Simultaneous Rocket Research Articles

Simultaneous Rocket and Scintillation Observations of Plasma Irregularities Associated With a Reversed Flow Event in the Cusp Ionosphere

AbstractWe present an overview of the ionospheric conditions during the launch of the Investigation of Cusp Irregularities 3 (ICI‐3) sounding rocket. ICI‐3 was launched from Ny‐Ålesund, Svalbard, at 7:21.31 UT on 3 December 2011. The objective of ICI‐3 was to intersect the reversed flow event (RFE), which is thought to be an important source for the rapid development of ionospheric irregularities in the cusp ionosphere. The interplanetary magnetic field was characterized by strongly negative Bz and weakly negative By. The EISCAT Svalbard radar (ESR) 32‐m beam was operating in a fast azimuth sweep mode between 180° (south) and 300° (northwest) at an elevation angle of 30°. The ESR observed a series of RFEs as westward flow channels that were opposed to the large‐scale eastward plasma flow in the prenoon sector. ICI‐3 intersected the first RFE in the ESR field of view and observed flow structures that were consistent with the ESR observations. Furthermore, ICI‐3 revealed finer‐scale flow structures inside the RFE. The high‐resolution electron density data show intense fluctuations at all scales throughout the RFE. The ionospheric pierce point of the GPS satellite PRN30, which was tracked at Hornsund, intersected the RFE at the same time. The GPS scintillation data show moderate phase scintillations and weak amplitude scintillations. A comparison of the power spectra reveals a good match between the ground‐based GPS carrier phase measurements and the spectral slope of the in situ electron density data in the lower frequency range. It demonstrates the possibility of modelling GPS scintillations from high‐resolution in situ electron density data.

Estimate of the NO concentration in the auroral region based on emission intensities of 391.4, 557.7, and 630.0 nm

Using numerical modeling, the influence of the NO concentration on the intensity of 557.7 nm emission in aurora caused by electron precipitation has been studied. It has been shown that the O2 + NO reaction, which reduces the contribution of the dissociative recombination of the O2 + ion into the formation of the 1S state of atomic oxygen, is the main channel of suppression of the intensity of the emission at 557.7 nm. A method of estimating the NO concentration in the aurora based on the data of photometric measurements of emissions at 391.4, 557.7, and 630.0 nm has been proposed. The method has been tested using the data of simultaneous rocket measurements of emissions at 391.4, 557.7, and 630.0 nm and the NO content in aurora. A good agreement of estimates of the NO concentrations performed by the method to the results of direct measurements has been obtained.

An experimental study of the nightglow OH(8-3) band emission process in the equatorial mesosphere

Simultaneous rocket measurements of the OH Meinel (8-3) band and O2 Atmospheric (0-0) band emission profiles are used to investigate the OH (v = 8) loss in the equatorial mesosphere due to collisions with O2 and N2. The O2 Atmospheric (0-0) band emission profile is used to obtain the atomic oxygen concentration. The derived branching ratios, A(8)A(8-3), and quenching parameters are found to be about a factor of two smaller than those obtained by McDade et al. (1987). Adopting branching ratios A(8)A(8-3) from the literature, the best agreement between the emission profiles of oxygen and OH is obtained using the Meinel band transition probabilities of Turnbull and Lowe (1989).

Turbulence energy dissipation rates and inner scale sizes from rocket and radar data

Estimates of turbulence energy dissipation rates and inner scale sizes have been obtained at altitudes of 80∼90 km, using simultaneous rocket and radar data from the STATE experiments. Spectral widths from radar Doppler spectra and the rocket‐derived temperatures were used to calculate the turbulence energy dissipation rate as a function of height; values generally ranged from 0.05 to 0.15 m2 s−3, with a long term average about 0.1 m2 s−3. The maximum observed energy dissipation rate was about 1.0 m2 s−3, but these occasional intense levels of turbulence lasted only a few minutes. The kinematic viscosity has been calculated from the rocket data, which was then used with the energy dissipation rates to estimate the turbulence microscale (η) as a function of height; values of about 1.5∼2.0 m were obtained from 80 to 87 km, with η increasing rapidly for heights above about 87 km. The inner scale for neutral turbulence is approximately 13 times η, which therefore possibly ranges from 20 to 26 m, which is in approximate agreement with other estimates for the mesosphere. This result shows that the 3‐m scattering wavelength for the Poker Flat Radar is well within the viscous subrange for neutral turbulence and raises questions as to why such large backscatterd signals are detected in the polar mesosphere. A companion paper (Kelley and Ulwick, this issue) discusses this within the context of the electron density fluctuation spectra measured during the STATE campaign.

