The extreme solar storm of May 1921: observations and a complex topological model
H. Lundstedt, T. Persson, and V. Andersson Ann. Geophys., 33, 109-116, 2015 AbstractFull Article (PDF, 3228 KB)
27 Jan 2015
A dominant acoustic-gravity mode in the polar thermosphere
Summary: The article presents a summary of the main findings of the systematic study of acoustic-gravity waves (AGWs) in the polar thermosphere. This study was based on the in situ measurements made by the Dynamics Explorer 2 spacecraft. It was found out that AGWs in the polar thermosphere are observed within a narrow frequency band and with horizontal wavelengths about 500-600km. The connection between the directions of motion of AGW and polar wind circulation was detected.
Observations and modeling of UHF-band scintillation occurrence probability over the low-latitude region of China during the maximum activity of solar cycle 24
Summary: Variations of UHF-band scintillation occurrence with latitude, time and season over the low-latitude region of China are presented. The ratio of the mean foF2 at 20:00LT between two equinoxes, which could act as a proxy of the equinoctial asymmetry in the occurrences of scintillation, is proportional to the ratio between the maximum scintillation occurrence in the autumn equinox and in the vernal equinox. The empirical climatological model of scintillation occurrence probability was validated.
H. Zhang, Y. Liu, J. Wu, T. Xu, and D. Sheng Ann. Geophys., 33, 93-100, 2015 AbstractFull Article (PDF, 151 KB)
16 Jan 2015
Experimental test of the ρ(1-α) evolution for rotational discontinuities: cluster magnetopause observations
Summary: Rotational discontinuities (RDs) in plasma allow a magnetic connection between different plasma regimes. One of their defining relations describes a balance between changes in plasma mass density and pressure anisotropy. The paper uses the high-time-resolution data from the Cluster satellites to directly test that relation at the terrestrial magnetopause, when standard analysis predicts that this boundary behaves like an RD. The experimental evidence shows that the said relation is not fulfilled
A. Blagau, G. Paschmann, B. Klecker, and O. Marghitu Ann. Geophys., 33, 79-91, 2015 AbstractFull Article (PDF, 9628 KB)
15 Jan 2015
Radiation dose of aircrews during a solar proton event without ground-level enhancement
Summary: Using a new air-shower simulation driven by the proton flux data obtained from GOES satellites, we show the possibility of significant enhancement of the effective dose rate of up to 4.5 µSv/hr at a conventional flight altitude of 12 km during the largest solar proton event that did not cause a ground-level enhancement. As a result, a new GOES-driven model is proposed to give an estimate of the contribution from the isotropic component of the radiation dose in the stratosphere.
R. Kataoka, Y. Nakagawa, and T. Sato Ann. Geophys., 33, 75-78, 2015 AbstractFull Article (PDF, 82 KB)
15 Jan 2015
Dipolarization fronts in the near-Earth space and substorm dynamics
Summary: Magnetospheric substorms are one of the most important phenomena occurring in planetary magnetotails, dynamically reconfiguring the near- planet space environment. They encompass various fundamental processes of plasma acceleration and transport in the magnetosphere/ionosphere. The key features of the paper are a new magnetospheric substorm model, a new explanation about the origin of dipolarization fronts (DFs), and a new explanation for energetic ion acceleration/injection in front of DFs.
I. I. Vogiatzis, A. Isavnin, Q.-G. Zong, E. T. Sarris, S. W. Lu, and A. M. Tian Ann. Geophys., 33, 63-74, 2015 AbstractFull Article (PDF, 1122 KB)
15 Jan 2015
Validation of GPS atmospheric water vapor with WVR data in satellite tracking mode
Summary: We present validation results covering 184 days of SIWV (slant-integrated water vapor) observed by a ground-based GPS receiver and a WVR (water vapor radiometer). SIWV data from GPS and WVR generally show good agreement, and the relation between their differences and possible influential factors are analyzed. The differences in SIWV show a relative elevation dependence. Besides the elevation, dependencies between the atmospheric humidity conditions, temperature and differences in SIWV are found.
M. Shangguan, S. Heise, M. Bender, G. Dick, M. Ramatschi, and J. Wickert Ann. Geophys., 33, 55-61, 2015 AbstractFull Article (PDF, 1826 KB)
13 Jan 2015
Three-dimensional multi-fluid model of a coronal streamer belt with a tilted magnetic dipole
Summary: First results from the three-fluid 3D model of the solar corona are reported. The model extends previous 2.5D three-fluid studies, and includes electron, protons, and oxygen ions (O5+) as coupled fluids in a tilted dipole solar magnetic field configuration. The model demonstrates the variation in abundances of the oxygen ions relative to protons in a coronal streamer belt, thus identifying the sources of the slow solar wind and helping in the interpretation of past spectroscopic observations.
The nightside magnetic field line open–closed boundary and polar rain electron energy-latitude dispersion
Summary: Magnetotail reconnection and E×B leads to dispersion in polar rain electrons. APL-OPM successfully models the polar rain energy-latitude dispersion. The magnetic field line open-closed boundary is located poleward of the auroral oval.
