scholarly journals Features of the F3 layer occurrence over the equatorial location of Trivandrum

2010 ◽  
Vol 28 (9) ◽  
pp. 1741-1747 ◽  
Author(s):  
V. Sreeja ◽  
S. Ravindran ◽  
T. K. Pant
Keyword(s):  
Solar Activity ◽  
Magnetic Activity ◽  
The Other ◽  
Layer Formation ◽  
Percentage Occurrence

Abstract. The general features of the F3 layer occurrence over the magnetic equatorial location of Trivandrum (8.5° N; 77° E; dip lat ~0.5° N) in India during the period from 1996–2005 are presented using the ionosonde observations. The study brings out that the F3 layer occurrence over Trivandrum is weak and rare compared to the other equatorial locations. The F3 layer occurrence is relatively more pronounced during the magnetically active conditions, thus indicating the dependence of the layer formation over Trivandrum on magnetic activity. It is also observed that the percentage occurrence of the F3 layer decreases with increasing solar activity.

Solar activity and its impact on the mid-latitude trough during geomagnetic storms

2021 ◽  
Author(s):  
Dorota Przepiórka ◽  
Barbara Matyjasiak ◽  
Agata Chuchra ◽  
Hanna Rothkaehl
Keyword(s):  
Solar Activity ◽  
Geomagnetic Activity ◽  
Evolutionary History ◽  
Geomagnetic Storms ◽  
Magnetic Activity ◽  
Topside Ionosphere ◽  
Auroral Region ◽  
Distinct Structure ◽  
Highly Sensitive ◽  
Rapid Changes

<p>Mid-latitude trough (MIT) is the distinct structure observed in Earth’s ionosphere at high latitudes especially at the nighttimes. The phenomenon is observed at both hemispheres. As it resides at the topside ionosphere in the sub-auroral region, its behaviour and properties are highly sensitive to the solar and geomagnetic activity. Generally as the geomagnetic activity is more pronounced the MIT is observed at lower latitudes, it also deepens and becomes much more distinct in comparison to the low magnetic activity periods. MIT responds as well to the rapid changes in geomagnetic conditions, as are the geomagnetic storms, mainly caused by the CMEs. </p><p>Based on the observations gathered by DEMETER data between 2005 and 2010 years  we present a set of geomagnetic storm cases and how the MIT properties has been changing as the storm evolves. We also discuss how it corresponds to the current solar activity and their evolutionary history  described by a set of different parameters.</p>

Observational Data: Overview and Fundamentals

2017 ◽  
Author(s):  
Sarbani Basu ◽  
William J. Chaplin
Keyword(s):  
Time Series ◽  
Magnetic Activity ◽  
The Other ◽  
Doppler Velocity ◽  
Near Surface ◽  
Photometric Observations ◽  
Typical Data ◽  
Observational Technique ◽  
Surface Convection ◽  
Basic Content

This chapter considers some of the fundamentals associated with the basic datasets from which the asteroseismic and other intrinsic stellar parameters are extracted (usually lightcurves of photometric observations or time series of Doppler velocity observations). In particular, the chapter looks at how the observational technique affects the amplitudes of the observed oscillations. It also introduces the other intrinsic stellar signals that manifest in the data, specifically those due to granulation (signatures of near-surface convection) and magnetic activity. The chapter's aim is to familiarize the reader with the basic content of the typical data and lay some important groundwork for the detailed presentations that follow in the next two chapters.

scholarly journals Model results for the ionospheric lower transition height over mid-latitude

2004 ◽  
Vol 22 (6) ◽  
pp. 2037-2045 ◽  
Author(s):  
J. Lei ◽  
L. Liu ◽  
W. Wan ◽  
S.-R. Zhang
Keyword(s):  
Solar Activity ◽  
Theoretical Calculations ◽  
Magnetic Activity ◽  
Composition Analysis ◽  
Time Asymmetry ◽  
Quantitative Studies ◽  
Semiannual Variation ◽  
Lower Transition ◽  
Ap Index ◽  
Opposite Tendency

