Yu. A. Sazonov

Study of wind characteristics at heights of 200 to 800 meters using a decimeter sodar

The results of the experiment carried out in July–August 1997 using a two-position sodar are reported. Different types of intensity and spectrum variations of scattered acoustic signals have been obtained. The possibilities of using the sodar for the study of atmospheric turbulence and search of signals caused by “Fresnel” scattering from “plane” irregularities are discussed.

Study of small variations of troposphere parameters by the radioacoustic sounding method

We consider a method based on the study of signal amplitude and phase variations in the radioacoustic sounding (RAS) of the atmosphere for the diagnostics of dynamical and wave processes in the troposphere. We give experimental data on phase variations of the RAS signal from scan to scan in daytime and nighttime sessions. Variations of the signal phase with characteristic time greater than 40 min are likely due to the passage of internal gravity waves (IGW) through the sounding region. The experimental data are in good agreement with the results of computer simulation of IGW propagation.

Study of the Wind Characteristics of the Atmospheric Turbulence using a Multibeam Sodar

We present the results of acoustic sounding of the atmosphere in summer of 2001. The experiments were carried out using a multibeam bistatic sodar with two parabolic antennas of 15xa0m in diameter. The distance between the antennas was about 425xa0m. The transmitting acoustic antenna having 8° beam width was pointed to the zenith. The four-beam operation of the receiving paraboloid was implemented by mounting four separate microphones in its focal plane. The width of each beam of the receiving antenna was 2.5°. The beams of the transmitting and receiving antennas crossed at a height about 500xa0m. The sounding frequency was equal to 576xa0Hz. The acoustic-pulse duration and repetition period were 2xa0s and 8xa0s, respectively. A new procedure for experimental-data processing on the basis of analysis of temporary variations in the Doppler frequency shift of a scattered signal is proposed and approved. The approach based on using structural functions is applied. The preliminary results of analysis of one observation session are presented.

Operating decameter RASS near Nishny Novgorod and perspectives for far radio-acoustic sounding using the Sura HF-radar

Abstract An investigation of a tropospheric radio-acoustic sounding system (RASS) on the basis of the powerful HF-heating facility, ‘SURA’ is proposed. The specifications of a RASS for regular temperature profile measurements up to a height of 15 km, where the main processes of energy exchange take place, are discussed. Temperature profile data measured with an existing low-frequency prototype are presented. They are for a height of up to 6 km and the time resolution is about a few minutes. Differences between the RASS and sonde profiles typically do not exceed 1 K.

The frequency spectrum of cosmic radioemission in the 10–207-Mc band at high galactic latitudes

The f requency spec t rum of cosmic r ad ioemiss ion is one of its fundamental c h a r a c t e r i s t i c s . Much effor t has been devoted to measu r ing the spect rum, but until r ecen t ly there has been a cons iderable spread in the resul t s , which has made it difficult to apply them to theore t ica l s tudies. The following basic f ac to r s l imi t the accuracy of m e a s u r e m e n t of the r ad ioemiss ion intensity, and consequent ly the accuracy of the spec t ra l index m e a s u r e m e n t s . 1. The use of r e l a t ive ly compl ica ted antennas with fa i r ly na r row radiat ion pat terns makes it diff icult to det e rmine the l o s se s in the antennas with the n e c e s s a r y accuracy. 2. In the case of antennas having signif icant side lobes, it is n e c e s s a r y to allow for the E a r t h s radio emiss ion fal l ing within the side lobes . 3. Diode noise genera tors , genera l ly used for c a l i b ra t ing the r ece iv ing apparatus, must in the i r turn be ca l ib ra ted against the radiat ion f rom a s tandard m a t e h e d r e c e i v e r load (blackbody radia t ion) . D i rec t ca l ib ra t ion is possible , but only over a r e l a t i ve ly n a r row range of noise t e m p e r a t u r e s ( T n ~ 700 ~ K). Measu remen t s of the spec t rum of cosmic r ad io emiss ion , the r e su l t s of which are given below, were made at the Sc i en t i f i c -Resea rch Radiophysieal Insti tute f rom 1965 to 1966. The method of m e a s u r e m e n t was such as to min imize the e r r o r s caused by the fac tors enumera ted above. The r e c e i v i n g antennas w e r e halfwave dipoles mounted at a height of 0.25), above me ta l l i c s c r eens . With this a r r a n g e m e n t there were no side lobes, and the antenna eff ic iency was near ly unity. The spec t ra l index de te rmined was the mean value over a cons iderable region of the sky, but the angular v a r i ations of the spec t ra l index at high ga lac t ic la t i tudes are insignificant . The diode noise gene ra to r s used to ca l ib ra te the r e c e i v e r s w e r e in turn ca l ibra ted against the noise f rom f i lm r e s i s t o r s of special construct ion which were heated to a t empe ra tu r e of the o rder of 400 ~ C. When m e a s u r i n g the effect ive t e m p e r a t u r e s of the sky at r e l at ively low f requenc ies , power d iv iders were used in the signal path. Recent ly s eve ra l papers descr ib ing m e a s u r e m e n t s of the cosmic r ad ioemis s ion f requency spec t rum have been published [1-4] . The method used was ve ry s i m i l a r to that employed by the authors of the p resen t paper. A compar i son of the r e su l t s of the m e a s u r e ments c a r r i e d out at the Radiophys ica l Institute with those given in [1-4] enables us to draw quite definite conclusions about the r ad ioemiss ion spec t rum in the f requency band 10-207 Mc at high galact ic lat i tudes.