scholarly journals Low latitude ionospheric effects of major geomagnetic storms observed using TOPEX TEC data

2009 ◽  
Vol 27 (8) ◽  
pp. 3133-3139 ◽  
Author(s):  
Y. O. Migoya-Orué ◽  
S. M. Radicella ◽  
P. Coïsson
Keyword(s):  
Geomagnetic Storms ◽  
Rate Of Change ◽  
Activity Level ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Ionospheric Effects ◽  
Spatial Gradients ◽  
Different Seasons ◽  
Global Ionospheric Maps ◽  
The One

Abstract. Low latitude ionospheric effects of two major geomagnetic storms are analysed using TOPEX TEC data for specific satellite passes. The storms are the one that started on 15 July 2000 and the one that started on 8 November 2004. The variation of vertical TEC as a function of latitude along the satellite passes during day-time mostly in the region of the Pacific Ocean have been analysed comparing the storm period with quiet conditions. It has to be noted that for obvious reasons the TEC behaviour over this region cannot be observed using ground-based instruments but TOPEX data give a reasonable overall view of the region covered by the Equatorial Anomaly, just as the storms were developing. The performance of vertical TEC obtained from GPS derived TEC of global ionospheric maps (GIMs) are compared with the TOPEX data in order to determine their accuracy when storms of this type take place. The results show that the Equatorial Anomaly TEC peaks move towards the poles by several degrees and increase their intensity with respect to the quiet conditions behaviour for both storms that occurred at different seasons and solar activity level. This behaviour is not well represented by the maps of the different GIMs used in this study. The rate of change obtained from TOPEX TEC were computed to look for vertical TEC spatial gradients variations.

scholarly journals Modification of the low-latitude ionosphere before the 26 December 2004 Indonesian earthquake

2006 ◽  
Vol 6 (5) ◽  
pp. 817-823 ◽  
Author(s):  
I. E. Zakharenkova ◽  
A. Krankowski ◽  
I. I. Shagimuratov
Keyword(s):  
Electron Content ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Total Electron ◽  
Ionospheric Effects ◽  
Earthquake Preparation ◽  
Low Latitude Ionosphere ◽  
Positive Effect ◽  
Possible Cause ◽  
Gps Observations

Abstract. This paper investigates the features of pre-earthquake ionospheric anomalies in the total electron content (TEC) data obtained on the basis of regular GPS observations from the IGS network. For the analysis of the ionospheric effects of the 26 December 2004 Indonesian earthquake, global TEC maps were used. The possible influence of the earthquake preparation processes on the main low-latitude ionosphere peculiarity – the equatorial anomaly – is discussed. Analysis of the TEC maps has shown that modification of the equatorial anomaly occurred a few days before the earthquake. For 2 days prior to the event, a positive effect was observed in the daytime amplification of the equatorial anomaly. Maximal enhancement in the crests reached 20 TECU (50–60%) relative to the non-disturbed state. In previous days, during the evening and night hours (local time), a specific transformation of the TEC distribution had taken place. This modification took the shape of a double-crest structure with a trough near the epicenter, though usually in this time the restored normal latitudinal distribution with a maximum near the magnetic equator is observed. It is assumed that anomalous electric field generated in the earthquake preparation zone could cause a near-natural "fountain-effect" phenomenon and might be a possible cause of the observed ionospheric anomaly.

scholarly journals A case-study of the low-latitude thermosphere during geomagnetic storms and its new representation by improved MSIS model

1998 ◽  
Vol 16 (11) ◽  
pp. 1513-1518 ◽  
Author(s):  
T. K. Pant ◽  
R. Sridharan
Keyword(s):  
Geomagnetic Storms ◽  
Correction Term ◽  
Atmospheric Model ◽  
Simple Relation ◽  
Rate Of Change ◽  
Low Latitude ◽  
Model Predictions ◽  
The Difference ◽  
Almost All

Abstract. The thermospheric temperatures from low and equatorial latitudes during geomagnetically disturbed periods are known to exhibit significant deviations from atmospheric model predictions. Also, the oscillatory features seen in the observations are not accounted for by the models. A simple relation has been established between the difference in the observed and model-predicted temperatures and the rate of change of Dst, the magnetic index representing the ring current variabilities. Using this relation, a correction term has been added to the latest MSIS-90 model algorithm and almost all the observed variations in neutral temperatures spectroscopically determined from Mt.Abu, a low-latitude station in India, are successfully reproduced for two moderate geomagnetic storms.Key words. Low-latitude thermosphere · MSIS model · Stormtime model predictions · FP spectroscopic temperatures  

Accuracy analysis of global ionospheric maps in relation to their temporal resolution and solar activity level.

