A discussion on the existence of the anomalous high and the anomalous low
Summary: The gradient wind is a basic issue in geophysics. In classic literature, two types of the gradient wind, the anomalous high and the anomalous low, are considered to be pure mathematical solutions with no physical meaning. However, through the detailed discussion on evolution mechanisms, the author proposes comprehensive and reasonable explanation of the gradient wind including the two confused types which probably exist in atmosphere. This gives a deep understanding of the Earth' atmosphere.
Ann. Geophys., 33, 1253-1261, doi:10.5194/angeo-33-1253-2015, 2015
Multi-satellite study of the excitation of Pc3 and Pc4-5 ULF waves and their penetration across the plasmapause during the 2003 Halloween superstorm
Ann. Geophys., 33, 1237-1252, doi:10.5194/angeo-33-1237-2015, 2015
Recent highlights from Cluster, the first 3-D magnetospheric mission
Summary: This paper presents recent highlights from the Cluster mission on solar wind turbulence, magnetopause asymmetries and magnetosheath density enhancements, dipolarisation currents, reconnection variability, FTE in greatest detail, plasmaspheric wind and re-filling of the plasmasphere, radiation belts, updates of magnetospheric electric and magnetic field models, and magnetosheath and magnetopause properties under low Mach number. Public access to all high-resolution data (CSA) is also presented.
Ann. Geophys., 33, 1221-1235, doi:10.5194/angeo-33-1221-2015, 2015
The far-ultraviolet main auroral emission at Jupiter – Part 2: Vertical emission profile
Summary: Early models of the main auroral emission at Jupiter assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use far-UV images from the Hubble Space Telescope to further characterize these variations on a statistical basis. We show that the dusk side sector is ~3 times brighter than the dawn side, and we suggest that such an asymmetry could be the result of a partial ring current in the nightside magnetosphere.
Ann. Geophys., 33, 1211-1219, doi:10.5194/angeo-33-1211-2015, 2015
The far-ultraviolet main auroral emission at Jupiter – Part 1: Dawn–dusk brightness asymmetries
Summary: Early models of the main auroral emission at Jupiter assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use Far-UV images from the Hubble Space Telescope to further characterise these variations on a statistical basis. We show that the dusk side sector is ~3 times brighter than the dawn side and we suggest that such an asymmetry could be the result of a partial ring current in the night side magnetosphere.
Ann. Geophys., 33, 1203-1209, doi:10.5194/angeo-33-1203-2015, 2015
The latitudinal structure of the nightside outer magnetosphere of Saturn as revealed by velocity moments of thermal ions
Summary: The latitudinal structure of the nightside outer magnetosphere of Saturn was studied by using Cassini CAPS plasma measurements. It was found that the plasma density and the azimuthal velocity decrease simultaneously as the spacecraft moves away from the magnetic equator. The magnetosphere exhibits an “onion shell like” structure: the inner regions spin rapidly corotating with the planet, but moving outward and/or further away from the equatorial plane one can encounter slower and slower shells.
Ann. Geophys., 33, 1195-1202, doi:10.5194/angeo-33-1195-2015, 2015
Multi-year observations of gravity wave momentum fluxes at low and middle latitudes inferred by all-sky meteor radar
Summary: Multi-year observations of gravity wave momentum fluxes have been analyzed at three different sites using meteor radar data. This is a first, as no such experimental results on the latitudinal dependence of these parameters at low latitudes had been derived with ground-based instruments in the MLT region before. Until now similar studies had been carried out with satellites and circulation models. Therefore this thematic can be lead to a valuable scientific contribution.
Ann. Geophys., 33, 1183-1193, doi:10.5194/angeo-33-1183-2015, 2015
Combined effects of concurrent Pc5 and chorus waves on relativistic electron dynamics
Ann. Geophys., 33, 1173-1181, doi:10.5194/angeo-33-1173-2015, 2015
Convective gravity wave propagation and breaking in the stratosphere: comparison between WRF model simulations and lidar data
Summary: In this work we perform numerical simulations of convective gravity waves, using the WRF model. We first run an idealized and highly resolved case. Then, we compare realistic simulations (model top at 68km) with lidar measurements of gravity wave potential energy (Ep) over southern France. Vertical structures of simulated potential energy profiles are found to be in good agreement with those measured by lidar. On the other hand, the magnitude of simulated wave energy is clearly underestimated.
Ann. Geophys., 33, 1155-1171, doi:10.5194/angeo-33-1155-2015, 2015
In situ evidence of breaking the ion frozen-in condition via the non-gyrotropic pressure effect in magnetic reconnection
Summary: Magnetic reconnection is a ubiquitous process that drives global-scale dynamics in plasmas. For reconnection to proceed, both ion and electrons must be unfrozen in a localized diffusion region. By analyzing in situ measurements, we show that the non-gyrotropic ion pressure is mainly responsible for breaking the ion frozen-in condition in reconnection. The reported non-gyrotropic ion pressure tensor can specify the reconnection electric field that controls how quickly reconnection proceeds.
