scholarly journals Analysis of the enhanced negative correlation between electron density and electron temperature related to earthquakes

2015 ◽  
Vol 33 (4) ◽  
pp. 471-479 ◽  
Author(s):  
X. H. Shen ◽  
X. Zhang ◽  
J. Liu ◽  
S. F. Zhao ◽  
G. P. Yuan
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Negative Correlation ◽  
Plasma Temperature ◽  
Lower Latitude ◽  
Coupling Mechanism ◽  
Plasma Parameters ◽  
Low Latitudes ◽  
Before And After ◽  
Large Earthquakes

Abstract. Ionospheric perturbations in plasma parameters have been observed before large earthquakes, but the correlation between different parameters has been less studied in previous research. The present study is focused on the relationship between electron density (Ne) and temperature (Te) observed by the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite during local nighttime, in which a positive correlation has been revealed near the equator and a weak correlation at mid- and low latitudes over both hemispheres. Based on this normal background analysis, the negative correlation with the lowest percent in all Ne and Te points is studied before and after large earthquakes at mid- and low latitudes. The multiparameter observations exhibited typical synchronous disturbances before the Chile M8.8 earthquake in 2010 and the Pu'er M6.4 in 2007, and Te varied inversely with Ne over the epicentral areas. Moreover, statistical analysis has been done by selecting the orbits at a distance of 1000 km and ±7 days before and after the global earthquakes. Enhanced negative correlation coefficients lower than −0.5 between Ne and Te are found in 42% of points to be connected with earthquakes. The correlation median values at different seismic levels show a clear decrease with earthquakes larger than 7. Finally, the electric-field-coupling model is discussed; furthermore, a digital simulation has been carried out by SAMI2 (Sami2 is Another Model of the Ionosphere), which illustrates that the external electric field in the ionosphere can strengthen the negative correlation in Ne and Te at a lower latitude relative to the disturbed source due to the effects of the geomagnetic field. Although seismic activity is not the only source to cause the inverse Ne–Te variations, the present results demonstrate one possibly useful tool in seismo-electromagnetic anomaly differentiation, and a comprehensive analysis with multiple parameters helps to further understand the seismo–ionospheric coupling mechanism. \\keywords{Ionosphere (plasma temperature and density)}

DIAGNOSTICS OF LASER INDUCED GRAPHITE PLASMA UNDER VARIOUS PRESSURES OF AIR, HELIUM AND ARGON

2016 ◽  
Vol 78 (3) ◽  
Author(s):  
Zuhaib Haider ◽  
Kashif Chaudhary ◽  
Sufi Roslan ◽  
Jalil Ali ◽  
Yusof Munajat
Keyword(s):  
Electron Density ◽  
Laser Energy ◽  
Ambient Pressure ◽  
Plasma Temperature ◽  
Sample Surface ◽  
Ambient Atmosphere ◽  
Plasma Parameters ◽  
Saha Equation ◽  
Laser Induced Plasma ◽  
Spectroscopic Information

Laser induced plasma provides information about the elemental composition of sample surface and through spectroscopy vital information about plasma dynamics can be obtained. In this paper we present the diagnostics of laser induced plasma at various pressures of Air, Helium and Argon gases. Graphite sample was ablated with Q-smart 850 laser while spectra were captured  Plasma parameters have been calculated by using well known methods based on Saha and Boltzmann equations. Plasma temperature was calculated relative intensity of ionic carbon lines CII 251.21 nm and CII 426.73 nm while the electron density was determined by using spectroscopic information of CI 247.85 nm and CII 426.73 nm emission lines in Saha equation. Plasma temperature and electron density were found to be dependent upon nature and pressure of the ambient atmosphere. Higher temperatures and electron densities were obtained in the presence of Air as ambient environment that is attributed to electrical and physical properties of the Air. Keeping into consideration the plasma expansion in various environments the selection of a suitable ambient pressure can be made on the basis of spectral diagnostics of plasma for a particular laser energy to obtain desirable plasma temperature and electron density suited for certain applications.

