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NEW METODS FOR THE DETECTION OF PLASMA LAYERS IN THE IONOSPHERE DURING

NEW METODS FOR THE DETECTION OF PLASMA LAYERS IN THE IONOSPHERE DURING RADIO OCCULTATION A. L. Gavrik, Y. A. Gavrik, T. F. Kopnina Kotelnikov Institute of Radio Engineering and Electronics of RAS, Fryazino, Russia, alg248@ire216.msk.su.

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NEW METODS FOR THE DETECTION OF PLASMA LAYERS IN THE IONOSPHERE DURING

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  1. NEW METODS FOR THE DETECTION OF PLASMA LAYERS IN THE IONOSPHERE DURING RADIO OCCULTATION A. L. Gavrik, Y. A. Gavrik, T. F. Kopnina Kotelnikov Institute of Radio Engineering and Electronics of RAS, Fryazino, Russia, alg248@ire216.msk.su The second Moscow Solar System Symposium (2M-S3) Moons of planets Moscow 2011 ИКИ РАН 10…14. 10.2011 г.

  2. Dual frequency VENERA-15,-16 occultation (4 & 1 GHz or 8 & 32 см) Схема двухчастотного радиопросвечивания The theory of occultation experiments is based on integral equations that relate the electron density N(h) to the measured characteristics of radio signals. Measured refraction attenuations induced by daytime Ionosphere and atmosphere ХСМХDМ 8 см32 см Measured residual frequency in the ionosphere and atmosphere fDМ 32 см The electron density ofdaytime Venusian ionosphere N(h), см-3 The time of occultation 2…20 minutes ionosphere atmosphere Radio rays to the Earth

  3. Количество сеансов радиопросвечивания~800 (number ofoccultations) Год Venus-Express >120 Magellan 20 Венера-15,16 155 Pioneer-Venus 441 Венера-9,-10 34 Mariner-10 2 Mariner-5 2 Число солнечных пятен (Wolf number)

  4. Altitude distributions N(h) of the electron densities in the Venus day-time ionosphere Распределения электронной концентрации N(h) в дневной ионосфере Венеры 700 600 500 400 300 200 100 19.09.84г. 560 14.10.83г. 580 20.09.84г. 550 Time-to-time variability 14.10.83г. 820 12.10.83г. 810 28.03.84г. 820 Coincidence of N(h) for some days 09.09.84г. 820 12.10.83г. 810 30.10.83г. 820 Time-to-time variability 12.10.83г. 560 20.03.84г. 520 23.09.84г. 610 Coincidence of N(h) for some days Altitude, км 102 103 104105102103 104 105102 103 104105102103 104 105 Electron density, см-3

  5. The traditional method to determine N(h) leads to wrong conclusions about the bottom ionosphere. We can see discrepancies between the model and calculated N(h). The error can be greater than the actual value of N(h) at altitudes of h < 120 km. That is why we can see the bottom boundary of the ionosphere at altitude of h = 117 km on the experimental profile N(h). But the real influence of ionospheric plasma is observed up to 85 km in the occultation data. 300 280 260 240 220 200 180 160 140 120 100 80 200 180 160 140 120 100 80 Model N(h) Calculation N(h) Calculation N(h) Altitude, km N(h) VENERA-15 25.10.1983 г. bottom part of the ionosphere 102 103104105 102 103104105 0 0.5 1.01.5 2.0 Electron density, сm-3 Refraction attenuation

  6. В области высот 80 < h < 120 km методом радиопросвечивания не определяется точно температура атмосферы. In the field of heights 80 < h < 120 km it is impossible to define atmosphere temperature precisely. VENUS-EXPRESS M. Pätzold et al. Altitude, km Temperature, K

  7. The well-known relationships The ray asymptote distance Н – the altitude of straight-line ray The refractive bending angle Δf – residual frequency in the ionosphere ΔF –residual frequency in the atmosphere The refraction attenuation L – the distance between the spacecraft and point  V┴ – the velocity of the satellite’s ingress The electron density f – the radiated frequency(1 GHz) The following newresult is obtainedfromp(t), (t), X(t): Variations of the defocusing attenuation X(t) in the occultation experiments are proportional to the velocity of residual frequency changes.

