scholarly journals Variations of the total electronic concentration in the ionosphere in seismically active region

2021 ◽  
Vol 333 ◽  
pp. 02012
Author(s):  
Valentin Kashkin ◽  
Tatyana Rubleva ◽  
Konstantin Simonov ◽  
Andrey Zabrodin ◽  
Aleksey Kabanov
Keyword(s):  
Solar Activity ◽  
Active Region ◽  
Electron Concentration ◽  
Navigation System ◽  
Active Regions ◽  
Computational Technique ◽  
Total Electron ◽  
Catastrophic Earthquake ◽  
Electronic Concentration ◽  
Geodynamic Activity

In this work we studied the variations in the total electron concentration (TEC) obtained from measurements of the global navigation system GPS in the preparation zone for the 2010 catastrophic Chilean earthquake (Mw = 8.8) under calm background conditions at a minimum of 24 solar activity (SA) cycles. The analysis of the geodynamic activity and ionospheric TEC disturbances in the seismically active region of this catastrophic earthquake is carried out. A computational technique has been developed that can be used to study TEC variations over seismically active regions.

Energy Balance and Structure Of Active Regions

1977 ◽  
Vol 36 ◽  
pp. 457-473 ◽  
Author(s):  
Frank Q. Orrall ◽  
Roger A. Kopp
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Active Region ◽  
Internal Structure ◽  
Solar Flares ◽  
Active Regions ◽  
Particle Emission ◽  
Space Astronomy ◽  
Coronal Bright Points ◽  
Definition Of

With the advent of radio and space astronomy it became necessary to extend the definition of a center of activity or active region (AR) originally proposed by L. d’Azambuja. At IAU Symposium 35, K.O. Klepenheuer (1968) defined an AR as “The totality of all observable phenomena preceding, accompanying and following the birth of sunspots, including radio-, X-, EUV-, and particle emission.” The recognition that there are other short-lived bipolar features with a distribution similar to that of active regions (ephemeral active regions) by Harveyet al. (1975) and their identification with coronal bright points by Golub et al. (1975) suggests that the definition will have to be extended further. Active regions manifest themselves in the photosphere as sunspots and faculae; in the chromosphere as the plage and its structures; in the corona as a coronal enhancement with a complex, often loop-like internal structure. (The termenhancementwas Introduced by Billings. The original termpermanent coronal condensation, introduced by Waldemeler, only referred to the very bright enhancements and was, moreover, often confused with hissporadic coronal condensations, a flareassodated phenomena. The termcoronal active regionhas, recently also been used for the coronal extension of the AR.) In keeping with the aims of this symposium the stress of this review will be on the chromosphere and corona. Active regions are especially Important as the site of most flare-associated phenomena. Here we shall be concerned with flares only as they affect the overall energy balance. Our concern is with the “quiet” active regions that cause the slowly varying components of solar activity and provide the ambiance within which solar flares occur.

scholarly journals Origine des régions actives solaires ‘anormales’

1968 ◽  
Vol 35 ◽  
pp. 25-32 ◽  
Author(s):  
M. J. Martres
Keyword(s):  
Solar Activity ◽  
Active Region ◽  
Active Center ◽  
Active Regions ◽  
The West ◽  
Magnetic Inversion ◽  
Solar Active Regions ◽  
Western Side ◽  
Magnetic Inversion Line

Solar active regions are considered ‘anomalous’ when they belong to magnetic classes γ,βγ and βf-αf. The study of the solar activity of the region where, later on, these groups are born shows an evident correlation between the presence of an old active center and the complexity of the new active region.It is found that the complexity is greater if the old active center is younger, and the superposition better. We also observe that the birth of anomalous sunspots groups occurs much more frequently on the western side of the magnetic inversion line of the old center.When the birth of an active center occurs outside and on the West of the faculae, we observe the weakly anomalous groups βf-αf. The ‘perturbation’ decreases with distance and is extended at least to 10 heliographic degrees of the boundaries of the old faculae.

