Rocket-borne Measurements Research Articles

Nighttime O(1D) and corresponding Atmospheric Band emission (762 nm) derived from rocket-borne experiment

Based on common volume rocket-borne measurements of temperature, densities of atomic oxygen and neutral air, we derived O(1D) nighttime concentrations and corresponding Atmospheric band emission (762 nm). This is one of the first retrievals of the nighttime O(1D) concentration. Recently, Kalogerakis, Sharma and co-workers have suggested a new production path of O(1D) based on the reaction of vibrationally excited OH and O. We calculate Atmospheric band volume emission related to the population of O2(b1Σg+) from O(1D) and compare with total Atmospheric band emissions observed during the same rocket launch. This allows an estimation of the relative contribution of the new Kalogerakis-Sharma mechanism (KSM) to the total Atmospheric band emission. The concentration of O(1D) due to KSM amounts to several tens cm−3 with a peak around 95 km. The KSM gives an essential contribution to the total Atmospheric band volume emission (762 nm). Additionally, we illustrate analytically that the expressions for volume emission by the new KSM and the traditional two-step mechanism have similar functional dependences on the atmospheric concentrations of O and O2. This causes an ambiguity, when interpreting Atmospheric band observations in terms of the one mechanism or the other.

Atmospheric band fitting coefficients derived from a self-consistent rocket-borne experiment

Abstract. Based on self-consistent rocket-borne measurements of temperature, the densities of atomic oxygen and neutral air, and the volume emission of the atmospheric band (762 nm), we examined the one-step and two-step excitation mechanism of O2b1Σg+ for nighttime conditions. Following McDade et al. (1986), we derived the empirical fitting coefficients, which parameterize the atmospheric band emission O2b1Σg+-X3Σg-0,0. This allows us to derive the atomic oxygen concentration from nighttime observations of atmospheric band emission O2b1Σg+-X3Σg-0,0. The derived empirical parameters can also be utilized for atmospheric band modeling. Additionally, we derived the fit function and corresponding coefficients for the combined (one- and two-step) mechanism. The simultaneous common volume measurements of all the parameters involved in the theoretical calculation of the observed O2b1Σg+-X3Σg-0,0 emission, i.e., temperature and density of the background air, atomic oxygen density, and volume emission rate, is the novelty and the advantage of this work.

Thermal structure of the mesopause region during the WADIS-2 rocket campaign

Abstract. This paper presents simultaneous temperature measurements by three independent instruments during the WADIS-2 rocket campaign in northern Norway (69∘ N, 14∘ E) on 5 March 2015. Vertical profiles were measured in situ with the CONE instrument. Continuous mobile IAP Fe lidar (Fe lidar) measurements during a period of 24 h, as well as horizontally resolved temperature maps by the Utah State University (USU) Advanced Mesospheric Temperature Mapper (AMTM) in the mesopause region, are analysed. Vertical and horizontal temperature profiles by all three instruments are in good agreement. A harmonic analysis of the Fe lidar measurements shows the presence of waves with periods of 24, 12, 8, and 6 h. Strong waves with amplitudes of up to 10 K at 8 and 6 h are found. The 24 and 12 h components play only a minor role during these observations. In contrast only a few short periodic gravity waves are found. Horizontally resolved temperatures measured with the AMTM in the hydroxyl (OH) layer are used to connect the vertical temperature profiles. In the field of view of 200 km×160 km only small deviations from the horizontal mean of the order of 5 K are found. Therefore only weak gravity wave signatures occurred. This suggests horizontal structures of more than 200 km. A comparison of Fe lidar, rocket-borne measurements, and AMTM temperatures indicates an OH centroid altitude of about 85 km.

Long-term trends in the D- and E-region based on rocket-borne measurements

Electron densities obtained from rocket borne measurements are compared to an empirical, steady state model built from these data. The ratios between each measured value and its corresponding model value vs. time yield trends which significantly vary with altitude. Notably above 120–130km the electron densities generally increase, whereas between 95 and 120km the ionosphere appears stable. Somewhere below 80–90km - depending on the investigated data subset - there is again a positive trend down to below 70km. Tentative explanations such as cooling of the mesosphere are suggested and may be confirmed by comprehensive theoretical models of the upper atmosphere.

