Timescales of Birkeland Currents Driven by the IMF

John C. Coxon; Robert M. Shore; Mervyn P. Freeman; Robert C. Fear; Stephen D. Browett; Andrew W. Smith; Daniel K. Whiter; Brian J. Anderson

doi:10.1029/2018gl081658

Extended period of polar cap auroral display: auroral dynamics and relation to the IMF and the ionospheric convection

Annales Geophysicae ◽

10.1007/s00585-995-0854-9 ◽

1995 ◽

Vol 13 (8) ◽

pp. 854-862 ◽

Cited By ~ 5

Author(s):

V. G. Vorobjev ◽

S. V. Leontyev ◽

Ya. I. Feldstein

Keyword(s):

Large Scale ◽

Interplanetary Space ◽

Extended Period ◽

Auroral Oval ◽

Polar Cap ◽

Substorm Activity ◽

Convection Patterns ◽

Northern And Southern Hemispheres ◽

Birkeland Currents ◽

The Imf

Abstract. An unusually extended period (5 h) of polar cap auroral display on 3 August 1986 is examined. Auroras have been investigated using ground-based data as well as measurements from the IMP-8 spacecraft in interplanetary space and simultaneous observations from the polar-orbiting satellites Viking and DE-1 in the northern and southern hemispheres, respectively. It is found that visible Sun-aligned arcs are located inside the transpolar band of the θ-aurora observed from the satellite in ultraviolet wavelengths. The transpolar band can contain several Sun-aligned arcs that move inside the band toward the morning or evening side of the auroral oval independent of the direction of the band movement. Intensifications of polar cap auroras with durations of up to about 30 min are observed. No change has been found in either IMF parameters or substorm activity that can be related to these intensifications. The θ-aurora occurred during a 2-h period when the B z-component of the IMF was negative. A tendency is noted for dawnward (duskward) displacement of the transpolar band when By>0 (By<0) in the southern hemisphere. Simultaneous observations of auroral ovals during interplanetary Bz<0, By<0 and Bx>0 in both hemispheres and convection patterns for Bz<0 and By<0 have been displayed using satellite and ground-based measurements. It was found that the transpolar band of the <theta>-aurora in the sunlit hemisphere was situated in the region of large-scale downward Birkeland currents.

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Comparison of Birkeland current observations during two magnetic cloud events with MHD simulations

Annales Geophysicae ◽

10.5194/angeo-26-499-2008 ◽

2008 ◽

Vol 26 (3) ◽

pp. 499-516 ◽

Cited By ~ 15

Author(s):

H. Korth ◽

B. J. Anderson ◽

J. G. Lyon ◽

M. Wiltberger

Keyword(s):

Magnetic Field ◽

Magnetic Cloud ◽

Topside Ionosphere ◽

Magnetic Perturbations ◽

Electric Potentials ◽

Current Densities ◽

Field Aligned Current ◽

Ionospheric Electric Field ◽

Birkeland Currents ◽

The Imf

Abstract. Low altitude field-aligned current densities obtained from global magnetospheric simulations are compared with two-dimensional distributions of Birkeland currents at the topside ionosphere derived from magnetic field observations by the constellation of Iridium satellites. We present the analysis of two magnetic cloud events, 17–19 August 2003 and 19–21 March 2001, where the interplanetary magnetic field (IMF) rotates slowly (~10°/h) to avoid time-aliasing in the magnetic perturbations used to calculate the Birkeland currents. In the August 2003 event the IMF rotates from southward to northward while maintaining a negative IMF By during much of the interval. During the March 2001 event the IMF direction varies from dawnward to southward to duskward. We find that the distributions of the Birkeland current densities in the simulations agree qualitatively with the observations for northward IMF. For southward IMF, the dayside Region-1 currents are reproduced in the simulation, but appear on average 5° further poleward of their observed location, while the nightside Region-1 currents and the Region-2 currents are largely under-represented. Comparison of the observed and simulated Birkeland current distributions, which are intimately related to the plasma drifts at the ionosphere, shows that the ionospheric convection pattern in the MHD model and its dependence on the IMF orientation is essentially correct. The Birkeland total currents in the simulations are about a factor of 2 larger than observed during southward IMF. For Bz>0 the disparity in the total current is reduced and the simulations for purely northward IMF agree with the observations to within 10%. The disparities in the magnitudes of the Birkeland currents between the observations and the simulation results are a combined effect of the simulation overestimating the ionospheric electric field and of the Iridium fits underestimating the magnetic perturbations. The marginal difference in the latitude resolution of the ionospheric grids in the simulations and the observations is shown to have only secondary effect on the magnitudes of the Birkeland currents. The electric potentials in the simulation for southward IMF periods are twice as large as those obtained from measurements of the plasma drift velocities by DMSP, implying that the reconnection rates in the simulation are too large.

