scholarly journals A new pair of indices to describe the relationship between ionospheric disturbances and geomagnetic activity

2014 ◽  
Vol 119 (12) ◽  
Author(s):  
Zhou Chen ◽  
Jing‐Song Wang ◽  
Chun‐Ming Huang ◽  
Lin‐Feng Huang
Keyword(s):  
Geomagnetic Activity ◽  
Ionospheric Disturbances ◽  
The Relationship

scholarly journals Geomagnetic control of the spectrum of traveling ionospheric disturbances based on data from a global GPS network

2001 ◽  
Vol 19 (7) ◽  
pp. 723-731 ◽  
Author(s):  
E. L. Afraimovich ◽  
E. A. Kosogorov ◽  
O. S. Lesyuta ◽  
I. I. Ushakov ◽  
A. F. Yakovets
Keyword(s):  
Geomagnetic Activity ◽  
Time Derivative ◽  
Power Spectra ◽  
Small Scale ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Geomagnetic Disturbances ◽  
Absolute Level ◽  
Total Electron ◽  
Traveling Ionospheric Disturbances

Abstract. In this paper an attempt is made to verify the hypothesis of the role of geomagnetic disturbances as a factor in determining the intensity of traveling ionospheric disturbances (TIDs). To improve the statistical validity of the data, we have used the method involving a global spatial averaging of disturbance spectra of the total electron content (TEC). To characterize the TID intensity quantitatively, we suggest that a new global index of the degree of disturbance should be used, which is equal to the mean value of the rms variations in TEC within the selected range of spectral periods (of 20– 60 min, in the present case). The analysis has been made for a set of 100 to 300 GPS stations for 10 days with a different level of geomagnetic activity (Dst from 0 to –350 nT; the Kp index from 3 to 9). It was found that power spectra of daytime TEC variations in the range of 20–60 min periods under quiet conditions have a power-law form with the slope index k = –2.5. With an increase in the level of magnetic disturbance, there is an increase in the total intensity of TIDs, with a concurrent kink of the spectrum caused by an increase in oscillation intensity in the range of 20–60 min. The TEC variation amplitude is found to be smaller at night than during the daytime, and the spectrum decreases in slope, which is indicative of a disproportionate increase in the amplitude of the small-scale part of the spectrum. It was found that an increase in the level of geomagnetic activity is accompanied by an increase in the total intensity of TEC; however, it does not correlate with the absolute level of Dst, but rather with the value of the time derivative of Dst (a maximum correlation coefficient reaches –0.94). The delay of the TID response of the order of 2 hours is consistent with the view that TIDs are generated in auroral regions, and propagate equatorward with the velocity of about 300–400 m/s.Key words. Ionosphere (ionospheric disturbances; auroral ionosphere; equatorial ionopshere)

scholarly journals The correlation between solar and geomagnetic activity – Part 3: An integral response model

2011 ◽  
Vol 29 (6) ◽  
pp. 1005-1018 ◽  
Author(s):  
Z. L. Du
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Correlation Coefficient ◽  
Geomagnetic Activity ◽  
Decay Time ◽  
Response Model ◽  
Integral Response ◽  
Lag Times ◽  
The Relationship ◽  
Aa Index

Abstract. An integral response model is proposed to describe the relationship between geomagnetic activity (aa index) and solar activity (represented by sunspot number Rz): The aa at a given time t is the integral of Rz at past times (t'≤t) multiplied by an exponential decay factor of the time differences (e−(t−t')/τ), where τ is the decay time scale (~40 months). The correlation coefficient of aa with the reconstructed series based on this model (rf=0.85) is much higher than that of aa with Rz (r0=0.61). If this model is applied to each solar cycle, the correlation coefficient will be higher (rf=0.95). This model can naturally explain some phenomena related to aa and Rz, such as (i) the significant increase in the aa index (and its baseline) over the twentieth century; (ii) the longer lag times of aa to Rz at solar cycle maxima than at minima; and (iii) the variations in the correlations related to solar and Hale cycles. These results demonstrate that aa depends not only on the present Rz but also on past values. The profile of aa can be better predicted from Rz by this model than by point-point correspondence.

scholarly journals MLT dependence in the relationship between plasmapause, solar wind, and geomagnetic activity based on CRRES: 1990-1991

2016 ◽  
Vol 121 (5) ◽  
pp. 4397-4408 ◽  
Author(s):  
Mario Bandić ◽  
Giuli Verbanac ◽  
Mark B. Moldwin ◽  
Viviane Pierrard ◽  
Giovanni Piredda
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
The Relationship

scholarly journals Scintillations of Radio Sources and Geomagnetic Activity

1962 ◽  
Vol 15 (4) ◽  
pp. 568 ◽  
Author(s):  
OB Slee
Keyword(s):  
Magnetic Field ◽  
Radio Source ◽  
Geomagnetic Activity ◽  
Auroral Zone ◽  
Radio Sources ◽  
Present Communication ◽  
Earth’S Magnetic Field ◽  
K Index ◽  
Northern Latitudes ◽  
The Relationship

