H.F. emission related to the Li+ ion beam injected into ionosphere — “PLAZMA” rocket experiment

Adv. Space Res. Vol. 13, No. 10, pp. (10)91—(10)94, 1993 Printedin Great Britain. All rights reserved.

0273—1177193 $24.00 Copyright © 1993 COSPAR

H.F. EMISSION RELATED TO THE Li~ION BEAM INJECTED INTO IONOSPHERE “PLAZMA” ROCKET EXPERIMENT -

Z. K1os,~Z. Zbyszynski,* U. F. Agafonov,** G. G. Managadze** and A. D. Mayorov** *

SpaceResearch Centre, 00-716 Warsaw, Bartycka l8’~,Poland

**

Space Research Institute, Moscow, Russia

ABSTRACT The H.F. emission generated by artificial ion beam injected into ionosphere was observed either with a wave detector and ion gun attached to the rocket through out the flight, or when the gun was deployed on subpayload. Generally the observations show unstructured shape of the H.F. spectrum. In the PLAZMA active rocket experiment when ionospheric plasma was perturbed by the operation of impulse ion gun, which injected 300 A, 8.3 eV Li + ions the waves in the 0.1 10 MHz frequency range were observed. The results have shown, that when the wave detector and the ion gun are attached to the rocket the emission enhances in the lower as well as in the upper parts of the spectrum. On the other hand only the lower increase is maintainedwhen ion gun is removing away on the subpayload. The observed sequence of H.F. spectra is presented. -

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INTRODUCTION A limited number of active experiments with the ion gun in which the H.F. waveswere observed has been carried out. The PORCUPINE with 200 eV Xe~ion beam injection /1/ and ARCS 1 and 2 12,3,4/ were the active rocket experiments in which H.F. waves have been registered. The PORCUPINE and ARCS-2 were the mother daughter typeexperiments and deployed the ion gun on the subpayloads and remote registration of H.F. waves was performed. In ARCS-i the receiver operatedclose to the gun on the rocket. From these experiments it has been concluded that during gun operation closed to the gun: the enhanced and unstructured spectrum in the 0.1-10 MHz frequency range is generated with amplitude increase by factor 2 [ARCS-lI the H.F. emission occurs only in a very limited spatial region around the beam and it was concluded that it is primarily electrostatic [PORCUPINE].At short distance from the gun ( 25m) the H.F. waves are generated in the region of large density gradient. The understanding of the nature of H.F. waves related to ion beam injected into the ionosphere seems to be crucial for the electron accelerationprocess in the L.F. ion turbulence. In this paper we report the H.F. wave registration during 300 A, 8.3 eV Li Impulse ion gun operation on the mother daughter typerocket. -

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“PLAZMA” ROCKET EXPERIMENT In the frame of PLAZMA experiment the rocket MR-20 was launched from the boat at North Atlantic (18N 30W), on March 18 1985, LT Oh 5 mm. Itwas mother daughter type experiment. The 300 A, 83 eV Li~impulse ion gun was located on the container attached to the rocket. The R.F. spectrometer (0.1-10 MHz) was installed on the rocket board. The spectrometer was the superheterodyne receiver with double frequency conversion. The pass-band filter was 15 kHz, dynamic range60 dB and sensitivity 3V. The sweeping time of the 10 Mhz range was 180 msec. The antenna system was the dipole 7 m from tip to tip with two preamplifiers. -

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“PLAZMA” ROCKET EXPERIMENT I

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Fig.1. The altitude v.s time sequence for “PLAZMA” rocket experiment. At the top the LF~ impulse ion gun pulse series are shown. The gun switching on and the gun separation from the mother payload is marked at the trajectory. The registered intensity of H.F. waves integrated in the frequencyranges 0.1 5 MHz and 5 10 MHz, respectively v.5 time is plotted below. -

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The Li+ impulse ion gun operated with rectangular pulses of 2,4 and 8 seconds of duration respectively with 2 seconds of break. The LF1 impulse gun has started its operation at 135 km of altitude The H.F. registration was switched on for 60 seconds before the gun operation thus the background H.F. emission was determined. After 30 seconds during which the registration of H.F. waves was performed close to the gun the containerwas separated from the payload with velocity 2.5 rn/sec. Afterseparation the containerwas stabilized with spinningperiod of4 sec. The rocket payload spinningperiod was 3 sec. The time of impulse gun operation along the rocket trajectoryis presented in Fig.1. The PLAZMA experiment made it possible to observe H.F. emission close to the ion gun as well as at different distance from it during and between ion pulses. .