Spatial and temporal variability in MLT turbulence inferred from in situ and ground-based observations during the WADIS-1 sounding rocket campaign

Abstract. In summer 2013 the WADIS-1 sounding rocket campaign was conducted at the Andøya Space Center (ACS) in northern Norway (69° N, 16° E). Among other things, it addressed the question of the variability in mesosphere/lower thermosphere (MLT) turbulence, both in time and space. A unique feature of the WADIS project was multi-point turbulence sounding applying different measurement techniques including rocket-borne ionization gauges, VHF MAARSY radar, and VHF EISCAT radar near Tromsø. This allowed for horizontal variability to be observed in the turbulence field in the MLT at scales from a few to 100 km. We found that the turbulence dissipation rate, ε varied in space in a wavelike manner both horizontally and in the vertical direction. This wavelike modulation reveals the same vertical wavelengths as those seen in gravity waves. We also found that the vertical mean value of radar observations of ε agrees reasonably with rocket-borne measurements. In this way defined 〈εradar〉 value reveals clear tidal modulation and results in variation by up to 2 orders of magnitude with periods of 24 h. The 〈εradar〉 value also shows 12 h and shorter (1 to a few hours) modulations resulting in one decade of variation in 〈εradar〉 magnitude. The 24 h modulation appeared to be in phase with tidal change of horizontal wind observed by SAURA-MF radar. Such wavelike and, in particular, tidal modulation of the turbulence dissipation field in the MLT region inferred from our analysis is a new finding of this work.

Multiple neutral density measurements in the lower thermosphere with cold-cathode ionization gauges

Cold-cathode ionization gauges were used for rocket-borne measurements of total neutral density and temperature in the aurorally forced lower thermosphere between 90 and 200km. A commercial gauge was adapted as a low-cost instrument with a spherical antechamber for measurements in molecular flow conditions. Three roll-stabilized payloads on different trajectories each carried two instruments for measurements near the ram flow direction along the respective upleg and downleg segments of a flight path, and six density profiles were obtained within a period of 22min covering spatial separations up to 200km. The density profiles were integrated below 125km to yield temperatures. The mean temperature structure was similar for all six profiles with two mesopause minima near 110 and 101km, however, for the downleg profiles, the upper minimum was warmer and the lower minimum was colder by 20–30K indicating significant variability over horizontal scales of 100–200km. The upper temperature minimum coincided with maximum horizontal winds speeds, exceeding 170m/s.

Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign

Abstract. The Hygrosonde-2 campaign took place on 16 December 2001 at Esrange/Sweden (68° N, 21° E) with the aim to investigate the small scale distribution of water vapour in the middle atmosphere in the vicinity of the Arctic polar vortex. In situ balloon and rocket-borne measurements of water vapour were performed by means of OH fluorescence hygrometry. The combined measurements yielded a high resolution water vapour profile up to an altitude of 75 km. Using the characteristic of water vapour being a dynamical tracer it was possible to directly relate the water vapour data to the location of the polar vortex edge, which separates air masses of different character inside and outside the polar vortex. The measurements probed extra-vortex air in the altitude range between 45 km and 60 km and vortex air elsewhere. Transitions between vortex and extra-vortex usually coincided with wind shears caused by gravity waves which advect air masses with different water vapour volume mixing ratios. From the combination of the results from the Hygrosonde-2 campaign and the first flight of the optical hygrometer in 1994 (Hygrosonde-1) a clear picture of the characteristic water vapour distribution inside and outside the polar vortex can be drawn. Systematic differences in the water vapour concentration between the inside and outside of the polar vortex can be observed all the way up into the mesosphere. It is also evident that in situ measurements with high spatial resolution are needed to fully account for the small-scale exchange processes in the polar winter middle atmosphere.