2020 ◽  
Author(s):  
Beata Milanowska ◽  
Paweł Wielgosz ◽  
Anna Krypiak-Gregorczyk ◽  
Wojciech Jarmołowski
Keyword(s):  
Solar Activity ◽  
Temporal Resolution ◽  
Geomagnetic Storms ◽  
Activity Level ◽  
Activity Period ◽  
Accuracy Evaluation ◽  
Accuracy Analysis ◽  
International Gnss Service ◽  
Wide Range ◽  
Global Ionospheric Maps

<p>Since 1998 Ionosphere Associate Analysis Centers (IAAC) of the International GNSS Service (IGS) routinely provide global ionosphere maps (GIMs). They are used for a wide range of geophysical applications, including supporting precise positioning and improving space weather analysis. These GIMs are generated by different analysis centers with the use of different modelling techniques. Therefore they have different accuracy levels, which has already been evaluated in several studies. Until 2014 all GIMs were provided with 2-hour temporal resolution, and since 2015 some of the IAACs have started to provide their products with higher resolutions, up to 30 - 60 minutes. Since GIMs have different temporal resolutions, we investigated whether map interval affected their accuracies.</p><p>In this study we carried out IAAC GIM accuracy analysis for years 2014 and 2018, corresponding to high and low solar activity periods, respectively. Since in 2014 IAAC GIMs had 2-hour resolution, we also evaluated UQRG maps supplied with 15-minute interval. For low solar activity period (2018) we evaluated 4 models: CASG, CODG, EMRG and  UQRG. In addition, we studied ionosphere map performance during two selected geomagnetic storms: on 19 February 2014 and 17 March 2015. Our accuracy evaluation was based on GIM-TEC comparisons to differential STEC derived from GNSS data and VTEC derived from altimetry measurements.</p><p>The results show that temporal interval has no significant impact on the overall, annual map RMS during both high and low solar activity periods. However, during geomagnetic storms, when reducing map interval, the map accuracy improves by almost 25%.</p>

scholarly journals Effects of strong IMF <I>B<sub>z</sub></I> southward events on the equatorial and mid-latitude ionosphere

2009 ◽  
Vol 27 (3) ◽  
pp. 1175-1187 ◽  
Author(s):  
E. Astafyeva
Keyword(s):  
Electric Fields ◽  
Geomagnetic Storms ◽  
The Other ◽  
Negative Events ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Sudden Drop ◽  
Ionospheric Response ◽  
Peak Structure ◽  
Low Latitude Ionosphere

Abstract. Dayside ionospheric response to five intense geomagnetic storms (Dst<−120 nT) that occurred in 2001–2005 was investigated by use of simultaneous TEC measurements by the CHAMP, SAC-C, TOPEX/Jason-1 satellites. Since the satellites passed over different longitudinal sectors and measured TEC in different range of altitudes, it was possible to obtain information about altitudinal and longitudinal ionosphere redistribution during these storms. Severe enhancements (up to ~350%) of the equatorial and mid-latitude TEC above ~430 km with concurrent traveling of the equatorial anomaly crests for a distance of 10–15° of latitude were observed during two of the five events analyzed here (6 November 2001 and 8 November 2004). This phenomenon, known as the dayside ionosphere uplift, or the "daytime super-fountain effect", occurred after sudden drop in IMF Bz and consequent penetration of the electric fields to the low-latitude ionosphere. However, the same order Bz negative events caused comparatively weak changes in the dayside TEC (up to ~80 TECU) during the other three events of 18 June 2003, 11 February 2004 and 24 August 2005. At the main phase of these storms there were mostly observed formation of the "typical" dual peak structure of the equatorial anomaly rather than the reinforcement of the fountain effect and the anomaly itself. Possible reasons and factors responsible for the development of the extreme ionosphere effects are discussed in the paper.

