Coherent Omnipresent Fluctuations in the Ionosphere

Open Access
Author:
Livneh, Dorey Joseph
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 03, 2009
Committee Members:
  • J Ohn D Mathews, Dissertation Advisor
  • John David Mathews, Committee Chair
  • C Russell Philbrick, Committee Member
  • Victor P Pasko, Committee Member
  • Hampton Nelson Shirer, Committee Member
Keywords:
  • ionosphere
  • gravity waves
  • coupling
  • MSTIDs
  • radar
  • magnetosphere
  • thermosphere
Abstract:
Incoherent Scatter Radar power observations at Arecibo, Millstone Hill, and the Poker Flat AMISR have revealed the continuous presence of Coherent Omnipresent Fluctuations in the Ionosphere (COFIs) with periods ranging from roughly 30 to 60 minutes and apparent vertical wavelengths increasing with altitude from tens to hundreds of km. Upon high-pass filtering of the radar power profile and electron concentration data, the COFIs are seen unambiguously and ubiquitously in Arecibo results from 22-23 March 2004, 5-6 June, 21-25 September, and 17-20 November 2005, as well as in Millstone Hill results from 4 October to 4 November 2002. The COFIs are strong throughout the F-region, often spanning altitudes of 160 km to above 500 km, and are detected day and night in the F2-layer (above ~ 200 km). In fact, the COFIs are seen at every time and altitude that there is sufficient plasma to produce a radar echo. The COFIs also are observed at Poker Flat, although the poor signal-to-noise ratio over segments of the data makes it difficult to determine whether or not they are always present. The consistent detection of the COFIs, along with the longitudinal alignment and large latitudinal spread of the observation sites suggests that these waves always are present over at least a major portion of the northern hemisphere. This phenomenon appears to have been reported in Total Electron Concentration (TEC) maps of the ionosphere over much of North America as well as in airglow images from Arecibo and many other mid-latitude sites around the world. These observations give us insight into the horizontal properties of the waves. Although Medium Scale Traveling Ionospheric Disturbances (MSTIDs) generally are associated with aurorally generated acoustic-gravity waves (AGWs), the properties of the COFIs may suggest otherwise. Other possible source mechanisms are presented; notably a possible link to oscillations in the solar wind and magnetosphere is described. Consistent fluctuations with periods of about an hour have been observed in magnetic field measurements taken at geosynchronous altitudes by the Geostationary Operational Environmental Satellites (GOES)-10 and -12 satellites that may be linked to the COFIs. Concurrent solar wind data from ACE are presented in an attempt to find a more primary source of the COFIs. Both the AGW and magnetospheric explanations for the COFIs are discussed, along with arguments for and against each scenario.