scholarly journals Estimation of geomagnetic activity using measure of anomalousness

2017 ◽  
Vol 59 (6) ◽  
Author(s):  
Anatoly Soloviev ◽  
Sergey Agayan ◽  
Shamil Bogoutdinov
Keyword(s):  
Geomagnetic Activity ◽  
Time Resolution ◽  
Activity Level ◽  
K Index ◽  
Single Scale ◽  
Update Rate ◽  
Using Data ◽  
Maximal Time ◽  
Index Calculation ◽  
Magnetic Station

Herein, we present a newly developed indicator for estimating geomagnetic activity. It is based on the magnitude of measure of anomalousness (MA) of magnetometer recordings at a given time or interval. It is intended for automated estimation of geomagnetic activity level in the area of a specific magnetic station or in a given region using data of a set of stations. It reflects geomagnetic activity level at different observatories in a single scale [-1, 1], regardless of their latitudinal location and consequently typical disturbance amplitudes. To a certain extent MA indicator is an analog of traditional K index. However, a well-known shortcoming of the latter is its long, 3-hour update rate. Moreover, K index calculation requires subtraction of Sq variation that also causes delays. At the same time there is a demand for operational geomagnetic indices that have maximal time resolution and are available in near real-time. The proposed MA indicator aims to address the shortcomings of the traditional K index. The MA calculation may be implemented automatically with the same time resolution as the initial data are recorded.

scholarly journals Multiscale variation model and activity level estimation algorithm of the Earth's magnetic field based on wavelet packets

2018 ◽  
Vol 36 (5) ◽  
pp. 1207-1225 ◽  
Author(s):  
Oksana V. Mandrikova ◽  
Igor S. Solovyev ◽  
Sergey Y. Khomutov ◽  
Vladimir V. Geppener ◽  
Dmitry M. Klionskiy ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Numerical Algorithms ◽  
Estimation Algorithm ◽  
Solar Wind Plasma ◽  
Activity Level ◽  
High Temporal Resolution ◽  
Suggested Approach ◽  
Characteristic Variation ◽  
Using Data ◽  
Multiscale Mathematical Model

Abstract. We suggest a wavelet-based multiscale mathematical model of geomagnetic field variations. The model is particularly capable of reflecting the characteristic variation and local perturbations in the geomagnetic field during the periods of increased geomagnetic activity. Based on the model, we have designed numerical algorithms to identify the characteristic variation component as well as other components that represent different geomagnetic field activity. The substantial advantage of the designed algorithms is their fully automatic performance without any manual control. The algorithms are also suited for estimating and monitoring the activity level of the geomagnetic field at different magnetic observatories without any specific adjustment to their particular locations. The suggested approach has high temporal resolution reaching 1 min. This allows us to study the dynamics and spatiotemporal distribution of geomagnetic perturbations using data from ground-based observatories. Moreover, the suggested approach is particularly capable of discovering weak perturbations in the geomagnetic field, likely linked to the nonstationary impact of the solar wind plasma on the magnetosphere. The algorithms have been validated using the experimental data collected at the IKIR FEB RAS observatory network. Keywords. Magnetospheric physics (storms and substorms)

scholarly journals Variability of Weddell Sea ionospheric anomaly as deduced from observations at the Akademik Vernadsky station

2021 ◽  
pp. 47-55
Author(s):  
A. Zalizovski ◽  
◽  
I. Stanislawska ◽  
V. Lisachenko ◽  
O. Charkina ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Electron Density ◽  
Geomagnetic Activity ◽  
Dynamic Equilibrium ◽  
Doppler Frequency ◽  
Weddell Sea ◽  
K Index ◽  
Weddell Sea Anomaly ◽  
Index Level ◽  
Solar Ultraviolet