Static and Dynamic Studies of Gasoline in View of its Octane Number and its Toxic Effect

2013 ◽  
Vol 12 (7) ◽  
pp. 451-459
Author(s):  
Ashraf Yehia El-Naggar ◽  
Mohamed A. Ebiad
Keyword(s):  
Toxic Effect ◽  
Aromatic Hydrocarbons ◽  
Octane Number ◽  
Liquid Fuel ◽  
Positive Impact ◽  
Hydrocarbon Composition ◽  
Different Temperatures ◽  
Different Seasons ◽  
The One ◽  
The Impact

Gasoline come primarily from petroleum cuts, it is the preferred liquid fuel in our lives. Two gasoline samples of octane numbers 91 and 95 from Saudi Arabia petrol stations were studied. This study was achieved at three different temperatures 20oC, 30oC and 50oC representing the change in temperatures of the different seasons of the year. Both the evaporated gases of light aromatic hydrocarbons (BTEX) of gasoline samples inside the tank were subjected to analyze qualitatively and quantitatively via capillary gas chromatography. The detailed hydrocarbon composition and the octane number of the studied gasoline samples were determined using detailed hydrocarbon analyzer. The idea of research is indicating the impact of light aromatic compounds in gasoline on the toxic effect of human and environment on the one hand, and on octane number of gasoline on the other hand. Although the value of octane number will be reduced but this will have a positive impact on the environment as a way to produce clean fuel.

Effects of Sex and Physical Activity Level on Serum Biomarker-Based Physiological Dysregulation: The Impact to Predict Frailty and Mortality in the Quebec NuAge Cohort

Gerontology ◽  
2021 ◽  
pp. 1-14
Author(s):  
Ahmed Ghachem ◽  
Frédérik Dufour ◽  
Tamas Fülöp ◽  
Pierrette Gaudreau ◽  
Alan A. Cohen
Keyword(s):  
Physical Activity ◽  
Older Adults ◽  
Kidney Function ◽  
Oxygen Transport ◽  
Physical Activity Level ◽  
Rate Of Change ◽  
Activity Level ◽  
Men And Women ◽  
Physiological Dysregulation ◽  
The Impact

<b><i>Background:</i></b> Age-related changes in biological processes such as physiological dysregulation (the progressive loss of homeostatic capacity) vary considerably among older adults and may influence health profiles in late life. These differences could be related, at least in part, to the impact of intrinsic and extrinsic factors such as sex and physical activity level (PAL). <b><i>Objectives:</i></b> The objectives of this study were (1) to assess the magnitude and rate of changes in physiologi­cal dysregulation in men and women according to PAL and (2) to determine whether/how sex and PAL mediate the apparent influence of physiological dysregulation on health outcomes (frailty and mortality). <b><i>Methods:</i></b> We used data on 1,754 community-dwelling older adults (age = 74.4 ± 4.2 years; women = 52.4%) of the Quebec NuAge cohort study. Physiological dysregulation was calculated based on Mahalanobis distance of 31 biomarkers regrouped into 5 systems: oxygen transport, liver/kidney function, leukopoiesis, micronutrients, and lipids. <b><i>Results:</i></b> As expected, mean physiological dysregulation significantly increased with age while PAL decreased. For the same age and PAL, men showed higher levels of physiological dysregulation globally in 3 systems: oxygen transport, liver/kidney function, and leukopoiesis. Men also showed faster global physiological dysregulation in the liver/kidney and leukopoiesis systems. Overall, high PAL was associated with lower level and slower rate of change of physiological dysregulation. Finally, while mortality and frailty risk significantly increased with physiological dysregulation, there was no evidence for differences in these effects between sexes and PAL. <b><i>Conclusion:</i></b> Our results showed that both sex and PAL have a significant effect on physiological dysregulation levels and rates of change. Also, although a higher PAL was associated with lower level and slower rate of change of physiological dysregulation, there was no evidence that PAL attenuates the effect of physiological dysregulation on subsequent declines in health at the end of life. Substantial work remains to understand how modifiable behaviors impact the relationship between physiological dysregulation, frailty, and mortality in men and women.

Acid Volatile Sulfide (AVS) and Simultaneously Extracted Metals (SEM) in Surface Sediments of Chaohu Lake, Anhui Province, China

2013 ◽  
Vol 779-780 ◽  
pp. 1213-1219
Author(s):  
Shu Qin Chen ◽  
Lei Zhang ◽  
Zhao Sheng Chu ◽  
She Rong Hu
Keyword(s):  
Surface Sediments ◽  
Local Scale ◽  
Acid Volatile Sulfide ◽  
Anthropogenic Factors ◽  
Chaohu Lake ◽  
Lake Surface ◽  
Different Seasons ◽  
The One ◽  
Short Time ◽  
Spot 5

