Superposed Epoch Analyses of electron-driven and proton-driven magnetic dips

2021 ◽  
Author(s):  
Hui Zhu ◽  
Lunjin Chen
Keyword(s):  
Statistical Characteristics ◽  
Relativistic Electrons ◽  
Magnetic Fluctuations ◽  
Inner Magnetosphere ◽  
Superposed Epoch Analysis ◽  
Van Allen Probes ◽  
Epoch Analysis ◽  
The Relationship ◽  
Statistical Results

<p>In this study, we use the Van Allen Probes data statistically to investigate the features of magnetic dips by the means of superposed epoch analysis. Based on the different max values of electron and proton plasma betas, we categorize the dips into two types: electron-driven dips and proton-driven dips. Superposed epoch analysis on two types of magnetic dips suggests the correlation between the magnetic fluctuations and plasma betas. Moreover, the occurrence of the butterfly distributions of relativistic electrons driven by the magnetic dips is confirmed by the statistical results. Our results reveal the statistical characteristics of magnetic dips and build up the relationship among the magnetic fluctuations and several parameters, indicating the potentially important role of magnetic dips in the dynamics of the inner magnetosphere.</p>

scholarly journals Statistical Analysis of the Relationship between AETA Electromagnetic Anomalies and Local Earthquakes

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 411
Author(s):  
Qinmeng Guo ◽  
Shanshan Yong ◽  
Xin’an Wang
Keyword(s):  
Earthquake Forecasting ◽  
Electromagnetic Signal ◽  
Superposed Epoch Analysis ◽  
Local Earthquakes ◽  
Skill Scores ◽  
Local Earthquake ◽  
Epoch Analysis ◽  
Few Data ◽  
The Relationship ◽  
Statistical Results

To verify the relationship between AETA (Acoustic and Electromagnetics to Artificial Intelligence (AI)) electromagnetic anomalies and local earthquakes, we have performed statistical studies on the electromagnetic data observed at AETA station. To ensure the accuracy of statistical results, 20 AETA stations with few data missing and abundant local earthquake events were selected as research objects. A modified PCA method was used to obtain the sequence representing the signal anomaly. Statistical results of superposed epoch analysis have indicated that 80% of AETA stations have significant relationship between electromagnetic anomalies and local earthquakes. These anomalies are more likely to appear before the earthquakes rather than after them. Further, we used Molchan’s error diagram to evaluate the electromagnetic signal anomalies at stations with significant relationships. All area skill scores are greater than 0. The above results have indicated that AETA electromagnetic anomalies contain precursory information and have the potential to improve local earthquake forecasting.

Association of chorus waves and source/seed electrons with the enhancement of relativistic electrons in the outer Van Allen belt

2020 ◽  
Author(s):  
Afroditi Nasi ◽  
Ioannis A. Daglis ◽  
Christos Katsavrias ◽  
Wen Li
Keyword(s):  
Relativistic Electron ◽  
Radiation Belt ◽  
Geomagnetic Disturbance ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Inner Magnetosphere ◽  
Superposed Epoch Analysis ◽  
Chorus Waves ◽  
Substorm Activity ◽  
Epoch Analysis

<p>Local acceleration driven by whistler-mode chorus waves is fundamentally important for the acceleration of seed electrons in the outer radiation belt to relativistic energies. Τhis mechanism strongly depends on substorm activity and on the source electron population injected by the substorms into the inner magnetosphere. In our work we use Van Allen Probes data to investigate the features of source electrons, seed electrons and chorus waves for events of enhancement versus events of depletion of relativistic electrons in the outer Van Allen belt. To that end we calculate the electron phase space density (PSD) for five values of the first adiabatic invariant corresponding to source and seed electrons, and we perform a superposed epoch analysis of 28 geomagnetic disturbance events, out of which, 20 result in enhancement and 8 in depletion of relativistic electron PSD. Our results indicate that events resulting in significant enhancement of relativistic electron PSD in the outer radiation belt are characterized by statistically stronger and more prolonged storm and substorm activity, leading to more efficient injections of source but mostly seed electrons to the inner magnetosphere, and also to more pronounced and long-lasting chorus and Pc5 wave activity. The effect of these parameters in the acceleration of electrons seems to be determined by the abundance of seed electrons at the region of L*=4-5.</p>

