Rocket Observations Research Articles

Modeling of Na airglow emission and first results on the nocturnal variation at midlatitude

AbstractA model for sodium airglow emission is developed by incorporating all the known reaction mechanisms. The neutral, ionic, and photochemical mechanisms are successfully implemented into this model. The values of reaction rate coefficients are based upon the theoretical calculations as well as from experimental observations. The densities of major species are calculated using the continuity equations, whereas for the minor, intermediating, and short‐lived species steady state approximation method is used. The modeled results are validated with the rocket, lidar, and photometer observations for a branching ratio of 0.04 for the production of Na(2P) in the reaction NaO + O Na(2P, 2S). The inputs have been obtained from other physics‐based models and ground‐ and satellite‐based observations to give the combined volume emission rate (VER) of Na airglow between 80 and 110 km altitude. In the present study, the model is used to understand the nocturnal variation of Na VER during the solstice conditions. The model results suggest a variation of peak emission layer between 85 and 90 km during summer solstice condition, indicating a lower value of peak emission rate during summer solstice. The emission rates bear a strong correlation with the O3 density during summer solstice, whereas the magnitude of VER follows the Na density during winter solstice. The altitude of peak VER shows an upward shift of 5 km during winter solstice.

Nonthermal radiative transfer of oxygen 98.9 nm ultraviolet emission: Solving an old mystery

AbstractSounding rocket measurements conducted in 1988 under high solar activity conditions revealed that the intensity of thermospheric OI emissions at 98.9 nm presents an anomalous vertical profile, showing exospheric intensities much higher than expected from radiative transfer model results, which included the known sources of excited oxygen. All attempts based on modeling of the photochemical processes and radiative transfer were unable to account for the higher than predicted brightnesses. More recently, the SOHO‐Solar Ultraviolet Measurements of Emitted Radiation instrument measured the UV solar flux at high‐spectral resolution, revealing the importance of a significant additional source of oxygen emission at 98.9 nm that had not been accounted for before. In this study, we simulate the radiative transfer of the OI‐98.9 nm multiplet, including the photochemical sources of excited oxygen, the resonant scattering of solar photons, and the effects of nonthermal atoms, i.e., a population of fast‐moving oxygen atoms in excess of the Maxwellian distribution. Including resonance scattering of the 98.9 nm solar multiplet, we find good agreement with the previous sounding rocket observation. The inclusion of a nonthermal oxygen population with a consistent increase of the total density produces a larger intensity at high altitude that apparently better accounts for the observation, but such a correction cannot be demonstrated given the uncertainties of the observations. A good agreement between model and sounding rocket observation is also found with the triplet at 130.4 nm. We further investigate the radiative transfer of the OI‐98.9 nm multiplet and the oxygen emissions at 130.4 and 135.6 nm using observations from the STP78‐1 satellite. We find a less satisfying agreement between the model and the STP78‐1 data that can be accounted for by scaling the modeled intensity within a range acceptable given the uncertainties on the STP78‐1 absolute calibration.

Structure of black aurora associated with pulsating aurora

AbstractMorphological behavior of black aurora as it relates to pulsating aurora is investigated by examining a collection of ground‐based observations from January 2007 in support of the Rocket Observations of Pulsating Aurora rocket campaign. Images were sampled from video recorded by a Xybion intensified camera (30 fps) at Poker Flat Research Range, AK. The primary observations of black aurora recorded during the substorm recovery phase were between separate patches of pulsating aurora as well as pulsating aurora separated from diffuse aurora. In these observations the black aurora forms an apparent firm boundary between the auroral forms in a new behavior that is in contrast with previously reported observations. Also presented for the first time are black curls in conjunction with pulsating aurora. Curl structures that indicate shear plasma flows in the ionosphere may be used as a proxy for converging/diverging electric fields in and above the ionosphere. This new subset of black auroral behavior may provide visual evidence of black aurora as an ionospheric feedback mechanism as related to pulsating aurora.