Influence of Magnetic Fields on Solar Hydrodynamics: Experimental Results

1977 ◽  
Vol 36 ◽  
pp. 143-180 ◽  
Author(s):  
J.O. Stenflo
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
General Problem ◽  
Solar Rotation ◽  
Active Regions ◽  
Physical Conditions ◽  
Dynamic Phenomena

It is well-known that solar activity is basically caused by the Interaction of magnetic fields with convection and solar rotation, resulting in a great variety of dynamic phenomena, like flares, surges, sunspots, prominences, etc. Many conferences have been devoted to solar activity, including the role of magnetic fields. Similar attention has not been paid to the role of magnetic fields for the overall dynamics and energy balance of the solar atmosphere, related to the general problem of chromospheric and coronal heating. To penetrate this problem we have to focus our attention more on the physical conditions in the ‘quiet’ regions than on the conspicuous phenomena in active regions.

On-the-Fly Determination of Active Region Centers in Adaptive-Partitioning QM/MM

2020 ◽  
Author(s):  
Zenghui Yang
Keyword(s):  
Quantum Mechanics ◽  
Active Region ◽  
Molecular Mechanics ◽  
Active Regions ◽  
Available Energy ◽  
Adaptive Partitioning ◽  
Different Levels

Quantum mechanics/molecular mechanics (QM/MM) methods partition the system into active and environmental regions and treat them with different levels of theory, achieving accuracy and efficiency at the same time. Adaptive-partitioning (AP) QM/MM methods allow on-the-fly changes to the QM/MM partitioning of the system. Many of the available energy-based AP-QM/MM methods partition the system according to distances to pre-chosen centers of active regions. For such AP-QM/MM methods, I develop an adaptive-center (AC) method that allows on-the-fly determination of the centers of active regions according to general geometrical or potential-related criteria, extending the range of application of energy-based AP-QM/MM methods to systems where active regions may occur or vanish during the simulation.

scholarly journals Topside Ionosphere and Plasmasphere Modelling Using GNSS Radio Occultation and POD Data

2021 ◽  
Vol 13 (8) ◽  
pp. 1559
Author(s):  
Fabricio S. Prol ◽  
M. Mainul Hoque
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Radio Occultation ◽  
Geomagnetic Latitude ◽  
Low Earth Orbit ◽  
Activity Level ◽  
Topside Ionosphere ◽  
Electron Content ◽  
Total Electron ◽  
Solar Activity Level

A 3D-model approach has been developed to describe the electron density of the topside ionosphere and plasmasphere based on Global Navigation Satellite System (GNSS) measurements onboard low Earth orbit satellites. Electron density profiles derived from ionospheric Radio Occultation (RO) data are extrapolated to the upper ionosphere and plasmasphere based on a linear Vary-Chap function and Total Electron Content (TEC) measurements. A final update is then obtained by applying tomographic algorithms to the slant TEC measurements. Since the background specification is created with RO data, the proposed approach does not require using any external ionospheric/plasmaspheric model to adapt to the most recent data distributions. We assessed the model accuracy in 2013 and 2018 using independent TEC data, in situ electron density measurements, and ionosondes. A systematic better specification was obtained in comparison to NeQuick, with improvements around 15% in terms of electron density at 800 km, 26% at the top-most region (above 10,000 km) and 26% to 55% in terms of TEC, depending on the solar activity level. Our investigation shows that the developed model follows a known variation of electron density with respect to geographic/geomagnetic latitude, altitude, solar activity level, season, and local time, revealing the approach as a practical and useful tool for describing topside ionosphere and plasmasphere using satellite-based GNSS data.

scholarly journals A Neural Network-Based TEC Model Capable of Reproducing Nighttime Winter Anomaly

2021 ◽  
Vol 13 (22) ◽  
pp. 4559
Author(s):  
Marjolijn Adolfs ◽  
Mohammed Mainul Hoque
Keyword(s):  
Neural Network ◽  
Solar Activity ◽  
Geomagnetic Latitude ◽  
Machine Learning Techniques ◽  
High Solar Activity ◽  
Electron Content ◽  
Solar Cycles ◽  
Total Electron ◽  
The Neural Network ◽  
Winter Anomaly

