Ground-based Pc5 ULF wave power: Solar wind speed and MLT dependence     

D.M. Pahud  I.J. Rae  I.R. Mann  K.R. Murphy  V. Amalraj 《Journal of Atmospheric and Solar》2009,71(10-11):1082-1092

Using over 20 years of ground-based magnetometer data from the CANOPUS/CARISMA magnetometer array, we present a statistical characterisation of Pc5 ultra-low frequency (ULF) power in the 2–10 mHz band as a function of magnetic local time (MLT), L-shell, and solar wind speed. We examine the power across L-shells between 4.2 and 7.9, using data from the PINA, ISLL, GILL and FCHU stations, and demonstrate that there is a significant MLT dependence in both the H- and D-component median 2–10 mHz power during both fast (>500 km/s) and slow (<500 km/s) solar wind speeds. The H-component power consistently dominates over D-component power at all MLTs and during both fast and slow solar wind. At the higher-L stations (L>5.4), there are strong MLT power peaks in the morning and midnight local time sectors; the morning sector dominating midnight during fast solar wind events. At lower L-shells, there is no evidence of the midnight peak and the 2–10 mHz power is more symmetric with respect to MLT except during the fastest solar wind speeds. There is little evidence in the ground-based power of a localised MLT peak in ULF power at dusk, except at the lowest L-shell station, predominantly in the H-component. The median 2–10 mHz power increases with an approximate power law dependence on solar wind speed, at all local times across the L-shell domain studied in both components. The H-component power peaks at the latitude of the GILL station, with significantly lower power at both higher and lower L-shells. Conversely, the D-component power increases monotonically. We believe that this is evidence for 2–10 mHz power accumulating at auroral latitudes in field line resonances. Finally, we discuss how such ULF wave power characterisation might be used to derive empirical radiation belt radial diffusion coefficients based on, and driven by, the solar wind speed dependence of ULF wave power.  相似文献   

Temporal evolution of neutral,thermospheric winds and plasma response using PFISR measurements of gravity waves     

Sharon L. Vadas  Michael J. Nicolls 《Journal of Atmospheric and Solar》2009,71(6-7):744-770

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Reply to comments on “burning molten metallic spheres: one class of ball lightning?”     

Karl D. Stephan  Nathan Massey 《Journal of Atmospheric and Solar》2009,71(8-9):1003-1004

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Atmospheric tides and mean winds in the meteor region over Santa Maria (29.7°S; 53.8°W)     

V.F. Andrioli  B.R. Clemesha  P.P. Batista  N.J. Schuch 《Journal of Atmospheric and Solar》2009,71(17-18):1864-1876

We compare meteor radar measurements of the MLT region winds at Santa Maria, Brazil (29.7°S, 53.8°W) with the Horizontal Neutral Wind Model (HWM-93) and the Global Scale Wave Model (GSWM-00). The observed annual variation of the prevailing zonal wind disagrees in some respects with the HWM-93 model. Also, the zonal diurnal tide amplitude shows an annual variation, whereas that of the GSWM-00 is semiannual, and its vertical wavelength is smaller than that suggested by the model. The observed semidiurnal tide shows seasonal and inter-annual variations and the phase is evanescent during almost the whole year.  相似文献   

Diurnal variation of surface currents at a tropical station     

M.N. Kulkarni  S.D. Pawar  P. Murugavel  V. Gopalakrishnan 《Journal of Atmospheric and Solar》2010,72(1):77-82

The surface measurements of different atmospheric electrical and meteorological parameters made at a tropical station were analyzed, to study their diurnal variation pattern with specific emphasis on convection current and the meteorological conditions responsible for its generation. The analysis shows that most of the time the displacement current is very small. The convection current is positive for most of the time of the day indicating transport of negative charge to the earth by convection. In spite of very low winds during night, the convection current is found to be more during night than during day. Large space charge density gradient near the earth's surface during stable and stratified atmosphere at night may be a reason for large convection current during that time. This study demonstrates that eddy diffusion during day time and large space charge gradient during night time are responsible for generation of convection current at this location.  相似文献   

Statistical properties of global geomagnetic indexes as a potential forecasting tool for strong perturbations     

