scholarly journals A statistical study of magnetic dipolarization for sawtooth events and isolated substorms at geosynchronous orbit with GOES data

2006 ◽  
Vol 24 (12) ◽  
pp. 3481-3490 ◽  
Author(s):  
X. Cai ◽  
M. G. Henderson ◽  
C. R. Clauer
Keyword(s):  
Statistical Analysis ◽  
Local Time ◽  
Tilt Angle ◽  
Equatorial Plane ◽  
Time Distribution ◽  
Statistical Study ◽  
Geosynchronous Orbit ◽  
Time Sector ◽  
Local Time Sector ◽  
Local Noon

Abstract. We investigate whether the dipolarization process during sawtooth events is global or not through an examination of the local time distribution of the magnetic tilt angle (i.e. the angle between the B vector and the equatorial plane in dipole VDH coordinates) at geostationary orbit. From the statistical analysis of 207 individual teeth and 212 isolated substorms, we find that individual teeth follow a dipolarization pattern similar to that observed for isolated substorms. The dipolarization for individual teeth initiates in the sector between 22:00 magnetic local time (MLT) and 00:00 MLT. Then the dipolarization expands both eastward and westward. However, relative to isolated substorms, we find that the nightside magnetosphere is much more stretched prior to the onset, and the change of the tilt angle during the dipolarization process is much larger during individual teeth. The magnetic dipolarization is seen over a wider local time sector during individual teeth than during isolated substorms. However, the magnetic dipolarization is rarely observed near local noon during individual teeth. This suggests that the magnetic dipolarization process during individual teeth is still confined primarily to the nightside.

scholarly journals Statistical analysis of plasmaspheric plumes with Cluster/WHISPER observations

2008 ◽  
Vol 26 (8) ◽  
pp. 2403-2417 ◽  
Author(s):  
F. Darrouzet ◽  
J. De Keyser ◽  
P. M. E. Décréau ◽  
F. El Lemdani-Mazouz ◽  
X. Vallières
Keyword(s):  
Statistical Analysis ◽  
Local Time ◽  
Plasma Frequency ◽  
Density Variation ◽  
Density Profiles ◽  
Before And After ◽  
Limited Frequency ◽  
Electron Density Profiles ◽  
Time Sector ◽  
Local Time Sector

Abstract. Plasmaspheric plumes have been routinely observed by the four Cluster spacecraft. This paper presents a statistical analysis of plumes observed during five years (from 1 February 2001 to 1 February 2006) based on four-point measurements of the plasmasphere (outside 4 Earth radii) as it is sampled by the spacecraft in a narrow local time sector before and after perigee. Plasmaspheric plumes can be identified from electron density profiles derived from the electron plasma frequency determined by the WHISPER wave sounder onboard Cluster. As the WHISPER instrument has a limited frequency range (2–80 kHz) only plumes with densities below 80 cm−3 can be identified in this way. Their occurrence is studied as a function of several geomagnetic indices (Kp, am and Dst). Their transverse equatorial size, magnetic local time distribution, L position and density variation are discussed. Plasmaspheric plumes are observed mostly for moderate Kp and never for small Dst. They are found mainly in the afternoon and pre-midnight MLT sectors. Comparisons are also made between the density profiles of the plumes as they are crossed on the in- and outbound legs of the orbit, before and after perigee crossing, respectively.

scholarly journals Cluster and Double Star observations of dipolarization

2005 ◽  
Vol 23 (8) ◽  
pp. 2915-2920 ◽  
Author(s):  
R. Nakamura ◽  
W. Baumjohann ◽  
T. L. Zhang ◽  
C. M. Carr ◽  
A. Balogh ◽  
...  
Keyword(s):  
Local Time ◽  
Double Star ◽  
Propagation Direction ◽  
Dissipation Process ◽  
Analysis Techniques ◽  
Point Analysis ◽  
Time Sector ◽  
Local Time Sector ◽  
The Imf

