scholarly journals On the seasonal dependence of relativistic electron fluxes

2010 ◽  
Vol 28 (5) ◽  
pp. 1101-1106 ◽  
Author(s):  
S. G. Kanekal ◽  
D. N. Baker ◽  
R. L. McPherron
Keyword(s):  
Solar Cycle ◽  
Relativistic Electron ◽  
Solar Wind Speed ◽  
Time Lag ◽  
Outer Zone ◽  
Cycle Phase ◽  
Relativistic Electrons ◽  
Phase Dependence ◽  
Autumnal Equinox ◽  
Seasonal Dependence

Abstract. The nature of the seasonal dependence of relativistic electron fluxes in the Earth's outer zone is investigated using 11 years of data from sensors onboard the SAMPEX spacecraft. It is found that, the relativistic electron fluxes show a strong semiannual modulation. However, the highest electron fluxes occur at times well away from the nominal equinoxes, lagging them by about 30 days. The time lag also shows a solar cycle phase dependence for the peak fluxes. The electron peak fluxes lag the vernal equinox by almost 60 days during the ascending phase of the solar cycle while the time lag near the autumnal equinox remains unchanged. The observed times of the peak electron fluxes during the descending phase of the solar cycle agrees most closely with the Russel-Mcpherron effect and less so with the equinoctial effect even after including propagation effects for finite solar wind speed. The observed times of the electron peaks are in disagreement with the axial effect. The asymmetrical response of the relativistic electrons during the ascending part of the solar cycle remains a puzzle.

Solar Cycle Phase Dependence of Supergranular Fractal Dimension

2011 ◽  
Vol 32 (1-2) ◽  
pp. 265-268
Author(s):  
U. Paniveni ◽  
V. Krishan ◽  
J. Singh ◽  
R. Srikanth
Keyword(s):  
Fractal Dimension ◽  
Solar Cycle ◽  
Cycle Phase ◽  
Phase Dependence

scholarly journals Geomagnetically Quiet Period Analysis of Relativistic Electrons, Auroral Precipitation, Joule Heating, and Ring Current During the Years of 1999, 2000 and 2004

2021 ◽  
Vol 7 (2) ◽  
pp. 126-137
Author(s):  
R. K. Mishra ◽  
A. Gautam ◽  
P. Poudel ◽  
N. Parajuli ◽  
A. Silwal ◽  
...  
Keyword(s):  
Relativistic Electron ◽  
Joule Heating ◽  
Time Variation ◽  
Ring Current ◽  
Time Lag ◽  
Winter Season ◽  
Relativistic Electrons ◽  
Quiet Time ◽  
Electron Population ◽  
Cross Correlation Analysis

This work presents the study of the quietest time variation in relativistic electrons, auroral precipitation, ring current, and joule heating during 1999, 2000, and 2004. Geostationary Operational Environmental Satellite (GOES) data on relativistic electrons with energies above 0.6 MeV, 2 MeV, and 4 MeV were analyzed. The time-series analysis of the relativistic electrons over a 24-hour averaged interval reveals a precise 24-hour modulation of the relativistic electron population during all seasons for energies above 0.6 MeV and 2 MeV, and during the winter season for higher energies above 4 MeV. In addition, relativistic electron fluxes at energies above 0.6 MeV and above 2 MeV were higher during the descending phase of the solar cycle compared to the ascending and solar-maximum phases. The cross-correlation analysis presented a strong correlation of Joule heating, ring current, and auroral precipitation with the relativistic electron population in three energy bands considered, as indicated by the zero-time lag. Studying the quiet time variation of relativistic electrons will lead to more complete ionospheric models, which were previously limited to the geomagnetically disturbed period.

scholarly journals One-Day-Shock, Two-Days-Shock and Three-Days-Shocks foF2 Diurnal Variation with Solar Cycle Phases at Ouagadougou Station from 1966 to 1998. Comparison with IRI 2012 Predictions

2019 ◽  
Vol 12 (1) ◽  
pp. 38
Author(s):  
Abdoul-kader SEGDA ◽  
Doua Allain GNABAHOU ◽  
Frédéric OUATTARA
Keyword(s):  
Solar Cycle ◽  
Time Variation ◽  
Solar Minimum ◽  
The Other ◽  
Cycle Phase ◽  
Minimum Phase ◽  
Solar Cycles ◽  
Night Time ◽  
Maximum Phase ◽  
Phase Dependence

The present work concerns foF2 time variation at Ouagadougou station for three solar cycles (from cycle 20 to cycle 22). We not only investigate solar cycle phase dependence under shock activity that is divided into one-shock-activity, two-shock-activity and three-shock-activity but also compare the IRI 2012 model values with the data carried out at Ouagadougou station. This study reveals that there is no one-day-shock during solar minimum phase. For the other solar cycle phases IRI 2012 reproduces the ionosphere electrodynamics at daytime except during the increasing phase. During night time the model is not suitable. The best subroutine under one-day-shock activity is URSI for increasing and decreasing phases. During the maximum phase it is CCIR. For two-days-shock activity IRI 2012 reproduces the ionosphere electrodynamics during the minimum and the increasing phases. The best subroutine is CCIR during the minimum phase and URSI for the other solar cycle phases. For three-days-shock activity IRI 2012 is not suitable. The best model is URSI for all solar cycle phases.

