Abstract
Abstract This paper aims at describing the ionospheric conditions during the DELTA (Dynamics and Energetics of the Lower Thermosphere in Aurora) campaign period based on EISCAT radar observations conducted at Tromsø (69.6°N, 19.2°E). We conducted EISCAT UHF radar observations on December 5 and from December 8 to December 13, 2004 with a beam-scanning mode for a total of 74 hours. Except for December 8 during a 2 hr interval operation, we operated the EISCAT UHF radar for 12 hour intervals everyday to make it possible to derive semidiurnal tidal amplitudes and phases in the lower thermosphere. Observed electron densities and derived electric fields by the EISCAT UHF radar indicate that magnetospheric activity was high during the period from December 5 to 13 except for the night of December 13. Derived semidiurnal amplitudes during December 9–12, 2004 exhibited a day to day variation at and below 110 km, while the corresponding phase was relatively stable over the four days except for the zonal component on December 12. Neutral and electron temperatures measured by the DELTA rocket were compared with neutral/ion and electron temperatures from the EISCAT UHF radar observations. Comparison of neutral/ion temperatures show some agreement, while poor agreements were found for the electron temperature. Possible causes of the discrepancy are discussed.
Highlights
Large-scale atmospheric circulation in the thermosphere has been investigated by modeling studies and satellite observations
Wind data obtained during eight consecutive day intervals from 1200 Universal time (UT) on December to 1200 UT on December 16, 2004 are used for calculation in order to determine the behavior of the quasi-2 day (Q2DW) wave together with the tides
EISCAT observations showed that the magnetospheric activity was high during the period from December 5 to 13 except for the night of December 13, the daily Ap index was within the range of 8 to 29
Summary
Large-scale atmospheric circulation in the thermosphere has been investigated by modeling studies and satellite observations. Based on 56 days of EISCAT data sets Nozawa and Brekke (1999) presented the seasonal and solar cycle variations of mean wind and diurnal and semidiurnal tidal winds at Tromsø In their studies, they showed that the diurnal tide is weak in winter season in the lower thermosphere, while the semidiurnal tide is dominant over the height region (95–120 km). Nozawa et al (2005) analyzed eight consecutive days of wind data obtained from November 11 to 19, 2003 at two locations of Tromsø and Longyearbyen (78.2◦ N, 16.0◦ E), and evaluated the importance of the iondrag effect on the neutral wind dynamics They demonstrated that the ion-drag effect started playing a role at and c The Society of Geomagnetism and Earth, Planetary and Space SciCopyright ences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