Statistical Distribution of Bifurcation of Earth's Inner Energetic Electron Belt at tens of keV

2021 ◽  
Author(s):  
Man Hua ◽  
Binbin Ni ◽  
Wen Li ◽  
Qianli Ma ◽  
Xudong Gu ◽  
...  
Keyword(s):  
Electron Energy ◽  
Energetic Electron ◽  
Low Frequency ◽  
Inner Magnetosphere ◽  
Near Earth Space ◽  
Naturally Occurring ◽  
Van Allen Probes ◽  
Radial Structure ◽  
Hemisphere Winter

<p>The Earth’s inner energetic electron belt typically exhibits one-peak radial structure with high flux intensities at radial distances < ~2.5 Earth radii. Recent studies suggested that human-made very-low-frequency (VLF) transmitters leaked into the inner magnetosphere can efficiently scatter energetic electrons, bifurcating the inner electron belt. In this study, we use 6-year electron flux data from Van Allen Probes to comprehensively analyze the statistical distributions of the bifurcated inner electron belt and their dependence on electron energy, season, and geomagnetic activity, which is crucial to understand when and where VLF transmitters can efficiently scatter electrons in addition to other naturally occurring waves. We reveal that bifurcation can be frequently observed for tens of keV electrons under relatively quiet geomagnetic conditions, typically after significant flux enhancements that elevate fluxes at L = 2.0 – ~2.5 providing the prerequisite for the bifurcation. The bifurcation typically lasts for a few days until interrupted by substorm injections or inward radial diffusion. The L-shells of bifurcation dip decrease with increasing electron energy, and the occurrence of bifurcation is higher during northern hemisphere winter than summer, supporting the important role of VLF transmitter waves in energetic electron loss in near-Earth space.</p>

scholarly journals Semiannual Variation in radiation belts particle fluxes: Van Allen probes observations

2018 ◽  
Author(s):  
Facundo L. Poblet ◽  
Francisco Azpilicueta
Keyword(s):  
Energy Range ◽  
Ring Current ◽  
Electron Flux ◽  
Current System ◽  
Energy Levels ◽  
Superposed Epoch Analysis ◽  
Van Allen Probes ◽  
Semiannual Variation ◽  
Weather Parameters ◽  
Epoch Analysis

Abstract. The Semiannual Variation (SAV) is an annual pattern characterized by maxima around the equinoxes and minima near solstices observed in many space weather parameters. Several authors have studied this variation in the electron fluxes of the magnetosphere, focusing only in a few energy levels. In this investigation, Van Allen probes data are processed to extend SAV studies in electron fluxes of a wider energy range. A superposed epoch analysis was applied to data of the REPT and MagEIS instruments obtaining a clear semiannual pattern in the superposed year for L-shell values between 2.5 and 6.5. The Day Of Year (DOY) at which the highest electron flux values are detected near the September equinox coincide with the Russel & McPherron prediction. However, the DOY of the maximum expected close the March equinox occurs with a one month lag from the prediction of the accepted models. In addition, integrating over L-shell the annual DOY-L data with the semiannual pattern resulted in temporal curves that enabled to determine the energy range for which the SAV can be detected: from MeV to tens MeV energy values. Finally, an additional analysis of the fluxes of the Ring Current principal components (H+ and O+ ions) was performed, obtaining no evidence of a SAV on them. This result could indicate that the widely recognized semiannual pattern in the geomagnetic activity is related to a different current system.

scholarly journals Variations in Energetic Particle Fluxes around Significant Geomagnetic Storms Observed by the Low-Altitude DEMETER Spacecraft

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 260
Author(s):  
Stefan Gohl ◽  
František Němec ◽  
Michel Parrot
Keyword(s):  
Energetic Particle ◽  
Geomagnetic Storms ◽  
Time Window ◽  
Relativistic Electrons ◽  
Superposed Epoch Analysis ◽  
High Energies ◽  
Low Altitude ◽  
Particle Fluxes ◽  
Solar Wind Parameters ◽  
Epoch Analysis