Ann. Geophys., 33, 1147-1153, doi:10.5194/angeo-33-1147-2015, 2015
Comparison of total column ozone obtained by the IASI-MetOp satellite with ground-based and OMI satellite observations in the southern tropics and subtropics
Ann. Geophys., 33, 1135-1146, doi:10.5194/angeo-33-1135-2015, 2015
Polar cap patches observed during the magnetic storm of November 2003: observations and modeling
Summary: We present multi-instrument measurements and multi-technique analysis of polar cap patches observed early during the recovery phase of the major magnetic storm of November 20 2003. During this event, the Qaanaaq imager observed variable airglow brightness of the patches between 20:33 and 20:43UT, probably associated with a large-scale gravity wave. Our numerical results indicate that variations in the airglow intensity up to 265R can be produced by a constant 70m/s downward vertical wind.
Ann. Geophys., 33, 1117-1133, doi:10.5194/angeo-33-1117-2015, 2015
Simulation of the Indian summer monsoon onset-phase rainfall using a regional model
Summary: The Indian summer monsoon rainfall climatology during the monsoon onset phase in different climate zones is simulated using the regional model ARW for the decade 2000-2009, using NNRP global reanalysis. Comparisons with IMD & NNRP rainfall show that the model could simulate the onset phase in terms of progression and distribution of rainfall in most zones (except over the northeast) with good correlations and low error metrics, and improves the onset time by 1-3 days in zones 4 and 7 over NNRP.
Ann. Geophys., 33, 1097-1115, doi:10.5194/angeo-33-1097-2015, 2015
First experimental verification of summertime mesospheric momentum balance based on radar wind measurements at 69° N
Summary: Imposed momentum from mesospheric breaking gravity waves (GWs) is conserved by a balance between vertical divergence of GW momentum flux and Coriolis acceleration of the mean meridional wind. We present the first experimental verification of the momentum balance from the Saura MF radar at 69°N. For contributions from GWs only this balance is fulfilled between 70 and 100km during summer when GWs dominate the mesospheric dynamics, but it does not exist in winter due to planetary wave impacts.
Ann. Geophys., 33, 1091-1096, doi:10.5194/angeo-33-1091-2015, 2015
Tropical upper tropospheric humidity variations due to potential vorticity intrusions
Summary: Four cases are presented in which the relative humidity (RH) shows consistent increase by more than 50% in the upper troposphere (200-250 hPa) over tropics at the eastward side of the potential vorticity (PV) intrusion region. The increase in RH is observed irrespective of whether the PV intrusions are accompanied by deep convection or not and is suggested to be due to poleward advection induced by the PV intrusions.
Ann. Geophys., 33, 1081-1089, doi:10.5194/angeo-33-1081-2015, 2015
Tomography of the ionospheric electron density with geostatistical inversion
Ann. Geophys., 33, 1071-1079, doi:10.5194/angeo-33-1071-2015, 2015
Energy–latitude dispersion patterns near the isotropy boundaries of energetic protons
Summary: We investigate the precipitated-to-trapped flux ratio patterns near the proton isotropy boundary (IB) using NOAA-POES observations. For 30 and 80keV proton energies, we found only 31% of events showing the dispersion pattern predicted by the non-adiabatic scattering in the tail current sheet. Most frequent pattern had no measureable IB energy dispersion (63%); structured IBs with a few Jprec/Jtrap dropouts were also usual (60%). Roles of current sheet and wave-induced scattering are discussed.
Ann. Geophys., 33, 1059-1070, doi:10.5194/angeo-33-1059-2015, 2015
Association of the pre-monsoon thermal field over north India and the western Tibetan Plateau with summer monsoon rainfall over India
Summary: In this paper inter-annual variability of tropospheric air temperature over the Asian summer monsoon region during the pre-monsoon months is examined in relation to Indian summer monsoon rainfall (ISMR; June to September total rainfall). The results indicate a strong and significant northwest–southeast dipole structure in the spatial correlations over the Indian region with highly significant positive (negative) correlations over the regions of north India and the western Tibetan Plateau region.
Ann. Geophys., 33, 1051-1058, doi:10.5194/angeo-33-1051-2015, 2015
Magnetohydrodynamic modeling of three Van Allen Probes storms in 2012 and 2013
Ann. Geophys., 33, 1037-1050, doi:10.5194/angeo-33-1037-2015, 2015
Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko
Summary: We present a first report on magnetic field measurements made in the coma of comet 67P/C-G in its low-activity state. The plasma environment is dominated by quasi-coherent, large-amplitude, compressional magnetic field oscillations around 40mHz, differing from the observations at strongly active comets where waves at the cometary ion gyro-frequencies are the main feature. We propose a cross-field current instability associated with the newborn cometary ions as a possible source mechanism.
Ann. Geophys., 33, 1031-1036, doi:10.5194/angeo-33-1031-2015, 2015