Eton 5: Simultaneous rocket measurements of the OH meinel Δυ = 2 sequence and (8,3) band emission profiles in the nightglow

Simultaneous rocket measurements of the emission profiles of the OH Meinel (8,3) band and the Δυ = 2 sequence at 1.61 μm are presented and analysed. It is shown that the υ = 8 level of the hydroxyl radical must suffer significant loss in the mesosphere due to collisions with O 2 and/or N 2. The rate coefficients for this removal process are obtained, for certain limiting assumptions about the excitation mechanism, and the coefficients are found to be in good agreement with those deduced from an independent analysis of ground-based observations. A variety of kinetic models, which reproduce the observed (8,3) band profile in some detail, predict Δυ = 2 sequence emission profiles which compare favourably with the measured profile in their total zenith intensities but not in their altitude distributions. The differences between the measured and modelled Δυ = 2 altitude profiles suggest that the 1.61 μm observations may have been contaminated by some unidentified vehicle-induced emission.

The Condor Equatorial Spread F Campaign: Overview and results of the large‐scale measurements

During the Condor campaign a number of instruments were set up in Peru to support the rocket experiments. In this series of papers we report on the results of the experiments designed to study the equatorial F region. In this overview paper we summarize the main results as well as report upon the macroscopic developments of spread F as evidenced by data from backscatter radars, from scintillation observations, and from digital ionosonde meaurements. In this latter regard, we argue here that at least two factors other than the classical gravitational Rayleigh‐Taylor plasma instability process must operate to yield the longest‐scale horizontal organization of spread F structures. The horizontal scale typical of plume separation distances can be explained by invoking the effect of a shear in the plasma flow, although detailed comparison with theory seems to require shear frequencies a bit higher than observations indicate. On the other hand, the largest‐scale organization or modulation of the scattering layer cannot be explained by the shear theory and must be due to local time variations in the ionospheric drift or to gravity wave induced vertical motions. Using simultaneous rocket and radar data, we were also able to confirm the oft quoted hypothesis that rapid overhead height variations in the scattering region over Jicamarca are primarily spatial structures advecting overhead. The detailed rocket‐radar comparison verified several other earlier results and speculations, particularly those made in the PLUMEX experiments. In particular, companion papers discuss and extend some of the PLUMEX results to include the role of anomalous diffusion (LaBelle et al., this issue) in the theory of equatorial spread F and to shed light upon the shallow spectral form often observed in the intermediate‐scale regime (LaBelle and Kelley, this issue).

Thermospheric odd nitrogen: 2. Comparison of rocket observations with a diffusive transport chemical model

A one‐dimensional model of thermospheric odd nitrogen chemistry is used to simulate simultaneous rocket measurements of NO, N(4S) and O(³P) at twilight. Good agreement between the observations and the model is obtained for the N(4S) densities above 100 km and for the NO densities above 130 km. Differences between the N(4S) profiles from the upleg nightglow and downleg twilight airglow measurements are consistent with the diurnal variation of N(4S) predicted by the theory. The model shows that with high thermospheric temperatures the diurnal variation of NO decreases, while the N(4S) diurnal variation increases. This behavior is attributed to the temperature sensitivity of the rate for the production of NO from N(4S) and O2. The model is used to predict the solar cycle dependence of the NO chemiluminescence.

Simultaneous rocket probe and radar measurements of equatorial spread F—Transitional and short wavelength results

During the PLUMEX I rocket flight from Kwajalein Island, plasma density and electric field fluctuations were measured in situ, simultaneous with ground‐based radar backscatter measurements at 0.96‐m and 0.36‐m wavelengths. The rocket penetrated an extremely turbulent topside region which had associated intense backscatter. As measured by the radar the backscatter power was decaying with time during and after the flight. The intermediate wavelength (0.1–10 km) in situ electron density measurements are described in a companion paper, while here we report the transitional and short wavelength results (λ < 100 m). These data include the first in situ equatorial spread F measurements of the electric field component of electrostatic fluctuations with wavelengths less than 1 m. At all altitudes above about 280 km, a repeatable form for the wave‐number spectrum was found for the electron density and electric field fluctuations at wavelengths less than about 100 m. The density spectrum varies approximately as k−5 and the electric field spectrum as k−3. The steepness of the density spectrum corresponds to an absence of steep edges in the density waveform on the scale of 100 m and less. These two spectral forms are shown to be consistent with an explanation involving low‐frequency waves with finite wave numbers parallel to the magnetic field (k∥). Both theory and laboratory experiments show a power law density fluctuation spectrum for gradient‐driven drift waves with negative index in the range 4.5–6.0. Since such waves do have finite k∥, and since sharp gradients exist in the spread F environment, we conclude that at sufficiently high altitudes, drift waves act on the steep gradients caused by a primary longer‐wavelength instability to create the observed spectral form. These waves may then create an anomalous diffusion as discussed by Huba and Ossakow (1981b). At lower altitudes a shallower spectral index was observed in the tens of meters range, which may be related to a collisional damping regime. This suggests an altitude threshold for the drift waves that is probably related to ion neutral collisions. The power law spectra show no marked change near k⊥ri ≈ 1 where ri is the ion gyroradius. Since low‐frequency drift waves are linearly stable for k⊥ri ≳ 1, it seems that a wave‐wave interaction (cascade) operates to deposit energy in a range where waves are linearly damped. There is a slight suggestion of a spectral change (smaller negative index) for k⊥re ≳ 0.2 which may be due to excitation of a lower‐hybrid drift wave and which may be related to the observed enhanced backscatter at wavelengths on the order of 1 m. A stability analysis shows that the plasma is near but on the stable side of the marginal stability boundary for the lower‐hybrid drift wave in the most intense region of backscatter. In regions devoid of drift waves, evidence is found for an exponential inner‐scale cutoff at a wavelength of 200 m.

