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Solar power satellites and the ionosphere
Adv. Space Ree.
Vol.2, No.3, pp. 104—109, 1982
Printed in Great Britain.
0273—1177/82/030104-06$03.00/0
All rights reserved.
Copyright © COSPAR
lic. SOLAR POWER SATELLITES AND THE IONOSPHERE The Effect of High Power Microwave Beams on the Ionosphere and the Chemical Effects due to Heavy-Lift Launch Vehicles
CCIR Document 6/46-E (3rd March, 1980): Presented by the U.K.
1.
Introduction
A significant contribution towands meeting the Earth’s future energy requirements could stem from Solar Power Satellites (SP5). In such systems, solar energy is collected by a large array of solar cells in geostationary orbit, converted to BF power at microwave frequencies and beamed to Earth for conversion into BC{l}. A conceptua.]. design of an SPS is given in OCIR Report 679 which describes a system having a transmitted RF power level of 6.5 GW from an antenna array approximately 1 km in diameter. The half-power beamwidth is 0.008° which confines the power to a column some 5 km in diameter; the power flux density at the centre 2. The frequency is 2.45 GHz, of the beam at the Earth’s surface is approximately 200 W m chosen at a value where the combined effects of the ionosphere and troposphere are expected to be a minimum. Since the power level associated with SPS systems is far in excess of that usually encountered in radio services, it is important to determine its effects on the environment. In particular, the microwave beam will interact with the ionosphere and troposphere and this could lead to serious effects on existing radio services; in turn, the interactions could affect the transmission of the power satellite
beam itself.
The construction of SPS systems will require many flights of large rockets called HeavyLift Launch Vehicles (HLLv). Powered flights of these large hydrogen or hydrocarbon burning rockets may cause temporary removal of ions and electrons from the F region. Severe depletions in the ionospheric density could result, in turn causing serious effects on teleconununications. This Report discusses the ionospheric interactions which may occur, paying particular attention to the interference potential to other radio services.
Some of
these interactions and their ramifications are essentially the same as those arising from high—power transmissions at HF and lower frequencies, discussed in COIR Reports 574—1 and 728. 2.
SPS Impacts on the Ionosphere
The ionospheric interactions may be separated broadly into two categories: (i) Passive interactions, in which the ionospheric plasma influences the propagation of the power satellite beam in some way, and in some instances possibly gives rise to cc— chamiel interference through scattering off the beam.
Effects of High Power Microwaves and Heavy—Lift Launch Vehicles
105
(ii) Active Interactions, in which the ionospheric plasma itself is modified. Strong electron heating from the power satellite beam may produce irregularities in the ionisation, capable of scattering radio waves of lower frequencies, thereby increasing the potential for broad-band interference. Ionospheric modification may also result from the emission of exhaust effluents from HLLV’s. The associated changes in ionospheric chemistry can lead to depletions in ionisation at F—region heights. 2.1.
Passive Interactions
The trans-ionospheric propagation of the power satellite beam may be influenced by naturally occurring electron density gradients and irregularities in the ionosphere. Refraction effects will cause an apparent change in the position of the beam source, the effect increasing with decreasing elevation angle. For reception of the power satellite beam at mid or low latitudes, however, the apparent displacement of the beam would be only a few metres during times of high ionospheric electron content. The compensation mechanisms incorporated in the SPS system will correct for any such displacement of the beam. More serious effects could result from naturally occurring electron density irregularities which are known to cause scintillation of trans—ionospheric radio signals. The irregularities responsible for scintillation at gigahertz frequencies are spaced typically 2(X) m apart, at an altitude of 300 kin, and their effect on trans—ionospheric radio—wave propagation may be likened to that of a diffraction grating. Intensity maxima are produced by diffraction grating effects • For an SPS transmission, radiation outside the main beam, incident on the Earth’s surface, would be associated with power flux densities several orders of magnitude greater than those of existing satellite services; this situation would exist over the entire region of the Earth visible to the SPS. Thus, propagation of the SPS beam through such irregularities could have serious consequences for co—channel radio services. The effects could be mitigated, however, by avoiding propagation of the bean through the equatorial and high-latitude scintillation regions. 2.2.