Spectrum analysis of short-period K index behaviour at high and mid-latitudes
Summary: In this study we performed a wavelet and Lomb-Scargle analysis of the geomagnetic activity K-index at Lerwick (LER), Hermanus (HER) and Canberra (CNB) for the period between 1960 and 2010, overlapping with solar cycles 20 to 23. Daily mean K indices are used to identify how several harmonics of the 27.0-day recurrent period change during each solar cycle when comparing high- and mid-latitude geomagnetic activity, applying a 95% confidence level.
Summary: Magnetic structures are important for studies of solar atmospheric heating. Combining computer simulations with observations of the Sun provides us with information not obtainable from pure observation. We use this to suggest and interpret the physical nature of a particular structure which is permeated by a continuous outflow of plasma. It is shown that the structure consists of multiple strands which undergo periodic heating and cooling.
Identification of slow magnetosonic wave trains and their evolution in 3-D compressible turbulence simulation
L. Zhang, L.-P. Yang, J.-S. He, C.-Y. Tu, L.-H. Wang, E. Marsch, and X.-S. Feng Ann. Geophys., 33, 13-23, 2015 AbstractFull Article (PDF, 1166 KB)
07 Jan 2015
Internally and externally induced deformations of the magnetospheric equatorial current as inferred from spacecraft data
Summary: A new quantitative model of the global shape of the neutral sheet in the Earth's magnetosphere is developed, parameterized by the dipole tilt, solar wind pressure, and IMF By and Bz. The model is based on data from the Polar, Cluster, Geotail, and Themis satellites taken in 1995-2013. The paper quantifies and further explains our earlier finding of the bowl-shaped deformation of the neutral sheet due to the Earth's dipole tilt (Tsyganenko and Andreeva, GRL, v.41(4), 2014).
N. A. Tsyganenko, V. A. Andreeva, and E. I. Gordeev Ann. Geophys., 33, 1-11, 2015 AbstractFull Article (PDF, 10502 KB)
06 Jan 2015
Correlation studies for B-spline modeled F2 Chapman parameters obtained from FORMOSAT-3/COSMIC data
Summary: The determination of ionospheric key quantities such as the maximum electron density of the F2 layer, the corresponding F2 peak height and the F2 scale height are of high relevance in 4-D ionosphere modeling to provide information on the vertical structure of the electron density distribution. This paper discusses mathematical correlations between these parameters as derived from FORMOSAT-3/COSMIC radio occultations and regionally parameterized by means of polynomial B-splines.
M. Limberger, W. Liang, M. Schmidt, D. Dettmering, M. Hernández-Pajares, and U. Hugentobler Ann. Geophys., 32, 1533-1545, 2014 AbstractFull Article (PDF, 4923 KB)
17 Dec 2014
TID characterised using joint effort of incoherent scatter radar and GPS
M. van de Kamp, D. Pokhotelov, and K. Kauristie Ann. Geophys., 32, 1511-1532, 2014 AbstractFull Article (PDF, 15149 KB)
17 Dec 2014
Energy exchange and wave action conservation for magnetohydrodynamic (MHD) waves in a general, slowly varying medium
Summary: The equation for conservation of wave action is explicitly derived for magnetohydrodynamic waves in a plasma that varies slowly in space and time. Together with generalized ray-tracing equations, it is equivalent to a WKBJ solution of the problem and allows the computation of energy exchange between wave and background plasma as well as the variation of the amplitudes of the field components along the ray. The method is illustrated by application to simple examples.
The numerical simulation on ionospheric perturbations in electric field before large earthquakes
S. F. Zhao, X. M. Zhang, Z. Y. Zhao, and X. H. Shen Ann. Geophys., 32, 1487-1493, 2014 AbstractFull Article (PDF, 353 KB)
09 Dec 2014
On the origin of falling-tone chorus elements in Earth's inner magnetosphere
H. Breuillard, O. Agapitov, A. Artemyev, V. Krasnoselskikh, O. Le Contel, C. M. Cully, V. Angelopoulos, Y. Zaliznyak, and G. Rolland Ann. Geophys., 32, 1477-1485, 2014 AbstractFull Article (PDF, 1201 KB)
08 Dec 2014
A possible influence of the Great White Spot on Saturn kilometric radiation periodicity
Summary: In this paper we show that the large thunderstorm called the "Great White Spot", which raged for about 9 months in Saturn's troposphere in 2010/2011, was accompanied by changes in the periodicity and phasing of auroral radio emissions. We suggest that the thunderstorm was a source of intense gravity waves causing a global change in Saturn’s ionospheric winds via energy and momentum deposition. This supports the theory that Saturn’s magnetospheric periodicities are driven by the upper atmosphere.
G. Fischer, S.-Y. Ye, J. B. Groene, A. P. Ingersoll, K. M. Sayanagi, J. D. Menietti, W. S. Kurth, and D. A. Gurnett Ann. Geophys., 32, 1463-1476, 2014 AbstractFull Article (PDF, 1478 KB)
04 Dec 2014
Correlation of very low and low frequency signal variations at mid-latitudes with magnetic activity and outer-zone particles