Ionospheric Weddell Sea anomaly is an inversion of diurnal variation of the electron density in the ionosphere over Antarctic Peninsula, Weddell Sea, and neighbor territories observed during Antarctic summer. This paper aims at analyzing the reaction of the ionosphere during the Weddell Sea anomaly to changes in solar and geomagnetic activity as deduced from the data of vertical sounding of the ionosphere conducted at the Akademik Vernadsky station. The aim is achieved by comparing the monthly median values of the critical frequencies of the ionosphere (foF2) during Weddell Sea anomaly for the years of high and low solar activity; as well as by comparison of median December height-time diagrams (HT-diagrams) of foF2 calculated separately for the time intervals characterized by low or high levels of F10.7 and K indices for the period from 2007 till 2016. It was experimentally demonstrated that the Weddell Sea anomaly depends on the levels of solar ultraviolet flux and local K indices. The biggest nighttime maximum of ionization corresponds to low K indices and high values of F10.7. The most accurate inversion of diurnal variation of electron density in the F region is observed under the low values of K index and low F10.7 flux. The growth of geomagnetic activity decreases the nighttime ionization under both low and high levels of F10.7 fluxes and leads to a blur of the night maximum. Visible virtual heights of maximums increase together with F10.7 independently of the K index level. Blurring of the night maximum can be explained by destruction of the field of thermospheric winds supporting the nighttime anomaly, and/or by increasing role of plasma drifts in comparison with wind impact. The growth of visible virtual height of the nighttime maximum with increasing solar F10.7 flux could be explained by the gain of equatorward thermospheric wind with increasing solar ultraviolet flux that leads to growth of plasma upwelling effect. The Doppler frequency shift of the signals reflected from the ionosphere during nighttime in presence of the Weddell Sea anomaly is close to zero which could be explained by a stable F2 layer formed as a result of dynamic equilibrium between photochemical processes and upward plasma transport.

A STUDY ON THE INTRINSIC TIME RESOLUTION OF THE MRPC USED IN THE STAR-TOF

2007 ◽  
Vol 16 (07n08) ◽  
pp. 2476-2483 ◽  
Author(s):  
◽  
MING SHAO ◽  
LIANG LI
Keyword(s):  
Time Resolution ◽  
Incident Angle ◽  
Signal Amplitude ◽  
Test Results ◽  
Beam Test ◽  
Intrinsic Time ◽  
200 Gev ◽  
Star Experiment ◽  
Calibration Study ◽  
Using Data

Time-Of-Flight (TOF) based on Multi-gap Resistive Plate Chamber (MRPC) detectors have been successfully operating at the STAR experiment since 2003.2,3 The MRPC time resolution is however found to be significantly worse2 (80-90 ps) than that previously obtained in beam test (60 ps).4 In order to fully understand MRPC working principles and operating requirements, an extensive calibration study is performed using data collected by STAR in 200 GeV Au + Au collisions in 2004. The relation between MRPC timing, signal amplitude, incident angle and momentum are discussed. Contributions from tracking properties of STAR-TPC are also studied by simulation. The intrinsic time resolution of the MRPCs used in STAR-TOF, after taking all factors into consideration, is found to be in good agreement with beam test results.

Long-term variations in the geomagnetic activity level Part II: Ascending phases of sunspot cycles

1994 ◽  
Vol 12 (10/11) ◽  
pp. 1065-1070 ◽  
Author(s):  
V. Mussino ◽  
O. Borello Filisetti ◽  
M. Storini ◽  
H. Nevanlinna
Keyword(s):  
Correlation Coefficient ◽  
Geomagnetic Activity ◽  
Activity Level ◽  
Activity Levels ◽  
Data Set ◽  
The Past ◽  
Long Term Trends ◽  
A Minor ◽  
Long Term Variations

Abstract. Monthly averages of the Helsinki Ak-values have been reduced to the equivalent aa-indices to extend the aa-data set back to 1844. A periodicity of about five cycles was found for the correlation coefficient (r) between geomagnetic indices and sunspot numbers for the ascending phases of sunspot cycles 9 to 22, confirming previous findings based on a minor number of sunspot cycles. The result is useful to researchers in topics related to solar-terrestrial physics, particularly for the interpretation of long-term trends in geomagnetic activity during the past, and to forecast geomagnetic activity levels in the future.

scholarly journals Pre-storm <I>Nm</I>F2 enhancements at middle latitudes: delusion or reality?