Active Interactions
2.2.1.
BlLectron heating.
As a radio wave passes through the ionosphere, the electrons are
set in motion by the electric field of the wave. When the electrons collide with ions and neutral particles this motion is destroyed and as a result the radio wave suffers absorption and is attenuated. The energy extracted from the radio wave increases the temperature and velocity of the free electrons, and this ohmic heating of the plasma increases the electron collision frequency, which results in further electron heating.
Sufficiently strong ohmic
heating can produce a continuously increasing electron temperature, saturating only at some level where compensating processes come into play. The phenomenon is referred to as thermal runaway. Calculations have been undertaken to determine the extent to which the ionosphere will be heated by the SPS beaiu[2} and results clearly demonstrate that significant increases in electron temperature will occur in the D and E regions. This heating may then affect some fundamental ionospheric processes, such as electron—ion recombination rates, ionospheric densities, or drive secondary non—linear ionosphere—microwave interactions, further disturbing the ambient plasma. All these disturbances could have serious effects on existing telecommunication services.
106
CCIR Document 6/46—E
Since ohmic heating is inversely proportional to the square of the frequency, it is possible to simulate experimentally the ohmic heating which should occur from an SPS transmission by scaling down both the frequency and the power of the heating wave. Attempts have been made, therefore, to verify experimentally the potential heating effects cited above but, as yet, results are inconclusive. A further detailed research programme is planned using ionospher-. Ic modification facilities at Arecibo (Puerto Rico) and Platteville (USA). 2.2.2.
Absorption.
The increase in electron collision frequency arising from the propaga-
tion of an electromagnetic wave through the ionosphere will cause increased absorption of any other radio wave traversing the same region of the ionosphere as the original wave. It is important, therefore, to consider the extent to which a radio wave nay be attenuated when propagating through a region of the ionosphere illuminated by the SPS beam. Calculations reveal that the collision frequency in such a region could increase substantially, and thus give rise to corresponding increases In the non-devlative absorption of a radio wave traversing the same region. However, because of the relatively small area in which the effect would occur, it Is thought unlikely that any significant disruption of ionospheric radio communications would take place. 2.2.3. Field—aligned irregularities. A further process arising from electron heating by electromagnetic waves is thermal self—focusing. There exist in the ionosphere small natural fluctuations In electron density which cause corresponding variations In the refractive index of the plasma. An electromagnetic wave propagating through the plasma is slightly focused and defocused by these variations and refracted Into those regions of lower electron density. Here, the electric field intensity increases causing more plasma to drift away from these focused regions, thereby amplifying the original perturbation. This self— focusing process continues until hydrodynamic equilIbrium is reached, creating large-scale (‘~1 km wide) irregularities aligned along the direction of the geomagnetic field. The formation of electron density irregularities, or striations, has been observed in ionospheric modification experiments performed over the last decade ~ 3}. CCIR Report 728 discusses the results of these experiments and the potential use of ionospheric modification for telecommunications purposes. However, the modified region has also the potential to cause serious interference to radio services at frequencies up to UHF, and it is important, therefore, to consider mechanisms such as thermal self-focusing as a potential interaction arising from the power satellite transmission. When the frequency ~h of the heating wave is greater than the ionospheric critical frequency ~c (as in the SPS case), the threshold power flux density to initiate thermal self—focusing, ~th is given by the following expression: 20 5 2 -6 —k 2 ~th
(9 x 10
)
Te
~h ~c
X~ sin
4’
where Te Is the electron temperature (K),
is the striation width
(in)
and
4’ is the
angle between the electromagnetic wave vector and the geomagnetic field. It is difficult to determine an absolute threshold power for theraal self—focusing because the instability threshold power depends non-linearly on the excited striation width. As the incident power flux increases, smaller striations become unstable; in addition, the power flux necessary to amplify any particular striation size becomes very small as self—focusing beam becomes parallel to the geomagnetic field.
