A study of low-latitude VHF scintillations in relation to electric fields during magnetic storms

Radio Science ◽  
1993 ◽  
Vol 28 (3) ◽  
pp. 389-400 ◽  
Author(s):  
D. R. Lakshmi ◽  
R. S. Dabas ◽  
B. C. N. Rao ◽  
B. M. Reddy
Keyword(s):  
Electric Fields ◽  
Magnetic Storms ◽  
Low Latitude

scholarly journals Sudden post-midnight decrease in equatorial F-region electron densities associated with severe magnetic storms

1997 ◽  
Vol 15 (3) ◽  
pp. 306-313 ◽  
Author(s):  
D. R. Lakshmi ◽  
B. Veenadhari ◽  
R. S. Dabas ◽  
B. M. Reddy
Keyword(s):  
Electric Fields ◽  
Magnetic Storms ◽  
Equatorial Region ◽  
Electron Densities ◽  
Low Latitude ◽  
General Behaviour ◽  
F Region ◽  
Short Period ◽  
Electric Field Direction ◽  
Meridional Winds

Abstract. A detailed analysis of the responses of the equatorial ionosphere to a large number of severe magnetic storms shows the rapid and remarkable collapse of F-region ionisation during post-midnight hours; this is at variance with the presently accepted general behaviour of the low-latitude ionosphere during magnetic storms. This paper discusses such responses as seen in the ionosonde data at Kodaikanal (Geomagn. Lat. 0.6 N). It is also observed that during magnetic storm periods the usual increase seen in the h'F at Kodaikanal during sunset hours is considerably suppressed and these periods are also characterised by increased foF2 values. It is suggested that the primary process responsible for these dramatic pre- and post-midnight changes in foF2 during magnetic storms could be due to changes in the magnitude as well as in the direction of usual equatorial electric fields. During the post-midnight periods the change in electric-field direction from westward to eastward for a short period causes an upward E × B plasma drift resulting in increased h'F and decreased electron densities in the equatorial region. In addition, it is also suggested that the enhanced storm-induced meridional winds in the thermosphere, from the poles towards the equator, may also cause the decreases in electron density seen during post-midnight hours by spatially transporting the F-region ionisation southwards away from Kodaikanal. The paper also includes a discussion on the effects of such decreases in ionisation on low-latitude HF communications.

CIR versus CME drivers of the ring current during intense magnetic storms

2010 ◽  
Vol 466 (2123) ◽  
pp. 3305-3328 ◽  
Author(s):  
Michael W. Liemohn ◽  
Matt Jazowski ◽  
Janet U. Kozyra ◽  
Natalia Ganushkina ◽  
Michelle F. Thomsen ◽  
...  
Keyword(s):  
Solar Wind ◽  
Boundary Conditions ◽  
Electric Fields ◽  
Data Model ◽  
Goodness Of Fit ◽  
Plasma Boundary ◽  
Magnetic Storms ◽  
Hot Electron ◽  
Interplanetary Coronal Mass Ejections ◽  
Interaction Regions

Ninety intense magnetic storms (minimum Dst value of less than −100 nT) from solar cycle 23 (1996–2005) were simulated using the hot electron and ion drift integrator (HEIDI) model. All 90 storm intervals were run with several electric fields and nightside plasma boundary conditions (five run sets). Storms were classified according to their solar wind driver, including corotating interaction regions (CIRs) and interplanetary coronal mass ejections (ICMEs). Data-model comparisons were made against the observed Dst index (specifically, Dst*) and dayside hot-ion measurements from geosynchronous orbiting spacecraft. It is found that the data-model goodness-of-fit values are different for CIR-driven storms relative to ICME-driven storms. The results are also different for the same storm category for different boundary conditions. None of the CIR-driven events was overpredicted by HEIDI, while the dayside comparisons were comparable for the different drivers. The results imply that the outer magnetosphere is responding differently to the two kinds of solar wind drivers, even though the resulting storm size might be similar. That is, for ICME-driven events, magnetospheric currents inside of geosynchronous orbit dominate the Dst perturbation, while for CIR-driven events, currents outside of this boundary have a systematically larger contribution.

Electric fields in the low latitude F-region

1996 ◽  
Vol 18 (6) ◽  
pp. 93-98 ◽  
Author(s):  
B.V. Krishna Murthy ◽  
S.S. Hari
Keyword(s):  
Electric Fields ◽  
Low Latitude ◽  
F Region

Modelling the ionospheric and plasmaspheric plasma

1989 ◽  
Vol 328 (1598) ◽  
pp. 255-270 ◽  
Keyword(s):  
Electric Fields ◽  
High Latitude ◽  
Thermal Plasma ◽  
Topside Ionosphere ◽  
Neutral Atmosphere ◽  
High Latitudes ◽  
Polar Wind ◽  
Low Latitude ◽  
Flux Tubes ◽  
Thermospheric Winds

Under magnetically quiet conditions, the outer plasmasphere is the equatorw ard boundary of the region in which high-latitude processes, such as convection, significantly affect the ionosphere. The low-latitude side of the ionospheric midlatitude trough is located in the plasmasphere. The behaviour of the nightside trough is influenced by field-aligned flows of plasma, as well as by convection drifts, thermospheric winds and particle precipitation. The modelling of field-aligned flow of thermal plasma at high latitudes (the polar wind) still presents problems. The composition of the background neutral atmosphere plays a role in causing the occasional dominance of He+ in the topside ionosphere. Penetration of magnetospheric electric fields into the outer plasmasphere can influence the rate of refilling of the upper reaches of the flux tubes.

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