On the effect of ULF waves on the outer radiation belt during geomagnetic storms

2021 ◽  
Author(s):  
Christopher Lara ◽  
Pablo S. Moya ◽  
Victor Pinto ◽  
Javier Silva ◽  
Beatriz Zenteno
Keyword(s):  
Relativistic Electron ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Cumulative Effect ◽  
Radiation Belts ◽  
Ulf Waves ◽  
Relativistic Electrons ◽  
Relative Role ◽  
Outer Radiation Belt ◽  
Ulf Wave

<p>The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.</p>

scholarly journals Seasonal-longitudinal variability of equatorial plasma bubbles

2004 ◽  
Vol 22 (9) ◽  
pp. 3089-3098 ◽  
Author(s):  
W. J. Burke ◽  
C. Y. Huang ◽  
L. C. Gentile ◽  
L. Bauer
Keyword(s):  
Solar Cycle ◽  
Phase Shifts ◽  
Linear Growth Rate ◽  
Cycle Phase ◽  
Loss Cone ◽  
Plasma Bubbles ◽  
Equatorial Plasma Bubbles ◽  
Evening Sector ◽  
Radiation Belt Electrons ◽  
Longitudinal Variability

Abstract. We compare seasonal and longitudinal distributions of more than 8300 equatorial plasma bubbles (EPBs) observed during a full solar cycle from 1989-2000 with predictions of two simple models. Both models are based on considerations of parameters that influence the linear growth rate, γRT, of the generalized Rayleigh-Taylor instability in the context of finite windows of opportunity available during the prereversal enhancement near sunset. These parameters are the strength of the equatorial magnetic field, Beq, and the angle, α, it makes with the dusk terminator line. The independence of α and Beq from the solar cycle phase justifies our comparisons. We have sorted data acquired during more than 75000 equatorial evening-sector passes of polar-orbiting Defense Meteorological Satellite Program (DMSP) satellites into 24 longitude and 12 one-month bins, each containing ~250 samples. We show that: (1) in 44 out of 48 month-longitude bins EPB rates are largest within 30 days of when α=0°; (2) unpredicted phase shifts and asymmetries appear in occurrence rates at the two times per year when α≈0°; (3) While EPB occurrence rates vary inversely with Beq, the relationships are very different in regions where Beq is increasing and decreasing with longitude. Results (2) and (3) indicate that systematic forces not considered by the two models can become important. Damping by interhemispheric winds appears to be responsible for phase shifts in maximum rates of EPB occurrence from days when α=0°. Low EPB occurrence rates found at eastern Pacific longitudes suggest that radiation belt electrons in the drift loss cone reduce γRT by enhancing E-layer Pedersen conductances. Finally, we analyze an EPB event observed during a magnetic storm at a time and place where α≈-27°, to illustrate how electric-field penetration from high latitudes can overwhelm the damping effects of weak gradients in Pedersen conductance near dusk.

scholarly journals Cell-cycle phase-dependence of drug-induced cycle progression delay.

1979 ◽  
Vol 27 (1) ◽  
pp. 470-473 ◽  
Author(s):  
W Göhde ◽  
M Meistrich ◽  
R Meyn ◽  
J Schumann ◽  
D Johnston ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromosomal Abnormalities ◽  
Cell Cycle Phase ◽  
Cycle Phase ◽  
Drug Induced ◽  
Phase Dependence ◽  
Cycle Progression ◽  
G2 Phase ◽  
Phase Progression ◽  
Pulse Cytophotometry

The effect of adriamycin on cell cycle phase progression of CHO cells synchronized into the various phases of the cell cycle by elutriation was investigated by high resolution pulse cytophotometry. Cells treated in all phases of the cell cycle showed delay in their subsequent progression. In addition to the wellknown block of cells in the G2-phase, a delay in passage of cells from G1 to S and a decreased rate of transit through the S-phase were observed. A broadening of the DNA distributions of the treated cells was observed after cell division indicating induction of chromosomal abnormalities.

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