4’ approaches zero, i.e. the
Effects of High Power Microwaves and Heavy—Lift Launch Vehicles
107
Predictions for SPS reveal that thermal self-focusing is expected to occur. Substituting 1’c = 10 MHz into the equation above, and putting 4’ = 30° typical values of T 5 = 1500K ~ as an appropriate value for reception of the beam at mid-latitudes, striations should be produced with widths of approximately 5(X) m. Since the Instability threshold depends on the square of the heating wave frequency, experiments using suitably scaled values of frequency and power can be used to verify the foregoing theory. It Is clearly important that the potential production of the self-focusing instabilities be fully investigated for SPS systems. Plasma interactions. In addition to large—scale field-aligned irregularities, small-scale plasma striatlons, having dimensions of a few metres, have been observed in HF ionospheric heating experiments. These observations helped in the discovery of a new mode 2.2.4.
of plasma reaction in which the heating between two high-frequency waves, the modifier wave and an electrostatic plasma wave, produces a low-frequency plasma wave which travels transversely to the geomagnetic field and causes small-scale (‘~3m) field-aligned density structures. These irregularities give rise to scattering, but at frequencies displaced from the transmitted signal frequency by an amount equal to the heating frequency. This scattering is far less aspect sensitive than that caused by large—scale striations, not being a strong function of the magnetic field geometry. The formation of these small-scale striationa therefore provides a further potential for increased interference, with consequent disruption of radio services. At first sight, it would appear unlikely for an SPS transmission to give rise to small—scale striations because the microwave frequency is too far removed from electrostatic plasma frequencies for production of the low—frequency component necessary for the formation of the striations.
However, certain reasons exist for pursuing studies of the phenomenon in the
SPS case: (i) The generation of small—scale plasma striations may be the result of secondary instabilities in the presence of thermal self—focusing irregularities and several possible mechanisms Some experimental evidence exists which indicates that small- and large—scale striations are closely related. are being investigated.
(ii)
The SPS microwave beam is to be controlled by information derived from a pilot signal
transmitted from the ground and received at the SF8 antenna.
The difference in frequency between the uplink pilot signal and the microwave power-beam could fortuitously give rise to plasma reactions by beating with an electrostatic wave and generating the small-scale density structures, as described above. The problem could be avoided by ensuring that the frequency difference always exceeds the highest expected plasma frequency; it must be borne in mind, however, that similar effects could occur if other transmissions, on frequencies close to that of the SPS, were incident on the same region of the ionosphere. (iii)
Even in the absence of organised small—scale striations,
small—scale electrostatic
turbulence in a plasma can lead to scattering and scintillation of electromagnetic waves, and there are many processes in plasmas which lead to locally strong levels of plasma turbulence, Such interactions are important for both the power beam and the uplink pilot signal. A thorough understanding of the generation of these small-scale plasma striatione is still required. It is hoped that their full relevance to SPS will become apparent following proposed heating experiments.
108
CCIR Document 6/46—E
2.2,5. SF8 constructional effects on the ionosphere. The construction of SPS systems necessitates numerous launches of HLLV’s. Ionospheric depletions of electron and ion densities are predicted to occur as a result of these launches, caused by the injection of exhaust products into the F region. At altitudes of approximately 200 kin, the normally occurring 0~ions transfer their charge to combustion products H
20, H and C02, forming polyatomic ions that recombine rapidly with free electrons. An enhancement of the electron— ion reconibination rate thus occurs, resulting in depletions of F—region ionisation density. Several observations of this effect have been made from previous rocket launches. A reduction of some 5(Y)~in total electron content was measured after the launch of Skylab 1 in May 1973.
The depletion extended over a region some 2000 km in diameter and was observed
for approximately four hours {4}. Fluctuations in electron density of 5-l(~ were also observed following the launches of spacecraft; during the disturbances, multiple reflections of HF radio waves occurred {5}. In addition to ionisation depletions, effects predicted to follow }ILV launches include disturbances of the electron density profile, electrical conductivities, ionosphere/magnetosphere coupling, and an increase in satellite drag. Decreases in electron density will directly affect HF communications and., in addition, cause changes in the propagation properties of other electromagnetic waves traversing the disturbed region.
3. Effects on Ebcisting Services The ionospheric interactions cited above fall into two categories~ (I) Disturbance of the SPS beam and the uplink pilot beam. Effects involve refraction by electron density gradients diffraction by naturally occurring ionospheric irregularities. (ii)
Modification of the ionosphere.
