K. D. Baker

Density and temperature structure over northern Europe

Abstract During the Energy Budget Campaign, a number of profiles of the density and temperature were obtained to study the structure and variability of the atmosphere. The measurements were made using rocket- borne instrumentation launched from Esrange, Sweden, and Andoya Rocket Range, Norway, during November and December 1980. The techniques included meteorological temperature sondes, passive falling spheres, accelerometer instrumented falling spheres, density gauges, mass spectrometers and infrared emission experiments. The instruments provided data covering the altitude range from 20 to 150 km. The measurements were made during periods which have been grouped into three categories by level of geomagnetic activity. Analysis has been made to compare the results and to examine the wave features and variations in the vertical profiles for scales ranging between hundreds of meters and tens of kilometers. Most of the features observed fit qualitatively within the range expected for internal gravity waves. However, the features in the profiles during one of the measurement periods are unusual and may be due to aurorally generated shock waves. The geomagnetic storm conditions caused temperature increases in the lower thermosphere which maximized in the 120–140 km region.

Measuring ionospheric electron density using the plasma frequency probe

During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes. 9 refs.

Mean state and long term variations of temperature in the winter middle atmosphere above northern Scandinavia

Abstract Stratosphere and mesosphere temperatures were measured during four winter months (November–February) at high latitudes (Andoya, ESRANGE) by means of numerous rocket flights during the Energy Budget Campaign 1980 and the MAP/WINE Campaign 1983–1984. They are compared to ground-based OH∗ measurements and SSU satellite data. The atmosphere was found to be very active, with several minor and one major stratospheric warming occurring. A harmonic analysis of the temperature oscillations observed is performed and found to be suitable to model the atmospheric disturbances (warmings) to a large extent by superposition of waves with appropriate periods. These periods are of the order of several days and weeks and are thus similar to those of planetary waves. Stratospheric warmings tend to be correlated with mesospheric coolings, and vice versa. This is reproduced by the model, giving details of the phase relationships as they depend on altitude. These are found to be more complicated than just an anticorrelation of the altitude regimes. Strong phase changes occur in narrow altitude layers, with oscillation amplitudes being very small at these places. These ‘quiet layers’ are frequent phenomena and are independently found in the data sets of the two campaigns. They are tentatively interpreted as the nodes of standing waves. The time development of temperature altitude profiles shows strong variations that lead to peculiar features, such as a split stratopause or a near-adiabatic lapse rate in the mesosphere on occasion. The superposition model is able to reproduce these features, too. On one occasion it even shows super-adiabatic temperature gradients in the lower mesosphere for several days. Though this should be taken as an artifact, it nevertheless suggests a considerable contribution of the long period waves to atmospheric turbulence. The many rocket data are also used to determine monthly mean temperature profiles. These are compared to reference atmospheres recently developed for the CIRA ( Barnett and Corney , 1985; Groves , 1985). Fair agreement is found, which is much better than with CIRA (1972). This is not true for February 1984, because of the major warming that occurred late in that month. Before this warming took place, atmospheric preconditioning appears to have been present for more than two months.

Mesospheric minor species determinations from rocket and ground-based i.r. measurements

Abstract As part of the MAP/WINE campaign the infrared hydroxyl airglow layer was investigated at Kiruna, Sweden, by simultaneous measurements with rocket probes of OH≠ and O2(a1Δg) infrared emissions and concentrations of odd oxygen species (O and O3). Coordinated measurements of OH≠ and O2(a1Δg) zenith radiance and emission spectra and their time histories were made from the ground. The rocket-borne Λ = 1.55 μm radiometer ( ΔΛ ≊ 0.23 μm ) provided volume emission rates for OH for both rocket ascent and descent, showing a peak near 87 km with a maximum of nearly 106 photons sec−1 cm−3. The atomic oxygen distribution showed a concentration of about 1011 cm−3 between 88 and 100 km, dropping off sharply below 85 km. The ground-based radiometer at Λ = 1.56 μm, which had a similar filter bandpass to the rocket-borne instrument, yielded an equivalent of 130 kR for the total OH Δv = 2 sequence, which is consistent with the zenith-corrected rocket-based sequence radiance value of ≌ 110 kR. The rotational temperature of the OH night airglow obtained from the rotational structure of the OH M (3,1) band observed by the ground-based interferometer was about 195K at the time of the rocket measurement. Atomic oxygen concentrations were calculated from the OH profile and show agreement with the directly measured values. Atomic hydrogen concentrations of a few times 107 cm−3 near 85 km were inferred from the data set.

