scholarly journals A numerical model of the ionospheric signatures of time-varying magneticreconnection: I. ionospheric convection

2004 ◽  
Vol 22 (1) ◽  
pp. 73-91 ◽  
Author(s):  
M. Lockwood ◽  
S. K. Morley
Keyword(s):  
Numerical Model ◽  
Time Varying ◽  
Plasma Convection ◽  
Reconnection Rate ◽  
Ionospheric Convection ◽  
Ionospheric Conductivity ◽  
Geomagnetic Tail ◽  
Dayside Magnetopause ◽  
Potential Applications ◽  
General Time

Abstract. This paper presents a numerical model for predicting the evolution of the pattern of ionospheric convection in response to general time-dependent magnetic reconnection at the dayside magnetopause and in the cross-tail current sheet of the geomagnetic tail. The model quantifies the concepts of ionospheric flow excitation by Cowley and Lockwood (1992), assuming a uniform spatial distribution of ionospheric conductivity. The model is demonstrated using an example in which travelling reconnection pulses commence near noon and then move across the dayside magnetopause towards both dawn and dusk. Two such pulses, 8min apart, are used and each causes the reconnection to be active for 1min at every MLT that they pass over. This example demonstrates how the convection response to a given change in the interplanetary magnetic field (via the reconnection rate) depends on the previous reconnection history. The causes of this effect are explained. The inherent assumptions and the potential applications of the model are discussed. Key words. Ionosphere (ionosphere-magnetosphere interactions; plasma convection) – Magnetospheric physics (magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions)

scholarly journals A numerical model of the ionospheric signatures of time-varying magnetic reconnection: III. Quasi-instantaneous convection responses in the Cowley-Lockwood paradigm

2006 ◽  
Vol 24 (3) ◽  
pp. 961-972 ◽  
Author(s):  
S. K. Morley ◽  
M. Lockwood
Keyword(s):  
The Other ◽  
Closed Field ◽  
Time Varying ◽  
Residual Flow ◽  
Numerical Implementation ◽  
Ionospheric Convection ◽  
Dayside Magnetopause ◽  
History Of ◽  
Closed Field Line ◽  
Magnetopause Reconnection

Abstract. Using a numerical implementation of the cowlock92 model of flow excitation in the magnetosphere-ionosphere (MI) system, we show that both an expanding (on a ~12-min timescale) and a quasi-instantaneous response in ionospheric convection to the onset of magnetopause reconnection can be accommodated by the Cowley-Lockwood conceptual framework. This model has a key feature of time dependence, necessarily considering the history of the coupled MI system. We show that a residual flow, driven by prior magnetopause reconnection, can produce a quasi-instantaneous global ionospheric convection response; perturbations from an equilibrium state may also be present from tail reconnection, which will superpose constructively to give a similar effect. On the other hand, when the MI system is relatively free of pre-existing flow, we can most clearly see the expanding nature of the response. As the open-closed field line boundary will frequently be in motion from such prior reconnection (both at the dayside magnetopause and in the cross-tail current sheet), it is expected that there will usually be some level of combined response to dayside reconnection.

scholarly journals Reconstruction of time-varying reconnection rate and X-line location

2008 ◽  
Vol 26 (11) ◽  
pp. 3445-3450 ◽  
Author(s):  
V. V. Ivanova ◽  
V. S. Semenov ◽  
I. B. Ivanov ◽  
H. K. Biernat ◽  
S. A. Kiehas
Keyword(s):  
Remote Sensing ◽  
Time Delay ◽  
Total Duration ◽  
Time Dependent ◽  
Magnetic Data ◽  
Time Varying ◽  
Reconnection Rate ◽  
Flux Transfer Events ◽  
First Time ◽  
Reconnection Model

Abstract. Remote-sensing method developed on the basis of time-dependent Petschek-type reconnection model is applied to Cluster magnetotail measurements from 8 September 2002, where a series of earthward propagating NFTEs (nightside flux transfer events) was observed. The method utilizes single-spacecraft magnetic data as an input and provides the reconnection rate and the location of X-line as an output. For the first time the method is applied to a composite reconnection event consisting of three successive NFTEs following each other without any time delay. The reconnection distance is found to be between 27 and 30 RE in the tail. The reconstructed electric field involves three 1-min scale pulses with total duration of ~4 min. The peak rates for individual pulses vary from 0.6 to 1.1 mV/m.