First mesospheric turbulence study using coordinated rocket and MST radar measurements over Indian low latitude region

Abstract. A campaign to study turbulence in the mesosphere, over low latitudes in India, using rocket-borne measurements and Indian MST radar, was conducted during July 2004. A rocket-borne Langmuir probe detected a spectrum of electron density irregularities, with scale sizes in the range of about 1 m to 1 km, in 67.5–78.0 km and 84–89 km altitude regions over a low latitude station Sriharikota (13.6° N, 80.2° E). A rocket-borne chaff experiment measured zonal and meridional winds about 30 min after the Langmuir probe flight. The MST radar located at Gadanki (13.5° N, 79.2° E), which is about 100 km west of Sriharikota, also detected the presence of a strong scattering layer in 73.5–77.5 km region from which radar echoes corresponding to 3 m irregularities were received. Based on the region of occurrence of irregularities, which was highly collisional, presence of significant shears in zonal and meridional components of wind measured by the chaff experiment, 10 min periodicity in zonal and meridional winds obtained by the MST radar and the nature of wave number spectra of the irregularities, it is suggested that the observed irregularities were produced through the neutral turbulence mechanism. The percentage amplitude of fluctuations across the entire scale size range showed that the strength of turbulence was stronger in the lower altitude regions and decreased with increasing altitude. It was also found that the amplitude of fluctuations was large in regions of steeper electron density gradients. MST radar observations showed that at smaller scales of turbulence such as 3 m, (a) the thickness of the turbulent layer was between 2 and 3 km and (b) and fine structures, with layer thicknesses of about a km or less were also embedded in these layers. Rocket also detected 3-m fluctuations, which were very strong (a few percent) in lower altitudes (67.5 to 71.0 km) and small but clearly well above the noise floor at higher altitudes. Rocket and radar results also point to the possibility of existence of thin layers of turbulence (<450 m). The turbulence parameters estimated from rocket-borne measurements of electron density fluctuations are consistent with those determined from MST radar observed Doppler spectra and the earlier works.

A neural network-based ionospheric model for the auroral zone

A new empirical model for the lower ionosphere in the auroral zone, called IMAZ, has been developed, tested and refined for use in the International Reference Ionosphere (IRI) global model. Available ionospheric data have been used to train neural networks (NNs) to predict the high latitude electron density profile. Data from the European Incoherent Scatter Radar (EISCAT), based near Tromsø, Norway (69.58°N, 19.23°E), combined with rocket-borne measurements (from 61° to 69° geomagnetic latitude) make up the database of reliable D- and E-region data. NNs were trained with different combinations of the following input parameters: day number, time of day, total absorption, local magnetic K index, planetary Ap index, 10.7 cm solar radio flux, solar zenith angle and pressure surface. The output that the NNs were trained to predict was the electron density for a given set of input parameters. The criteria for determining the optimum NN are (a) the root mean square (RMS) error between the measured and predicted output values, and (b) the ability to reproduce the absorption they are meant to represent. An optimum input space was determined and then adapted to suit the requirements of the IRI community. In addition, the true quiet electron densities were simulated and added to the database, thus allowing the final model to be valid for riometer absorptions down to 0 dB. This paper discusses the development of a NN-based model for the high-latitude, lower ionosphere, and presents results from the version developed specifically for the IRI user community.

Conductivity, electric field and electron drift velocity within the equatorial electrojet

Abstract Rocket-borne in-situ measurements of electron density and current density made from Thumba, India, on four occasions between 1966 and 1973 and on one flight from Peru in 1965 are studied along with the corresponding ground magnetometer data. The Cowling conductivity is computed using the yearly mean magnetic field values of 1965 and the atmospheric density values from the MSIS 1986 model. The rocket-borne measurements from Thumba cover different geophysical conditions of strong, moderate and partial counter-electrojet events. The vertical profiles of the measured current density and electron density are presented along with the computed Cowling conductivity, electron drift velocity and electric field. The peak current density occurred at 106–107 km over Thumba and at 109 km over Peru compared to 104 km over Brazil. Cowling conductivity peaks occurred at 102 km over Huancayo and 101 km over Thumba, while electron drift velocity and electric field peaks occurred at approximately 105–107 km over Thumba, 108 and 110 km over Huancayo and 104 km over Brazil, respectively. While the electron density near the level of peak current density shows some variability, electron drift velocity and electric field show large variability. We conclude that the local electric field plays an important role in the spatial and temporal variability of the strength of the electrojet.