Effects involve
increasing absorption disturbance of local ionospheric thermal budget, In turn affecting other ionospheric mechanisms depletion of ionospheric densities generation of large—scale striations initiation of other plasma interactions, in turn leading to the generation of small—scale striations. Interactions in both categories would cause interference to existing radio services.
Go—
channel interference at the SPS frequency could arise from scattering of the beam from naturally occurring ionospheric irregularities. Such irregularities, known to cause scintillation on trans—ionospheric radio waves, could be produced artificially by mechanisms in category (ii). MF and HF services could be directly affected by increased absorption in the lower ionosphere and by ionospheric density depletions in the F region. More serious broad-band interference could stem from radio-wave scattering of artificially
generated striations causing severe disruption to terrestrial
services up to UHF and to some trans—ionospheric services. More precise quantification of these effects is required but initially a much improved understanding of the relevant mechanisms must be achieved. A need exists for meaningful heating experiments in which SPS heating effects are simulated.
Effects of High Power Microwaves and Heavy—Lift Launch Vehicles
References 1. 2.
3. 4.
5.
P.E. Glaser, Proc. Inst. Elect. Electron. Engrs. F.W. Perkins and R.G. Roble, J. Geophys. Res. ~, W.F. Utlaut, Proc. Inst. Elect. Electron. Eagrs.
1162 (1977). 1611 (1978). ~, 1022 (1975). ~,
M. Mendillo, G.S. Hawkins and. J.A. Klobuchar, J. Geophys. Res. 80, 2217 (1975). G.F. Zasov, V.D. Karlov, T.Ye. Romanchuk, G.K. Solodovnikov, G.N. Tkachev and. M.G. frukhan, Geomagn. i Aeronomiya~, 2314. (1977).
Note added in proof A very recent paper on this subject is: N. Kaya and H. Matsuinoto, Space c~ia~nber experiments of ohmic heating by high-power microwaves from the Solar Power Satellite, Geophys. Res. Lett. ~, 1289 (1981).
109
Vol.2, No.3, pp. 104—109, 1982
Printed in Great Britain.
0273—1177/82/030104-06$03.00/0
All rights reserved.
Copyright © COSPAR
lic. SOLAR POWER SATELLITES AND THE IONOSPHERE The Effect of High Power Microwave Beams on the Ionosphere and the Chemical Effects due to Heavy-Lift Launch Vehicles
CCIR Document 6/46-E (3rd March, 1980): Presented by the U.K.
1.
Introduction
A significant contribution towands meeting the Earth’s future energy requirements could stem from Solar Power Satellites (SP5). In such systems, solar energy is collected by a large array of solar cells in geostationary orbit, converted to BF power at microwave frequencies and beamed to Earth for conversion into BC{l}. A conceptua.]. design of an SPS is given in OCIR Report 679 which describes a system having a transmitted RF power level of 6.5 GW from an antenna array approximately 1 km in diameter. The half-power beamwidth is 0.008° which confines the power to a column some 5 km in diameter; the power flux density at the centre 2. The frequency is 2.45 GHz, of the beam at the Earth’s surface is approximately 200 W m chosen at a value where the combined effects of the ionosphere and troposphere are expected to be a minimum. Since the power level associated with SPS systems is far in excess of that usually encountered in radio services, it is important to determine its effects on the environment. In particular, the microwave beam will interact with the ionosphere and troposphere and this could lead to serious effects on existing radio services; in turn, the interactions could affect the transmission of the power satellite
beam itself.
The construction of SPS systems will require many flights of large rockets called HeavyLift Launch Vehicles (HLLv). Powered flights of these large hydrogen or hydrocarbon burning rockets may cause temporary removal of ions and electrons from the F region. Severe depletions in the ionospheric density could result, in turn causing serious effects on teleconununications. This Report discusses the ionospheric interactions which may occur, paying particular attention to the interference potential to other radio services.
Some of
these interactions and their ramifications are essentially the same as those arising from high—power transmissions at HF and lower frequencies, discussed in COIR Reports 574—1 and 728. 2.