Abstract. Theoretical calculations of the ionospheric lower transition height (LTH), a level of equal O+ and molecular ion densities, were performed and compared with empirical models by Zhang et al. (1996). This paper represents a substantial extension of the prior work by including the AE-C data of ion composition analysis and by detailed quantitative studies of the LTH simulation, and by creating a new LTH empirical model based on our simulations. Results show that: (1) the calculated LTH, in general, is lowest near 11-13LT and reaches the diurnal maximum after midnight (about 01~02LT). The local time asymmetry becomes more evident in summer, when the time of minimum shifts to 16LT. (2) The simulated LTH presents a dominant, semiannual variation during nighttime, and a pronounced annual variation during daytime. (3) The simulated LTH increases with solar activity at night and decreases by day, while the standard IRI option has an opposite tendency at night in summer and equinox. Therefore, the day-night difference of simulated LTH significantly increases with solar activity. (4) Both daytime and nighttime LTHs, tend to increase with the increasing geomagnetic activity Ap index, with a mean slope about 0.1455km per Ap unit. (5) The diurnal variation of LTH is found to be more than 20 km, which is much larger than the seasonal variation under F107=100 and Ap=10. Thus, the diurnal and solar activity variations of LTH are more pronounced than its seasonal and magnetic activity variations.

scholarly journals Reflection of Solar Activity Dynamics in Radionuclide Data

Radiocarbon ◽  
1992 ◽  
Vol 34 (2) ◽  
pp. 207-212 ◽  
Author(s):  
A. V. Blinov ◽  
M. N. Kremliovskij
Keyword(s):  
Nonlinear Dynamics ◽  
Solar Activity ◽  
Numerical Methods ◽  
Chaotic Behavior ◽  
Magnetic Activity ◽  
Data Sets ◽  
Cosmogenic Nuclide ◽  
Proxy Records ◽  
Solar Magnetic Activity ◽  
Activity Dynamics

Variability of solar magnetic activity manifested within sunspot cycles demonstrates features of chaotic behavior. We have analyzed cosmogenic nuclide proxy records for the presence of the solar activity signals. We have applied numerical methods of nonlinear dynamics to the data showing the contribution of the chaotic component. We have also formulated what kind of cosmogenic nuclide data sets are needed for investigations on solar activity.

scholarly journals Temporal variations of different solar activity indices through the solar cycles 21-23

2017 ◽  
pp. 59-70 ◽  
Author(s):  
Ü.D. Gäoker ◽  
J. Singh ◽  
F. Nutku ◽  
M. Priyal
Keyword(s):  
Solar Activity ◽  
Detailed Comparison ◽  
Temporal Variations ◽  
Total Solar Irradiance ◽  
Magnetic Activity ◽  
Unexpected Finding ◽  
Solar Cycles ◽  
Percentage Decrease ◽  
Solar Activity Indices ◽  
Activity Indices

Here, we compare the sunspot counts and the number of sunspot groups (SGs) with variations of total solar irradiance (TSI), magnetic activity, Ca II K-flux, faculae and plage areas. We applied a time series method for extracting the data over the descending phases of solar activity cycles (SACs) 21, 22 and 23, and the ascending phases 22 and 23. Our results suggest that there is a strong correlation between solar activity indices and the changes in small (A, B, C and H-modified Zurich Classification) and large (D, E and F) SGs. This somewhat unexpected finding suggests that plage regions substantially decreased in spite of the higher number of large SGs in SAC 23 while the Ca II K-flux did not decrease by a large amount nor was it comparable with SAC 22 and relates with C and DEF type SGs. In addition to this, the increase of facular areas which are influenced by large SGs, caused a small percentage decrease in TSI while the decrement of plage areas triggered a higher decrease in the magnetic field flux. Our results thus reveal the potential of such a detailed comparison of the SG analysis with solar activity indices for better understanding and predicting future trends in the SACs.