Modelling the impact of noctilucent cloud formation on atomic oxygen and other minor constituents of the summer mesosphere

Abstract. The formation, evolution and eventual sublimation of noctilucent clouds (NLC) may have a significant effect on the odd oxygen and hydrogen chemistry of the high latitude summer mesosphere. Three mechanisms are considered here: the direct uptake of atomic oxygen on the surface of the ice particles; the redistribution of water vapour, which changes the photochemical source of odd hydrogen species; and the direct photolysis of the ice particles themselves to produce odd hydrogen species in the gas phase. A 1-D photochemical model is employed to investigate the potential importance of these mechanisms. This shows, using the recently measured uptake coefficients of O on ice, that the heterogeneous removal of O on the surface of the cloud particles is too slow by at least a factor of 5x103 to compete with gas-phase O chemistry. The second and third mechanisms involve the solar Lyman-α photolysis of H2O in the gas and solid phase, respectively. During twilight, Lyman-α radiation is severely attenuated and these mechanisms are insignificant. In contrast, when the upper mesosphere is fully illuminated there is a dramatic impact on the O profile, with depletion of O at the base of the cloud layer of close to an order of magnitude. A correspondingly large depletion in O3 is also predicted, while H, OH, HO2 and H2O2 are found to be enhanced by factors of 3-5. In fact, rocket-borne mass spectrometer measurements during summer have revealed local H2O2 enhancements in the region of the clouds. Rocket-borne measurements of atomic O and O3 profiles in the presence of mesospheric clouds in the daytime are highly desirable to test the predictions of this model and our understanding of the genesis of mesospheric clouds.

A new approach to modelling the daytime lower ionosphere at auroral latitudes

In this paper the results of an attempt to model the auroral daytime lower ionosphere using the procedure of Neural Networks(NNs) are presented. Data from the European Incoherent Scatter facility (EISCAT) combined with rocket borne measurements were used to provide a database of reliable lower ionosphere data for NN modelling. Combinations of various input parameters known to produce a response in the daytime lower ionosphere were investigated as potential contributors to the input space. These parameters consisted of day number, hour, solar activity, riometer absorption, magnetic activity and an indication of the altitude. The output was the electron density for a given set of input parameters. Therefore, an average electron density profile describing the shape and location of the D- and E-regions at high latitudes can be determined for a particular set of inputs. A process of minimisation of mean squared errors was used to optimise the NNs. Predicted profiles are compared with actual data as well as an existing ionospheric model built from the same data. Results show that the NN can predict reasonable average electron density profiles for the high latitude lower ionosphere within the limits of the input space.

Atomic oxygen depletion in the vicinity of noctilucent clouds

There is growing evidence that noctilucent clouds play an important role in the chemistry of the upper mesosphere. Their volumetric surface area appears to be sufficiently large for heterogeneous reactions to compete with their gasphase counterparts, so long as the relevant uptake coefficients are large enough. Rocket-borne measurements have shown that atomic oxygen is substantially depleted in the vicinity of noctilucent clouds. Gumbel et al. (1998) proposed that this is caused by the efficient uptake of atomic O on the surface of the ice particles, requiring an uptake coefficient of at least 2 × 10 −5 In the present study a low-temperature fast flow tube was used to measure the uptake coefficient of O on ice as a function of temperature and O 2 concentration. Under the conditions pertinent to NLC in the upper mesosphere, the uptake coefficient is 1 × 10 −5, and hence probably too small to explain the magnitude of the observed depletions of O. Instead it appears that a greater contribution to the removal of O (and O 3) arises from gas-phase catalytic cycles driven b y odd hydrogen s pecies (H, OH and HO 2). The sources of additional odd hydrogen are most likely the Lyman-α photolysis of enhanced gas-phase H 2O around the clouds, and the photolysis of the ice particles themselves.