SPS Impacts on the Ionosphere
The ionospheric interactions may be separated broadly into two categories: (i) Passive interactions, in which the ionospheric plasma influences the propagation of the power satellite beam in some way, and in some instances possibly gives rise to cc— chamiel interference through scattering off the beam.
Effects of High Power Microwaves and Heavy—Lift Launch Vehicles
105
(ii) Active Interactions, in which the ionospheric plasma itself is modified. Strong electron heating from the power satellite beam may produce irregularities in the ionisation, capable of scattering radio waves of lower frequencies, thereby increasing the potential for broad-band interference. Ionospheric modification may also result from the emission of exhaust effluents from HLLV’s. The associated changes in ionospheric chemistry can lead to depletions in ionisation at F—region heights. 2.1.
Passive Interactions
The trans-ionospheric propagation of the power satellite beam may be influenced by naturally occurring electron density gradients and irregularities in the ionosphere. Refraction effects will cause an apparent change in the position of the beam source, the effect increasing with decreasing elevation angle. For reception of the power satellite beam at mid or low latitudes, however, the apparent displacement of the beam would be only a few metres during times of high ionospheric electron content. The compensation mechanisms incorporated in the SPS system will correct for any such displacement of the beam. More serious effects could result from naturally occurring electron density irregularities which are known to cause scintillation of trans—ionospheric radio signals. The irregularities responsible for scintillation at gigahertz frequencies are spaced typically 2(X) m apart, at an altitude of 300 kin, and their effect on trans—ionospheric radio—wave propagation may be likened to that of a diffraction grating. Intensity maxima are produced by diffraction grating effects • For an SPS transmission, radiation outside the main beam, incident on the Earth’s surface, would be associated with power flux densities several orders of magnitude greater than those of existing satellite services; this situation would exist over the entire region of the Earth visible to the SPS. Thus, propagation of the SPS beam through such irregularities could have serious consequences for co—channel radio services. The effects could be mitigated, however, by avoiding propagation of the bean through the equatorial and high-latitude scintillation regions. 2.2.
Active Interactions
2.2.1.
BlLectron heating.
As a radio wave passes through the ionosphere, the electrons are
set in motion by the electric field of the wave. When the electrons collide with ions and neutral particles this motion is destroyed and as a result the radio wave suffers absorption and is attenuated. The energy extracted from the radio wave increases the temperature and velocity of the free electrons, and this ohmic heating of the plasma increases the electron collision frequency, which results in further electron heating.
Sufficiently strong ohmic
heating can produce a continuously increasing electron temperature, saturating only at some level where compensating processes come into play. The phenomenon is referred to as thermal runaway. Calculations have been undertaken to determine the extent to which the ionosphere will be heated by the SPS beaiu[2} and results clearly demonstrate that significant increases in electron temperature will occur in the D and E regions. This heating may then affect some fundamental ionospheric processes, such as electron—ion recombination rates, ionospheric densities, or drive secondary non—linear ionosphere—microwave interactions, further disturbing the ambient plasma. All these disturbances could have serious effects on existing telecommunication services.
106
CCIR Document 6/46—E
Since ohmic heating is inversely proportional to the square of the frequency, it is possible to simulate experimentally the ohmic heating which should occur from an SPS transmission by scaling down both the frequency and the power of the heating wave. Attempts have been made, therefore, to verify experimentally the potential heating effects cited above but, as yet, results are inconclusive. A further detailed research programme is planned using ionospher-. Ic modification facilities at Arecibo (Puerto Rico) and Platteville (USA). 2.2.2.
Absorption.