  8. New method provides a possibility to distinguish the effect of plasma and to detect the ionized layers during occultation. It is necessary to determine same parameters from the experimental data: XDM(t) - the refraction attenuations of L-band (32 cm) signal. XCM(t) - the refraction attenuations of C-band ( 8 cm) signal. δf(t) =16/15(fDM(t) - fCM(t)/4) - the reduced frequency difference (plasma influence). Δf(t) = function [δf(t)] - frequency variation of L-band (32 cm) signal. XΔf (t) = 1 + value*d/dt[Δf(t)] - predicted refraction attenuation of the L-band signal. Coincidence between variations of refraction attenuation of the radio signal XDM(t) and variations XΔf (t) will be indicative of the influence of the regular structures of the ionosphere under investigation. The absence of this correspondence is an indication of the influence of the noise or other factors that are not taken into account. This method considerably increased the sensitivity of the radio probing method to refractive index variations and makes possible to detect small variations in electron density.

  9. This technique will allow one to investigate wave processes in the top atmosphere and the bottom ionosphere.We observed wave processes in the top atmosphere and bottom ionosphere of Venus. Refraction attenuation of a DМ-signal in the atmosphere Х 1 0 Refraction attenuation of a CМ-signal in the atmosphere Refraction attenuation in the ionosphere calculated from the frequency ofa DМ-signal Correlation between the powers of DM- and CM-signals due to the wave structure layered structurein the atmosphere Layers in the bottom ionosphere: correlation between ХDМandХf ХдмandХf are different in the atmosphere 25 50 75 100 125 Altitude of the spacecraft-to-Earth straight lineh, km

  10. Venera-15,-16 Gavrik A. et al. bottom ionosphere A variations of refraction attenuation of DM signalcoincide with calculated dataХ∆f(t) in the day-time ionosphere of Venus. The refraction attenuation, Х One layer night-time ionosphere A variations of refraction attenuation of DM signalcoincide with calculated dataХ∆f(t) in the night-time ionosphere of Venus. Two layers night-time ionosphere Two layers night-time ionosphere Altitude of spacecraft-Earth straight-lineh, км

  11. This method can be extended to occultation experiment Satellite → Satellite L1 – the distance between the first spacecraft and point of ray closest to the surface of planet. L2 – the distance between the second spacecraft and point of ray closest to the surface of planet. The method is correct for high-precision measurements of signal power and phase during dual frequency radio sounding.

  12. Realization of informative experiments requires the development of a good on-board receiver. http://isdc.gfz-potsdam.de In these occultation experiments GPS → CHAMP we can see very high frequency fluctuations. GPS → CHAMP λ = 19 см, Δt = 0.02 s Residual frequency,Hz invalid measurements (little signal/noise) Small frequency fluctuations in the occultation experiments VENERA-15,-16 → Earth achieved by the high output transmitter power (100 W) and large diameter (>2m) on-board antenna. plasma influence λ = 32см, Δt = 0.058 s ВЕНЕРА-16 → Земля Altitude of radio ray straight lineh, km

  13. Δt = 0.06 s The method gives correct results for high-precision measurements during dual frequency radio sounding. Δt = 0.11 s Invalid data (little S/N) The refraction attenuation, Х Δt = 0.23 s If we choose a very long measurement interval Δt, then the effects of focusing of a signal and layered structures will not manifest themselves. Δt = 0.47 s Altitude of radio ray straight lineh, km

  14. High S / N ratio can be achieved if emit powerful coherent radio signals from Earth. In this case, at the same time we can perform six radio physical experiments, in addition to the work of other onboard devices. High S / N ratio give the possibility of obtaining new information concerning the structure of the planetary ionospheres and atmospheres. ОА SS Interplanetary plasma on the two separated tracks Earth → OA and Earth → SS Two-frequency radio sounding of the ionosphere signals to the ETs… Two-frequency radio sounding of the atmosphere bistatic radar experiment radar experiment

  15. C o n c l u s i o n s We have shown that the new methods proposed make it possible to carry out high-quality analysis of the planetary ionospheres and atmospheres during dual-frequency occultation experiments. There are a few conditions for this investigation: 1. High-precision phase measurements. 2. High-precision power measurements with the necessary dynamic range. 3. All the measurements should be carried out within a short time interval. Работа выполнена при частичной поддержке программы Президиума РАН №VI.15 Спасибо за вниманиеThank you for attention

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