The uptake of atomic oxygen on ice films: Implications for noctilucent clouds

Rocket-borne measurements show that atomic oxygen is often depleted by more than an order of magnitude in the vicinity of noctilucent clouds (NLCs). These are clouds that occur in the upper mesosphere around 82 km, during the summer at high latitudes. The volumetric surface area of NLCs is large enough for the heterogeneous removal of atomic O potentially to account for the observed depletion. In order to explore the possibility that the ice surface provides an efficient catalyst for the recombination of O with O or O2, the uptake coefficient (γ) of atomic O on ice was measured in a fast flow tube under conditions relevant to NLCs. Ice was deposited from the vapour at 90 K, and then annealed at 160 K to form a cubic-crystalline ice film suitable for performing kinetic uptake measurements between 112 and 151 K. The effective ice surface area was determined using the BET isotherm technique with Kr. O atoms were produced by the microwave dissociation of N2 followed by titration with NO, and monitored by resonance fluorescence at 130 nm. For the purposes of atmospheric modelling, the overall uptake rate is then given by γ(112–151 K) = 7 × 10−6 + 1.5 × 10−10 exp(11.4 kJ mol−1/RT) [O2], with an uncertainty of ±24%. In a separate set of experiments, pulses of atomic O were generated in the flow tube by the photolysis of O3 at 248 nm, and a chromatographic analysis of the pulse shape indicated that O was bound relatively strongly (binding energy = 35–40 kJ mol−1) to some sites on the ice surface. Quantum calculations using the ONIOM technique were employed to show that O adsorbs weakly (binding energy = 11 kJ mol−1) on a perfectly crystalline ice surface by bonding to a single dangling H (and a second H bound within the surface), but can adsorb much more strongly at a disordered site where two dangling H's are in close proximity. A kinetic model of O uptake was then developed consistent with both the experimental and theoretical results. Finally, γ is almost certainly too small to explain the depletion of O around NLCs. Instead, it appears that O and O3 are removed by gas-phase catalytic cycles driven by elevated concentrations of odd hydrogen species (H and OH), produced by the Lyman-α photolysis of the layer of enhanced H2O vapour around an NLC, and by the direct photolysis of the ice particles.

First observational evidence of the modulation of gravity wave activity in the low latitude middle atmosphere by equatorial waves

Evidence for the modulation of the gravity wave activity by the equatorial waves in the tropical middle atmosphere is presented using the Rayleigh lidar observations of the temperature over Gadanki (13.5°N, 79.2°E) and the rocketborne measurements of winds over Shriharikota Range (13.7°N, 80.2°E) during the period of 29 February to 31 March, 2000. The potential energy per unit mass associated with the gravity wave activity in the upper stratosphere and mesosphere is found to undergo periodic fluctuations, which is well correlated with the zonal and meridional wind oscillations in the stratosphere produced by the equatorial waves. The most dominant modulation of the gravity wave activity due to equatorial waves is found to occur at periods around 4‐days and 12‐days. Minimum gravity wave activity in the mesosphere is observed during the southward phase of meridional wind and the westward phase of zonal wind oscillations in the lower stratosphere.

Rarefied gas flows through meshes and implications for atmospheric measurements

Abstract. Meshes are commonly used as part of instruments for in situ atmospheric measurements. This study analyses the aerodynamic effect of meshes by means of wind tunnel experiments and numerical simulations. Based on the Direct Simulation Monte Carlo method, a simple mesh parameterisation is described and applied to a number of representative flow conditions. For open meshes freely exposed to the flow, substantial compression effects are found both upstream and downstream of the mesh. Meshes attached to close instrument structures, on the other hand, cause only minor flow disturbances. In an accompanying paper, the approach developed here is applied to the quantitative analysis of rocket-borne density measurements in the middle atmosphere.Key words. Atmospheric composition and structure (instruments and techniques; middle atmosphere – composition and chemistry)

