Rocket Observations Research Articles

Measurement of electron density profile in the lower ionosphere during nighttime by rocket observations of MF and VLF radio waves

Measurements are made on the magnetic field strength of MF and VLF radio stations by rocket observations during nighttime, along with measurements made on the Langmuir probe (dc probe) current and Doppler observations of MF. In the E layer, we can observe the standing wave of the VLF magnetic field strength, and also the ordinary and extraordinary components of MF. In order to make the theoretical values by the full-wave calculation coincide with these observed values with reference to the dc probe currents, we adjust the electron density and the distribution of the electron collision frequency with altitude. By these methods, the electron density of the E layer is estimated from the bottom to the top, and we find the existence of multiple weak Es layers. By MF Doppler observation, we successfully estimate the electron density of the upper E layer, and can estimate the effective electron collision frequency near 110 km in altitude from the strength of the upward component of the extraordinary wave. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 83(2): 20–28, 2000

Electron-impact excitation/emission and photoabsorption cross sections important in the terrestrial airglow and auroral analysis of rocket and satellite observations

The UV line intensities appearing in the spectra of terrestrial auroral and airglow observational data by rockets and high altitude satellites contain important diagnostic information on energy input taking place into the thermosphere. The intensities of the observed emissions are dependent on the atomic and molecular cross sections for both electrons and photons. UV extinction weakens the emission intensity along the line-of-sight to the spacecraft and is determined by the absorption cross sections of the principal constituents: O2, N2□ and O. An accurate knowledge of both excitation (emission) and photoabsorption cross sections of the dominant atmospheric molecular gases (O2 and N2) is needed for the analysis and interpretation of rocket and satellite observations of airglow and auroral emissions. The absorption cross sections of O2 and N2 are difficult to measure since they are highly structured in the UV from predissociation of Rydberg and valence states.The aim of this article is to focus upon certain outstanding issues concerning the available experimental excitation (emission) and photoabsorption cross section data primarily in the far UV (FUV) spectral region. These cross sections are important to terrestrial airglow and auroral observations of N2 and O UV emission fluorescence and to critically review the available data.

Nonlinear Dynamics and Chaos in Space Plasmas

The theory and observation of nonlinear wave coupling phenomena in solar-system plasmas are reviewed. Rocket and satellite observations have provided evidence of nonlinear wave interactions in space plasmas, in particular, in relation to the generation and propagation of radio waves in solar corona, interplanetary medium and Earth’s magnetosphere. These radio waves represent the electromagnetic signature of solar-terrestrial coupling and are useful for forecasting and monitoring of space weather. Nonlinear wave-wave coupling in plasmas can be modeled as a dynamical system of coupled oscillators involving one, two or higher-order wave triplets. For a three-wave dissipative system, the temporal transition from order to chaos may evolve via period doubling or intermittence. For a four-wave Hamiltonian system involving two coupled wave triplets, the spatiotemporal transition from order to chaos is analyzed using the concepts of stable and unstable homogeneous manifolds. Plasma dynamics is governed by a variety of wave motions resulting from the collective electrodynamic interactions involving plasma fields and plasma particles. Nonlinear wave-wave coupling in plasmas can occur due to the growth of parametric instabilities. In this paper, we present an overview of theoryand observation of nonlinear mode coupling in space plasmas. In §2 we discuss the theoryof nonlinear interaction involving a single wave triplet in the presence of source and dissipation. We consider the transition from order to low-dimensional temporal chaos. In § 3w e discuss the theoryof nonlinear interaction involving two wave triplets in the absence of source and dissipation. We treat the transition from order to high-dimensional spatiotemporal chaos. Before discussing the theorylet us first summarize some recent observational evidence of nonlinear wave-wave interactions in the solar system. Comprehensive reviews of this topic are given in Refs. 1) and 2). Radio waves provide the electromagnetic signature of solar-terrestrial relation and serve as a tool to forecast and monitor the space weather. The radio emis

Rocket observation of sporadic-E layers and electron density irregularities over midlatitude

Abstract Irregularities in electron density related to a nighttime sporadic-E (Es) layer were measured by a fixed-bias Langmuir probe onboard the sounding rocket S-310-25, launched at 23:00:00 JST on August 26, 1996 during the SEEK observation campaign. The most interesting finding was the existence of multiple-Es layers which were separated by 10 – 12 km within a wide altitude range of 90 – 130 km. Meter-scale irregularities generated in association with the multiple-Es layers were found to exist in a similar altitude range as quasi-periodic (QP) echoes, which were detected with frequency agile radar (FAR) operating at 24.5 MHz around the time of the rocket flight.