Abstract. We studied two types of dipolarization events with different IMF conditions when Cluster and Double Star (TC-1) were located in the same local time sector: 7 August 2004, 18:00-24:00 UT, during a disturbed southward/northward IMF interval, and 14 August 2004, 21:00-24:00 UT, when the IMF was stably northward. Cluster observed dipolarization as well as fast flows during both intervals, but this was not the case for TC-1. For both events the satellites crossed near the conjugate location of the MIRACLE stations. By using multi-point analysis techniques, the direction/speed of the propagation is determined using Cluster and is then compared with the disturbances at TC-1 to discuss its spatial/temporal scale. The propagation direction of the BZ disturbance at Cluster was mainly dawnward with a tailward component for 7 August and with a significant Earthward component for 14 August associated with fast flows. We suggest that the role of the midtail fast flows can be quite different in the dissipation process depending on the condition of the IMF and resultant configuration of the tail.

The Nightside Auroral Oval

1996 ◽  
Author(s):  
Charles F. Kennel
Keyword(s):  
Local Time ◽  
First Generation ◽  
Basic Structure ◽  
Auroral Oval ◽  
Optical Wavelength ◽  
Field Lines ◽  
Auroral Phenomena ◽  
Auroral Imaging ◽  
Time Sector ◽  
Local Time Sector

The basic structure of the auroral oval was pieced together from relatively local magnetometer measurements and all-sky photographs taken on the ground. The all-sky cameras picked out relatively intense features whose intensities exceeded roughly one kilorayleigh. Their fields of view had a 500-1000 km radius at auroral altitudes, and so extended over 5-10 degrees of latitude and about 90 minutes of local time. Had the aurora been stationary and time-independent, this would have been enough, and it was enough to spot the existence of substorms. It was not enough to solve the substorm problem. As the instruments to study auroral phenomena grew in sophistication and comprehensiveness, so also did our understanding of the concept of the auroral oval. This chapter is dedicated to communicating some of this modern understanding as a prelude to the discussion of substorms in the next chapter. Ground instruments can follow the time development of events within their fields of view but have difficulty separating changes in space and time on scales longer than an hour of universal time or local time, because the observing station rotates with the earth to a local time sector where the aurora may differ. This difficulty can be offset to some extent by airplane flights that remain at a constant local time. However, the real breakthrough came with auroral imaging from space. In the 1970s, optical wavelength imaging from low-altitude polar orbit provided snapshots of the aurora over several thousand kilometer scale portions of the oval on each polar pass of the spacecraft (Shepherd et al., 1973; Anger et al., 1973; Lui and Anger, 1973; Pike and Whalen, 1974; Snyder and Akasofu, 1974). And the spacecraft could detect the precipitating particles responsible for the auroral light emitted from the magnetic footprint of the field lines along its path. The results from the first generation of auroral imaging experiments have been summarized in excellent reviews (Akasofu, 1974, 1976; Hultquist, 1974; Burch, 1979). Ultraviolet imaging allows one to see the dayside aurora.

HIGH-LATITUDE BOUNDARY OF THE OUTER RADIATION ZONE AT 1000 KM

1964 ◽  
Vol 42 (4) ◽  
pp. 616-626 ◽  
Author(s):  
I. B. McDiarmid ◽  
J. R. Burrows
Keyword(s):  
Magnetic Field ◽  
Local Time ◽  
Equatorial Plane ◽  
High Latitude ◽  
Earth’S Magnetic Field ◽  
Particle Detectors ◽  
Earth's Magnetic Field ◽  
Radiation Zone ◽  
Local Noon

Particle detectors on the Alouette satellite have been used to determine the average high-latitude boundary of the outer radiation zone at 1000 km as a function of local time. The boundary for electrons with energies greater than 40 kev is approximately symmetrical with respect to the noon–midnight meridian and occurs at the highest latitude near local noon, shifting between 4° and 5° to its lowest value near local midnight. There is very little difference in the average boundaries of so-called trapped and precipitated electrons. The results are discussed in terms of measurements of electrons with similar energies in the equatorial plane and models of the earth's magnetic field.