Modelling of particle charging in the polar summer mesosphere: Part 1—General results

Rocketborne measurements of electron and positive ion number densities in the vicinity of noctilucent clouds and/or polar mesosphere summer echoes frequently give evidence of pronounced disturbances relative to a smooth background profile. A model is applied to study the disturbances in terms of diffusional charging of aerosol particles with special regard to the background plasma conditions, i.e. the electron/ion production rate and the coefficient of dissociative recombination which depends on the positive ion composition. It is demonstrated that the disturbances in electron and positive ion profiles are a complex function of the aerosol radius, the aerosol number density, the production rate, and the recombination coefficient. However, if the latter two are known, the model allows the determination of aerosol radii and number densities from the measurement of positive ion and electron number densities. Furthermore, we show that nearly all combinations of electron biteouts, positive ion biteouts, and positive ion enhancements can exist depending on the properties of the aerosol particles and the background plasma conditions. Concerning electrons the presence of aerosol particles will always lead to a depletion. The magnitude of this depletion increases with increasing aerosol size and number density. Concerning positive ions both depletions and enhancements can occur. While small electron/ion production rates favour deep depletions in both electrons and positive ions, enhancements in positive ions are most likely created if the recombination coefficient is large implying large positive cluster ions. However, enhancements of electrons cannot be created by the variation of the above mentioned parameters. Thus observations of electron enhancements are a strong indication of a charging mechanism different from the diffusional charging discussed in this paper, e.g. photo emission. We have applied the charging model to in situ observations of electrons and positive ions in the vicinity of noctilucent clouds and polar mesosphere summer echoes. These results are presented in a companion paper by Lübken and Rapp (J. Atmos. Sol. Terr. Phys. (2001), 63, 771–780).

The D-region background at high latitudes

At high latitudes the ion-pair production is most of the time dominated by fluxes of energetic particles. The resulting electron densities exceed the ones expected due to solar control alone; the D-region part of these excess densities is responsible for the absorption measured by a riometer. Hence riometer absorption is a good parameter to describe the disturbed ionosphere. An approach is presented in which a huge number of lower ionosphere electron densities from EISCAT and in-situ measurements from sounding rockets are analysed jointly. The much smaller number of rocket borne measurements constitutes an important extension to lower altitudes and densities. The undisturbed ionosphere deduced from these data sets is compared to a model of the non-auroral D-region extrapolated to high latitudes. Typical profiles for disturbed conditions are given separately for day and night as a function of riometer absorption.

Features of lower ionosphere during day and night over magnetic equator

Rocketborne measurements of ionospheric parameters over magnetic equator Thumba, India are presented in this paper. Results obtained from another rocket range, SHAR, India situated off the equator are also presented. The production mechanism of plasma irregularities in 80–150 km altitude in various scale sizes are discussed. Similarities and differences in various kind of plasma processes like gradient drift instability, two stream instability and wind induced effects at both the locations are discussed.

Monte Carlo studies of the resonance fluorescence technique for atmospheric atomic oxygen measurements

The resonance fluorescence of the O (3P3S) triplet has been used extensively for rocket-borne measurements of atomic oxygen in the mesosphere and lower thermosphere. The accuracy and compatibility of different experimental configurations are however still a subject of controversy. In order to better quantify the measurements, we have developed a 3-dimensional Monte Carlo model which simulates the radiative transfer inherent to atom detection by means of resonance lamps. Angle-dependent partial frequency redistribution describes the fluorescence process, natural broadening becoming significant when the line center optical thickness exceeds 10. Applying the model to a recently flown rocket instrument, a strong temperature dependence and nonlinear relations between atomic oxygen abundance and fluorescence signal are found at densities above 5.1010 cm−3. Above 1.1012 cm−3, the signal gradually saturates and useful measurements cannot be obtained. The spatial distribution of the scattering events and effects of the payload motion are analyzed. A discussion of the results is applied to different calibration techniques for rocket instruments.