A superposed epoch analysis is conducted for five geomagnetic storms in the years 2005 and 2006 with the aim to understand energetic particle flux variations as a function of L-shell, energy and time from the Dst minimum. Data measured by the low-altitude DEMETER spacecraft were used for this purpose. The storms were identified by a Dst index below −100 nT, as well as their being isolated events in a seven-day time window. It is shown that they can be categorized into two types. The first type shows significant variations in the energetic particle fluxes around the Dst minimum and increased fluxes at high energies (>1.5 MeV), while the second type only shows increased fluxes around the Dst minimum without the increased fluxes at high energies. The first type of storm is related to more drastic but shorter-lasting changes in the solar wind parameters than the second type. One storm does not fit either category, exhibiting features from both storm types. Additionally, we investigate whether the impenetrable barrier for ultra-relativistic electrons also holds in extreme geomagnetic conditions. For the highest analyzed energies, the obtained barrier L-shells do not go below 2.6, consistent with previous findings.

scholarly journals Evaluating the relationship between strong geomagnetic storms and electric grid failures in Poland using the geoelectric field as a GIC proxy

2021 ◽  
Author(s):  
Agnieszka Gil-Świderska ◽  
Monika Berendt-Marchel ◽  
Renata Modzelewska ◽  
Szczepan Moskwa ◽  
Agnieszka Siluszyk ◽  
...  
Keyword(s):  
Geomagnetic Storms ◽  
Earth Model ◽  
Geoelectric Field ◽  
Self Organizing Maps ◽  
Superposed Epoch Analysis ◽  
Electrical Grid ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Epoch Analysis ◽  
The Relationship

We study intense geomagnetic storms (Dst < -100nT) during the first half of the solar cycle 24. This type of storm appeared only a few times, mostly associated with southwardly directed heliospheric magnetic field Bz. Using various methods such as self-organizing maps, statistical and superposed epoch analysis, we show that during and right after intense geomagnetic storms, there is growth in the number of transmission line failures. We also examine the temporal changes in the number of failures during 2010-2014 and find that the growing linear tendency of electrical grid failure occurrence is possibly connected with solar activity. We compare these results with the geoelectric field calculated for the region of Poland using a 1-D layered conductivity Earth model.

Increase in seismic activity near the footprints of new radiation belts forming after geomagnetic storms

2021 ◽  
Author(s):  
Nursultan Toyshiev ◽  
Galina Khachikyan ◽  
Beibit Zhumabayev
Keyword(s):  
Geomagnetic Storm ◽  
Seismic Activity ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Radiation Belts ◽  
Tien Shan ◽  
Relativistic Electrons ◽  
Inner Magnetosphere ◽  
Van Allen Probes ◽  
Northern Tien Shan

&lt;p&gt;Recently, attention was drawn [1] that after geomagnetic storms that cause formation of new radiation belts in slot region or in the inner magnetosphere, after about 2 months, there is an increase in seismic activity near the footprints of geomagnetic lines of new radiation belts. More detailed studies showed [2] that on May 30, 1991, an earthquake M=7.0 occurred in Alaska with (54.57N, 161.61E) near the footprint of geomagnetic line L = 2.69 belonging to new radiation belt, which was observed by the CRRES satellite [3] around geomagnetic lines 2&lt;L&lt;3 after geomagnetic storm on March 24, 1991. After geomagnetic storm on September 3, 2012, the Van Allen Probes satellites observed new radiation belt around 3.0&amp;#8804;L&amp;#8804;3.5 [4], and about 2 months later, on October 28, 2012, earthquake M=7.8 occurred off the coast of Canada (52.79N, 132.1W) near the footprint of geomagnetic line L=3.32 belonging to the new radiation belt. Also, Van Allen Probes observed new radiation belt around L=1.5-1.8 after geomagnetic storm on June 23, 2015 [5], and ~2 months later, in September 2015, seismic activity noticeably increased near the footprint of these geomagnetic lines. We consider variations in seismic activity in connection with the strongest geomagnetic storms in 2003 with Dst~- 400 nT (Halloween Storm) and the formation of a belt of relativistic electrons in the inner magnetosphere around L~1.5 existed until the end of 2005 as observed SAMPEX [6]. Analysis of data from the USGS global seismological catalog showed that near the footprint of geomagnetic lines L=1.4-1.6 the number of earthquakes with M&amp;#8805;4.5 increased in 2003-2004 by ~70% compared with their number in two previous years. On the Northern Tien Shan, on December 1, 2003 a strong for the region earthquake M=6.0 occurred on the border of Kazakhstan and China (42.9N, 80.5E) near the footprint of L = 1.63, adjacent to the new radiation belt.&lt;/p&gt;

scholarly journals The Two-step Forbush Decrease: A Tale of Two Substructures Modulating Galactic Cosmic Rays within Coronal Mass Ejections

