scholarly journals Properties of the F2-layer maximum density variability over Irkutsk under different levels of the solar and geomagnetic activity

10.12737/6558 ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 56-62 ◽  
Author(s):  
Марат Деминов ◽  
Marat Deminov ◽  
Галина Деминова ◽  
Galina Deminova ◽  
Гелий Жеребцов ◽  
...  
Keyword(s):  
Geomagnetic Activity ◽  
Maximum Density ◽  
Activity Level ◽  
Solar Activity Level ◽  
Absolute Value ◽  
Layer Maximum ◽  
First Approximation ◽  
Hourly Data ◽  
General Dispersion ◽  
Different Levels

Using hourly data (1958–1992) from Irkutsk ionosonde station, we analyzed properties of variability of the F2-layer maximum density, Nm, under different levels of the solar and geomagnetic activity. The standard deviation s(x) of Nm fluctuations relative to the quiet level (x=(Nm/Nm0–1)·100 %), and the average shift of these fluctuations x-ave were used as characteristics of this variability. For this purpose, the empirical model of the F2-layer maximum density for quiet magnetic conditions, Nm0, was constructed. The Nm variability was found to depend weakly on the solar activity level; in the first approximation, this dependence can be neglected. The Nm variability dependence on geomagnetic activity is among the principal ones, along with the dependences on local time and season. In general, dispersion of Nm fluctuations under quiet conditions is smaller than that during the periods of high geomagnetic activity. During the periods of high geomagnetic activity, however, the dispersion does not increase with the further growth of this activity, while the absolute value of shift x-ave (which is mainly negative under high geomagnetic activity) still increases with growing geomagnetic activity. As a result, if this activity is high enough, the condition |x-ave|>|s(x)| can be fulfilled.

scholarly journals The impact of IFRS-based accounting standards on earnings management: evidence from Malaysia

2016 ◽  
Vol 5 (1) ◽  
pp. 1
Author(s):  
Yosra Makni Fourati ◽  
Rania Chakroun Ghorbel
Keyword(s):  
Earnings Management ◽  
Financial Reporting ◽  
Emerging Market ◽  
Accounting Standards ◽  
Absolute Value ◽  
Financial Reporting Standards ◽  
Ifrs Adoption ◽  
Earning Quality ◽  
The Impact ◽  
Different Levels

This study aims to examine the consequences of International Financial Reporting Standards (IFRS) convergence in an emerging market. More specifically, we investigate whether the adoption of the new set of accounting standards in Malaysia is associated with lower earnings management. Using a sample of 3,340 firm-year observations across three reporting periods with different levels of IFRS adoption, we provide evidence that IFRS convergence improves earning quality. In particular, we find a significant decrease in the absolute value of discretionary acccruals in the partial IFRS-convergence period (2007-2011), whereas this effect is restrictive after the complete IFRS- implementation.

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 Offsets in the geomagnetic indices of the magnetospheric ring current

2021 ◽  
Vol 7 (3) ◽  
pp. 31-38
Author(s):  
Georgy Makarov
Keyword(s):  
Ring Current ◽  
Magnetic Disturbance ◽  
Absolute Value ◽  
Daily Average ◽  
Geomagnetic Indices ◽  
Asymmetric Component ◽  
Different Levels

The paper considers changes in the daily average values of the Dst, SYM-H, ASY-H, and ASY-D indices and their dependence on the level of magnetic disturbance for the period 1981–2016. These indices are geomagnetic characteristics of the magnetospheric ring current. It has been established that the indices of the asymmetric component of the ring current ASY-H and ASY-D during relatively magnetically quiet periods are not equal to zero. The values of the offsets in the dependences of the ASY-H and ASY-D indices on the level of magnetic disturbance have been determined. The behavior of the index of the degree of symmetry of the ring current, the ratio SYM-H / ASY-H, is analyzed during the year at different levels of disturbance. This ratio has been found to grow in absolute value with increasing disturbance and to exceed 1 at large disturbances (at Dst <–50).

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.

scholarly journals The dependence of plasma density in the topside ionosphere on the solar activity level

2007 ◽  
Vol 25 (6) ◽  
pp. 1337-1343 ◽  
Author(s):  
L. Liu ◽  
W. Wan ◽  
X. Yue ◽  
B. Zhao ◽  
B. Ning ◽  
...  
Keyword(s):  
Solar Activity ◽  
Plasma Density ◽  
Rate Of Change ◽  
Activity Level ◽  
Nonlinear Dependence ◽  
High Solar Activity ◽  
Topside Ionosphere ◽  
Ion Density ◽  
Solar Activity Level ◽  
F Region

Abstract. In this paper, the ten-year (1996–2005) total ion density Ni measurements from the Defense Meteorological Satellite Program (DMSP) spacecraft in the morning and evening (09:30 and 21:30 LT) sectors have been analyzed to explore the dependence of plasma densities in the topside ionosphere at middle and low latitudes on the solar activity level. Results indicate that there is a strong solar activity dependence of DMSP Ni at 848 km altitude, which has latitudinal and seasonal features. The plasma density in the topside ionosphere has an approximately linear dependence on daily F107 and a strongly nonlinear dependence on SEM/SOHO EUV, such that the change rate of Ni becomes greater with increasing solar EUV. This is quite different from the dependence of Ni near the F-Region peak (NmF2), at which the rate of change of NmF2 decreases with increasing solar EUV. The rate of change of Ni at the DMSP altitude is greatest in the latitude range where Ni is greatest during high solar activity. We suggest that this greater rate of change (or amplification effect) of Ni at the DMSP altitude is mainly a consequence of the solar activity variations of the topside scale height. The changes in the height of the F-Region peak (hmF2) and the density NmF2 play a secondary role.

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 Possible heliogeophysical effects on human physiological state

2008 ◽  
Vol 4 (S257) ◽  
pp. 65-67 ◽  
Author(s):  
Svetla Dimitrova
Keyword(s):  
Blood Pressure ◽  
Cosmic Rays ◽  
Healthy Volunteers ◽  
Geomagnetic Activity ◽  
Pulse Pressure ◽  
Pressure Pulse ◽  
Physiological State ◽  
Activity Increase ◽  
Hourly Data ◽  
The Mean

AbstractA group of 86 healthy volunteers was examined in periods of high solar and geomagnetic activity. In this study hourly Dst-index values and hourly data about intensity of cosmic rays were used. Results revealed statistically significant increments for the mean systolic and diastolic blood pressure, pulse pressure and subjective psycho-physiological complaints of the group with geomagnetic activity increase and cosmic rays intensity decrease.

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