The increase in electron collision frequency arising from the propaga-
tion of an electromagnetic wave through the ionosphere will cause increased absorption of any other radio wave traversing the same region of the ionosphere as the original wave. It is important, therefore, to consider the extent to which a radio wave nay be attenuated when propagating through a region of the ionosphere illuminated by the SPS beam. Calculations reveal that the collision frequency in such a region could increase substantially, and thus give rise to corresponding increases In the non-devlative absorption of a radio wave traversing the same region. However, because of the relatively small area in which the effect would occur, it Is thought unlikely that any significant disruption of ionospheric radio communications would take place. 2.2.3. Field—aligned irregularities. A further process arising from electron heating by electromagnetic waves is thermal self—focusing. There exist in the ionosphere small natural fluctuations In electron density which cause corresponding variations In the refractive index of the plasma. An electromagnetic wave propagating through the plasma is slightly focused and defocused by these variations and refracted Into those regions of lower electron density. Here, the electric field intensity increases causing more plasma to drift away from these focused regions, thereby amplifying the original perturbation. This self— focusing process continues until hydrodynamic equilIbrium is reached, creating large-scale (‘~1 km wide) irregularities aligned along the direction of the geomagnetic field. The formation of electron density irregularities, or striations, has been observed in ionospheric modification experiments performed over the last decade ~ 3}. CCIR Report 728 discusses the results of these experiments and the potential use of ionospheric modification for telecommunications purposes. However, the modified region has also the potential to cause serious interference to radio services at frequencies up to UHF, and it is important, therefore, to consider mechanisms such as thermal self-focusing as a potential interaction arising from the power satellite transmission. When the frequency ~h of the heating wave is greater than the ionospheric critical frequency ~c (as in the SPS case), the threshold power flux density to initiate thermal self—focusing, ~th is given by the following expression: 20 5 2 -6 —k 2 ~th
(9 x 10
)
Te
~h ~c
X~ sin
4’
where Te Is the electron temperature (K),
is the striation width
(in)
and
4’ is the
angle between the electromagnetic wave vector and the geomagnetic field. It is difficult to determine an absolute threshold power for theraal self—focusing because the instability threshold power depends non-linearly on the excited striation width. As the incident power flux increases, smaller striations become unstable; in addition, the power flux necessary to amplify any particular striation size becomes very small as self—focusing beam becomes parallel to the geomagnetic field.
4’ approaches zero, i.e. the
Effects of High Power Microwaves and Heavy—Lift Launch Vehicles
107
Predictions for SPS reveal that thermal self-focusing is expected to occur. Substituting 1’c = 10 MHz into the equation above, and putting 4’ = 30° typical values of T 5 = 1500K ~ as an appropriate value for reception of the beam at mid-latitudes, striations should be produced with widths of approximately 5(X) m. Since the Instability threshold depends on the square of the heating wave frequency, experiments using suitably scaled values of frequency and power can be used to verify the foregoing theory. It Is clearly important that the potential production of the self-focusing instabilities be fully investigated for SPS systems. Plasma interactions. In addition to large—scale field-aligned irregularities, small-scale plasma striatlons, having dimensions of a few metres, have been observed in HF ionospheric heating experiments. These observations helped in the discovery of a new mode 2.2.4.
of plasma reaction in which the heating between two high-frequency waves, the modifier wave and an electrostatic plasma wave, produces a low-frequency plasma wave which travels transversely to the geomagnetic field and causes small-scale (‘~3m) field-aligned density structures. These irregularities give rise to scattering, but at frequencies displaced from the transmitted signal frequency by an amount equal to the heating frequency. This scattering is far less aspect sensitive than that caused by large—scale striations, not being a strong function of the magnetic field geometry. The formation of these small-scale striationa therefore provides a further potential for increased interference, with consequent disruption of radio services. At first sight, it would appear unlikely for an SPS transmission to give rise to small—scale striations because the microwave frequency is too far removed from electrostatic plasma frequencies for production of the low—frequency component necessary for the formation of the striations.
However, certain reasons exist for pursuing studies of the phenomenon in the
SPS case: (i) The generation of small—scale plasma striations may be the result of secondary instabilities in the presence of thermal self—focusing irregularities and several possible mechanisms Some experimental evidence exists which indicates that small- and large—scale striations are closely related. are being investigated.
(ii)
The SPS microwave beam is to be controlled by information derived from a pilot signal
transmitted from the ground and received at the SF8 antenna.
