Omnipresent vertically coherent fluctuations in the ionosphere with a possible worldwide‐midlatitude extent

Abstract

Incoherent Scatter Radar power profile 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 kilometers. Upon high‐pass filtering of the Incoherent Scatter 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 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. In fact, the COFIs are seen at every time and altitude that there is sufficient plasma to detect them. The COFIs are also 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 are always present over at least North America. This phenomenon appears to have been reported in Total Electron Concentration (TEC) maps of the ionosphere over much of North America Tsugawa et al. (2007b) as well as in airglow images from Arecibo and many other midlatitude sites around the world. These observations give us insight into the horizontal properties of the waves. While Medium‐Scale Ionospheric Disturbances (MSTIDs) are generally associated with aurorally generated acoustic gravity waves, the properties of the COFIs may suggest otherwise. We present other possible source mechanisms, notably a possible link to oscillations in the solar wind and magnetosphere. We have observed consistent fluctuations with periods of about an hour observed in magnetic field measurements taken at geosynchronous altitudes by the Geostationary Operational Environmental Satellites (GOES)‐10 and ‐12 satellites, which may be linked to the COFIs. We give corresponding solar wind results from ACE and discuss possible coupling mechanisms.

Relation between magnetospheric state parameters and the occurrence of plasma depletion events in the nighttime midlatitudeFregion

“…[28] Furthermore, recent studies using satellite data also suggest that there might be a connection between the quasiperiodic MSTIDs and the periodicities observed in the solar wind [Huang et al, 2000;Livneh et al, 2009]. So, it might be very interesting to study in more detail the relation between the magnetospheric state parameters and various properties of these events (such as wavelength, orientation, scale, speed, and especially period).…”

A 3‐D empirical model of F region Medium‐Scale Traveling Ionospheric Disturbance bands using incoherent scatter radar and all‐sky imaging at Arecibo

“…In other words, depending on the altitude of the F layer, the imager dark depletion bands extend from 200 to 300 km up to 300–400 km and the enhancement bands extend from 400 to 500 km up to 500–600 km assuming that the F layer is ∼200 km thick. Livneh et al [2007, 2009] report the presence of quasiperiodic ∼1 h period waves from 200 km up to 600 km. At this time, we assume the nighttime “bands” we report on here are the same phenomena.…”

“…Typically, MSTIDs are characterized as medium‐scale, quasiperiodic, F region plasma depletion bands that are aligned northwest to southeast and that propagate southwestward at night in the northern hemisphere. Livneh et al [2009] uses the term “Coherent, Quasi‐Periodic, Omnipresent Waves (CQPOWs)” to emphasize the coherence, periodicity, and prevalence of these bands. Livneh et al [2007] showed, using high pass‐filtered incoherent scatter radar (ISR) results that these waves also exist during the day; and Tsugawa et al [2007b] showed, using TEC maps, that the MSTIDs propagate southwestward during the night and southeastward during the day over the continental United States.…”

“… Livneh et al [2007] showed, using high pass‐filtered incoherent scatter radar (ISR) results that these waves also exist during the day; and Tsugawa et al [2007b] showed, using TEC maps, that the MSTIDs propagate southwestward during the night and southeastward during the day over the continental United States. Although their origins are not yet clear, several possible explanations have been proposed: Perkin's instability [ Perkins , 1973; Garcia et al , 2000; Kelley and Makela , 2001; Zhou et al , 2006; Zhou and Mathews , 2006], atmospheric gravity waves [ Livneh et al , 2007, 2009], and magnetosphere [ Livneh et al , 2009], all of which have different shortcomings. For example, Perkin's instability works only during the night, and requires a seeding mechanism.…”

“…Recent papers such as Otsuka et al [2004], Shiokawa et al [2005], Vlasov et al [2005], Martinis et al [2006], Tsugawa et al [2007a], and Seker et al [2008] used all‐sky imagers to observe MSTIDs. The MSTIDs have also been observed recently using single‐point instruments such as ISR [ Nicolls et al , 2004; Vlasov et al , 2005; Livneh et al , 2007, 2009; Seker et al , 2007, 2008], and GPS satellites [ Vlasov et al , 2005; Martinis et al , 2006; Tsugawa et al , 2007a; Seker et al , 2008]. One way to have a larger coverage is to create TEC maps using multiple GPS receivers [ Nicolls et al , 2004; Tsugawa et al , 2007a, 2007b].…”