scholarly journals Magnetopause surface oscillation frequencies at different solar wind conditions

2009 ◽  
Vol 27 (12) ◽  
pp. 4521-4532 ◽  
Author(s):  
F. Plaschke ◽  
K.-H. Glassmeier ◽  
D. G. Sibeck ◽  
H. U. Auster ◽  
O. D. Constantinescu ◽  
...  
Keyword(s):  
Solar Wind ◽  
Local Time ◽  
Cone Angle ◽  
Low Frequency ◽  
Flow Speed ◽  
Statistical Analyses ◽  
Surface Modes ◽  
Oscillation Frequencies ◽  
Time Sector ◽  
Local Time Sector

Abstract. Statistical analyses of the magnetopause (MP) motion observed by THEMIS suggested that the MP oscillates preferably at some prominent (sometimes called "magic") frequencies, which were found to stand out also in ground-based and ionospheric measurements of geomagnetic ultra-low frequency pulsations. In this paper we present an extension to these statistical analyses of the observed MP oscillations examining their dependence on the prevalent interplanetary magnetic field (IMF), solar wind (SW) flow speed and cone angle conditions as well as their local time of occurrence. Our results show enhanced oscillation activity at these frequencies in the noon local time sector during periods of northward IMF, slow or moderate SW speed and low SW cone angle. This combination of conditions supports an interpretation in terms of standing Alfvénic Kruskal-Schwarzschild surface modes on the MP.

scholarly journals Sabermetría y nuevas tendencias en el análisis estadístico del juego de béisbol (Sabermetrics and new trends in statistical analysis of baseball)

Retos ◽  
2015 ◽  
pp. 122-127
Author(s):  
César Soto Valero ◽  
Mabel González Castellanos
Keyword(s):  
Statistical Analysis ◽  
Empirical Analysis ◽  
Statistical Study ◽  
Team Sports ◽  
Baseball Game ◽  
Objective Evidence ◽  
Individual Value

La sabermetría es reconocida actualmente como una tendencia novedosa en el estudio del juego de béisbol. Con mucho auge y utilización en el análisis empírico, esta se basa en el estudio estadístico riguroso de la evidencia objetiva obtenida durante el juego. Teniendo en cuenta tanto sus aportes teóricos como prácticos, la sabermetría se fundamenta en una constante búsqueda por comprender cómo jugar mejor y más eficientemente al béisbol, lo cual se expresa y soporta mediante un tipo de análisis de actuación único entre todos los deportes colectivos. El presente trabajo aborda los aspectos esenciales de la sabermetría, fundamentando la necesidad de su surgimiento y utilización, como una forma de perfeccionar la manera en que tradicionalmente se ha llevado a cabo el análisis estadístico en el béisbol. Además, se brinda un resumen de los estadísticos sabermétricos más utilizados, tanto de bateo y picheo como otros de valor individual para el equipo, con el propósito de hacer más clara su comprensión, estudio y posterior utilización entre los seguidores de este deporte.Abstract. Sabermetrics is recognized as a new trend in the study of baseball game. This is based on the rigorous statistical study of the objective evidence obtained and has been used extensively in its empirical analysis. Considering both theoretical and practical contributions, sabermetrics involves the constant quest of understanding how to play baseball better and more efficiently, which is expressed and supported by an exceptional type of analysis performance unique among all team sports. This paper describes the essential aspects of sabermetrics, pointing in the necessity of its emergence and use, as a way to improve the traditional statistical analysis of baseball. Moreover, a summary of the sabermetrics statistics most widely used is given. Both batting and pitching, as well as others of individual value for the team are stated throughout this work in order to make sabermetrics understanding, study and further use clearer among followers of this sport.

