GPS-TEC variations, generated in midlatitude and highlatitude ionosphere by powerful HF-heating. Kunitsyn V.E. 1 , Padokhin A.M. 1 , Andreeva E.S. 1 , Frolov V.L. 2 , Komrakov G.P. 2 , Blagoveshchenskaya N.F. 3 and Rietveld M.T. 4 1 M.V. Lomonosov Moscow State University, Faculty of Physics, Leninskie Gory, Moscow 119991, Russia kunitsyn@phys.msu.ru 2 Radiophysical Research Institute (NIRFI), N. Novgorod, Russia 3 Arctic and Antarctic Research Institute, St. Petersburg, Russia 4 EISCAT Scientific Association, Ramfjordbotn, Norway Abstract In this work we report on the results of the ionospheric heating experiments, which were carried out at the Sura (Russia) and EISCAT/Heating (Norway) facilities during several heating campaigns in 2009 and 2010. We present experimental evidences for the influence of the electron density perturbations, induced by HF-heating in the midlatitude and highlatitude ionosphere, on the GNSS radio signals. Variations in the total electron content (TEC), proportional to the reduced phases of navigational signals, were studied. Examples of the identification of the heating-induced variations in TEC, including determination of the amplitudes and temporal characteristics are presented. 1. Introduction Numerous studies of the influence of powerful HF radio waves on the ionospheric plasma [1-3] showed the development of ponderomotive parametric, thermal (resonant) parametric and self-focusing instabilities near the reflection height of the powerful radio wave, which leads, in particular, to the strong electron heating of ionospheric plasma in this region and to the generation of artificial irregularities in the ionospheric electron density with the scale sizes from fractions of meter to dozens of kilometers [1]. These irregularities should have a considerable effect on the VHF/UHF/L-band radio waves propagating through the heated area of the ionosphere. Recently, methods for sounding of the heated ionosphere by radio signals from high-orbiting navigational GNSS satellites at frequencies 1.2–1.5 GHz started to develop [4-7]. In this paper, we present the experimental results of the influence of electron density perturbations produced by the high-frequency heating of the ionosphere on the GNSS signals at the Sura (Radiophysical Research Institute, N. Novgorod, Russia) and EISCAT/Heating (Tromsø, Norway) facilities . 2. Description of the experiments and processing scheme The experiments were carried out at the Sura heating facility (56.15N, 46.1E) and at Tromsø heating facility (69.6N, 19.2E) during several heating campaings. The measurements were conducted when foF2>f (here f is the heater frequency and foF2 is a critical frequency of the F2 layer) and the ionospheric penetration points, calculated at the reflection height of the HF pump wave, of one or more GNSS satellites crossed the heated area. HF pump wave with O-mode polarization radiated with different heating schemes: 30 s heating with maximum effective radiated power followed by 30 s pause (or, in brief notation, ±30 s); ±3 min; ±5 min; ±10 min; +10 min -5 min. The half-power beamwidth for the Sura facility is ~12 O , for the EISCAT/Heating ~14 O , so ionospheric penetration points of slowly moving GNSS satellites could remain within the heated area for 35–50 min, which allows to obtain some information about the temporal characteristics of the heater-induced ionospheric disturbances. The experimental data for the experiments at Tromsø were taken from the IGS station tro1, located near Tromsø. For the experimets at the Sura facility we specially installed dual frequency GNSS receiver near the facility. GPS satellite radio transmissions were recorded with 10 Hz sampling at Sura and we obtained tro1 station data with the rate 1 measurement each 15 seconds from IGS. Both L1 and L2 GPS carrier phases were used in the analysis for calculating the relative slant total electron content (sTEC). The time series of sTEC were then detrended and TEC variations during the heating sessions were analyzed using the wavelet transform to estimate the local energy spectra of these variations. 978-1-4244-6051-9/11/$26.00 ©2011 IEEE