Vitor H.A. Dias  Andrés R.R. Papa 《Journal of Atmospheric and Solar》2010,72(1):109-114

Here we extend to global level, through the SYM-H index and for the period 1981–2003, a study recently published by our group regarding distributions of local geomagnetic measurements near the South Atlantic anomaly, for the period 1998–2003, advanced as a potential forecasting tool. We have found, once more, a correlation between distributions and the corresponding storm intensities. A step forward was the finding of a correlation between the temporal variation of distributions and the corresponding storm intensities which could also serve as a probabilistic storm forecasting method. The data was obtained at the World Data Centre for Geomagnetism, Kyoto, Japan.  相似文献   

Polar mesosphere summer echoes with ESRAD,Kiruna, Sweden: Variations and trends over 1997–2008     

M. Smirnova  E. Belova  S. Kirkwood  N. Mitchell 《Journal of Atmospheric and Solar》2010,72(5-6):435-447

Measurements of Polar Mesosphere Summer Echoes (PMSE) with the MST radar ESRAD, in northern Sweden, from 1997 to 2008, were used to study diurnal, day-to-day and year-to-year variations of PMSE. The PMSE occurrence rate and volume reflectivity on a daily scale show predominantly semidiurnal variations with small interannual variability in the shape of the diurnal curves. Day-to-day and interannual variations of PMSE are found to correlate with geomagnetic activity while they do not correlate with mesopause temperature or solar activity. No statistically significant trends in PMSE occurrence rate and length of PMSE season were detected over the observation interval.  相似文献   

A new time-dependent ionosphere–magnetosphere coupling model: Comparison of field-aligned currents against ST5 observations     

T.S. Huang  E. Romashets  G. Le  Y. Wang  J.A. Slavin 《Journal of Atmospheric and Solar》2010,72(4):369-373

By using Tsyganenko's model for the magnetosphere's magnetic field, which links two hemispheres of the ionosphere, and adopting a practical boundary condition for the electric potential around the polar cap, we developed a new ionosphere–magnetosphere coupling model based on prairie view dynamo code (PVDC). The new model takes the variations in solar wind and interplanetary magnetic field, as well as the geomagnetic activity, into account. Rather than the previous version of PVDC that is useful only for quiet conditions, the new model enables to calculate the electric potential and currents in the ionosphere and the field-aligned current (FAC) off the ionosphere in quiet and disturbed times. Comparison of the calculated FAC with the measurements of Space Technology 5 (ST5) mission shows a good agreement.  相似文献   

Spatio-temporal exploratory analysis of urban surface temperature field in Shanghai, China   总被引：1，自引：0，他引：1  

Xiaoyan Dai  Zhongyang Guo  Liquan Zhang  Dan Li 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(2):247-257

The integrated application of remote sensing, geographic information system and quantitative analytical modeling can provide scientific and effective methods for monitoring and studying urban heat island, based on land surface temperature (LST) retrieved from thermal infrared channel data of sensors. In this paper, LST is retrieved from Landsat TM6 and ETM + 6 data of Shanghai central city in 1989, 1997, 2000 and 2002, by using the mono-window algorithm. Based on the data, global and local spatial autocorrelation analysis, and geostatistical methods are adopted to quantitatively describe the characteristics of spatial heterogeneity and temporal evolution of land surface thermal landscape at different scales and periods in Shanghai central city, by utilizing exploratory spatial data analysis. Results show that LST field in Shanghai central city tends to fragmentize and complicate with the development of Shanghai, and its global spatial difference becomes greater gradually. The spatial variance pattern of the change of LST field from 1997 to 2002 indicates that the dynamic change of LST presents a tendency of increase in circularity. LST declines distinctly in the districts of Puxi and Pudong near and inside the inner ring road, while it rises obviously outside the central city and near the out ring road. The extrema of temporal change in LST field have a characteristic of spatial clustering. Besides, as the city of Shanghai expands in a circular pattern as a whole, the directional difference of dynamic change of urban surface thermal landscape exists but is not very obvious.  相似文献   

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张晓东  王亮  韩立钦  兰小机  王志红 《大地测量与地球动力学》2010,30(6):131-134

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