With the availability of fast computing machines, as well as the advancement of machine learning techniques and Big Data algorithms, the development of a more sophisticated total electron content (TEC) model featuring the Nighttime Winter Anomaly (NWA) and other effects is possible and is presented here. The NWA is visible in the Northern Hemisphere for the American sector and in the Southern Hemisphere for the Asian longitude sector under solar minimum conditions. During the NWA, the mean ionization level is found to be higher in the winter nights compared to the summer nights. The approach proposed here is a fully connected neural network (NN) model trained with Global Ionosphere Maps (GIMs) data from the last two solar cycles. The day of year, universal time, geographic longitude, geomagnetic latitude, solar zenith angle, and solar activity proxy, F10.7, were used as the input parameters for the model. The model was tested with independent TEC datasets from the years 2015 and 2020, representing high solar activity (HSA) and low solar activity (LSA) conditions. Our investigation shows that the root mean squared (RMS) deviations are in the order of 6 and 2.5 TEC units during HSA and LSA period, respectively. Additionally, NN model results were compared with another model, the Neustrelitz TEC Model (NTCM). We found that the neural network model outperformed the NTCM by approximately 1 TEC unit. More importantly, the NN model can reproduce the evolution of the NWA effect during low solar activity, whereas the NTCM model cannot reproduce such effect in the TEC variation.

scholarly journals Characterization of ionospheric irregularities over Vietnam and adjacent region for the 2008-2018 period

2021 ◽  
Author(s):  
Dung Nguyen Thanh ◽  
Minh Le Huy ◽  
Christine Amory-Mazaudier ◽  
Rolland Fleury ◽  
Susumu Saito ◽  
...  
Keyword(s):  
Solar Activity ◽  
Correlation Coefficients ◽  
Rate Of Change ◽  
Occurrence Rate ◽  
High Solar Activity ◽  
Electron Content ◽  
Total Electron ◽  
Plasma Irregularities ◽  
Almost All ◽  
Continuous Gps

This paper presents the variations of the rate of change of Total Electron Content (TEC) index (ROTI), characterizing the occurrence of ionospheric plasma irregularities over Vietnam and neighboring countries in the Southeast Asian region using the continuous GPS data during the 2008-2018 period. The results showed that the occurrence of strong ROTI in all stations is maximum in equinox months March/April and September/October and depends on solar activity. The ROTI is weak during periods of low solar activity and strong during periods of high solar activity. There is an asymmetry between the two equinoxes. During maximum and declining phases of 2014-2016, occurrence rates in March equinox are larger than in September equinox, but during the descending period of 2010-2011, the occurrence rates in September equinox at almost all stations are larger than in March equinox. The correlation coefficients between the monthly occurrence rate of irregularities and the F10.7 solar index at the stations in the equatorward EIA crest region are higher than at those in the magnetic equatorial and the poleward EIA crest regions. The irregularity occurrence is high in the pre-midnight sector, maximum between 2000 LT to 2200 LT. The maximum irregularity occurrence is located around 4-5° degrees in latitude equator-ward away from the anomaly crests.

Numerical Short-Term Solar Activity Forecasting

2017 ◽  
Vol 13 (S335) ◽  
pp. 243-249 ◽  
Author(s):  
Huaning Wang ◽  
Yihua Yan ◽  
Han He ◽  
Xin Huang ◽  
Xinghua Dai ◽  
...  
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Active Regions ◽  
Short Term ◽  
Solar Active Regions ◽  
Solar Eruptions ◽  
Dimensional Reconstruction

AbstractIt is well known that the energy for solar eruptions comes from magnetic fields in solar active regions. Magnetic energy storage and dissipation are regarded as important physical processes in the solar corona. With incomplete theoretical modeling for eruptions in the solar atmosphere, activity forecasting is mainly supported with statistical models. Solar observations with high temporal and spatial resolution continuously from space well describe the evolution of activities in the solar atmosphere, and combined with three dimensional reconstruction of solar magnetic fields, makes numerical short-term (within hours to days) solar activity forecasting possible. In the current report, we propose the erupting frequency and main attack direction of solar eruptions as new forecasts and present the prospects for numerical short-term solar activity forecasting based on the magnetic topological framework in solar active regions.

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