scholarly journals Simultaneous 6300 Å airglow and radar observations of ionospheric irregularities and dynamics at the geomagnetic equator

2018 ◽  
Vol 36 (2) ◽  
pp. 473-487 ◽  
Author(s):  
Dustin A. Hickey ◽  
Carlos R. Martinis ◽  
Michael Mendillo ◽  
Jeffrey Baumgardner ◽  
Joei Wroten ◽  
...  
Keyword(s):  
Plasma Temperature ◽  
Radar Data ◽  
Ionospheric Irregularities ◽  
Group Separation ◽  
Plasma Parameters ◽  
Zonal Winds ◽  
Fabry Perot ◽  
Low Latitudes ◽  
Spread F ◽  
Plasma Depletions

Abstract. In March 2014 an all-sky imager (ASI) was installed at the Jicamarca Radio Observatory (11.95∘ S, 76.87∘ W; 0.3∘ S MLAT). We present results of equatorial spread F (ESF) characteristics observed at Jicamarca and at low latitudes. Optical 6300 and 7774 Å airglow observations from the Jicamarca ASI are compared with other collocated instruments and with ASIs at El Leoncito, Argentina (31.8∘ S, 69.3∘ W; 19.8∘ S MLAT), and Villa de Leyva, Colombia (5.6∘ N, 73.52∘ W; 16.4∘ N MLAT). We use Jicamarca radar data, in incoherent and coherent modes, to obtain plasma parameters and detect echoes from irregularities. We find that ESF depletions tend to appear in groups with a group-to-group separation around 400–500 km and within-group separation around 50–100 km. We combine data from the three ASIs to investigate the conditions at Jicamarca that could lead to the development of high-altitude, or topside, plumes. We compare zonal winds, obtained from a Fabry–Pérot interferometer, with plasma drifts inferred from the zonal motion of plasma depletions. In addition to the ESF studies we also investigate the midnight temperature maximum and its effects at higher latitudes, visible as a brightness wave at El Leoncito. The ASI at Jicamarca along with collocated and low-latitude instruments provide a clear two-dimensional view of spatial and temporal evolution of ionospheric phenomena at equatorial and low latitudes that helps to explain the dynamics and evolution of equatorial ionospheric/thermospheric processes. Keywords. Ionosphere (equatorial ionosphere; ionospheric irregularities; plasma temperature and density)

scholarly journals Studies on the ns-IR-Laser-Induced Plasma Parameters in the Vanadium Oxide

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Arnab Sarkar ◽  
Raju V. Shah ◽  
D. Alamelu ◽  
Suresh K. Aggarwal
Keyword(s):  
Vanadium Oxide ◽  
Electron Density ◽  
Plasma Temperature ◽  
Spectroscopic Studies ◽  
Decay Rates ◽  
Plasma Parameters ◽  
Boltzmann Plot ◽  
Saha Equation ◽  
Laser Induced Plasma ◽  
Light Pulses

We report spectroscopic studies of laser-induced plasma (LIP) produced by ns-IR-Nd:YAG laser light pulses of different energies onto four different oxides of vanadium (VO, V2O3, VO2, and V2O5) in air under atmospheric pressure. For each oxide with a different oxidation state of vanadium, both electron density and plasma temperature were calculated for different time delays and laser pulse energies. The plasma temperature was determined from Boltzmann plot method, whereas the electron number density was estimated from the Saha equation. The decay rates for plasma temperature as well as electron density were observed to follow power law and were independent of the nature of vanadium oxide. These investigations provide an insight to optimize various parameters during LIBS analysis of vanadium-based matrices.

scholarly journals Observations of the April 2002 geomagnetic storm by the global network of incoherent scatter radars

