scholarly journals A statistical study of spatial distribution and source region size of chorus waves using Van Allen Probes data

2018 ◽  
Author(s):  
Shangchun Teng ◽  
Xin Tao ◽  
Wen Li ◽  
Yi Qi ◽  
Xinliang Gao ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Equatorial Plane ◽  
Statistical Study ◽  
Continuous Wave ◽  
Source Region ◽  
Occurrence Rate ◽  
Data Set ◽  
Chorus Waves ◽  
Van Allen Probes ◽  
Region Size

Abstract. Spatial distribution and source region size of chorus waves are important parameters in understanding their generation.In this work, we analyze over 3 years of continuous wave burst mode data from Van Allen Probes and build a data set of rising and falling tone chorus. For the L shell range covered by Van Allen Probes data (3.5 ≤ L ≤ 7), statistical results demonstrate that the sector where rising tones are most likely to be observed is the dayside during geomagnetically quiet and moderate times and the dawnside during active times. Moreover, rising tone chorus waves have a higher occurrence rate near the equatorial plane, while the falling tone chorus waves have a higher possibility to be observed at lower L-shell and higher magnetic latitude. By analyzing the direction of Poynting wave vector, we statistically investigate the chorus source region size along a field line, and compare the results with previous theoretical estimates. Our analysis confirms previous conclusions that both rising tone and falling tone chorus waves are generated near the equatorial plane, and shows that previous theoretical estimates roughly agree with the observation within a factor of two. Our results provide important insights into further understanding of chorus generation.

scholarly journals A statistical study of the spatial distribution and source-region size of chorus waves using Van Allen Probes data

2018 ◽  
Vol 36 (3) ◽  
pp. 867-878 ◽  
Author(s):  
Shangchun Teng ◽  
Xin Tao ◽  
Wen Li ◽  
Yi Qi ◽  
Xinliang Gao ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Equatorial Plane ◽  
Statistical Study ◽  
Continuous Wave ◽  
Source Region ◽  
Occurrence Rate ◽  
Data Set ◽  
Chorus Waves ◽  
Van Allen Probes ◽  
Region Size

Abstract. The spatial distribution and source-region size of chorus waves are important parameters for understanding their generation. In this work, we analyze over 3 years of continuous wave burst-mode data from the Van Allen Probes mission and build a data set of rising-tone and falling-tone chorus waves. For the L shell range covered by Van Allen Probes data (3.5≤L≤7), statistical results demonstrate that the sector where rising tones are most likely to be observed is the dayside during geomagnetically quiet and moderate times and the dawn side during active times. Moreover, rising-tone chorus waves have a higher occurrence rate near the equatorial plane, while the falling-tone chorus waves have a higher possibility to be observed at lower L shell and higher magnetic latitudes. By analyzing the direction of the Poynting wave vector, we statistically investigate the chorus source-region size along a field line, and compare the results with previous theoretical estimates. Our analysis confirms previous conclusions that both rising-tone and falling-tone chorus waves are generated near the equatorial plane, and shows that previous theoretical estimates roughly agree with the observation within a factor of 2. Our results provide important insights into further understanding of chorus generation.

Storm time occurrence and spatial distribution of Pc4 poloidal ULF waves in the inner magnetosphere: A Van Allen Probes statistical study

2015 ◽  
Vol 120 (6) ◽  
pp. 4748-4762 ◽  
Author(s):  
Lei Dai ◽  
Kazue Takahashi ◽  
Robert Lysak ◽  
Chi Wang ◽  
John R. Wygant ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Statistical Study ◽  
Ulf Waves ◽  
Inner Magnetosphere ◽  
Van Allen Probes

scholarly journals Do galactic bars depend on environment?: an information theoretic analysis of Galaxy Zoo 2

2020 ◽  
Vol 501 (1) ◽  
pp. 994-1001
Author(s):  
Suman Sarkar ◽  
Biswajit Pandey ◽  
Snehasish Bhattacharjee
Keyword(s):  
Spatial Distribution ◽  
Mutual Information ◽  
Local Density ◽  
Statistical Significance ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
Host Galaxy ◽  
Data Sets ◽  
Data Set ◽  
Information Theoretic