2009 ◽  
Vol 27 (3) ◽  
pp. 1321-1330 ◽  
Author(s):  
A. V. Mikhailov ◽  
L. Perrone
Keyword(s):  
Magnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Activity ◽  
Critical Analysis ◽  
Geomagnetic Storms ◽  
Activity Level ◽  
Quiet Time ◽  
Auroral Activity ◽  
Middle Latitudes ◽  
Plasma Ring

Abstract. A critical analysis of recent publications devoted to the NmF2 pre-storm enhancements is performed. There are no convincing arguments that the observed cases of NmF2 enhancements at middle and sub-auroral latitudes bear a relation to the following magnetic storms. In all cases considered the NmF2 pre-storm enhancements were due to previous geomagnetic storms, moderate auroral activity or they presented the class of positive quiet time events (Q-disturbances). Therefore, it is possible to conclude that there is no such an effect as the pre-storm NmF2 enhancement as a phenomenon inalienably related to the following magnetic storm. The observed nighttime NmF2 enhancements at sub-auroral latitudes may result from plasma transfer from the plasma ring area by meridional thermospheric wind. Enhanced plasmaspheric fluxes into the nighttime F2-region resulted from westward substorm-associated electric fields is another possible source of nighttime NmF2 enhancements. Daytime positive Q-disturbances occurring under very low geomagnetic activity level may be related to the dayside cusp activity.

Long-term variations in the geomagnetic activity level Part II: Ascending phases of sunspot cycles

1994 ◽  
Vol 12 (10) ◽  
pp. 1065 ◽  
Author(s):  
V. Mussino ◽  
O. Borello Filisetti ◽  
M. Storini ◽  
H. Nevanlinna
Keyword(s):  
Geomagnetic Activity ◽  
Activity Level ◽  
Long Term Variations

scholarly journals A new southern high-latitude index

1998 ◽  
Vol 16 (12) ◽  
pp. 1589-1598 ◽  
Author(s):  
P. Ballatore ◽  
C. G. Maclennan ◽  
M. J. Engebretson ◽  
M. Candidi ◽  
J. Bitterly ◽  
...  
Keyword(s):  
High Latitude ◽  
Activity Level ◽  
Polar Cap ◽  
Geomagnetic Index ◽  
Level Indicator ◽  
Ae Index ◽  
Average Activity ◽  
Using Data ◽  
Auroral Phenomena ◽  
Southern High Latitude

Abstract. We have developed and examined a new regional geomagnetic index AES-80, defined similarly to the classical auroral electrojet AE index, using data from five Antarctic stations located at corrected geomagnetic latitudes about 80 °S. Because only sparse ground-based information can be derived from auroral latitudes in the Southern Hemisphere, and because no index comparable to AE can be constructed from locations in the south, the possibility of using AES-80 as a measure of high latitudes and polar cap activity is investigated. As a global average activity level indicator, it is found that in general AES-80 gives results rather similar to the classical AE index. However AES-80 provides a more robust measure of the occurrence of high-latitude geomagnetic activity.Key words. Magnetospheric physics (auroral phenomena; polar cap phenomena).

scholarly journals Good perception of own lifestyle associated with poor attendance at Diabetic RetinaScreen Programme

2021 ◽  
Vol 31 (Supplement_3) ◽  
Author(s):  
S Syed ◽  
P Fitzpatrick
Keyword(s):  
Logistic Regression ◽  
Diabetic Retinopathy ◽  
Activity Level ◽  
Multivariate Logistic Regression ◽  
Factors Associated ◽  
Diabetic Retinopathy Screening ◽  
Working Age ◽  
National Cohort ◽  
Using Data ◽  
Formed Part

