scholarly journals Statistical study of the proton isotropy boundary

2005 ◽  
Vol 23 (4) ◽  
pp. 1311-1316 ◽  
Author(s):  
E. A. Lvova ◽  
V. A. Sergeev ◽  
G. R. Bagautdinova
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Empirical Relationship ◽  
Large Data ◽  
Magnetic Activity ◽  
Least Square ◽  
Quiet Time ◽  
Data Set ◽  
Ae Index ◽  
Solar Wind Parameters

Abstract. Based on a large data set of polar NOAA-type satellite observations we studied the latitude-MLT shape of the 80keV proton isotropy boundary (IB) as a function of the solar wind parameters and magnetic activity. Using "snapshots" of isotropy boundaries near-simultaneously crossed at four points we found that its equatorward expansion, as well as its dawn-dusk shift, depends mostly on the AE-index and on the corrected Dst*, whereas the amplitude of the IB daily variation is mostly controlled by the solar wind dynamic pressure. Applying a nonlinear, multi-parametric, least-square regression procedure, the empirical relationship describing the IB latitude as a function of MLT and AE, Pd, Dst* parameters was obtained. Comparing it with the predictions from the Tsyganenko-2001 model we found a good agreement during the quiet time but some important differences during the disturbed periods. Interpretation of these results in terms of the properties of the magnetospheric configuration is briefly discussed.

scholarly journals The geomagnetic cutoff rigidities at high latitudes for different solar wind and geomagnetic conditions

2016 ◽  
Vol 34 (1) ◽  
pp. 45-53 ◽  
Author(s):  
W. Chu ◽  
G. Qin
Keyword(s):  
Solar Wind ◽  
Cosmic Rays ◽  
Strong Correlation ◽  
Geomagnetic Storms ◽  
Dynamic Pressure ◽  
Threshold Value ◽  
High Latitudes ◽  
Dst Index ◽  
Ae Index ◽  
Geomagnetic Cutoff

Abstract. Studying the access of the cosmic rays (CRs) into the magnetosphere is important to understand the coupling between the magnetosphere and the solar wind. In this paper we numerically studied CRs' magnetospheric access with vertical geomagnetic cutoff rigidities using the method proposed by Smart and Shea (1999). By the study of CRs' vertical geomagnetic cutoff rigidities at high latitudes we obtain the CRs' window (CRW) whose boundary is determined when the vertical geomagnetic cutoff rigidities drop to a value lower than a threshold value. Furthermore, we studied the area of CRWs and found out they are sensitive to different parameters, such as the z component of interplanetary magnetic field (IMF), the solar wind dynamic pressure, AE index, and Dst index. It was found that both the AE index and Dst index have a strong correlation with the area of CRWs during strong geomagnetic storms. However, during the medium storms, only AE index has a strong correlation with the area of CRWs, while Dst index has a much weaker correlation with the area of CRWs. This result on the CRW can be used for forecasting the variation of the cosmic rays during the geomagnetic storms.

scholarly journals The Horwitz Function Revisited

1997 ◽  
Vol 80 (3) ◽  
pp. 676-680 ◽  
Author(s):  
Michael Thompson ◽  
Philip J Lowthian
Keyword(s):  
Performance Studies ◽  
Analytical Method ◽  
Empirical Relationship ◽  
Large Data ◽  
Statistical Test ◽  
Method Performance ◽  
Data Set ◽  
Large Data Set ◽  
Low Concentrations ◽  
Special Circumstances

Abstract A statistical test was made of the Horwitz function, an empirical relationship between the reproducibility precision of an analytical method and the concentration of the analyte regardless of the nature of the analyte, matrix, and the method. The large data set (7502 observations) was compiled by Horwitz from collaborative trials (method performance studies) spanning the period 1915 to 1995. The data followed the Horwitz function well down to concentrations of about 10-8 (10 ppb), but they followed a more stringent specification at lower concentrations. This discrepancy may be due to special circumstances prevailing in collaborative trials at very low concentrations. Deviations of individual observations from the function were in large part accounted for by random variations. No consequential improvement in precision with time was found.