The difference in frequency between the uplink pilot signal and the microwave power-beam could fortuitously give rise to plasma reactions by beating with an electrostatic wave and generating the small-scale density structures, as described above. The problem could be avoided by ensuring that the frequency difference always exceeds the highest expected plasma frequency; it must be borne in mind, however, that similar effects could occur if other transmissions, on frequencies close to that of the SPS, were incident on the same region of the ionosphere. (iii)
Even in the absence of organised small—scale striations,
small—scale electrostatic
turbulence in a plasma can lead to scattering and scintillation of electromagnetic waves, and there are many processes in plasmas which lead to locally strong levels of plasma turbulence, Such interactions are important for both the power beam and the uplink pilot signal. A thorough understanding of the generation of these small-scale plasma striatione is still required. It is hoped that their full relevance to SPS will become apparent following proposed heating experiments.
108
CCIR Document 6/46—E
2.2,5. SF8 constructional effects on the ionosphere. The construction of SPS systems necessitates numerous launches of HLLV’s. Ionospheric depletions of electron and ion densities are predicted to occur as a result of these launches, caused by the injection of exhaust products into the F region. At altitudes of approximately 200 kin, the normally occurring 0~ions transfer their charge to combustion products H
20, H and C02, forming polyatomic ions that recombine rapidly with free electrons. An enhancement of the electron— ion reconibination rate thus occurs, resulting in depletions of F—region ionisation density. Several observations of this effect have been made from previous rocket launches. A reduction of some 5(Y)~in total electron content was measured after the launch of Skylab 1 in May 1973.
The depletion extended over a region some 2000 km in diameter and was observed
for approximately four hours {4}. Fluctuations in electron density of 5-l(~ were also observed following the launches of spacecraft; during the disturbances, multiple reflections of HF radio waves occurred {5}. In addition to ionisation depletions, effects predicted to follow }ILV launches include disturbances of the electron density profile, electrical conductivities, ionosphere/magnetosphere coupling, and an increase in satellite drag. Decreases in electron density will directly affect HF communications and., in addition, cause changes in the propagation properties of other electromagnetic waves traversing the disturbed region.
3. Effects on Ebcisting Services The ionospheric interactions cited above fall into two categories~ (I) Disturbance of the SPS beam and the uplink pilot beam. Effects involve refraction by electron density gradients diffraction by naturally occurring ionospheric irregularities. (ii)
Modification of the ionosphere.
Effects involve
increasing absorption disturbance of local ionospheric thermal budget, In turn affecting other ionospheric mechanisms depletion of ionospheric densities generation of large—scale striations initiation of other plasma interactions, in turn leading to the generation of small—scale striations. Interactions in both categories would cause interference to existing radio services.
Go—
channel interference at the SPS frequency could arise from scattering of the beam from naturally occurring ionospheric irregularities. Such irregularities, known to cause scintillation on trans—ionospheric radio waves, could be produced artificially by mechanisms in category (ii). MF and HF services could be directly affected by increased absorption in the lower ionosphere and by ionospheric density depletions in the F region. More serious broad-band interference could stem from radio-wave scattering of artificially
generated striations causing severe disruption to terrestrial
services up to UHF and to some trans—ionospheric services. More precise quantification of these effects is required but initially a much improved understanding of the relevant mechanisms must be achieved. A need exists for meaningful heating experiments in which SPS heating effects are simulated.
Effects of High Power Microwaves and Heavy—Lift Launch Vehicles
References 1. 2.
3. 4.
5.
P.E. Glaser, Proc. Inst. Elect. Electron. Engrs. F.W. Perkins and R.G. Roble, J. Geophys. Res. ~, W.F. Utlaut, Proc. Inst. Elect. Electron. Eagrs.
1162 (1977). 1611 (1978). ~, 1022 (1975). ~,
M. Mendillo, G.S. Hawkins and. J.A. Klobuchar, J. Geophys. Res. 80, 2217 (1975). G.F. Zasov, V.D. Karlov, T.Ye. Romanchuk, G.K. Solodovnikov, G.N. Tkachev and. M.G. frukhan, Geomagn. i Aeronomiya~, 2314. (1977).
Note added in proof A very recent paper on this subject is: N. Kaya and H. Matsuinoto, Space c~ia~nber experiments of ohmic heating by high-power microwaves from the Solar Power Satellite, Geophys. Res. Lett. ~, 1289 (1981).
109