Abstract
Abstract. A new incoherent scatter (IS) diagnostic technique for the actively heated D-region ionosphere is presented. In this approach, an exponential autocorrelation function (ACF) was fitted to the data by using a Markov Chain Monte Carlo (MCMC) inversion and the Sodankylä Ion Chemistry model (SIC). The method was applied for a set of combined EISCAT heating and VHF radar experiments carried out in November 2006. A newly designed radar experiment, sippi, based on optimised phase codes and direct sampling of the transmitted and the received IS signal, was used to produce ACF estimates of the target plasma. Systematic features associated with the heating were found by comparing the mean ACFs corresponding to heated and unheated periods. However, the data analysis revealed reasonable electron temperature estimates at the altitudes of the expected maximum effect (70–75 km) only in three cases out of six, corresponding to the highest signal-to-noise ratio (SNR) conditions. In two of these cases, the electron temperature was increased by a factor of 5 to 7, which is in a good agreement with the theoretical heating modelling. In the case of the first presented data example, the model overestimates the effect. These are the first successful IS observations of the HF-induced maximum electron temperature enhancements in the D-region ionosphere.
Highlights
Powerful radio waves can heat an electron gas via collisions between the electrons and neutral particles
Modelling of the electron temperature increase due to the HF heating is based on finding thermal equilibrium between the ohmic heating of the electron gas and the electron energy loss associated with excitation processes
It turns out that the theoretical approach described in the previous section was able to produce a reasonable set of stable temperature estimates only in three cases out of six, corresponding to the high signal-to-noise ratio (SNR) conditions
Summary
Powerful radio waves can heat an electron gas via collisions between the electrons and neutral particles. In November 2006, three daytime experiments were carried out in order to detect the D-region heating effect by using the EISCAT VHF radar and the heater. These six periods were analysed with 2-s time resolution synchronised to the heating cycle. After manual removal of clearly bad individual ACF profiles, such as contaminated by meteors, the data was averaged separately over the o-, x- and off-mode periods These ACF profiles were scaled into m−3 units by 1) removing the spatial 1/r2-factor and 2) calibrating the IS power to the Tromsø Dynasonde electron density at 120 km altitude (see Fig. 2). The average IS power at the PMWE layer during the heater on period is roughly half of the off-period value, which confirms the first findings of the heater induced PMWE modulation (Kavanagh et al, 2006)
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.