2005 ◽  
Vol 23 (1) ◽  
pp. 163-181 ◽  
Author(s):  
L. P. Goncharenko ◽  
J. E. Salah ◽  
A. van Eyken ◽  
V. Howells ◽  
J. P. Thayer ◽  
...  
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Geomagnetic Storm ◽  
Meridional Wind ◽  
Western Hemisphere ◽  
Global Network ◽  
Lower Latitude ◽  
Incoherent Scatter ◽  
Middle Latitudes ◽  
Incoherent Scatter Radars

Abstract. This paper describes the ionospheric response to a geomagnetic storm beginning on 17 April 2002. We present the measurements of ionospheric parameters in the F-region obtained by the network of eight incoherent scatter radars. The main effects of this storm include a deep decrease in the electron density observed at high and middle latitudes in the pre-noon sector, and a minor enhancement in the density observed in the daytime sector at middle latitudes. Extreme plasma heating (>1000-3000 K) is observed at high latitudes, subsiding to 200-300K at subauroral latitudes. The western hemisphere radar chain observed the prompt penetration of the electric field from auroral to equatorial latitudes, as well as the daytime enhancement of plasma drift parallel to the magnetic field line, which is related to the enhancement in the equatorward winds. We suggest that in the first several hours after the storm onset, a negative phase above Millstone Hill (pre-noon sector) results from counteracting processes - penetration electric field, meridional wind, and electrodynamic heating, with electrodynamic heating being the dominant mechanism. At the lower latitude in the pre-noon sector (Arecibo and Jicamarca), the penetration electric field becomes more important, leading to a negative storm phase over Arecibo. In contrast, in the afternoon sector at mid-latitudes (Kharkov, Irkutsk), effects of penetration electric field and meridional wind do not counteract, but add up, leading to a small (~15%), positive storm phase over these locations. As the storm develops, Millstone Hill and Irkutsk mid-latitude radars observe further depletion of electron density due to the changes in the neutral composition.

scholarly journals Plasma Temperature and Electron Density of Dry µ-EDM on Stainless Steel and Silicon: A Comparison

2011 ◽  
Vol 5 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Kanmani Subbu Subbian ◽  
◽  
Ramkumar Janakarajan ◽  
Dhamodaran Santhanagopalan ◽  
Keyword(s):  
Stainless Steel ◽  
Electron Density ◽  
Plasma Temperature ◽  
Optical Emission ◽  
Machining Process ◽  
Lead Times ◽  
Line Pair ◽  
Plasma Parameters ◽  
Pair Method ◽  
2D And 3D

Fabricating micro/nano-features in devices and largescale production with short lead times is challenging, and many individual and hybrid processes have been developed to meet this challenge. Among nonconventional processes, micro-electric discharge machining (µ-EDM) has many advantages due to the possibility of precise and accurate 2D and 3D machining of complex shapes. Dry µ-EDM is used to process assembled or semi-assembled products. Attempts are being made to improve the µ-EDM process, and further improvement is possible through better understanding the role of discharge plasma in the machining process. We studied plasma and crater characteristics during dry µ-EDM, calculating plasma parameters for different discharge energies using optical emission spectroscopy. Line pair method and modified Saha equations are used to calculate plasma temperature and electron density respectively. Craters were morphologically analyzed using scanning electron microscopy (SEM), and plasma and crater characteristics on stainless steel and silicon were compared.

scholarly journals Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra

2007 ◽  
Vol 7 (5) ◽  
pp. 625-628 ◽  
Author(s):  
A. Rozhnoi ◽  
M. Solovieva ◽  
O. Molchanov ◽  
P.-F. Biagi ◽  
M. Hayakawa
Keyword(s):  
Gravity Waves ◽  
Fresnel Zone ◽  
Signal Amplitude ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Atmospheric Gravity Waves ◽  
Period Range ◽  
Before And After ◽  
Atmospheric Gravity ◽  
Large Earthquakes