Electron Energization by Alfvén Waves: Freja and Sounding Rocket Observations

Recent sounding rockets observations highlight some space-time ambiguities in phenomena taking place in the auroral ionosphere, previously observed by the Freja spacecraft. Field aligned electron populations with energies from a few tens of eV to a few keV streaming through cold background plasma are usually observed in the auroral zone in association with strongly nonlinear electromagnetic perturbations. Simultaneous observations of bursty Langmuir emissions indicate the unstable character of these plasma distributions. A detailed analysis shows that the electromagnetic perturbations take the form of quasi-stationary nonlinear spatial structures related to inertial Alfvén waves. We suggest that inhomogeneous altitude distribution of the parallel electric field of these structures due to ionospheric density gradientis responsible for the observed electron distributions.

Sounding rocket data base of E- and D-region ion composition

Detailed in situ ion composition measurements in the E- and D- region ionosphere are available only from eccentric orbiting satellites with very low perigees and from sounding rockets. The lower limit for existing satellite data is about 130 km. Below this altitude mostly sounding rockets have sampled the ion composition. These sounding rocket data sets have been analyzed in the literature individually in the past on a case-by-case basis. In order to provide the best empirical picture possible of the lower ionosphere molecular ion distributions all available published sounding rocket observations of O 2 + and NO + ion concentrations were scanned and digitized to provide an empirical data base of the lower ionosphere. There were 43 such flights selected, which were scattered in latitude and local time. There were few low latitude observations, most of the measurements were made from middle and high latitude launch sites. The distributions are characterized at all latitudes by large drops in the concentrations from day to night with the molecular ion O 2 + having the greatest range of variation above ∼ 100 km and NO + below 90 km. Features of the sounding rocket data distributions at low latitudes, middle latitudes and at high latitudes and its limitations are discussed and the measurements compared with the International Reference Ionosphere (IRI) to investigate the accuracy of the IRI ion composition model in the lower ionosphere. The IRI ion composition model is based predominantly on dayside midlatitude observations for equinoctial and summer conditions. Our results show that winter nighttime measurements need to be expanded in order to improve the model.

High‐frequency and time resolution rocket observations of structured low‐ and medium‐frequency whistler mode emissions in the auroral ionosphere

High bandwidth electric field waveform measurements on a recent auroral sounding rocket reveal structured whistler mode signals at 400–800 kHz. These are observed intermittently between 300 and 500 km with spectral densities 0–10 dB above the detection threshold of 1.5 × 10−11 V2/m2 Hz. The lack of correlation with local particle measurements suggests a remote source. The signals are composed of discrete structures, in one case having bandwidths of about 10 kHz and exhibiting rapid frequency variations of the order of 200 kHz per 100 ms. In one case, emissions near the harmonic of the whistler mode signals are detected simultaneously. Current theories of auroral zone whistler mode emissions have not been applied to explain quantitatively the fine structure of these signals, which resemble auroral kilometric radiation (AKR) rather than auroral hiss.

Absolute solar 30.4 nm flux from sounding rocket observations during the solar cycle 23 minimum

A transmission grating extreme ultraviolet (EUV) spectrometer, nominally identical to the Charge, Element, and Isotope Analysis System/Solar EUV Monitor (CELIAS/SEM) instrument on the Solar and Heliospheric Observatory (SOHO), has obtained accurate measurements of the integrated absolute solar extreme ultraviolet irradiance in an 8 nm band pass centered at 30.4 nm. The spectrometer also measured the EUV/soft X‐ray flux, but those data will be reported in a later paper. The instrument was launched on two sounding rocket flights from White Sands Missile Range, New Mexico, on June 26, 1996, and again on August 11, 1997, to provide a SOHO underflight calibration database in the EUV. The full disk solar 30.4 ± 40 nm fluxes measured by it on the above 2 days were 1.21 × 1010 and 1.42 × 1010 photons cm−2 s−1 at 1 AU, respectively. These measurements have an absolute 1σ uncertainty of 8.1%.