At present there are few studies on the AVS and SEM in sediments of Chaohu Lake. Most of the previous studies on heavy metals based on the one time, the short-time or a local-scale survey. In this paper, [AVS] and [SEM] in Chaohu Lake surface sediments were studied for different seasons in 2007, 2008 and 2009. The results showed that: (a) The three-year average of [AV and [ΣSE in surface sediments of Chaohu Lake is 4.2μmolg-1and 2.31μmolg-1, respectively. The maximum of [AV appears on spot 5 (14.845μmolg-1) in summer while the minimum appears on spot 9 (0.13μmolg-1) in winter. (b) In spot 5 which near the estuary of Yuxi River, three-year average of [SE was the maximum (5.81μmolg-1), and the minimum of [ΣSE (0.07μmolg-1) appears on spot 8 which locates in the middle of Chaohu Lake. In spot 13 the [ΣSEM]-[AVS]=3.2>2 and [ΣSEM]/[AVS]=4.45>2.34 indicate that heavy metal contaminants from Hefei city have threatened the biosafety of Chaohu Lake. (c) The spatial autocorrelation of SEMCdis weak, which indicates that spatial distribution of SEMCdis determined by anthropogenic factors rather than sediments' own attribute. Chaohu Lake has been heavily polluted by Cd from no-point source and electronic electroplating industry.

scholarly journals Case study on total electron content enhancements at low latitudes during low geomagnetic activities before the storms

2008 ◽  
Vol 26 (4) ◽  
pp. 893-903 ◽  
Author(s):  
◽  
◽  
◽  
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Activity ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Defense Meteorological Satellite Program ◽  
Low Latitudes ◽  
Global Ionospheric Maps ◽  
Geomagnetic Activities

Abstract. Sometimes the ionospheric total electron content (TEC) is significantly enhanced during low geomagnetic activities before storms. In this article, we investigate the characteristics of those interesting TEC enhancements using regional and global TEC data. We analyzed the low-latitude TEC enhancement events that occurred around longitude 120° E on 10 February 2004, 21 January 2004, and 4 March 2001, respectively. The TEC data are derived from regional Global Positioning System (GPS) observations in the Asia/Australia sector as well as global ionospheric maps (GIMs) produced by Jet Propulsion Laboratory (JPL). Strong enhancements under low geomagnetic activity before the storms are simultaneously presented at low latitudes in the Asia/Australia sector in regional TEC and JPL GIMs. These TEC enhancements are shown to be regional events with longitudinal and latitudinal extent. The regions of TEC enhancements during these events are confined at narrow longitude ranges around longitude 120° E. The latitudinal belts of maxima of enhancements locate around the northern and southern equatorial ionization anomaly (EIA) crests, which are consistent with those low-latitude events presented by Liu et al. (2008). During the 4 March 2001 event, the total plasma density Ni observed by the Defense Meteorological Satellite Program (DMSP) spacecraft F13 at 840 km altitude are of considerably higher values on 4 March than on the previous day in the TEC enhanced regions. Some TEC enhancement events are possibly due to contributions from auroral/magnetospheric origins; while there are also quasi-periodic enhancement events not related to geomagnetic activity and associated probably with planetary wave type oscillations (e.g. the 6 January 1998 event). Further investigation is warrented to identify/separate contributions from possible sources.

scholarly journals Remote auroral activity detection and modeling using low frequency transmitter signal reception at a midlatitude site

2010 ◽  
Vol 28 (9) ◽  
pp. 1807-1811 ◽  
Author(s):  
E. D. Schmitter
Keyword(s):  
Power Systems ◽  
Low Frequency ◽  
Solar Energetic Particle ◽  
Auroral Oval ◽  
Activity Level ◽  
Propagation Model ◽  
Low Latitude ◽  
Activity Data ◽  
Auroral Activity ◽  
Local Intensity

Abstract. The low frequency propagation conditions along the path from Iceland to Germany (52° N 8° E) using the NRK/TFK 37.5 kHz transmitter (63.9° N 22.5° W) prove as an easy to monitor and reliable proxy for north auroral activity. Signal processing using wavelet decomposition allows for quantitative activity level estimations. Calibration is based upon NOAA POES auroral activity data. Using an auroral oval model for the local intensity distribution of solar energetic particle precipitation and a wave propagation model ionospheric D-layer height decreases along the path can be derived. This in turn gives a hint to the low latitude extension and intensity of the auroral electrojet currents that can be responsible for communication and power systems failures.

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