Association of radiation belt electron enhancements with earthward penetration of Pc5 ULF waves: a case study of intense 2001 magnetic storms
Summary: Our study demonstrates a remarkable association between the earthward penetration of ULF waves and radiation belt electron enhancements during four magnetic storms that occurred in 2001. In the past, ULF waves had been observed at unusual depths during rare superstorms. But ULF wave activity, reaching magnetic shells as low as 2, was also observed during relatively intense storms when it played a key role in diffusing electrons radially inward and thereby accelerating them to higher energies.
Ann. Geophys., 33, 1431-1442, doi:10.5194/angeo-33-1431-2015, 2015
A comparative study of GPS ionospheric scintillations and ionogram spread F over Sanya
Ann. Geophys., 33, 1421-1430, doi:10.5194/angeo-33-1421-2015, 2015
Non-elliptic wavevector anisotropy for magnetohydrodynamic turbulence
Summary: A lot of efforts have been put into understanding the turbulence structure in space and astrophysical plasmas, in particular how the filamentary structure develops as the length scale of the turbulent fluctuations changes from large to smaller ones. Motivated by the recent spacecraft observations in the solar wind, an analytic model is proposed to explain the nature of filament-formation processes in space plasma turbulence with a successful test against the spacecraft observations.
Ann. Geophys., 33, 1413-1419, doi:10.5194/angeo-33-1413-2015, 2015
Radar and satellite investigations of equatorial evening vertical drifts and spread F
Ann. Geophys., 33, 1403-1412, doi:10.5194/angeo-33-1403-2015, 2015
Defining and resolving current systems in geospace
Summary: A number of current systems exist in the Earth's magnetosphere. It is very difficult to identify local measurements as belonging to a specific current system. Therefore, there are different definitions of supposedly the same current, leading to unnecessary controversy. This study presents a robust collection of these definitions of current systems in geospace, particularly in the near-Earth nightside magnetosphere, as viewed from a variety of observational and computational analysis techniques.
Ann. Geophys., 33, 1369-1402, doi:10.5194/angeo-33-1369-2015, 2015
Superimposed disturbance in the ionosphere triggered by spacecraft launches in China
Ann. Geophys., 33, 1361-1368, doi:10.5194/angeo-33-1361-2015, 2015
Interhemispheric structure and variability of the 5-day planetary wave from meteor radar wind measurements
Summary: The quasi-5-day wave at mid- and high-latitudes in the mesosphere and lower-thermosphere was compared between the hemispheres using meteor radar horizontal wind measurements, spanning June 2010 to December 2012. Variances of the quasi-5-day wave showed a wave activity from July to August in both hemispheres and in April 2012 in the Northern Hemisphere and November 2012 in the Southern Hemisphere with unique characteristics at each site.
Ann. Geophys., 33, 1349-1359, doi:10.5194/angeo-33-1349-2015, 2015
Dust devil vortex generation from convective cells
Ann. Geophys., 33, 1343-1347, doi:10.5194/angeo-33-1343-2015, 2015
Self-consistent electrostatic simulations of reforming double layers in the downward current region of the aurora
Summary: In a simulation study of the downward current region of the aurora, i.e. where electrons are accelerated upward, double layers are seen to form at low altitude and move upward until they are disrupted at altitudes of ten thousand kilometres or thereabouts. When one double layer is disrupted a new one forms below, and the process repeats itself. The repeated demise and reformation allows ions to flow upward without passing through the double layers that otherwise would have kept them down.
Ann. Geophys., 33, 1331-1342, doi:10.5194/angeo-33-1331-2015, 2015
Observational evidence of quasi-27-day oscillation propagating from the lower atmosphere to the mesosphere over 20° N
Ann. Geophys., 33, 1321-1330, doi:10.5194/angeo-33-1321-2015, 2015
Climatology of the ionospheric slab thickness along the longitude of 120° E in China and its adjacent region during the solar minimum years of 2007–2009
Summary: The climatology of ionospheric slab thickness is analysed using dual-frequency GPS and COSMIC measurements in China during the solar minimum. It is found that a pronounced peak of slab thickness occurs during the post-midnight period. A large diurnal ratio exists at the EIA, and a large night-to-day ratio occurs near the equatorial latitudes and mid- to high latitudes. The behaviours of the slab thickness and the mF2 are well correlated at the middle latitudes and during the daytime.
Ann. Geophys., 33, 1311-1319, doi:10.5194/angeo-33-1311-2015, 2015
A physical explanation for the magnetic decrease ahead of dipolarization fronts
Summary: We use THEMIS large data set of dipolarization front events to build a 2-D pressure distribution in XZ plane, and thus derive the current system around the dipolarization front. Our results show that a banana current loop is formed around the dipolarization front. This current is also suggested to be the reason for the magnetic dip observed ahead of the dipolarization front. In addition, the current density is too small to contribute a substorm current wedge.
Ann. Geophys., 33, 1301-1309, doi:10.5194/angeo-33-1301-2015, 2015
Wide-banded NTC radiation: local to remote observations by the four Cluster satellites
Summary: We present here cases of wide banded Non Thermal Continuum (NTC) observed from the multi-point Cluster observatory. We point out that a large portion of the plasmasphere boundary layer, covering magnetic latitudes from 0 to above 30°, is radiating these radio waves. The radiation is confined inside multiple beams of small cone angles. We show how the spectral signature evolves, from integer harmonics of the electron gyrofrequency, when the observatory moves away from their sources.
Ann. Geophys., 33, 1285-1300, doi:10.5194/angeo-33-1285-2015, 2015
The relationship between plasmapause, solar wind and geomagnetic activity between 2007 and 2011
Summary: Using Cluster data, we develop plasmapause Lpp models parameterized by solar wind coupling functions and geomagnetic activity indices. We show that the Lpp response to the changes in the interplanetary conditions depends on the magnetic local time. The faster plasmapause response is observed in the post-midnight sector. At low activity, Lpp exhibits the largest values on the dayside. For enhanced activity, displacements towards larger values on the evening side are identified.
Ann. Geophys., 33, 1271-1283, doi:10.5194/angeo-33-1271-2015, 2015
Relating field-aligned beams to inverted-V structures and visible auroras
Ann. Geophys., 33, 1263-1269, doi:10.5194/angeo-33-1263-2015, 2015
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