On the Fatigue-Life Distributions of Engineering Materials

1997 ◽  
Vol 04 (01) ◽  
pp. 93-115 ◽  
Author(s):  
M. A. Khaleel ◽  
S. C. Saunders
Keyword(s):  
Fatigue Life ◽  
Prestressed Concrete ◽  
Large Data ◽  
Least Square ◽  
Linear Functions ◽  
Maximum Likelihood Estimates ◽  
Stress Regime ◽  
Data Set ◽  
Realistic Condition ◽  
Censored Samples

The applicability of the fatigue-life distribution of Birnbaum–Saunders for modeling the components of partially prestressed concrete girder bridges is argued by the agreement of the calculated distribution with a large data set comprised of many small censored samples, each put into standardized form, of the fatigue-lives of bridge components. Also, the Weibull and lognormal distributions are compared by the appropriateness of the assumptions in their derivation to the cumulative damage to bridge components. The maximum likelihood estimates of the parameters of the fatigue lives of the prestressing steel, mild steel, and concrete are found from randomly censored samples, for several censored data-sets under various stress regimes. The parameters are postulated to be log-linear functions of the maximum stress and stress regimes. Weighted least-square regression is applied to determine the unknown coefficients. To compensate for differences in the precision of the estimates obtained under each stress regime the variances are calculated by the bootstrap statistical method. This procedure gives an estimated distribution of the fatigue life with its parameters functions of the stress regime which is applicable under virtually any realistic condition.

scholarly journals Azimuthally asymmetric ring current as a function of <i>D<sub>st</sub></i> and solar wind conditions

2004 ◽  
Vol 22 (8) ◽  
pp. 2989-2996 ◽  
Author(s):  
Y. P. Maltsev ◽  
A. A. Ostapenko
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Spatial Distribution ◽  
Interplanetary Magnetic Field ◽  
Ring Current ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Magnetic Data ◽  
Under Five ◽  
Solar Wind Parameters

Abstract. Based on magnetic data, spatial distribution of the westward ring current flowing at |z|<3 RE has been found under five levels of Dst, five levels of the interplanetary magnetic field (IMF) z component, and five levels of the solar wind dynamic pressure Psw. The maximum of the current is located near midnight at distances 5 to 7 RE. The magnitude of the nightside and dayside parts of the westward current at distances from 4 to 9 RE can be approximated as Inight=1.75-0.041 Dst, Inoon=0.22-0.013 Dst, where the current is in MA. The relation of the nightside current to the solar wind parameters can be expressed as Inight=1.45-0.20 Bs IMF + 0.32 Psw, where BsIMF is the IMF southward component. The dayside ring current poorly correlates with the solar wind parameters.

scholarly journals Study of the Very Slow Speed Solar Wind Streams with Cosmic Ray Intensity and Ae Index for Solar Cycle 24 (2008-2013)

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Meena Pokharia ◽  
Lalan Prasad
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Cosmic Ray ◽  
Magnetic Activity ◽  
Slow Speed ◽  
Cosmic Ray Intensity ◽  
Ae Index ◽  
Solar Cycle 24 ◽  
Speed Solar Wind ◽  
Cycle 24

The aim of this paper is to investigate the association of the variation of very slow speed solar wind streams (VSSSWS) with the cosmic ray intensity (CRI) and Ae index for solar cycle 24 (2008-2013). A Chree analysis by the superposed epoch method has been done in the study. The results of the present analysis showed that VSSSWS are not able to produce decreases in CRI. The prime source of the variation in magnetic activity near aurora zone is the wind interaction with the magnetosphere, but the speed of VSSSWS is low enough to produce any significant impact on aurora zone magnetic activity.

scholarly journals Study of the Very Slow Speed Solar Wind Streams with Cosmic Ray Intensity and Ae Index for Solar Cycle 24 (2008-2013)

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Meena Pokharia ◽  
Lalan Prasad
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Cosmic Ray ◽  
Magnetic Activity ◽  
Slow Speed ◽  
Cosmic Ray Intensity ◽  
Ae Index ◽  
Solar Cycle 24 ◽  
Speed Solar Wind ◽  
Cycle 24

The aim of this paper is to investigate the association of the variation of very slow speed solar wind streams (VSSSWS) with the cosmic ray intensity (CRI) and Ae index for solar cycle 24 (2008-2013). A Chree analysis by the superposed epoch method has been done in the study. The results of the present analysis showed that VSSSWS are not able to produce decreases in CRI. The prime source of the variation in magnetic activity near aurora zone is the wind interaction with the magnetosphere, but the speed of VSSSWS is low enough to produce any significant impact on aurora zone magnetic activity

scholarly journals Earth’s geomagnetic response to solar wind changes associated with solar events at low latitude regions at the TRE MAGDAS Station

