Response of the equatorial ionosphere to the geomagnetic DP 2 current system

The response of equatorial ionosphere to the magnetospheric origin DP 2 current system fluctuations is examined using ground‐based multiinstrument observations. The interaction between the solar wind and magnetosphere generates a convection electric field that can penetrate to the ionosphere and cause the DP 2 current system. The quasiperiodic DP 2 current system, which fluctuates coherently with fluctuations of the interplanetary magnetic field (IMF) Bz, penetrates nearly instantaneously to the dayside equatorial region at all longitudes and modulates the electrodynamics that governs the equatorial density distributions. In this paper, using magnetometers at high and equatorial latitudes, we demonstrate that the quasiperiodic DP 2 current system penetrates to the equator and causes the dayside equatorial electrojet (EEJ) and the independently measured ionospheric drift velocity to fluctuate coherently with the high‐latitude DP 2 current as well as with the IMF Bz component. At the same time, radar observations show that the ionospheric density layers move up and down, causing the density to fluctuate up and down coherently with the EEJ and IMF Bz.Key PointsThe solar wind‐magnetosphere interaction generates DP 2 current fluctuationThe DP 2 current fluctuations penetrate to the equator and cause the equatorial electrodynamics to fluctuateIt also causes the equatorial density to fluctuate which might affect the communication and navigation systemsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134255/1/grl54722.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134255/2/grl54722_am.pd

Latitudinal profile of the ionospheric disturbance dynamo magnetic signature: comparison with the DP2 magnetic disturbance

During magnetic storms, the auroral electrojets intensification affects the thermospheric circulation on a global scale. This process which leads to electric field and current disturbance at middle and low latitudes, on the quiet day after the end of a storm, has been attributed to the ionospheric disturbance dynamo (Ddyn). The magnetic field disturbance observed as a result of this process is the reduction of the H component amplitude in the equatorial region which constitutes the main characteristic of the ionospheric disturbance dynamo process, associated with a westward electric current flow. The latitudinal profile of the Ddyn disturbance dynamo magnetic signature exhibits an eastward current at mid latitudes and a westward one at low latitudes with a substantial amplification at the magnetic equator. Such current flow reveals an "anti-Sq" system established between the mid latitudes and the equatorial region and opposes the normal Sq current vortex. However, the localization of the eastward current and consequently the position and the extent of the "anti-Sq" current vortex changes from one storm to another. Indeed, for a strong magnetic storm, the eastward current is well established at mid latitudes about 45° N and for a weak magnetic storm, the eastward current is established toward the high latitudes (about 60° N), near the Joule heating region, resulting in a large "anti-Sq" current cell. The latitudinal profile of the Ddyn disturbance as well as the magnetic disturbance DP2 generated by the mechanism of prompt penetration of the magnetospheric convection electric field in general, show a weak disturbance at the low latitudes with a substantial amplification at the magnetic equator. Due to the intensity of the storm, the magnitude of the DP2 appears higher than the Ddyn over the American and Asian sector contrary to the African sector

Correction to 'Simulation of electric field and current during the 11 June 1993 disturbance dynamo event: Comparison with the observations'

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On equatorial geophysics studies: a review on the IGIRGEA results during the last decade.

During the years 1993–1994, a continuous campaign of measurements has been held in the frame of the International Equatorial Electrojet Year (IEEY) with a network of 10 magneto-telluric stations and a network of three ionosondes. Other instruments have participated during shorter periods, HF radar and optical Fabry-Perot 630 nm interferometer.After the IEEY campaigns, the International Group of Research in Geophysics in Europe Africa (IGRGEA created in January 1995), has organized the research in geophysics. This paper report the main results of the IGRGEA during the last decade at local, regional and planetary scales.At a local scale, the HF radar data highlighted the complex structure of echoes in the equatorial zone and allowed to explain the “necklace” echoes as due to oblique propagation into the type I instability levels. This radar observed atmospheric storm electric field discharges at Es layer for the daytime and Equatorial Spread F at night-time. A series of original results concern Doppler spectra and the electric field change on plasma drifts across the ionosphere, gravity waves effects as well the ESF multi-process sources.At a regional scale, magnetic data were used to parametrize the Equatorial Electrojet (EEJ). Ionospheric data, magnetic data and UARS satellite were brought together as input parameters of the Richmond's EEJ model to reproduce the EEJ and the magnetic field variations associated to EEJ. The comparisons between magnetic data, and the magnetic field computed from the physical model and from the parametrization of the EEJ are all in good agreement. Ionosonde data were included in the IRI. Ionosonde data revealed the field aligned f0F2 crests of ionization at mid morning and early afternoon hours. Measurements of equatorial night-time wind variations, obtained for the first time over African equatorial zone with the Fabry-Perot interferometer, shown the strong variability of atmospheric winds.At a planetary scale, the parametrization of the EEJ was done using the magnetometers chain involved during IEEY in the three longitude sectors. Finally, we present the results on electrodynamic coupling between high and low latitudes with overshielding or shielding events