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Poleward moving auroral forms (PMAFs) revisited: responses of aurorae, plasma convection and Birkeland currents in the pre- and postnoon sectors under positive and negative IMF <I>B<sub>y</sub></I> conditions

Annales Geophysicae ◽

10.5194/angeo-25-1629-2007 ◽

2007 ◽

Vol 25 (7) ◽

pp. 1629-1652 ◽

Cited By ~ 35

Author(s):

P. E. Sandholt ◽

C. J. Farrugia

Keyword(s):

Dynamical Evolution ◽

Plasma Convection ◽

Ion Drift ◽

Flow Vorticity ◽

Flow Channels ◽

Major Interest ◽

First Time ◽

East West ◽

Birkeland Currents ◽

The Imf

Abstract. Using five case studies, we investigate the dynamical evolution of dayside auroral precipitation in relation to plasma convection, classifying it by the IMF By component and position with respect to noon. Auroral observations were made by meridian scanning photometers (MSPs) and an all-sky camera (ASC) in Ny Ålesund, Svalbard at 76° MLAT, while the spatial structure of the ionospheric plasma convection is inferred from SuperDARN radars and ion drift observations from spacecraft in polar orbit. The IMF configuration of major interest here is one pointing southward and with a dominant east-west component. Our emphasis is on the auroral phenomenon of PMAFs (poleward moving auroral forms), which are ionospheric signatures of pulsed reconnection at the magnetopause. We distinguish between PMAFs/prenoon and PMAFs/postnoon. These two activities are found to be separated by an auroral form around noon with attenuated emission at 630.0 nm. We document for the first time that this "midday gap aurora" appears in the form of a midday auroral brightening sequence (MABS). We study the PMAF activity consisting of an initial brightening phase and the later stages of PMAF evolution in relation to plasma convection cells, flow vorticity, and precipitation boundaries in the prenoon and postnoon sectors for both By polarities. Flow channels (PIFs) associated with PMAFs are strengthened by polarization effects at auroral boundaries. Addressing the implications of our proposed, extended perspective on dayside auroral morphology under southeast/west IMF for M-I coupling associated with pulsed magnetopause reconnection (FTEs), we draw inferences on the MLT-dependent geoeffectiveness (Birkeland current/auroral intensity) of magnetopause FTEs (subsolar region versus flanks).

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The role of interstellar filaments in shaping the IMF and regulating star formation

EAS Publications Series ◽

10.1051/eas/1575023 ◽

2015 ◽

Vol 75-76 ◽

pp. 137-141

Author(s):

P. André ◽

V. Könyves ◽

A. Roy

Keyword(s):

Star Formation ◽

The Imf

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FALSE ECONOMY :A SURPRISING HISTORY OF THE WORLD BY ALAN BEATTIE

GBAMS- Vidushi ◽

10.26829/vidushi.v6i01.9680 ◽

2014 ◽

Vol 6 (01) ◽

Author(s):

Roli Pradhan

Keyword(s):

The World ◽

History Of ◽

The Imf

The book is a thorough examination of economics from the age of empire to the age of the IMF. Beattie's analysis dazzles with economic particulars. The book discusses Roosvelt's attempt to save capitalism from itself.

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IMF Stabilization Programs, Policy Conduct and Macroeconomic Outcomes: A Case Study of Pakistan

THE LAHORE JOURNAL OF ECONOMICS ◽

10.35536/lje.2006.v11.i1.a3 ◽

2006 ◽

Vol 11 (1) ◽

pp. 35-62

Author(s):

Nawaz A. Hakro ◽

Wadho Waqar Ahmed

Keyword(s):

Current Account ◽

Inflation Rate ◽

Current Account Balance ◽

Macroeconomic Policies ◽

Explanatory Variables ◽

Fiscal Balance ◽

Macroeconomic Impacts ◽

The Individual ◽

The Imf

This study is designed to assess the macroeconomic performance of fund-supported programs, and the sequencing and ordering of macroeconomic policies in the context of the Pakistan economy. The generalized evaluation estimator technique has been used to assess the macroeconomic impacts of the IMF supported programs. GDP growth, inflation rate, current account balance, fiscal balance and unemployment are used as the target variables in order to gauge economic performance during the program years. The vector of policy variables (that might have been adopted in the absence of programs) and the vector of foreign exogenous variables are also taken as explanatory variables in the model, so that the individual effect of the IMF supported programs could be assessed. The result suggests that as the IMF prescriptions were applied, the current account balance has worsened, the unemployment rate has significantly increased, and the inflation rate has increased during the years of fund-supported programs. Only the budget balance has shown signs of improvement. Furthermore an inadequate sequencing of reforms has contributed to the further worsening of the economic scenario during the program period.

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