Bibliography



Notice:

  • Clicking on the title will open a new window with all details of the bibliographic entry.
  • Clicking on the DOI link will open a new window with the original bibliographic entry from the publisher.
  • Clicking on a single author will show all publications by the selected author.
  • Clicking on a single keyword, will show all publications by the selected keyword.



Found 2 entries in the Bibliography.


Showing entries from 1 through 2


2015

The response of the ionosphere to intense geomagnetic storms in 2012 using GPS-TEC data from East Africa longitudinal sector

The response of the ionosphere to intense magnetic storms has been studied using total electron content (TEC). TEC data recorded by a series of GPS receivers at a longitude\~35\textdegreeE\ covering a wide range of latitudes (32\textdegreeS\ to\ 68\textdegreeN, geographic) is analyzed to study spatio-temporal modifications of the vertical TEC (vTEC) during storms on 07 and 09 March 2012 and on 14 July 2012. We have observed main phase positive response at equatorial ionization anomaly (EIA) crests and mid latitude regions in all the storms. These main phase positive responses are associated with vertical drift enhancement (intensified equatorial electrojet (EEJ)) and the mechanical effect of equatorward neutral wind after an auroral activity. A daytime substantial depletion of TEC at low latitude region was observed on 08 March 2012. This is due to the combined effects of oversheilding and disturbance dynamo electric field that drive large downward drifts during the day. The low latitude and equatorial ionospheric response in the recovery phase days of March storm is found to be largely associated with the disturbance dynamo field that suppressed the upward\ E\texttimesB\ drift from EEJ observations. The summer negative and winter positive response in July storm as well as mid latitude positive response in March storm was associated with the composition changes as depicted by the\ O\ to\ N2\ ratio from GUVI measurements.

Tesema, F.; Damtie, B.; Nigussie, M.;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 12/2015

YEAR: 2015     DOI: 10.1016/j.jastp.2015.10.021

Equatorial Electrojet; geomagnetic storm; Ionosphere

2012

Longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics

Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian \~37\textdegreeE and 290\textdegreeE, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation, such as from VEFI onboard Communication/Navigation Outage Forecasting System (C/NOFS) satellite and JULIA radar, is equally promising. The observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences; especially the equatorial anomaly peaks expand to higher latitudes more in American sector than the African sector, indicating that the vertical drift in the American sector is stronger than the African sector.

Yizengaw, E.; Zesta, E.; Moldwin, M.; Damtie, B.; Mebrahtu, A.; Valladares, C.; Pfaff, R.;

Published by: Journal of Geophysical Research      Published on: 07/2012

YEAR: 2012     DOI: 10.1029/2011JA017454

Tomography; vertical drift



  1