Engineering topics

Lyatsky, Sonya

Publications and source records attributed to Lyatsky, Sonya.

3 records

NASA NTRS2016

Penetration of Magnetosheath Plasma into Dayside Magnetosphere: 1. Density, Velocity, and Rotation

In this study, we examine a large number of plasma structures (filaments), observed with the Cluster spacecraft during 2 years (2007-2008) in the dayside magnetosphere but consisting of magnetosheath plasma. To reduce the effects observed in the cusp regions and on magnetosphere flanks, we consider these events predominantly inside the narrow cone less than 30 about the subsolar point. Two important features of these filaments are (i) their stable antisunward (earthward) motion inside the magnetosphere, whereas the ambient magnetospheric plasma moves usually in the opposite direction (sunward), and (ii) between these filaments and the magnetopause, there is a region of magnetospheric plasma, which separates these filaments from the magnetosheath. The stable earthward motion of these magnetopause show the possible disconnection of these filaments from the magnetosheath, as suggested earlier by many researchers. The results also show that these events cannot be a result of back-and-forth motions of magnetopause position or surface waves propagating on the magnetopause. Another important feature of these filaments is their rotation about the filament axis, which might be a result of their passage through the velocity shear on magnetopause boundary. After crossing the velocity shear, the filaments get a rotational velocity, which has opposite directions in the noon-dusk and noon-dawn sectors. This rotation velocity may be an important factor, supporting the stability of these filaments and providing their motion into the magnetosphere.

Lyatsky, Wladislaw↗

NASA NTRS2016

Effect of Interhemispheric Currents on Equivalent Ionospheric Currents in Two Hemispheres: Simulation Results

In this research, we used numerical simulation to study the effect of interhemispheric field-aligned currents (IHCs), going between two conjugate ionospheres in two hemispheres, on the equivalent ionospheric currents (EICs). We computed the maps of these EICs In two hemispheres during summer-winter conditions, when the effect of the IHCs is especially significant. The main results may be summarized as follows. In winter hemisphere, the IHCs may significantly exceed and be a substitute for the local R1 currents, and they may strongly affect the magnitude, location, and direction of the EICs In the nightside winter auroral ionosphere. While in summer polar cap the EICs tend to flow sunward, and in winter polar cap the EICs turn toward dawn due to the effect of the IHCs. The well-known reversal in the direction of the EICs in the vicinity of the midnight meridian, in winter hemisphere, is observed not at the polar caps boundary (as usually expected) but equatorward of this boundary in the region of the IHCs location. The IHCs in winter hemisphere may be, in fact, not only a substitute for the R1 currents but also the major source of the Westward Auroral Electrojet, observed In both hemispheres during substorm activity.

Lyatsky, Sonya↗

NASA NTRS2015

Effect of Interhemispheric Field-Aligned Currents on Region-1 Currents

An asymmetry in ionospheric conductivity between two hemispheres results in the formation of additional, interhemispheric field-aligned currents flowing between conjugate ionospheres within two auroral zones. These interhemispheric currents are especially significant during summer-winter conditions when there is a significant asymmetry in ionospheric conductivity in two hemispheres. In such conditions, these currents may be comparable in magnitude with the Region 1 field-aligned currents. In this case, the R1 current is the sum of two FACs: one is going from to the solar wind, and another is flowing between conjugate ionospheres. These interhemispheric currents can also cause the formation of auroras extended along the nightside polar cap boundary, which may be related to the so-called double auroral oval. In this study, we present the results of analytical and numerical solutions for the interhemispheric currents and their effect on the Region 1 currents.

interhemispherical currents↗