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Artificial plasma cloud evolution in the low latitude ionosphere
Jmamd of AmosphrrL md Terrestrrul Physics, Vol. 55, No. 2, pp. 193-195. 1993 Printed in Great Britam
OW-9169193 %5.00+ .oO ic” 1992 Pergamon Press Ltd
Artificial plasma cloud evolution in the low latitude ionosphere A. 1. KASHIRIN, 0.
F. KLYUEV* and G. P. MILINEVSKY~
* Institute of Experimental Meteorology, Scientific and Production Association ‘Typhoon’, Obninsk, Russia ; f Kiev State University, Kiev, Ukraine
The active rocket experiment ‘Contrast-3’ was carried out on 21 August 1991 at the position with the geographic coordinates 18”N, 53.2”W. The MR-20 rocket was Iaunched from the research vessel ‘Prof Zubov’ in the evening twilight at 2225 UT. During the flight the rocket head was separated into a payload with diagnostics and a module with the pyrotechnical container for the rapid generation and injection of I kg of barium vapour. The pyrotechnical composition and container design allow the injection of pure barium vapour in such a way that practically all other combustion products remained inside the container in the solid state. The barium cloud was formed at the rocket apogee at a height of 224 km and registered by TV and spectral devices. Neutral barium was quickly ionized by solar radiation and, in some minutes, the cloud was extended along the magnetic field. The observation of the cloud from one point (in this case from the research vessel) does not allow us to single out its horizontal and vertical motions. To do this extra data (or assumptions) on the character of the motion or on the cloud position are considered to be necessary. In the case of observing neutral luminous clouds, their height is assumed to be constant and the cloud coordinates are then determined unambiguously. For an artificial plasma cloud the suggestion that they drift across the Earth’s magnetic field can be made. However this depends on height and density and is not always true. In this experiment, to obtain additional data on the artificial plasma cloud position, the time when it was intersected by the terminator was considered. The angular cloud coordinates were determined from the star sky and the height was calculated by finding the point of intersection of the line of sight directed to the cloud and terminator surface. The cloud extent was estimated by tracing along the magnetic field. In the evening the ionized barium cloud was observed during approximately 28 min (after injection) when it was sunlit. At the end of the observational period it was in the 200-300 km height range
and so had not significantly shifted in height. The cloud travelled mainly eastward, the rate being about 50 m/s, without any striation during the whole observational period. A specific feature of this experiment by which it differs from other similar experiments is the fact that the ionized barium cloud was surely observed at dawn the next day, more than IO h after the injection. At this time the vessel was at the position with coordinates 18.1“N, 52.8”W. The cloud was discovered visually at about 0800 UT and was recorded by TV cameras from 0802 UT for more than 40 min until sunrise. From the first minutes of observation the cloud had a stratified structure (TV image obtained at 0802 UT is shown in Fig. I a) and a linear spectrum typical of an ionized barium cloud existed in the ionosphere. The angular cloud size at 0802 UT was 4 x 12 ‘. In this case it was not fully sunlit; the terminator line passed through its lower edge. This height of 290 km was estimated from the angular coordinates of the cloud intersecting the terminator. A part of the cloud shown in Fig. la is much above this height. One more fact that is clear from Fig. la should be noted : some cloud striations were not parallel to each other. We consider that this is the result of parallax caused by the long cloud extent and a small angle between the magnetic field and tine of sight (of about 20’). The estimates of cloud size showed that, early on, it was about 300 km in length and about 40 km in width (across the magnetic field). Considering that all the injected barium ions were concentrated in this volume, it is possible to obtain an upper value for the average ion concentration in the cloud, that is, 1O4 cm ‘. This concentration is much lower than the background plasma concentration ; therefore for this period the barium cloud can be considered as weak inhomogeneity drifting together with ionospheric plasma. Having appeared, the barium cloud travelled north eastward. When moving, the cloud significantly varied its visible structure. Figure 1b shows the cloud image 193
A. I.
194 Barium cloud position (projection on meridional IOh otter iniection
KASHIRIN et al
plain)
i
600
-
z 400 .!? al
-
E 2
I
p___h*-
------
Shadow
(UT=06-02)
200
t
-0500
IA
I
-100
-300
Distance
from
I
I
100
300
vessel
(km)
Fig. 2.