Simultaneous rocket and radar measurements of currents in an auroral arc

A detailed study of electric field, current and conductivities associated with an auroral arc was made in a coordinated rocket and radar experiment in Alaska on March 9, 1978. The payload, designated 29.007 UE, was launched at 1013 p.m. local time. It penetrated the diffuse aurora on the upleg and at apogee traversed field lines connected to a stable auroral arc of 40 kR intensity. Among the instruments carried by the payload were a vector magnetometer, a set of electrostatic double probes and a set of electron and proton spectrometers. Simultaneous electron density and line‐of‐sight velocity measurements were made by the Chatanika radar operating in an elevation scan mode in the magnetic meridian plane. Both the radar and rocket measurements indicated that the zonal electric field was westward and approximately constant across the arc with a magnitude of about 7 mV/m. Small differences between the rocket and radar zonal electric field measurements indicated the presence of upward drifting ions in the region of the arc. The meridional field was large and northward equatorward of the arc, but negligible within the arc. Conductivities computed from measured fluxes of energetic electrons agreed well with the conductivities derived from the radar measurements of electron density. The electric field and conductivity measurements indicated that the zonal currents were eastward equatorward of the arc and westward within the arc. These electrojet currents agreed well with those inferred from the rocket magnetometer data. Better agreement was obtained when a westward neutral wind was added. The westward wind was also consistent with differences between the rocket and radar meridional electric fields. The meridional currents computed from the electric field measurements were northward over the entire region. Since the northward current was enhanced within the arc, a pair of oppositely directed field‐aligned current sheets associated with the arc edges was inferred. However, these current sheets were not detected by the rocket‐borne vector magnetometer. The magnetometer measured a downward current in the diffuse aurora equatorward of a wide region of upward current within which the arc was embedded. The differences in the field‐aligned current patterns inferred from the two methods are attributed either to a time dependent field‐aligned current profile or east‐west current divergence in the region of the Harang discontinuity.

Simultaneous rocket probe, scintillation, and incoherent scatter radar observations of irregularities in the auroral zone ionosphere

Two rocket payloads carrying plasma density probes with high spatial resolution have been flown in the auroral zone during active conditions. Simultaneous Wideband satellite scintillation and Chatanika incoherent scatter radar observations were made in order to study the properties of high‐latitude irregularities and their effects on radio wave transmission. Unlike barium cloud striations and bottomside equatorial spread F, the observed power law dependence of the irregularities does not seem to be due to steepening of kilometer‐scale structures, rather, a turbulent process seems to occur. In addition the power law indexes determined both from the probe and from the scintillation measurements indicates an in situ one‐dimensional spectrum less steep than the k−2 value often reported. Both the probe and the scintillation data indicate absolute electron density fluctuations (Δn2e)½ of several times 109 m−3 during the expansion phase of an auroral substorm, with a layer thickness of several hundred kilometers. The observed S4 levels at VHF were in the range of 0.1–0.4. This level of scintillation, as well as the absolute density fluctuation levels and the power spectral density at the kilometer scale, are shown to be comparable with bottomside equatorial spread F. It is suggested that differences between the power spectral index in the present data set and the other ionospheric experiments mentioned above may be due to a highly conductive E layer and its effects upon the nonlinear evolution of irregularities. During another flight with lower magnetic activity but several bright auroral areas in the trajectory, much lower levels of absolute and relative density fluctuations were observed with a corresponding lower value for S4. Two very sharp changes in electron density were observed (e‐folding scales of 1.45 and 0.7 km) near the field line projected position of the auroral arcs. The associated density spectra were peaked at short wavelengths. The detection of very structured plasma within minutes of the poleward expansion phase of a substorm suggests that the F layer irregularities were formed in the precipitation event. On the other hand, evidence is also presented for production or enhancement of irregularities in the presence of horizontal density gradients which suggests that plasma instabilities also play a role in the production of auroral zone irregularities.

Coordinated measurements of E-layer drifts.

