Seasonal Propagation Characteristics of MSTIDs Observed at High Latitudes Over Central Alaska Using the Poker Flat Incoherent Scatter Radar. Issue 7 (7th July 2018)

• Record Type: Journal Article
• Authors: Negale, M. R.; Taylor, M. J.; Nicolls, M. J.; Vadas, S. L.; Nielsen, K.; Heinselman, C. J.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 7(2018)
• Page Start: 5717
• Page End: 5737
• Publication Date: 2018-07-07
• Subjects: MSTID -- atmospheric gravity waves -- Poker Flat ISR -- traveling ionospheric disturbance -- seasonal GW characteristics -- ANGWIN; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2017JA024876
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Near‐continuous electron density measurements obtained over a ∼3 year period, 2010–2013, using the Poker Flat Incoherent Scatter Radar (PFISR) in central Alaska (69°N, 147°W) have been analyzed to quantify the properties of over 650 high‐latitude medium‐scale traveling ionospheric disturbances (MSTIDs). Our analysis focused on the altitude range 100–300 km encompassing the lower ionosphere/thermosphere and yielded first full seasonal day/night distributions of MSTIDs at high northern latitudes with mean values: horizontal wavelength 446 km, horizontal phase speed 187 m/s, and period 41 min. These year‐round measurements fill an important summertime gap in existing MSTID measurements revealing predominantly eastward wave propagation during the summer, while continued winter season observations agree well with previous reports of near southward propagating MSTIDs. Our 3 years of results suggest a cyclic change in the seasonal horizontal propagation directions that was found to be quantitatively consistent with critical level wind and dissipative filtering. Concurrent measurements of the vertical wavelength spectrum as a function of altitude also compared favorably in shape with that calculated using a theoretical dispersion relation (Vadas & Fritts, 2005, https://doi.org/10.1029/2004JD005574 ) for the thermosphere, but with a higher mean value. Evidence supporting the systematic broadening and shrinking in the azimuthal distributions of the MSTIDs during the course of the year was also found, as well as an unexpected correlation between the MSTID propagation directions and the AE index, both of which are under further investigation. Key Points: A multiyear investigation of over 650 MSTIDs observed in the high latitudes, providing first full seasonal propagation characteristics This study provides novel statistical measurements of the vertical gravity wave spectrum in the lower thermosphere This study supports strong evidence for critical level and dissipative filtering of the gravity wave field with altitude