Scintillation and EISCAT investigations of gradient-drift irregularities in the high latitude ionosphere

Kersley, L.; Russell, C. D.; Pryse, S. E.

doi:10.1016/0021-9169(89)90075-5

Cited by 9 publications

(4 citation statements)

References 10 publications

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“…It is known that small-scale irregularities, which can exist in the ionosphere, are predominately magnetic field aligned. The Earth's ionosphere can contain short-scale irregularities, having cross-section diameters of about hundreds of meters [8][9][10][11]. Also, radio aurora or small-scale turbulence of the E layer is the well-known example of short-scale irregularities [12].…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of the Time Evolution of Small-Scale Irregularities in the F-Layer Ionospheric Plasma

Мингалев

Mingaleva

Melnik

et al. 2011

International Journal of Geophysics

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Dynamics of magnetic field-aligned small-scale irregularities in the electron concentration, existing in the F-layer ionospheric plasma, is investigated with the help of a mathematical model. The plasma is assumed to be a rarefied compound consisting of electrons and positive ions and being in a strong, external magnetic field. In the applied model, kinetic processes in the plasma are simulated by using the Vlasov-Poisson system of equations. The system of equations is numerically solved applying a macroparticle method. The time evolution of a plasma irregularity, having initial cross-section dimension commensurable with a Debye length, is simulated during the period sufficient for the irregularity to decay completely. The results of simulation indicate that the small-scale irregularity, created initially in the F-region ionosphere, decays accomplishing periodic damped vibrations, with the process being collisionless.

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Section: Introductionmentioning

confidence: 99%

Numerical Simulation of the Time Evolution of Small-Scale Irregularities in the F-Layer Ionospheric Plasma

Мингалев

Mingaleva

Melnik

et al. 2011

International Journal of Geophysics

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“…Plasma patches, amorphous “islands” of high electron concentration observed most frequently in the winter nighttime polar cap ionosphere [ Hunsucker and Hargreaves , 2003], are associated with scintillation of Global Positioning System (GPS) L1 band radio signals [ Chaturvedi et al , 1994; Coley and Heelis , 1995; Gondarenko and Guzdar , 1999, 2001, 2004a, 2004b, 2006a, 2006b; Gondarenko et al , 2003, 2005; Kersley et al , 1989; Kivanç and Heelis , 1997; Sojka et al , 1998]. Such patches are hundreds to thousands of kilometers in scale and appear only when the interplanetary magnetic field points southward and the geomagnetic field is disturbed [ Hunsucker and Hargreaves , 2003].…”

Section: Introductionmentioning

confidence: 99%

“…Two mechanisms of irregularity formation in plasma patches have been proposed. The most thoroughly studied is the gradient drift instability (GDI) [ Chaturvedi et al , 1994; Coley and Heelis , 1995; Gondarenko and Guzdar , 1999, 2001, 2004a, 2004b, 2006a, 2006b; Gondarenko et al , 2003, 2005; Kersley et al , 1989; Kivanç and Heelis , 1997; Sojka et al , 1998]. This is a plasma instability that can occur when an electric field, a magnetic field, and a gradient in electron concentration are all present and mutually perpendicular to each other.…”

Section: Introductionmentioning

confidence: 99%

Turbulent times in the northern polar ionosphere?

et al. 2010

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[1] A model is presented of the growth rate of turbulently generated irregularities in the electron concentration of northern polar cap plasma patches. The turbulence is generated by the short-term fluctuations in the electric field imposed on the polar cap ionosphere by electric field mapping from the magnetosphere. The model uses an ionospheric imaging algorithm to specify the state of the ionosphere throughout. The growth rates are used to estimate mean amplitudes for the irregularities, and these mean amplitudes are compared with observations of the scintillation indices S 4 and s by calculating the linear correlation coefficients between them. The scintillation data are recorded by GPS L1 band receivers stationed at high northern latitudes. A total of 13 days are analyzed, covering four separate magnetic storm periods. These results are compared with those from a similar model of the gradient drift instability (GDI) growth rate. Overall, the results show better correlation between the GDI process and the scintillation indices than for the turbulence process and the scintillation indices. Two storms, however, show approximately equally good correlations for both processes, indicating that there might be times when the turbulence process of irregularity formation on plasma patches may be the controlling one.

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“…However other experiments involving coordinated scintillation measurements and incoherent scatter radar, the latter to monitor t.he background ionosphere, have provided evidence for several possible formation mechanisms for irregularities in the auroral ionosphere, including unstable gradients [Kersley et al, 1989], soft particle precipitation and velocity shears [Kersley et al, 1988]. The equatorward boundary of the auroral oval is displaced by many degrees of latitude farther poleward than the equatorward edge of the F region irregularity boundary (e.g., compare Figures 1, 2, and 3).…”

Section: The Equatorward Boundary Of the Irregularity Regionmentioning

confidence: 99%

The sunspot cycle and “auroral” F layer irregularities

Aarons¹,

Kersley²,

Rodger³

1995

Radio Science

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The use of the word “aurora” for many different observations at high latitudes has limited the concepts involved; this is particularly true for F region irregularities. Observations setting the position of the auroral oval (Starkov and Fel'dshtein, 1970) were made using primarily the 555.7‐nm green line, which is emitted predominantly at E layer heights. These observations have shown that the change in position of the auroral oval for low values of Kp as a function of sunspot cycle is of the order of 1° to 2° between sunspot maximum and sunspot minimum. However, irregularities in the F region show much larger solar cycle variations in the locations of the equatorward boundary, typically 10°. A review of scintillation data indicates that at a given auroral latitude, the scintillation activity increases with sunspot number. In addition, for a constant scintillation intensity, the equatorward boundary moves to lower latitudes as sunspot maximum is approached. We review existing spread F studies and show that for quiet geomagnetic conditions, there is lower occurrence during years of low sunspot numbers than during years of high sunspot numbers. However, the spread F index, related to Δ ƒ/ƒ0F2, is higher during years of low sunspot number than during years of high sunspot number. We demonstrate that this apparent dichotomy can be reconciled by using a new method of normalizing the spread F index by the maximum electron concentration of the F layer. We briefly discuss the possible explanations for the observed solar cycle variations of irregularity occurrence in terms of the absolute values and gradients of electron concentration and the E region conductivity.

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Scintillation and EISCAT investigations of gradient-drift irregularities in the high latitude ionosphere

Cited by 9 publications

References 10 publications

Numerical Simulation of the Time Evolution of Small-Scale Irregularities in the F-Layer Ionospheric Plasma

Numerical Simulation of the Time Evolution of Small-Scale Irregularities in the F-Layer Ionospheric Plasma

Turbulent times in the northern polar ionosphere?

The sunspot cycle and “auroral” F layer irregularities

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