obtained at 0814 UT (in this and in Fig. Ic the scale is 2.7 times smaller than in Fig. I a) ; Fig. Ic presents the cloud image obtained at 0817 UT. It should be noted that during this period some cloud structures were also not parallel; in Fig. Ic at the upper right of the principal cloud there are the weak striations inclined at such an angle to the cloud which cannot be explained by the parallax effect. In our opinion the observed cloud deformation can be caused by variations in the observational angle (the zenith cloud angle during the observations varied from 40” to 0°) as well as by different travel speeds of its separate
structures. It is possible that the latter phenomenon is caused by an electric field inhomogeneity in the ionosphere during this period. The direction and intensity of the electric field in the ionosphere were estimated from the initial height of one cloud part (290 km) and from the angular cloud motion, supposing its crossfield drift. The mean electric field directed towards the geomagnetic east was 7 mV/m; across the magnetic field, downward, it was about 1.5 mV/m. The drift velocity was about 200 m/s; in 20 min the cloud was about 300 km higher. Figure 2 shows the cloud projections on the meridional plane for different times, illustrating its significant vertical elevation. For the geographical region where this experiment was carried out, such an electric field (and the corresponding vertical plasma drift velocity) is rather high. It must have strongly changed the structure of the background ionosphere and, in particular, resulted in a significant increase of the F2 layer height. The experimental data presented allow us to draw some conclusions. The ionospheric drift system at low latitudes may have a structure exhibiting a certain ‘closeness’ of drift paths, resulting in possible periodic ingress of any ionospheric inhomogeneity into one and the same geographical region. Also long lived artificial plasma (atomic ion) inhomogeneities in the nonsunlit ionosphere can exist in the form of rather compact clouds. The electric field in the low latitude ionosphere was unusually intense on this morning ; this must result in the significant raising of the F2 region.
Artificial plasma cloud evolution
Fig. 1.
195
OW-9169193 %5.00+ .oO ic” 1992 Pergamon Press Ltd
Artificial plasma cloud evolution in the low latitude ionosphere A. 1. KASHIRIN, 0.
F. KLYUEV* and G. P. MILINEVSKY~
* Institute of Experimental Meteorology, Scientific and Production Association ‘Typhoon’, Obninsk, Russia ; f Kiev State University, Kiev, Ukraine
The active rocket experiment ‘Contrast-3’ was carried out on 21 August 1991 at the position with the geographic coordinates 18”N, 53.2”W. The MR-20 rocket was Iaunched from the research vessel ‘Prof Zubov’ in the evening twilight at 2225 UT. During the flight the rocket head was separated into a payload with diagnostics and a module with the pyrotechnical container for the rapid generation and injection of I kg of barium vapour. The pyrotechnical composition and container design allow the injection of pure barium vapour in such a way that practically all other combustion products remained inside the container in the solid state. The barium cloud was formed at the rocket apogee at a height of 224 km and registered by TV and spectral devices. Neutral barium was quickly ionized by solar radiation and, in some minutes, the cloud was extended along the magnetic field. The observation of the cloud from one point (in this case from the research vessel) does not allow us to single out its horizontal and vertical motions. To do this extra data (or assumptions) on the character of the motion or on the cloud position are considered to be necessary. In the case of observing neutral luminous clouds, their height is assumed to be constant and the cloud coordinates are then determined unambiguously. For an artificial plasma cloud the suggestion that they drift across the Earth’s magnetic field can be made. However this depends on height and density and is not always true. In this experiment, to obtain additional data on the artificial plasma cloud position, the time when it was intersected by the terminator was considered. The angular cloud coordinates were determined from the star sky and the height was calculated by finding the point of intersection of the line of sight directed to the cloud and terminator surface. The cloud extent was estimated by tracing along the magnetic field. In the evening the ionized barium cloud was observed during approximately 28 min (after injection) when it was sunlit. At the end of the observational period it was in the 200-300 km height range