scholarly journals Relation between the asymmetric ring current effect and the anti-sunward auroral currents, as deduced from CHAMP observations

2020 ◽  
Vol 38 (3) ◽  
pp. 749-764 ◽  
Author(s):  
Hermann Lühr ◽  
Yun-Liang Zhou
Keyword(s):  
Ring Current ◽  
Current System ◽  
Main Phase ◽  
Current Effect ◽  
Morning Sector ◽  
Wind Input ◽  
Ring Current Effect ◽  
Time Sector ◽  
Dawn Sector ◽  
Local Time Sector

Abstract. During magnetically active periods the storm-time disturbance signal on the ground commonly develops an azimuthal asymmetry. Negative deflections of the magnetic horizontal (H) component are enhanced in the 18:00 local time sector and smallest in the morning sector. This is commonly attributed to the asymmetric ring current effect. In this study we investigate the average characteristics of anti-sunward net currents that are not closing in the ionosphere. Their intensity is growing proportionally with the amount of solar wind input to the magnetosphere. There is almost twice as much current flowing across the polar region in the winter hemisphere as on the summer side. This seasonal dependence is more pronounced in the dusk sector than in the dawn sector. Event studies reveal that anti-sunward currents are closely related to the main phase of a magnetic storm. Since the asymmetry of storm-time disturbances also builds up during the main phase, we suggest a relation between these two phenomena. From a statistical study of ground-based disturbance levels during magnetically active periods, we obtain support for our suggestion. We propose a new 3D current system responsible for the zonally asymmetric storm-time disturbance signal that does not involve the ring current. The high-latitude anti-sunward currents are connected at their noon and midnight ends to field-aligned currents that lead the currents to the outer magnetosphere. The auroral net current branch on the morning side is closed along the dawn flank near the magnetopause, and the evening side currents flow along the dusk flank magnetosphere. Regardless through which loop the current is flowing, near-Earth storm-time disturbance levels will in both cases be reduced in the morning sector and enhanced in the evening.

Correlation of SaO2 in patients of COVID-19 with and without COPD

2021 ◽  
Vol 15 (11) ◽  
pp. 2945-2947
Author(s):  
Ali Faheem ◽  
Misbah-ul- Qamar ◽  
Saveela Sadaqat ◽  
Muhammad Akram ◽  
Rizwan Masud ◽  
...  
Keyword(s):  
Experimental Study ◽  
Statistical Analysis ◽  
Gold Standard ◽  
Time Distribution ◽  
Blood Samples ◽  
Paired Sample ◽  
The World ◽  
Pulmonary Cells ◽  
Study Methodology ◽  
The Difference

Background: The Covid-19 pandemic has wreaked havoc throughout the world, with 150 million cases to date and over 3 million lives claimed worldwide. Aim: To explored the difference in levels of SaO2 of COVID-19 positive patients with and without COPD. Study design: Experimental Study. Methodology: From May2020 to 2021 patients admitted at Aziz Bhatti Shaheed hospital were included in this studies. COVID-19 was confirmed by RT-PCR.COPD was confirmed by using GOLD standard of diagnostic criteria. SaO2 was measured by using pulse oximeter and confirmed by blood samples measurement of SaO2. Statistical analysis: SPSS version 22 was used for data analysis. Paired sample t test was performed to evaluate the hypoxia levels between three pairs among the time distribution of 1st, 3rd, and 6th, day. Results: Levels of SaO2 were statistically significant between COVID-19 positive patients and COVID-19 positive patients with COPD. We calculated the levels of SaO2 at day1, 3rd, and 6th day and results were significant to show that COPD might be having some protective effect against hypoxia and that might be due to use of medications or adaptation of pulmonary cells. Conclusion: It was concluded that levels of SaO2 was significantly reduced in COVID-19 patients without COPD in comparison to patients without COPD. Keywords: COVID-19, COPD and SaO2.

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