Modeling particle precipitation and effects on the ionospheric conductivity

2020 ◽  
Author(s):  
Yiqun Yu ◽  
Xingbin Tian ◽  
Minghui Zhu ◽  
Shreedevi Pr
Keyword(s):  
Ring Current ◽  
Transport Model ◽  
Current Model ◽  
Electron Precipitation ◽  
Plasma Convection ◽  
Particle Precipitation ◽  
Ionospheric Conductivity ◽  
Emic Wave ◽  
Intense Storm ◽  
Stream Transport

<p>Particle precipitation originated from the magnetosphere provides important energy source to the upper atmosphere, leading to ionization and enhancement of conductivity, which in turn changes the electric potential in the MI system to influence the plasma convection in the magnetosphere. In this study, we simulate ring current particle precipitation caused by several important loss mechanisms, including electron precipitation due to whistler wave scattering, ion precipitation due to EMIC wave diffusion and field line curvature scattering. These physical mechanisms are implemented in the kinetic ring current model via diffusion equation with associated pitch angle diffusion coefficients. The precipitation is subsequently input to a two-stream transport model at the top of ionosphere in order to examine its impact on the ionsopheric conductivity. It is found that during intense storm time, electron precipitation of tens of keV dominates in the dawn sector and leads to significant enhancement of conductivity at low altitudes. On the other hand, proton precipitation on the nightside mostly occurs for energy below 10 keV, and contributes to ionization above 100 km, resulting in enhancement of conductivity there. Consequently, the height profile of both Pedersen and Hall conductivity exhibits two layers, potentially complicating the current closure in the ionosphere system.</p>

scholarly journals Excitation of twin-vortex flow in the nightside high-latitude ionosphere during an isolated substorm

2002 ◽  
Vol 20 (10) ◽  
pp. 1577-1601 ◽  
Author(s):  
A. Grocott ◽  
S. W. H. Cowley ◽  
J. B. Sigwarth ◽  
J. F. Watermann ◽  
T. K. Yeoman
Keyword(s):  
Flow Pattern ◽  
High Latitude ◽  
Large Scale ◽  
Local Times ◽  
Closed Field ◽  
Plasma Convection ◽  
Expansion Phase ◽  
Ionospheric Conductivity ◽  
Large Scale Flow ◽  
Open Flux

Abstract. We present SuperDARN radar observations of the ionospheric flow during a well-observed high-latitude substorm which occurred during steady northward IMF conditions on 2 December 1999. These data clearly demonstrate the excitation of large-scale flow associated with the substorm expansion phase, with enhanced equatorward flows being observed in the pre-midnight local time sector of the expansion phase auroral bulge and westward electrojet, and enhanced return sunward flows being present at local times on either side, extending into the dayside sector. The flow pattern excited was thus of twin-vortex form, with foci located at either end of the substorm auroral bulge, as imaged by the Polar VIS UV imager. Estimated total transpolar voltages were ~40 kV prior to expansion phase onset, grew to ~80 kV over a ~15 min interval during the expansion phase, and then decayed to ~35 kV over ~10 min during recovery. The excitation of the large-scale flow pattern resulted in the development of magnetic disturbances which extended well outside of the region directly disturbed by the substorm, depending upon the change in the flow and the local ionospheric conductivity. It is estimated that the nightside reconnection rate averaged over the 24-min interval of the substorm was ~65– 75 kV, compared with continuing dayside reconnection rates of ~30–45 kV. The net closure of open flux during the sub-storm was thus ~0.4–0.6 × 108 Wb, representing ~15–20% of the open flux present at onset, and corresponding to an overall contraction of the open-closed field line boundary by ~1° latitude.Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; plasma convection)

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