2021 ◽  
Vol 880 (1) ◽  
pp. 012009
Author(s):  
R Umar ◽  
S N A Syed Zafar ◽  
N H Sabri ◽  
M H Jusoh ◽  
A Yoshikawa ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storms ◽  
Interplanetary Space ◽  
Coronal Holes ◽  
Magnetic Activity ◽  
Study Results ◽  
Geomagnetic Fields ◽  
Solar Events ◽  
Solar Wind Parameters ◽  
Mass Ejection

Abstract The Sun’s magnetic activity influences disturbances that perturb interplanetary space by producing large fluxes of energetic protons, triggering geomagnetic storms and affecting the ground geomagnetic field. The effect of two solar events, namely Coronal Mass Ejection (CME) and Coronal Holes, on geomagnetic indices (SYM/H), solar wind parameters and ground geomagnetic fields has provided magnetic ground data, which were extracted from the Terengganu (TRE, -4.21° N, 175.91° E) Magnetometer (MAGDAS) station, and investigated in this study. Results show that the physical dynamic mechanism in the Earth’s magnetosphere is triggered by various solar wind parameters associated with CMEs and Coronal hole events during the minimum solar cycle of 24 at low latitudes. It is important to study solar wind-magnetosphere coupling because it has an impact on ground-based technological systems and human activities.

scholarly journals Magnetopause energy and mass transfer: results from a global MHD simulation

2006 ◽  
Vol 24 (12) ◽  
pp. 3467-3480 ◽  
Author(s):  
M. Palmroth ◽  
T. V. Laitinen ◽  
T. I. Pulkkinen
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Solar Wind ◽  
Energy Transfer ◽  
Dynamic Pressure ◽  
Solar Wind Dynamic Pressure ◽  
Closed Field ◽  
Dayside Magnetopause ◽  
Solar Wind Parameters ◽  
The Imf

Abstract. We use the global MHD model GUMICS-4 to investigate the energy and mass transfer through the magnetopause and towards the closed magnetic field as a response to the interplanetary magnetic field (IMF) clock angle θ=arctan (BY/BZ), IMF magnitude, and solar wind dynamic pressure. We find that the mass and energy transfer at the magnetopause are different both in spatial characteristics and in response to changes in the solar wind parameters. The energy transfer follows best the sin2 (θ/2) dependence, although there is more energy transfer after large energy input, and the reconnection line follows the IMF rotation with a delay. There is no clear clock angle dependence in the net mass transfer through the magnetopause, but the mass transfer through the dayside magnetopause and towards the closed field occurs preferably for northward IMF. The energy transfer occurs through areas at the magnetopause that are perpendicular to the subsolar reconnection line. In contrast, the mass transfer occurs consistently along the reconnection line, both through the magnetopause and towards the closed field. Both the energy and mass transfer are enhanced in response to increased solar wind dynamic pressure, while increasing the IMF magnitude does not affect the transfer quantities as much.

scholarly journals Local magnitude scale in Slovenia

2013 ◽  
Vol 34 ◽  
pp. 23-28 ◽  
Author(s):  
J. Bajc ◽  
Ž. Zaplotnik ◽  
M. Živčić ◽  
M. Čarman
Keyword(s):  
Vertical Component ◽  
Large Data ◽  
Least Square Method ◽  
Least Square ◽  
Magnitude Scale ◽  
Local Magnitude ◽  
Data Set ◽  
Seismic Stations ◽  
Short Period ◽  
Environment Agency

Abstract. In the paper a calibration study of the local magnitude scale in Slovenia is presented. The Seismology and Geology Office of the Slovenian Environment Agency routinely reports the magnitudes MLV of the earthquakes recorded by the Slovenian seismic stations. The magnitudes are computed from the maximum vertical component of the ground velocity with the magnitude equation that was derived some thirty years ago by regression analysis of the magnitudes recorded by a Wood-Anderson seismograph in Trieste and a short period seismograph in Ljubljana. In the study the present single magnitude MLV equation is replaced by a general form of the Richter local magnitude MWA equation. The attenuation function and station-component corrections that compensate the local effects near seismic stations are determined from the synthetic Wood-Anderson seismograms of a large data set by iterative least-square method. The data set used consists of approximately 18 000 earthquakes during a period of 14 yr, each digitally recorded on up to 29 stations. The derived magnitude equation is used to make the final comparison between the new MWA magnitudes and the routinely calculated MLV magnitudes. The results show good overall accordance between both magnitude equations. The main advantage of the introduction of station-component corrections is the reduced uncertainty of the local magnitude that is assigned to a certain earthquake.

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