Electric and magnetic field measurements inside a high-velocity neutral beam undergoing ionization

Vector electric field measurements have been made inside two ionizing, high-velocity streams of barium atoms in the Earths ionosphere. A variety of electrical phenomena were observed across the frequency spectrum and are presented in this paper, which emphasizes the experimental results. Comparisons with a theoretical model for the interactions of the stream with the magnetic field and the ionosphere are presented in a companion paper (Brenning et al., this issue (a)). A most startling result is that a very large quasi-dc electric field was detected antiparallel to the beam velocity. This by itself is not unreasonable since newly ionized barium ions with their large gyroradii are expected to create such a field. But since the beam had roughly a 45° angle with the magnetic field, Bo, we find a very large (≳500 mV/m) component of E parallel to Bo. The fluctuating electric fields were also quite large, in fact, of the same order of magnitude as the quasi-dc pulse. The wave energy was found to maximize at frequencies below the barium lower hybrid frequency and included strong signatures of the oxygen cyclotron frequency. Measurements made on a subpayload separated across Bo by several hundred meters and along Bo by several kilometers do not show the large pulse, although a variety of wave emissions were seen. In addition, very large amplitude magnetic field fluctuations were detected in both bursts. Although we have no clear explanation, they appear to be a real phenomenon and worthy of future study. Finally, we note that even though the critical ionization velocity effect did not go into a discharge mode in this experiment, remarkable electromagnetic effects were seen in the neutral beam-plasma interaction.

Measurements of odd oxygen in the polar region on 10 February 1984 during MAP/WINE

Abstract Abundances of atomic oxygen and ozone have been measured by various techniques over northern Scandinavia during the MAP/WINE campaign in the winter 1983–1984. On 10 February at Kiruna, Sweden, rocket experiments used resonance fluorescence and twin path absorption at 130 nm to measure [O]between 70 and 178 km. Rocket-borne measurements of nightglow at 557.7, 761.9 and 551.1 nm and at 1.27 μm have also been obtained and [O]values derived from the atmospheric band intensities. Ozone abundances between 50 and 90 km have been determined from rocket-borne measurements of the ν 3 9.6 μm nightglow intensity from Andoya, Norway, and Kiruna. These have been compared with [O 3 ] measured on the same day from the Solar Mesospheric Explorer satellite, using measurements of dayglow at 1.27 μm, and with results from other rocket launchings in MAP/WINE. The results show evidence of low, perhaps exceedingly low, [O] and below normal [O 3 ] above the mesopause. Below 75 km at night [O 3 ] exceeded earlier and subsequent observations in the campaign. The measurements were made during a minor stratospheric warming, characterised by an offset polar vortex centred near the measurement zone.

Lower thermosphere densities of N2, O and Ar under high latitude winter conditions

Measurements of the neutral thermosphere were conducted in northern Scandinavia during the Energy Budget Campaign. These measurements included determinations of N2, O, and Ar densities using rocket-borne experiments. The results obtained in the experiments are presented, taking into account also details regarding the employed experimental methods, and an evaluation of the significance of the data. It is found that there are striking differences in thermospheric distributions of the neutral constituents under different geomagnetic conditions. Under quiet geomagnetic conditions there was reasonable agreement with the United States Standard Atmosphere. The concentrations of N2 and Ar were about 70 percent of the predicted values, while the O concentration was about 2.5 times greater.

Rocketborne Observations of Atmospheric Infrared Emissions in the Auroral Region

This paper briefly reviews the preliminary results of spectral measurements of IR atmospheric emissions in the wavelength region from 1.6 to 23 μm. These measurements were achieved using cryogenic spectrometers on six recent rocket flights conducted under the Air Force Cambridge/DNA ICECAP program for coordinated auroral measurements from Poker Flat, Alaska.

Rocket-borne measurements of atmospheric infrared fluxes

Abstract In the Energy Budget Campaign two rockets, one from Andoya Rocket Range, Norway, and one from Esrange, Sweden, each carrying a liquid helium cooled infrared spectrometer, were simultaneously launched as part of salvo B. The launches occurred during the recovery phase of the last of four auroral magnetic events after a Joule heating criteria was exceeded. At Andoya, zenith radiance altitude profiles were obtained of nitric oxide (NO) near 5.4μm from 70 to 185 km (rocket apogee), of ozone (O 3 ) near 9.6 μm from 70 to 105 km (instrument sensitivity) and of carbon dioxide (CO 2 ) near 15 μm from 70 to 150 km (instrument sensitivity). Measured CO 2 spectra at 72 km are shown to compare favorably to those calculated for local thermodynamic equilibrium conditions and instrument resolution. By comparing Andoya and Esrange CO 2 radiance profiles it is shown that there is evidence for spatial variation in the emission. Further, it is shown that the very disturbed conditions of salvo B prior to and during these launches appears to have significantly changed the O 3 9.6μm radiance profiles compared to previous rocket measurements in polar disturbed and quiet atmospheres. Using the nitric oxide radiance profiles and spectrum, previous rocket results and computed models it is shown that no radiance increase could be detected from prompt auroral energy deposition. The results support the thesis that the NO density in auroral regions is significantly enhanced over mid-latitude values and that for weak auroras, the reaction NO ( v = 0) + O → NO ( r = 1) + O is the dominant radiation mechanism.

Synopsis of the D- and E-regions during the Energy Budget Campaign

Electron density profiles derived from rocket-borne measurements are presented. These data were obtained at two different sites in northern Scandinavia under various degrees of geophysical disturbance. The observed electron density profiles are related to ionospheric absorption as observed with the dense riometer network in that area.