The relationship between variations in the Earth's magnetic field and radio source scintillation has been somewhat obscure since the first observation by Little and Maxwell (1952) that, for sources observed through the Northern Auroral Zone, the scintillation rate, but not the amplitude, was closely correlated with the planetary K index. Since then a number of observers, mainly situated in high northern latitudes, also found no relation between the scintillation amplitude and geomagnetic activity. It is the purpose of the present communication to show that at southern temperate latitudes a relationship does exist between these quantities.

scholarly journals Geomagnetic control of the <i>fo</i>F2 long-term trends

2000 ◽  
Vol 18 (6) ◽  
pp. 653-665 ◽  
Author(s):  
A. V. Mikhailov ◽  
D. Marin
Keyword(s):  
Geomagnetic Activity ◽  
Early Morning ◽  
Lower Latitude ◽  
Ionospheric Disturbances ◽  
Trend Magnitude ◽  
Layer Parameter ◽  
Long Term Trends ◽  
First Time ◽  
Further Development

Abstract. Further development of the method proposed by Danilov and Mikhailov is presented. The method is applied to reveal the foF2 long-term trends on 30 Northern Hemisphere ionosonde stations. Most of them show significant foF2 trends. A pronounced dependence of trend magnitude on geomagnetic (invariant) latitude is confirmed. Periods of negative/positive foF2 trends corresponding to the periods of long-term increasing/decreasing geomagnetic activity are revealed for the first time. Pronounced diurnal variations of the foF2 trend magnitude are found. Strong positive foF2 trends in the post-midnight-early-morning LT sector and strong negative trends during daytime hours are found on the sub-auroral stations for the period with increasing geomagnetic activity. On the contrary middle and lower latitude stations demonstrate negative trends in the early-morning LT sector and small negative or positive trends during daytime hours for the same period. All the morphological features revealed of the foF2 trends may be explained in the framework of contemporary F2-region storm mechanisms. This newly proposed F2-layer geomagnetic storm concept casts serious doubts on the hypothesis relating the F2-layer parameter long-term trends to the thermosphere cooling due to the greenhouse effect.Key words: Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances)

The relationship between DSCS III sunlit surface charging and geomagnetic activity indices

2000 ◽  
Vol 47 (6) ◽  
pp. 2224-2230 ◽  
Author(s):  
L.H. Krause ◽  
B.K. Dichter ◽  
D.J. Knipp ◽  
K.P. Ray
Keyword(s):  
Geomagnetic Activity ◽  
Surface Charging ◽  
The Relationship ◽  
Activity Indices

scholarly journals The Variation of Geomagnetic Storm Duration with Intensity

Solar Physics ◽  
2019 ◽  
Vol 294 (11) ◽  
Author(s):  
C. Haines ◽  
M. J. Owens ◽  
L. Barnard ◽  
M. Lockwood ◽  
A. Ruffenach
Keyword(s):  
Geomagnetic Storm ◽  
Geomagnetic Activity ◽  
Geomagnetic Disturbance ◽  
Nonlinear Behaviour ◽  
Superposed Epoch Analysis ◽  
Storm Intensity ◽  
Storm Duration ◽  
Average Profile ◽  
Log Normal ◽  
The Relationship

Abstract Variability in the near-Earth solar wind conditions can adversely affect a number of ground- and space-based technologies. Such space-weather impacts on ground infrastructure are expected to increase primarily with geomagnetic storm intensity, but also storm duration, through time-integrated effects. Forecasting storm duration is also necessary for scheduling the resumption of safe operating of affected infrastructure. It is therefore important to understand the degree to which storm intensity and duration are correlated. The long-running, global geomagnetic disturbance index, $\mathit{aa}$aa, has recently been recalibrated to account for the geographic distribution of the component stations. We use this $\mathit{aa}_{H}$aaH index to analyse the relationship between geomagnetic storm intensity and storm duration over the past 150 years, further adding to our understanding of the climatology of geomagnetic activity. Defining storms using a peak-above-threshold approach, we find that more intense storms have longer durations, as expected, though the relationship is nonlinear. The distribution of durations for a given intensity is found to be approximately log-normal. On this basis, we provide a method to probabilistically predict storm duration given peak intensity, and test this against the $\mathit{aa}_{H}$aaH dataset. By considering the average profile of storms with a superposed-epoch analysis, we show that activity becomes less recurrent on the 27-day timescale with increasing intensity. This change in the dominant physical driver, and hence average profile, of geomagnetic activity with increasing threshold is likely the reason for the nonlinear behaviour of storm duration.

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