field data
Elena S. Belenkaya, Vladimir V. Kalegaev, Stanley W. H. Cowley, Gabrielle Provan, Marina S. Blokhina, Oleg G. Barinov, Alexander A. Kirillov, and Maria S. Grigoryan
Ann. Geophys., 34, 641-656, doi:10.5194/angeo-34-641-2016, 2016
The paraboloid model of Saturn’s magnetosphere describes the magnetic field of the planet, the ring current, magnetopause current, and the tail current. The model parameters are determined by comparison with the Cassini magnetic field data from 18 near-equatorial passes that span wide ranges of LT. The best-fit model parameters are employed to determine how the parameters vary with the subsolar distance of the magnetopause, governed by pressure balance at the magnetospheric boundary.
- Multi-year GNSS monitoring of atmospheric IWV over Central and South
America for climate studies
Abstract: Multi-year GNSS monitoring of atmospheric IWV over Central and South America for climate studies
Clara Eugenia Bianchi, Luciano Pedro Oscar Mendoza, Laura Isabel Fernández, María Paula Natali, Amalia Margarita Meza, and Juan Francisco Moirano
Ann. Geophys., 34, 623-639, doi:10.5194/angeo-34-623-2016, 2016
Long-term monitoring of the amount of water vapour in the lower atmosphere is essential for climate studies. We analysed satellite observations, at hundreds of locations in Central and South America, to look for changes in this parameter over several years. We found evidence of drying of the troposphere in temperate regions, and also evidence of slow moistening over the tropics. Moreover, we openly provide the complete data collection to the scientific community.
- Two-point observations of low-frequency waves at 67P/Churyumov-Gerasimenko
during the descent of PHILAE: comparison of RPCMAG and ROMAP
Abstract: Two-point observations of low-frequency waves at 67P/Churyumov-Gerasimenko during the descent of PHILAE: comparison of RPCMAG and ROMAP
Ingo Richter, Hans-Ulrich Auster, Gerhard Berghofer, Chris Carr, Emanuele Cupido, Karl-Heinz Fornaçon, Charlotte Goetz, Philip Heinisch, Christoph Koenders, Bernd Stoll, Bruce T. Tsurutani, Claire Vallat, Martin Volwerk, and Karl-Heinz Glassmeier
Ann. Geophys., 34, 609-622, doi:10.5194/angeo-34-609-2016, 2016
We have analysed the magnetic field measurements performed on the ROSETTA orbiter and the lander PHILAE during PHILAE's descent to comet 67P/Churyumov-Gerasimenko on 12 November 2014. We observed a new type of low-frequency wave with amplitudes of ~ 3 nT, frequencies of 20–50 mHz, wavelengths of ~ 300 km, and propagation velocities of ~ 6 km s−1. The waves are generated in a ~ 100 km region around the comet a show a highly correlated behaviour, which could only be determined by two-point observations.
- Solar energetic particle interactions with the Venusian atmosphere
Abstract: Solar energetic particle interactions with the Venusian atmosphere
Christina Plainaki, Pavlos Paschalis, Davide Grassi, Helen Mavromichalaki, and Maria Andriopoulou
Ann. Geophys., 34, 595-608, doi:10.5194/angeo-34-595-2016, 2016
In the context of planetary space weather, we estimate the ion production rates in the Venusian atmosphere due to the interactions of solar energetic particles (SEPs) with gas. The assumed concept for our estimations is based on two cases of SEP events, previously observed in near-Earth space: the event in October 1989 and the event in May 2012. For both cases, we assume that the directional properties of the flux and the interplanetary magnetic field configuration would have allowed the SEPs' arrival at Venus and their penetration to the planet's atmosphere. For the event in May 2012, we consider the solar particle properties (integrated flux and rigidity spectrum) obtained by the Neutron Monitor Based Anisotropic GLE Pure Power Law (NMBANGLE PPOLA) model (Plainaki et al., 2010, 2014) applied previously for the Earth case and scaled to the distance of Venus from the Sun. For the simulation of the actual cascade in the Venusian atmosphere initiated by the incoming particle fluxes, we apply the DYASTIMA code, a Monte Carlo (MC) application based on the Geant4 software (Paschalis et al., 2014). Our predictions are afterwards compared to other estimations derived from previous studies and discussed. Finally, we discuss the differences between the nominal ionization profile due to galactic cosmic-ray–atmosphere interactions and the profile during periods of intense solar activity, and we show the importance of understanding space weather conditions on Venus in the context of future mission preparation and data interpretation.
- Daytime twin-peak structures observed at southern African and European
middle latitudes on 8–13 April 2012
Abstract: Daytime twin-peak structures observed at southern African and European middle latitudes on 8–13 April 2012
Zama T. Katamzi, John Bosco Habarulema, and Nigussie M. Giday
Ann. Geophys., 34, 581-590, doi:10.5194/angeo-34-581-2016, 2016
Daytime twin-peak structures, also known as bite-out or diurnal double-maxima structures, are ionospheric phenomena in which the diurnal ionospheric trend shows two peaks (instead of the normal one) during the daytime. This study reports on first simultaneous observations of these structures in the Global Positioning System and ionosonde measurements from the southern African and European middle-latitude stations during a mostly quiet geomagnetic condition period of 8–13 April 2012.