scholarly journals Influence of the semidiurnal lunar tide on the equatorial plasma bubble zonal drifts over Brazil

2021 ◽  
Author(s):  
Igo Paulino ◽  
Ana Roberta Paulino ◽  
Amauri F. Medeiros ◽  
Cristiano M. Wrasse ◽  
Ricardo A. Buriti ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Southern Hemisphere ◽  
Electron Concentration ◽  
The Other ◽  
High Solar Activity ◽  
Lunar Tide ◽  
Plasma Bubble ◽  
Other Hand ◽  
Equatorial Plasma Bubble

Abstract. Using OI6300 airglow images collected over São João do Cariri (7.4° S, 36.5° W) from 2000 to 2007, the equatorial plasma bubble (EPB) zonal drifts were calculated. A strong day-to-day variability was observed in the EPB zonal drifts due to the complexity in the dynamics of the nighttime thermosphere-ionosphere system near the equator. The present work investigated the contribution of the semidiurnal lunar tide M2 for the EPB zonal drifts. On average, the M2 contributes 5.6 % to the variability of the EPB zonal drifts, presenting an amplitude of 3.1 m/s. The results showed that the M2 amplitudes in the EPB zonal drifts were solar cycle and seasonal dependents. The amplitude of the M2 was stronger during the high solar activity reaching over 10 % of the EPB zonal drift average. Regarding the seasons, during the southern hemisphere summer, the M2 amplitude was twice larger (12 %) compared to the equinox ones. The seasonality agrees with other observations of the M2 in the ionospheric parameters such as vertical drifts and electron concentration, for instance. On the other hand, the very large M2 amplitudes found during the high solar activity must be further investigated.

scholarly journals The Relationship Between Coronal Bright Points as Seen in He I ?10830 and the Evolution of the Photospheric Network Magnetic Fields

1985 ◽  
Vol 38 (6) ◽  
pp. 875 ◽  
Author(s):  
Karen L Harvey
Keyword(s):  
Solar Activity ◽  
Sunspot Number ◽  
Inverse Correlation ◽  
Opposite Polarity ◽  
Magnetic Polarity ◽  
The Other ◽  
Coronal Bright Points ◽  
Low Levels ◽  
The Relationship ◽  
Magnetic Network

Transient 'dark points' in He I,,10830 are found to be associated with small magnetic bipoles. The number of these dark points varies inversely with the sunspot number. Sampled over a solar cycle, about one-third of the dark points are associated with erupting magnetic flux (ephemeral regions) while the other two-thirds are associated with chance encounters of opposite magnetic polarity features. Since coronal bright points are associated with He I dark points, it is suggested that the inverse correlation of both of these events with the sunspot number results from the higher probability of chance encounters between magnetic network of opposite polarity (larger areas of mixed magnetic polarity) during low levels of solar activity.

scholarly journals Structural and Evolutionary Features of Flare-Producing Active Regions During 1988-1990

1993 ◽  
Vol 141 ◽  
pp. 388-390
Author(s):  
A. A. Golovko
Keyword(s):  
Solar Activity ◽  
Radio Emission ◽  
Solar Radio ◽  
Active Regions ◽  
Magnetic Activity ◽  
High Solar Activity ◽  
Solar Radio Emission ◽  
Evolutionary Features ◽  
Siberian Solar Radio Telescope ◽  
Flare Productivity

During the period of high solar activity (1988-1990) the Sayan and Baikal Observatories of the ISTP carried out observations of the chromosphere in the H-alpha line, the photosphere and of sunspot magnetic fields; at the Siberian Solar Radio Telescope, solar radio emission observations at 5.2 cm wavelength were made. Using those observations a study is made of the evolution of “centers of magnetic activity” (Bumba, 1986) in nine active regions with different flare productivity, for which the most complete observations were available. In three cases (NOAA Nos. 5229, 5643 and 5669) they were the targets of the cooperative international Max’91 program.

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