Abstract Background Untreated diabetic retinopathy is the most common cause of sight loss in people of working age. The Diabetic RetinaScreen programme (DRS) is the national diabetic retinopathy screening programme in Ireland which commenced in 2013 with aim to prevent diabetic retinopathy and subsequent blindness, through free screening and ophthalmology services. High uptake is crucial for the effectiveness of the programme. This study aimed to determine the sociodemographic, lifestyle and healthcare factors associated with attendance at the DRS programme in Ireland, using data from a national cohort study, the Irish Longitudinal Study on Ageing (TILDA). Methods The TILDA wave-4 dataset (anonymised) was utilised for the current study. Questions on DRS invitation and attendance formed part of the wave 4 study questionnaire. Multivariate logistic regression was used to examine independent factors associated with attendance. SPSS was used for analysis. Results 418 respondents (7.3%) were invited to DRS and 373 (89.2%) attended. Among all those who were invited to DRS, 244 (58.4%) were male and 174 (41.6%) were female. The mean age was 69.8 years (53-84 years). Following multivariate logistic regression, following a good diet/taking exercise (OR = 0.29, 95% CI 0.10-0.82) was negatively associated with attendance, after adjustment for age, male gender, higher education and medical card. Conclusions Recognising factors linked with uptake is important to develop goal directed strategies. Interestingly those who stated they followed a good diet & took exercise and were compliant with DM prevention were less likely to attend DRS. Previous research has also indicated that a higher physical activity level is associated with higher self-perceived health status Key messages Persons with DM with good compliance to diet and exercise were found to have poor attendance at the DRS programme. Targeted advertising is required to raise awareness of diabetic retinopathy.

scholarly journals Scintillations of Radio Sources and Geomagnetic Activity

1962 ◽  
Vol 15 (4) ◽  
pp. 568 ◽  
Author(s):  
OB Slee
Keyword(s):  
Magnetic Field ◽  
Radio Source ◽  
Geomagnetic Activity ◽  
Auroral Zone ◽  
Radio Sources ◽  
Present Communication ◽  
Earth’S Magnetic Field ◽  
K Index ◽  
Northern Latitudes ◽  
The Relationship

The relationship between variations in the Earth's magnetic field and radio source scintillation has been somewhat obscure since the first observation by Little and Maxwell (1952) that, for sources observed through the Northern Auroral Zone, the scintillation rate, but not the amplitude, was closely correlated with the planetary K index. Since then a number of observers, mainly situated in high northern latitudes, also found no relation between the scintillation amplitude and geomagnetic activity. It is the purpose of the present communication to show that at southern temperate latitudes a relationship does exist between these quantities.

scholarly journals High Temporal Sub-millisecond Time Resolution Stimulation Increases Performances of Retina Prosthetic Vision

2018 ◽  
Author(s):  
S. Kime ◽  
C. Simon-Shane ◽  
Q. Sabatier ◽  
F. Galluppi ◽  
R. Benosman
Keyword(s):  
Temporal Resolution ◽  
Time Resolution ◽  
Clinical Studies ◽  
Vision Loss ◽  
Discrimination Performance ◽  
Performance Improvements ◽  
Fundamental Limitations ◽  
Retinal Stimulation ◽  
Retinal Implants ◽  
Using Data

AbstractVision loss has an enormous impact on affected individuals, and increasing social and economics costs for the whole of society. Important approaches have been introduced, aimed at restoring visual functionality in the case of vision degradation and loss. Currently the most promising technology is represented by retinal implants, with companies producing devices approved for commercialization. The first clinical studies encouragingly reported perception elicited by both devices. Some patients retrieve autonomy, but only a few could reach satisfactory perception levels, allowing more complex tasks such as reading. Fundamental limitations however still exist in both spatial and temporal resolution, and these limitations call for improvements of the technology and of the stimulation strategies used therein. This study focuses on the importance of temporal resolution for retinal stimulation, and how it can be used to improve restored perception for implanted patients. We show a quantification of the improvement of discrimination performance when stimulating with high frame rates compared to conventional 30-60Hz frame rates. Such effect is evaluated using data collected from implanted patients, and deriving from it a realistic phosphene model. This study allowed to accurately replicate the perceptual effects of the studied technologies, and to evaluate the hypotheses regarding performance improvements using higher temporal resolutions for stimulation strategies in visual restoration devices.

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