Rocket observations of banded structure in waves near the Langmuir frequency in the auroral ionosphere

Using data from the PHAZE II sounding rocket, launched from Poker Flat, Alaska, we present high‐resolution observations of structure in auroral HF waves at and below the local plasma frequency. These observations were made in the altitude range of 390–945 km where the local plasma frequency is below the electron cyclotron frequency. We observe monochromatic, long‐lived, narrowband emissions occuring below the local plasma frequency during times of intense HF wave emission. We have termed these emissions “HF bands” due to their appearance in spectrogram images. These emissions are probably identical to the “spike” emissions identified by previous observers using lower time resolution data from the AUREOL/ARGAD3 satellite which showed a narrow peak spectra below the local plasma frequency. HF bands often occur when the local plasma density is varying and are associated with regions of intense Langmuir wave generation. We investigate the hypothesis that the HF bands are created when a Langmuir wave propagates from a low‐density region into a higher density region. The wave moves onto the whistler mode branch and propagates as an HF band. Theoretical calculations of propagation times of whistler mode waves support this hypothesis.

Auroral ion acceleration from lower hybrid solitary structures: A summary of sounding rocket observations

In this paper we present a review of sounding rocket observations of the ion acceleration seen in nightside auroral zone lower hybrid solitary structures. Observations from Topaz3, Amicist, and Phaze2 are presented on various spatial scales, including the two‐point measurements of the Amicist mission. From this collection of observations we will demonstrate the following characteristics of transverse acceleration of ions (TAI) in lower hybrid solitary structures (LHSS). The ion acceleration process is narrowly confined to 90° pitch angle, in spatially confined regions of up to a few hundred meters across B. The acceleration process does not affect the thermal core of the ambient distribution and does not directly create a measurable effect on the ambient ion population outside the LHSS themselves. This precludes observation with these data of any nonlinear feedback between the ion acceleration and the existence or evolution of the density irregularities on which these LHSS events grow. Within the LHSS region the acceleration process creates a high‐energy tail beginning at a few times the thermal ion speed. The ion acceleration events are closely associated with localized wave events. Accelerated ions bursts are also seen without a concurrent observation of a localized wave event, for two possible reasons. In some cases, the pitch angles of the accelerated tail ions are elevated above perpendicular; that is, the acceleration occurred below the observer and the mirror force has begun to act upon the distribution, moving it upward from the source. In other cases, the accelerated ion structure is spatially larger than the wave event structure, and the observation catches only the ion event. The occurrence rate of these ion acceleration events is related to the ambient environment in two ways: its altitude dependence can be modeled with the parameter B2/ne, and it is highest in regions of intense VLF activity. The cumulative ion outflow from these LHSS TAI is consistent with Freja statistics for VLF‐type premidnight auroral upflow.

Far‐Ultraviolet Absolute Flux of α Virginis

We present the far-ultraviolet spectrum of α Virginis taken with Espectrografo Ultravioleta extremo para la Radiacion Difusa (EURD) spectrograph on board MINISAT-01. The spectral range covered is from ~900 to 1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE spectra of α Vir and compared the extension of the model to our wavelengths with EURD data. This comparison shows that EURD fluxes are consistent with the prediction of the model within ~20%-30%, depending on the reddening assumed. EURD fluxes are consistent with Voyager observations but are ~60% higher than most previous rocket observations of α Vir.

