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 The Influence of Binarity on Stellar Activity

2006 ◽  
Vol 2 (S240) ◽  
pp. 442-452 ◽  
Author(s):  
Katalin Oláh
Keyword(s):  
Binary Systems ◽  
Magnetic Energy ◽  
Theoretical Calculations ◽  
Deep Convection ◽  
Magnetic Activity ◽  
Close Binary ◽  
Convective Envelope ◽  
Flux Tubes ◽  
Gravitational Forces ◽  
Magnetic Flux Tubes

AbstractActivity of late type stars is enhanced by fast rotation, which is maintained in nearly synchronized close binary systems. Magnetic activity originates in the deep convection zones of stars from where magnetic flux tubes emerge to their surfaces. The gravitational forces in binaries help the clustering of activity features giving rise to active longitudes. These preferred longitudes are observed in binaries from dwarfs to giants. Differential rotation is found in many active stars that are components of binary systems. If these binaries are circularized and nearly synchronized, then there will be a corotation latitude in their surfaces, and its position can be determined by observations and by theoretical calculations. Enhanced activity in binaries could have a reverse effect as well: strong magnetism in a binary component can modify the orbital period by the cyclic exchange of kinetic and magnetic energy in its convective envelope.

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>

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 Semiannual and annual variations in the height of the ionospheric F2-peak

2000 ◽  
Vol 18 (3) ◽  
pp. 285-299 ◽  
Author(s):  
H. Rishbeth ◽  
K. J. F. Sedgemore-Schulthess ◽  
T. Ulich
Keyword(s):  
Solar Activity ◽  
Computational Models ◽  
Annual Variation ◽  
Late Summer ◽  
Early Summer ◽  
Atmospheric Composition ◽  
Annual Variations ◽  
Composition And Structure ◽  
Semiannual Variation ◽  
Quiet Day

Abstract. Ionosonde data from sixteen stations are used to study the semiannual and annual variations in the height of the ionospheric F2-peak, hmF2. The semiannual variation, which peaks shortly after equinox, has an amplitude of about 8 km at an average level of solar activity (10.7 cm flux = 140 units), both at noon and midnight. The annual variation has an amplitude of about 11 km at northern midlatitudes, peaking in early summer; and is larger at southern stations, where it peaks in late summer. Both annual and semiannual amplitudes increase with increasing solar activity by day, but not at night. The semiannual variation in hmF2 is unrelated to the semiannual variation of the peak electron density NmF2, and is not reproduced by the CTIP and TIME-GCM computational models of the quiet-day thermosphere and ionosphere. The semiannual variation in hmF2 is approximately "isobaric", in that its amplitude corresponds quite well to the semiannual variation in the height of fixed pressure-levels in the thermosphere, as represented by the MSIS empirical model. The annual variation is not "isobaric". The annual mean of hmF2 increases with solar 10.7 cm flux, both by night and by day, on average by about 0.45 km/flux unit, rather smaller than the corresponding increase of height of constant pressure-levels in the MSIS model. The discrepancy may be due to solar-cycle variations of thermospheric winds. Although geomagnetic activity, which affects thermospheric density and temperature and therefore hmF2 also, is greatest at the equinoxes, this seems to account for less than half the semiannual variation of hmF2. The rest may be due to a semiannual variation of tidal and wave energy transmitted to the thermosphere from lower levels in the atmosphere.Key words: Atmospheric composition and structure (thermosphere - composition and chemistry) - Ionosphere (mid-latitude ionosphere)

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.

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 Theoretical Calculations of the Seasonal and Solar Activity Variations for Ionospheric Collision Frequency and Debye Length over Baghdad City

2017 ◽  
Vol 27 (4) ◽  
Author(s):  
Ali Hussein Ni'ma
Keyword(s):  
Solar Activity ◽  
Collision Frequency ◽  
Theoretical Calculations ◽  
Molecular Nitrogen ◽  
Debye Length ◽  
Maximum Height ◽  
Atmospheric Gases ◽  
Height Range ◽  
Singly Charged ◽  
Charged Ions

In this study, two important ionospheric factors have been calculated, the collision frequency of electron and Deby length for a height range from 80 Km to a height approaching the maximum height of the F2 region of the ionosphere above the Earth's surface. Both above factors have been calculated for two different levels of solar activity and for two seasons (winter and summer). Also, six months were adopted for every level of solar activity and season. The estimation of collision frequency of electron is depends on the contribution of neutral constituents and ions. Three neutral atmospheric gases have been adopted to calculate the collision frequency, Molecular and atomic oxygen O2 and O respectively and molecular nitrogen N2, as well as the singly charged ions were taken into account in calculation.

scholarly journals AIM-E auroral ionosphere model adjustment for the regular E layer

2021 ◽  
Vol 7 (1) ◽  
pp. 41-46
Author(s):  
Vera Nikolaeva ◽  
Evgeniy Gordeev ◽  
Denis Rogov ◽  
Aleksandr Nikolaev
Keyword(s):  
Electron Density ◽  
Input Parameter ◽  
Magnetic Activity ◽  
Auroral Zone ◽  
Auroral Ionosphere ◽  
Solar Radio Flux ◽  
Ionosphere Model ◽  
E Region ◽  
Ap Index ◽  
Euv Spectrum

The E-Region Auroral Ionosphere Model (AIM-E) was developed to determine the chemical composition and electron density in the auroral zone at E-layer heights (90–150 km). Solar and magnetic activity input parameters for AIM-E are the three-hour Ap index and the daily solar radio flux at a wavelength of 10.7 cm (index F10.7). In this paper, we compare AIM-E calculations of the electron density for the daytime with EUV radiation spectrum specified in two different ways: 1) the EUV spectrum theoretically calculated using the F10.7 index as an input parameter; 2) using TIMED satellite direct measurements of the EUV spectrum. We have corrected the EUVAC EUV radiation model to specify a photoionization source in AIM-E. Calculations of regular E-region critical frequencies show good agreement with the vertical sounding data from Russian high-latitude stations. Results we obtained make it possible to do a quick on-line assessment of the regular E layer, using the daily index F10.7 as an input parameter.

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