2021 ◽  
Vol 922 (2) ◽  
pp. 216
Author(s):  
Miho Janvier ◽  
Pascal Démoulin ◽  
Jingnan Guo ◽  
Sergio Dasso ◽  
Florian Regnault ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
Coronal Mass Ejections ◽  
Forbush Decrease ◽  
Recovery Phase ◽  
Galactic Cosmic Rays ◽  
Space Environment ◽  
Interplanetary Coronal Mass Ejections ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis

Abstract Interplanetary coronal mass ejections (ICMEs) are known to modify the structure of the solar wind as well as interact with the space environment of planetary systems. Their large magnetic structures have been shown to interact with galactic cosmic rays (GCRs), leading to the Forbush decrease (FD) phenomenon. We revisit in the present article the 17 yr of Advanced Composition Explorer spacecraft ICME detection along with two neutron monitors (McMurdo and Oulu) with a superposed epoch analysis to further analyze the role of the magnetic ejecta in driving FDs. We investigate in the following the role of the sheath and the magnetic ejecta in driving FDs, and we further show that for ICMEs without a sheath, a magnetic ejecta only is able to drive significant FDs of comparable intensities. Furthermore, a comparison of samples with and without a sheath with similar speed profiles enable us to show that the magnetic field intensity, rather than its fluctuations, is the main driver for the FD. Finally, the recovery phase of the FD for isolated magnetic ejecta shows an anisotropy in the level of the GCRs. We relate this finding at 1 au to the gradient of the GCR flux found at different heliospheric distances from several interplanetary missions.

scholarly journals Mapping Statistical Characteristics of Frosts in Iran

2014 ◽  
Vol XL-2/W3 ◽  
pp. 175-180 ◽  
Author(s):  
P. Mahmoudi
Keyword(s):  
Dominant Role ◽  
Growing Season ◽  
Spatial Arrangement ◽  
Statistical Characteristics ◽  
Frequency Of Occurrence ◽  
Climate Factors ◽  
Kriging Interpolation Method ◽  
Frost Period ◽  
The Relationship

To model and map the statistical characteristics of frost in Iran, the data related to the minimum daily temperature for a 15-year period (1990&ndash;2005) was obtained from Iran Meteorological Organization. Then using multivariate regression models, the relationship among five statistical characteristics, i.e. the mean Julian day of the first frost, mean Julian day of the last frost, mean number of frost days per year, mean length of the frost period and mean length of growing season were modeled by three geo – climate factors: elevation, longitude and latitude. The precision of each model was explored using four hypotheses: linearity of the relationship between independent variables and the dependent variable, normality of errors, constancy of error variance and lake of correlation of errors were tested, and their precisions were confirmed. At the second stage, contour lines resulting from STRM were converted to the point features class. Altogether, 661 474 points were gathered from all over Iran. Then, the studied five frost characteristics were generalized to 661 474 points; then, the regionalization maps of statistical characteristics of frost were obtained for Iran using Kriging interpolation method. <br><br> The results showed that the temperature of highland areas above 4200 m above sea level always was at least zero and below zero during the year, and also the coastal strip of southern Iran had no frost. Elevation was the most effective factor in the spatial arrangement for the frequency of occurrence of Julian day of the first frost. The most effective factors in spatial arrangement for the frequency of occurrence of Julian day of the last frost, length of frost period and length of growing season were elevation and latitude. Finally, spatial arrangement for the frequency of occurrence of the frost days was also a function of three factors of elevation, longitude and latitude. The dominant role of elevation in spatial arrangement for the occurrence of the first frost day in Iran showed that the occurrence of the first frost day in Iran could be of the type of radiation frosts and the dominant role of elevation and latitude demonstrated that late-winter frosts can be mostly of the type of advection frosts. Therefore, arrangement of statistical features of frost in Iran is both a function of geo – climate factors and the synoptic systems which have entered the country.

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