THE RESULTS OF H.F. OBSERVATIONS. In Fig.2. the typical spectra observed with R.F. receiver are presented. The background H.F. emission is shown atthe top. During the gun operationclose to the ion source H.F. emissionincrease strongly in the frequencyrange up to 5 MHz. and above 5 MHzthe increase is slightly weaker. After gun separation the intensity goes down with the increase of gun antenna distance. The decrease of intensity is quicker at lower and middle frequency part of spectrum. As the H.F. spectra show the decrease of the intensity above 5 MHz, we have integrated the intensityin two frequencyranges 0.1 5 MHz and 5 10 MHz, respectively. These effects are shown in Fig.1. where integrated spectrum intensity up to and above 5 MHz as function of average background intensity is presented. The integrated up to 5 MHz intensity related to the gun pulses is also presented in Fig.3.. It can be seen that H.F. turbulence quickly decreases in the break between pulses. The integrated H.F. wave intensity decreases gradually with the distance from the beam source but it is still registered to 100 m from the gun. The long period modulation can be the result of overlapping of period of the gun pulses, container, as well as rocket payload spinning. Because of limited telemetry capacity it was not possible to analyze this question in detail. -

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U~Ion Beam Injected into Ionosphere

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Fig.2. T~,picalH.F. spectra related to the 8.3 eV, 300 A Li~impulse ion gun operation. At the top left panel the background spectrum registered just before the gun operation and the spectra for 0, 5 and 10 m of gun receiver separation during gun impulse. PLAZMW I

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Fig.3. The observed intensityof H.F. emission integratedin the 0.1 -5 MHz rangev.s time related to the sequence of Li~i mpulse ion gun pulses.

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CONCLUSION We have observed H.F. turbulence related to the Li~impulse ion beam injected into the weakly ionized nitrogen and oxygen dominated lower ionosphere. The pulsed ion gun was used and the separation of the gun from the main payload has been performed. Thus it was possible to register H.F. turbulence just after gun turn off as well as at different distances from the beam source. The results of observations can be summarized as follows: the Li~impulse ion beam excited H.F. waves mainly below 5 MHz (the typical background f = 1 MHz) the HF. wave dumps quickly after termination of the beam injection to the average level of background, which is lower with compared to that before beam injection the H.F. emission intensity decreases with the distance from the gun but it is still registered up to lOOm the present results show that this H.F. turbulence is electrostatic in its nature and is created only in the region penetrated by the ion beam. -

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REFERENCES 1. Pottelette,R., J.M.Illiano, O.H.Bauer, and R.Treumann, Observation of high-frequency turbulence inducted by artificial ion beam in the ionosphere, J.Geophys.Res., 89, 2324-2334, 1984. 2. Erlandson,R.E.,L.J.Cahill, C.J.Pollock, R.L.Arnoldy,WAScales, and P.M.Kintner, Initial results from the operation of two argon ion generators in the ionosphere, J.Geophys.Res., 92, 4601-4616, 1987. 3. Moore,T.E., R.L.Arnoldy, R.L.Kaufmann, LJ.Cahill, P.M.Kintner, and .N.Walker, Anomalous auroral electron distributions due to an artificial ion beam in the ionosphere, J.Geophys.Res.,87, 7569-7579, 1982. 4. Moore,T.E., R.L.Arnoldy, L.J.Cahill, and P.M.Kintner, Plasma jet effects on the ionospheric plasma, Eur. Space Agency Spec. Pub!., Active Experiments in Space ESA-SP-195, 197-206, 1983.