Rocket‐borne Long‐Slit Ultraviolet Spectroscopy of Comet Hale‐Bopp

A sounding rocket observation of comet Hale-Bopp was conducted on 1997 April 6 at 3:51 UT when the comet was at heliocentric and geocentric distances of 0.92 and 1.39 AU, respectively. The instrument was a telescope and long-slit (65 × 260''), ultraviolet (1280-1880 A) spectrograph that sampled the coma parallel to the Sun-comet line from ~105 km sunward of the nucleus to ~2 × 105 km tailward with ~6'' (6000 km) spatial resolution. Two spectral images were obtained with the slit offset 20'' and 40'' from the nucleus in the direction perpendicular to the long axis of the slit. Spatial profiles and production rates for C, O, CO, and S are presented. Modeling of the spatial profiles of CO and C emissions indicate that photodissociation of the detected CO can account for all of the C I emissions observed. The brightnesses of the strong bands of the CO Fourth Positive system and the S I λ1814 multiplet along near-nuclear lines of sight were diminished by self-absorption. A CO production rate of ~3 × 1030 molecules s-1 is derived.

A comparison of f0F hmE model calculations with El Arenosillo digisonde observations. Seasonal variations

Seasonal variations of hmE and f0F2 are analyzed using El Arenosillo digisonde observations during solar minimum (1995-1996). Unlike some widely used empirical models daytime hmE show seasonal variations with winter hmE being higher than summer ones and seasonal differences increase with solar zenith angle. Model calculations enable us to reproduce the observed hmE seasonal variations but the calculated daytime f0E values are too low if conventional EUV fluxes and dissociative recombination rate constants are used. A reduction of a (NO+ ) by taking into account Te > Tn in the E-region as it follows from probe measurements seems to be a plausible solution. The E-region ion composition corresponding to rocket observations may be obtained in model calculations using an appropriate [NO] height distribution. Calculated summer concentrations of [NO] are by a factor of 3-4 larger than winter ones at the hmE-heights.

Effect of hot oxygen on thermospheric O I UV airglow

The role of nonthermal oxygen atoms in the vertical distribution of the O I 989 Å EUV multiplet intensity is investigated using a thermospheric radiative transfer code. The superthermal oxygen concentration and temperatures are derived from the energy distribution functions of the O(3P) atoms calculated by a Monte Carlo stochastic model, and their effect on UV radiative transfer is compared to sounding rocket observations. The calculated intensity increase associated with the perturbation of the Doppler profile by the presence of hot O(3P) atoms is shown to be insufficient to account for the set of sounding rocket EUV intensity data.

The Spectroscopic Detectability of Argon in the Lunar Atmosphere

Direct measurements of the abundance of argon in the lunar atmosphere were made in 1973 by instruments placed on the Moon during the Apollo 17 mission, but the total daytime abundance is unknown because of instrument saturation effects; thus, until we are able to return to the Moon for improved direct measurements, we must use remote sensing to establish the daytime abundance. In this Letter, we present a complete analysis of the potential for measuring argon in the lunar atmosphere via emission-line or absorption-line observations. We come to the surprising conclusion that the lower limit established by the in situ lunar argon measurements implies that any absorption-line measurement of argon in the lower, dayside lunar atmosphere requires analysis in the optically thick regime. In light of this result, we present the results of our extreme-ultraviolet spectrograph sounding rocket observations of the lunar occultation of Spica, which provide a new upper limit on the abundance of argon in the daytime lunar atmosphere. We also reanalyze a recently reported weak detection by the ORFEUS satellite of lunar atmospheric Ar I λ1048 in emission and show that those data are inconsistent with the emission being due to argon over a wide range of temperatures (up to at least 2000 K). This result is primarily due to our use of a more complete curve-of-growth analysis and improved values for the argon fluorescent emission rates from radiation and solar wind interactions. We find that the detection reported by ORFEUS would imply an argon surface density significantly greater than the total surface density of the lunar atmosphere for argon accommodated to typical daytime surface temperatures (~400 K) and also is inconsistent with a high-density transient event. Therefore, we conclude that the reported argon detection is untenable.