A statistical analysis of a vast global experimental material of irregularity ionization horizontal drift radio physical measurements at ionospheric levels up to 130km allows one to reveal the basic features of the dynamical regime of the lower thermosphere. Intercalibration of radiomethods by simultaneous rocket and radio meteor measurements and physical considerations allow the measurements to be interpreted as an information on the neutral wind in the radio wave reflection region. In the mid-latitude ionospheric E-region the prevailing wind has a clearly pronounced seasonal variation in contrast to equatorial and high-latitude zone. In the high-latitude E-region there is observed an independent circulation cell probably linked with the properties of the thermal regime in the polar lower thermosphere. The drift measurements for 85-95km by the method of spaced receivers in the long waveband in Eastern Siberia are reported for 1974-1976. The results are compared with simultaneous similar measurements at the same latitudes in Central Europe. The differences which are thought to be associated with climatic conditions at the observation sites, are emphasized.

Vertical incidence absorption calculated using electron density profiles from rocket experiments and comparison with observations during the winter anomaly

In the first part of this paper ground-based measurements of vertical incidence absorption are compared with values calculated from electron density profiles from simultaneous rocket experiments. These data were obtained at Wallops Island during an investigation of the winter anomaly in radiowave absorption. The measurements were made at 3.03 MHz during five of the rocket flights and at 1.8 MHz on four others. Satisfactory agreement between observed and calculated values of absorption is obtained for an electron collision frequency model v m = 6.3 × 10 5 p where p is the pressure (in N m −2) from CIRA 1972. In the second part of the paper this electron collision frequency model is used in the calculation of vertical incidence absorption as a function of frequency between 1.7 and 3.0 MHz. The nine electron density profiles from the winter season are used together with five additional profiles from rocket flights in other seasons, all profiles being for a solar zenith angle of about 60°. Examination of the calculated values shows that the absorption is more sensitive to frequency changes than expected particularly for winter days, even at frequencies much less than ƒoE. The occurrence and number of multiple echoes in the ionograms is consistent with the calculated absorption values.

Variations in the stratospheric ozone field inferred from Nimbus satellite observations

The ultraviolet Earth radiance data from the backscatter ultraviolet experiment on Nimbus 4 have been inverted to infer ozone profiles using a single Rayleigh scattering model. Two methods of solution give essentially the same results. Comparison of these profiles with simultaneous rocket sounding data shows satisfactory agreement at low and middle latitudes.Vertical cross-sections of ozone mixing ratio along the orbital tracks indicate that while the gross characteristics of the ozone field above 10 mb are under photochemical control, the influence of atmospheric motions can be found up to the 4 mb level.

Electric field and fine structure in aurora

Simultaneous rocket measurements of electric field and optical aurora during a weak PCA event are presented. The aurora consisted of faint structures superposed on a homogeneous glow and on-board photometers showed that the rocket passed through two discrete auroral forms. These enhanced auroral emissions coincided with variations in the d.c. electric field and an increase in the a.c. field. A detailed comparison between electric fields and optical emissions shows that the relation is quite complex. The results are compared with earlier electric field and optical auroral measurements.

Electron densities measured by the partial reflection method compared with simultaneous rocket measurements

Electron densities measured by the partial reflection method and by rocket techniques during the solar eclipse of 20 May 1966, are in satisfactory agreement below about 82 km height. A discrepancy above 82 km is almost certainly due to a systematic error in the partial reflection experiment caused by an increasing importance of oblique echoes at high altitudes.

Coordinated rocket measurements on the D-region winter anomaly—I. Experimental results

Because of possible associations between D-region warmings and enhanced electron densities on winter days of high radio-wave absorption, nearly simultaneous rocket measurements of D-region temperatures and electron densities were conducted on an anomalous winter day at Wallops Island, Virginia. Groundbased radio-wave absorption measurements on 3.03 MHz and sweep-frequency ionosonde observations revealed that 31 January 1967 was an anomalous winter day, and rockets were launched to measure electron densities, neutral temperatures, and winds in the D-region. On 3 February 1967, the 3.03 MHz radio wave absorption had decreased to normal levels and a second rocket-grenade experiment was launched to measure neutral temperatures and winds in the mesosphere. The electron density profile for 31 January 1967 was generally similar to the one measured on the anomalous winter day of 10 January 1966, the densities in the 70–80 km height range being about five times greater than those on a normal winter day. The rocket-grenade temperature profile for the anomalous day revealed a strong temperature inversion at 70 km and a warm layer extending from the inversion to 84 km; this temperature structure was significantly different from that at the same altitudes on the normal day of 3 February 1967.

Simultaneous rocket and satellite measurements of the topside ionosphere

Charged-particle profiles of upper ionosphere from alouette topside satellite sounding, compared with rocket- & ground-based backscatter measurements