ABSTRACT We use an information theoretic framework to analyse data from the Galaxy Zoo 2 project and study if there are any statistically significant correlations between the presence of bars in spiral galaxies and their environment. We measure the mutual information between the barredness of galaxies and their environments in a volume limited sample (Mr ≤ −21) and compare it with the same in data sets where (i) the bar/unbar classifications are randomized and (ii) the spatial distribution of galaxies are shuffled on different length scales. We assess the statistical significance of the differences in the mutual information using a t-test and find that both randomization of morphological classifications and shuffling of spatial distribution do not alter the mutual information in a statistically significant way. The non-zero mutual information between the barredness and environment arises due to the finite and discrete nature of the data set that can be entirely explained by mock Poisson distributions. We also separately compare the cumulative distribution functions of the barred and unbarred galaxies as a function of their local density. Using a Kolmogorov–Smirnov test, we find that the null hypothesis cannot be rejected even at $75{{\ \rm per\ cent}}$ confidence level. Our analysis indicates that environments do not play a significant role in the formation of a bar, which is largely determined by the internal processes of the host galaxy.

Statistical study of the storm time radiation belt evolution during Van Allen Probes era: CME- versus CIR-driven storms

2017 ◽  
Vol 122 (8) ◽  
pp. 8327-8339 ◽  
Author(s):  
Xiao-Chen Shen ◽  
Mary K. Hudson ◽  
Allison N. Jaynes ◽  
Quanqi Shi ◽  
Anmin Tian ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Statistical Study ◽  
Van Allen Probes

scholarly journals Spatial impact and triggering conditions of the exceptional hydro-geomorphological event of December 1909 in Iberia

2016 ◽  
Vol 16 (2) ◽  
pp. 371-390 ◽  
Author(s):  
S. Pereira ◽  
A. M. Ramos ◽  
J. L. Zêzere ◽  
R. M. Trigo ◽  
J. M. Vaquero
Keyword(s):  
Spatial Distribution ◽  
Iberian Peninsula ◽  
Large Scale ◽  
Extreme Event ◽  
Social Impacts ◽  
Meteorological Conditions ◽  
Pressure System ◽  
Data Set ◽  
Upper Level ◽  
Disaster Event

Abstract. According to the DISASTER database the 20–28 December 1909 event was the hydro-geomorphologic event with the highest number of flood and landslide cases that occurred in Portugal in the period 1865–2010 (Zêzere et al., 2014). This event also caused important social impacts over the Spanish territory, especially in the Douro Basin, having triggered the highest floods in more than 100 years at the river's mouth in the city of Oporto. This work has a dual purpose: (i) to characterize the spatial distribution and social impacts of the December 1909 hydro-geomorphologic DISASTER event over Portugal and Spain; (ii) to analyse the meteorological conditions that triggered the event and the spatial distribution of the precipitation anomalies. Social impacts that occurred in Portugal were obtained from the Disaster database (Zêzere et al., 2014) whereas the data collection for Spain was supported by the systematic analysis of Spanish daily newspapers. In addition, the meteorological conditions that triggered the event are analysed using the 20th Century Reanalysis data set from NOAA and precipitation data from Iberian meteorological stations. The Iberian Peninsula was spatially affected during this event along the SW-NE direction spanning from Lisbon, Santarém, Oporto, and Guarda (in Portugal), to Salamanca, Valladolid, Zamora, Orense, León, and Palencia (in Spain). In Iberia, 134 DISASTER cases were recorded (130 flood cases; 4 landslides cases) having caused 89 casualties (57 due to floods and 32 due to landslides) and a further total of 3876 affected people, including fatalities, injured, missing, evacuated, and homeless people. This event was associated with outstanding precipitation registered at Guarda (Portugal) on 22 December 1909 and unusual meteorological conditions characterized by the presence of a deep low-pressure system located over the NW Iberian Peninsula with a stationary frontal system striking the western Iberian Peninsula. The presence of an upper-level jet (250 hPa) and low-level jet (900 hPa) located SW–NE oriented towards Iberia along with upper-level divergence and lower-level convergence favoured large-scale precipitation. Finally, associated with these features it is possible to state that this extreme event was clearly associated with the presence of an elongated Atmospheric River, crossing the entire northern Atlantic Basin and providing a continuous supply of moisture that contributed to enhance precipitation. This work contributes to a comprehensive and systematic synoptic evaluation of the second most deadly hydro-geomorphologic DISASTER event that has occurred in Portugal since 1865 and will help to better understand the meteorological system that was responsible for triggering the event.