Abstract. We analyze variations of the LF subionospheric signal amplitude and phase from JJY transmitter in Japan (F=40 kHz) received in Petropavlovsk-Kamchatsky station during seismically quiet and active periods including also periods of magnetic storms. After 20 s averaging, the frequency range of the analysis is 0.28–15 mHz that corresponds to the period range from 1 to 60 min. Changes in spectra of the LF signal perturbations are found several days before and after three large earthquakes, which happened in November 2004 (M=7.1), August 2005 (M=7.2) and November 2006 (M=8.2) inside the Fresnel zone of the Japan-Kamchatka wavepath. Comparing the perturbed and background spectra we have found the evident increase in spectral range 10–25 min that is in the compliance with theoretical estimations on lithosphere-ionosphere coupling by the Atmospheric Gravity Waves (T>6 min). Similar changes are not found for the periods of magnetic storms.

scholarly journals Gamma entrainment frequency affects mood, memory and cognition: an exploratory pilot study

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Ryan L. S. Sharpe ◽  
Mufti Mahmud ◽  
M. Shamim Kaiser ◽  
Jianhui Chen
Keyword(s):  
Pilot Study ◽  
Correlation Analysis ◽  
Negative Correlation ◽  
Cognitive Abilities ◽  
Statistical Significance ◽  
Assessment Scores ◽  
Frequency Group ◽  
Before And After ◽  
Mood Score ◽  
40 Hz

AbstractHere we provide evidence with an exploratory pilot study that through the use of a Gamma 40 Hz entrainment frequency, mood, memory and cognition can be improved with respect to a 9-participant cohort. Participants constituted towards three binaural entrainment frequency groups: the 40 Hz, 25 Hz and 100 Hz. Participants attended a total of eight entrainment frequency sessions twice over the duration of a 4-week period. Additionally, participants were assessed based on their cognitive abilities, mood as well as memory, where the cognitive and memory assessments occurred before and after a 5-min binaural beat stimulation. The mood assessment scores were collected from sessions 1, 4 and 8, respectively. With respect to the Gamma 40 Hz entrainment frequency population, we observed a mean improvement in cognitive scores, elevating from 75% average to 85% average upon conclusion of the experimentation at weak statistical significance ($$\alpha$$ α = 0.10, p = 0.076). Similarly, memory score improvements at a greater significance ($$\alpha$$ α = 0.05, p = 0.0027) were noted, elevating from an average of 87% to 95%. In pertinence to the mood scores, a negative correlation across all populations were noted, inferring an overall increase in mood due to lower scores correlating with elevated mood. Finally, correlation analysis revealed a stronger R$$^2$$ 2 value (0.9838) within the 40 Hz group between sessions as well as mood score when compared across the entire frequency group cohort.

scholarly journals Polar patches observed by ESR and their possible origin in the cusp region

2000 ◽  
Vol 18 (9) ◽  
pp. 1043-1053 ◽  
Author(s):  
A. M. Smith ◽  
S. E. Pryse ◽  
L. Kersley
Keyword(s):  
Energy Distribution ◽  
Electron Density ◽  
Plasma Flow ◽  
Plasma Temperature ◽  
Soft Particle ◽  
Polar Ionosphere ◽  
Polar Cap ◽  
Particle Precipitation ◽  
Cusp Region ◽  
Reconnection Site

Abstract. Observations by the EISCAT Svalbard radar in summer have revealed electron density enhancements in the magnetic noon sector under conditions of IMF Bz southward. The features were identified as possible candidates for polar-cap patches drifting anti-Sunward with the plasma flow. Supporting measurements by the EISCAT mainland radar, the CUTLASS radar and DMSP satellites, in a multi-instrument study, suggested that the origin of the structures lay upstream at lower latitudes, with the modulation in density being attributed to variability in soft-particle precipitation in the cusp region. It is proposed that the variations in precipitation may be linked to changes in the location of the reconnection site at the magnetopause, which in turn results in changes in the energy distribution of the precipitating particles.Key words: Ionosphere (ionosphere-magnetosphere interactions; plasma temperature and density; polar ionosphere)

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