and so had not significantly shifted in height. The cloud travelled mainly eastward, the rate being about 50 m/s, without any striation during the whole observational period. A specific feature of this experiment by which it differs from other similar experiments is the fact that the ionized barium cloud was surely observed at dawn the next day, more than IO h after the injection. At this time the vessel was at the position with coordinates 18.1“N, 52.8”W. The cloud was discovered visually at about 0800 UT and was recorded by TV cameras from 0802 UT for more than 40 min until sunrise. From the first minutes of observation the cloud had a stratified structure (TV image obtained at 0802 UT is shown in Fig. I a) and a linear spectrum typical of an ionized barium cloud existed in the ionosphere. The angular cloud size at 0802 UT was 4 x 12 ‘. In this case it was not fully sunlit; the terminator line passed through its lower edge. This height of 290 km was estimated from the angular coordinates of the cloud intersecting the terminator. A part of the cloud shown in Fig. la is much above this height. One more fact that is clear from Fig. la should be noted : some cloud striations were not parallel to each other. We consider that this is the result of parallax caused by the long cloud extent and a small angle between the magnetic field and tine of sight (of about 20’). The estimates of cloud size showed that, early on, it was about 300 km in length and about 40 km in width (across the magnetic field). Considering that all the injected barium ions were concentrated in this volume, it is possible to obtain an upper value for the average ion concentration in the cloud, that is, 1O4 cm ‘. This concentration is much lower than the background plasma concentration ; therefore for this period the barium cloud can be considered as weak inhomogeneity drifting together with ionospheric plasma. Having appeared, the barium cloud travelled north eastward. When moving, the cloud significantly varied its visible structure. Figure 1b shows the cloud image 193
A. I.
194 Barium cloud position (projection on meridional IOh otter iniection
KASHIRIN et al
plain)
i
600
-
z 400 .!? al
-
E 2
I
p___h*-
------
Shadow
(UT=06-02)
200
t
-0500
IA
I
-100
-300
Distance
from
I
I
100
300
vessel
(km)
Fig. 2.
obtained at 0814 UT (in this and in Fig. Ic the scale is 2.7 times smaller than in Fig. I a) ; Fig. Ic presents the cloud image obtained at 0817 UT. It should be noted that during this period some cloud structures were also not parallel; in Fig. Ic at the upper right of the principal cloud there are the weak striations inclined at such an angle to the cloud which cannot be explained by the parallax effect. In our opinion the observed cloud deformation can be caused by variations in the observational angle (the zenith cloud angle during the observations varied from 40” to 0°) as well as by different travel speeds of its separate
structures. It is possible that the latter phenomenon is caused by an electric field inhomogeneity in the ionosphere during this period. The direction and intensity of the electric field in the ionosphere were estimated from the initial height of one cloud part (290 km) and from the angular cloud motion, supposing its crossfield drift. The mean electric field directed towards the geomagnetic east was 7 mV/m; across the magnetic field, downward, it was about 1.5 mV/m. The drift velocity was about 200 m/s; in 20 min the cloud was about 300 km higher. Figure 2 shows the cloud projections on the meridional plane for different times, illustrating its significant vertical elevation. For the geographical region where this experiment was carried out, such an electric field (and the corresponding vertical plasma drift velocity) is rather high. It must have strongly changed the structure of the background ionosphere and, in particular, resulted in a significant increase of the F2 layer height. The experimental data presented allow us to draw some conclusions. The ionospheric drift system at low latitudes may have a structure exhibiting a certain ‘closeness’ of drift paths, resulting in possible periodic ingress of any ionospheric inhomogeneity into one and the same geographical region. Also long lived artificial plasma (atomic ion) inhomogeneities in the nonsunlit ionosphere can exist in the form of rather compact clouds. The electric field in the low latitude ionosphere was unusually intense on this morning ; this must result in the significant raising of the F2 region.
Artificial plasma cloud evolution
Fig. 1.
195