scholarly journals Melt segregation from partially molten source regions: The importance of melt density and source region size

1981 ◽  
Vol 86 (B7) ◽  
pp. 6261-6271 ◽  
Author(s):  
Edward Stolper ◽  
David Walker ◽  
Bradford H. Hager ◽  
James F. Hays
Keyword(s):  
Source Region ◽  
Source Regions ◽  
Melt Density ◽  
Melt Segregation ◽  
Region Size

scholarly journals Three-dimensional Sonography in the Assessment of Normal Fetal Anatomy in Late Pregnancy

2010 ◽  
Vol 4 (3) ◽  
pp. 217-231
Author(s):  
Badreldeen Ahmed ◽  
Ulrich Honemeyer
Keyword(s):  
Continuous Wave ◽  
Power Doppler ◽  
Three Dimensional ◽  
Late Pregnancy ◽  
Research Field ◽  
Surface Rendering ◽  
Volume Data ◽  
Data Set ◽  
3D Volume ◽  
Color And Power Doppler

Abstract Three-dimensional, multiplanar sonography, using a volume data set acquired with a 3D probe, has revolutionized ultrasonographic imaging and takes sonographers to a new perception of the fetus in 3 dimensions. Real time scanning, until the late nineties only possible in B-mode, can now be performed in 3D with up to 40 frames/sec. Fetal neurology emerged as a new perinatal research field with the 4D visualization of fetal behavior. Doppler ultrasound, diversified and refined from continuous wave and pulsed Doppler to Color – and Power Doppler, when added to 3D sonography, creates fascinating options of noninvasive fetal vascular mapping (sonoangiography) and vascular assessment of placenta. The diagnostic and demonstrative potential of an acquired 3D volume data set can be maxed with the help of postprocessing and rendering software. After storage, the evaluation of fetal 3D data sets can happen without the patient, with the option of specialist consultation, using telemedicine. In the article, the new 3D “modes” like surface rendering, maximum mode, 3D Color and Power Doppler, STIC, volume rendering, and glass body rendering, are described and illustrated in their display of normal fetal anatomy.

scholarly journals Detecting changes in Labrador Sea Water through a water mass analysis of BATS data

2005 ◽  
Vol 2 (4) ◽  
pp. 417-435 ◽  
Author(s):  
A. Henry-Edwards ◽  
M. Tomczak
Keyword(s):  
Water Mass ◽  
Sea Water ◽  
Source Region ◽  
Labrador Sea ◽  
Sargasso Sea ◽  
Mass Analysis ◽  
Data Set ◽  
Water Mass Analysis ◽  
Quadratic Programming Method ◽  
Labrador Sea Water

Abstract. A new water mass analysis technique is used to analyse the BATS oceanographic data set in the Sargasso Sea of 1988-1998 for changes in Labrador Sea Water (LSW) properties. The technique is based on a sequential quadratic programming method and requires careful definition of constraints to produce reliable results. Variations in LSW temperature and salinity observed in the Labrador Sea are used to define the constraints. It is shown that to minimize the residuals while matching the observed temperature and salinity changes in the source region the nitrate concentration in the Labrador Sea has to be allowed to vary as well. It is concluded that during the period of investigation nitrate underwent significant variations in the Labrador Sea.

scholarly journals A short geostatistical study of the three-dimensional spatial structure of fumonisins in stored maize