PHAZE II observations of lower hybrid burst structures occurring on density gradients

PHAZE II sounding rocket observations of VLF waves and plasma density measurements made with a HF wave instrument rather than a fixed bias Langmuir probe show conclusively that the observed lower hybrid solitary structures (LHSS) are associated with density fluctuations. LHSS occur on the positive and negative gradients of plasma density fluctuations of 25–50%. These findings lend support to theories of ambient lower hybrid waves exciting resonances created by pre‐existing density gradients rather than wave collapse or refraction mechanisms; the issue of how the gradients are created is still unresolved.

Mechanism for the Green Glow of the Upper Ionosphere

The generation of the green line of atomic oxygen by dissociative recombination of O 2 + occurs by the capture of an electron into a repulsive state of O 2 followed by dissociation along another state of a different electronic symmetry. The two states are coupled together by mixed symmetry Rydberg states. Quantum chemical calculations give a rate coefficient at room temperature of (0.39 −0.19 +0.31 ) × 10 −8 cubic centimeters per second. The quantum yield of excited oxygen is within the range deduced from ground, rocket, and satellite observations. The rate coefficients and yields are needed in models of the optical emission, chemistry, and energy balance of planetary ionospheres.

Proton transport model in the ionosphere: 1. Multistream approach of the transport equations

The suprathermal particles, electrons and protons, coming from the magnetosphere and precipitating into the high‐latitude atmosphere are an energy source of the Earth's ionosphere. They interact with ambient thermal gas through inelastic and elastic collisions. The physical quantities perturbed by these precipitations, such as the heating rate, the electron production rate, or the emission intensities, can be provided in solving the kinetic stationary Boltzmann equation. This equation yields particle fluxes as a function of altitude, energy, and pitch angle. While this equation has been solved through different ways for the electron transport and fully tested, the proton transport is more complicated. Because of charge‐changing reactions, the latter is a set of two‐coupled transport equations that must be solved: one for protons and the other for H atoms. We present here a new approach that solves the multistream proton/hydrogen transport equations encompassing the collision angular redistributions and the magnetic mirroring effect. In order to validate our model we discuss the energy conservation and we compare with another model under the same inputs and with rocket observations. The influence of the angular redistributions is discussed in a forthcoming paper.

Evidence and effects of a wave-driven nonlinear current in the equatorial electrojet

Abstract. Ionospheric two-stream waves and gradient-drift waves nonlinearly drive a large-scale (D.C.) current in the E-region ionosphere. This current flows parallel to, and with a comparable magnitude to, the fundamental Pedersen current. Evidence for the existence and magnitude of wave-driven currents derives from a theoretical understanding of E-region waves, supported by a series of nonlinear 2D simulations of two-stream waves and by data collected by rocket instruments in the equatorial electrojet. Wave-driven currents will modify the large-scale dynamics of the equatorial electrojet during highly active periods. A simple model shows how a wave-driven current appreciably reduces the horizontally flowing electron current of the electrojet. This reduction may account for the observation that type-I radar echoes almost always have a Doppler velocity close to the acoustic speed, and also for the rocket observation that electrojet regions containing gradient-drift waves do not appear also to contain horizontally propagating two-stream waves. Additionally, a simple model of a gradient-drift instability shows that wave-driven currents can cause nonsinusoidal electric fields similar to those measured in situ.

A model for particle acceleration in lower hybrid collapse

A model for particle acceleration during the nonlinear collapse of lower hybrid waves is described. Using the Musher-Sturman wave equation to describe the effects of nonlinear processes and a velocity diffusion equation for the particle velocity distribution, the model self-consistently describes the exchange of energy between the fields and the particles in the local plasma. Two-dimensional solutions are presented for the modulational instability of a plane wave and the collapse of a cylindrical wave packet. These calculations were motivated by sounding rocket observations in the vicinity of auroral arcs in the Earth’s ionosphere, which have revealed the existence of large-amplitude lower-hybrid wave packets associated with ions accelerated to energies of 100 eV. The scaling of the sizes of these wave packets is consistent with the theory of lower-hybrid collapse and the observed lower-hybrid field amplitudes are adequate to accelerate the ionospheric ions to the observed energies.