2010 ◽  
Vol 3 (1) ◽  
pp. 95-103 ◽  
Author(s):  
M. Rivas Casado ◽  
D. Parsons ◽  
N. Magan ◽  
R. Weightman ◽  
P. Battilani ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Spatial Structure ◽  
Spatial Correlation ◽  
Three Dimensional ◽  
Sample Collection ◽  
Data Set ◽  
Research Areas ◽  
Geostatistical Approach ◽  
Sampling Protocols ◽  
Current Sample

The heterogeneous three-dimensional spatial distribution of mycotoxins has proven to be one of the main limitations for the design of effective sampling protocols. Current sample collection protocols for mycotoxins have been designed to estimate the mean concentration and fail to characterise the spatial distribution of the mycotoxin concentration due to the aggregation of the incremental samples. Geostatistical techniques have been successfully applied to overcome similar problems in many research areas. However, little work has been developed on the use of geostatistics for the design of sampling protocols for mycotoxins. This paper focuses on the analysis of the two and three-dimensional spatial structure of fumonisins B1 (FB1) and B2 (FB2) in maize in a bulk store using a geostatistical approach and on how results help determine the number and location of incremental samples to be collected. The spatial correlation between FB1 and FB2, as well as between the number of kernels infected and the level of contamination was investigated. For this purpose, a bed of maize was sampled at different depths to generate a unique three-dimensional data set of FB1 and FB2. The analysis found no clear evidence of spatial structure in either the two-dimensional or three-dimensional analyses. The number of Fusarium infected kernels was not a good indicator for the prediction of fumonisin concentration and there was no spatial correlation between the concentrations of the two fumonisins.

scholarly journals Satellite-based sea ice thickness changes in the Laptev Sea from 2002 to 2017: comparison to mooring observations

2020 ◽  
Vol 14 (7) ◽  
pp. 2189-2203
Author(s):  
H. Jakob Belter ◽  
Thomas Krumpen ◽  
Stefan Hendricks ◽  
Jens Hoelemann ◽  
Markus A. Janout ◽  
...  
Keyword(s):  
Sea Ice ◽  
Source Region ◽  
European Space Agency ◽  
The Arctic ◽  
Ice Thickness ◽  
Laptev Sea ◽  
Validation Data ◽  
Data Set ◽  
Sea Ice Thickness ◽  
The Laptev Sea

Abstract. The gridded sea ice thickness (SIT) climate data record (CDR) produced by the European Space Agency (ESA) Sea Ice Climate Change Initiative Phase 2 (CCI-2) is the longest available, Arctic-wide SIT record covering the period from 2002 to 2017. SIT data are based on radar altimetry measurements of sea ice freeboard from the Environmental Satellite (ENVISAT) and CryoSat-2 (CS2). The CCI-2 SIT has previously been validated with in situ observations from drilling, airborne remote sensing, electromagnetic (EM) measurements and upward-looking sonars (ULSs) from multiple ice-covered regions of the Arctic. Here we present the Laptev Sea CCI-2 SIT record from 2002 to 2017 and use newly acquired ULS and upward-looking acoustic Doppler current profiler (ADCP) sea ice draft (VAL) data for validation of the gridded CCI-2 and additional satellite SIT products. The ULS and ADCP time series provide the first long-term satellite SIT validation data set from this important source region of sea ice in the Transpolar Drift. The comparison of VAL sea ice draft data with gridded monthly mean and orbit trajectory CCI-2 data, as well as merged CryoSat-2–SMOS (CS2SMOS) sea ice draft, shows that the agreement between the satellite and VAL draft data strongly depends on the thickness of the sampled ice. Rather than providing mean sea ice draft, the considered satellite products provide modal sea ice draft in the Laptev Sea. Ice drafts thinner than 0.7 m are overestimated, while drafts thicker than approximately 1.3 m are increasingly underestimated by all satellite products investigated for this study. The tendency of the satellite SIT products to better agree with modal sea ice draft and underestimate thicker ice needs to be considered for all past and future investigations into SIT changes in this important region. The performance of the CCI-2 SIT CDR is considered stable over time; however, observed trends in gridded CCI-2 SIT are strongly influenced by the uncertainties of ENVISAT and CS2 and the comparably short investigation period.

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