Ion upflow dependence on ionospheric density and solar photoionization

AbstractMotivated by rocket observations showing a variety of different ionospheric responses to precipitation, this paper explores the influence of the background ionospheric density on upflow resulting from auroral precipitation. Simulations of upflow driven by auroral precipitation were conducted using a version of the Varney et al. (2014) model driven by precipitation characterized by observations made during the 2012 Magnetosphere‐Ionosphere Coupling in the Alfvén resonator rocket mission and using a variety of different initial electron density profiles. The simulation results show that increased initial density before the onset of precipitation leads to smaller electron temperature increases, longer ionospheric heating timescales, weaker ambipolar electric fields, lower upflow speeds, and longer upflow timescales but larger upflow fluxes. The upflow flux can increase even when the ambipolar electric field strength decreases due to the larger number of ions that are accelerated. Long‐term observations from the European Incoherent Scatter (EISCAT) Svalbard radar taken during the International Polar Year support the effects seen in the simulations. This correlation between ionospheric density and ion upflows emphasizes the important role of photoionization from solar ultraviolet radiation, which the EISCAT observations show can increase ionospheric density by as much as an order of magnitude during the summer months.

MICA sounding rocket observations of conductivity‐gradient‐generated auroral ionospheric responses: Small‐scale structure with large‐scale drivers

AbstractA detailed, in situ study of field‐aligned current (FAC) structure in a transient, substorm expansion phase auroral arc is conducted using electric field, magnetometer, and electron density measurements from the Magnetosphere‐Ionosphere Coupling in the Alfvén Resonator (MICA) sounding rocket, launched from Poker Flat, AK. These data are supplemented with larger‐scale, contextual measurements from a heterogeneous collection of ground‐based instruments including the Poker Flat incoherent scatter radar and nearby scanning doppler imagers and filtered all‐sky cameras. An electrostatic ionospheric modeling case study of this event is also constructed by using available data (neutral winds, electron precipitation, and electric fields) to constrain model initial and boundary conditions. MICA magnetometer data are converted into FAC measurements using a sheet current approximation and show an up‐down current pair, with small‐scale current density and Poynting flux structures in the downward current channel. Model results are able to roughly recreate only the large‐scale features of the field‐aligned currents, suggesting that observed small‐scale structures may be due to ionospheric feedback processes not encapsulated by the electrostatic model. The model is also used to assess the contributions of various processes to total FAC and suggests that both conductance gradients and neutral dynamos may contribute significantly to FACs in a narrow region where the current transitions from upward to downward. Comparison of Poker Flat Incoherent Scatter Radar versus in situ electric field estimates illustrates the high sensitivity of FAC estimates to measurement resolution.

Scattering cross section of mesospheric echoes and turbulence parameters from Gadanki radar observations

We present a comprehensive study on radar scattering cross section of mesospheric echoes and mesospheric turbulence parameters based on several days of observations made during two rocket-radar campaigns, one in July 2004 and another in April 2005, meant for studying mesospheric turbulence. Radar scattering cross section was found to have large local time and day-to-day variability and was found to be as low as 3.1×10−18m−1 and as high as 1×10−14m−1 and the median values were in the range of 4.4×10−18–4.7×10−16m−1. Echoes connected with the low value of scattering cross section could be detected only when a long pulse width was used. Turbulence parameters were found to vary remarkably with time of the day and also from one day to another. In July, the turbulent kinetic energy (TKE) dissipation rate, outer scale and inner scale were in the range of 0.08–150mW/kg, 33–1500m, and 1.9–50m, respectively, and their median values were in the range of 5–52mW/kg, 293–977m, and 2–31m, respectively. In April, these estimates were in the range of 0.9–69mW/kg, 38–1081m, and 4–21m, respectively, and their median values were in the range of 1–12mW/kg, 140–378m, and 8–13m, respectively. These parameters are found to agree quite well with those estimated from rocket-borne observations, which were in the range of 4–117mW/kg, 220–1475m, and 15–31m, respectively, in July and 2–36mW/kg, 170–680m, and 17–37m, respectively, in April. Interestingly, the inner and outer scales estimated using both radar and rocket observations agree exceedingly well with model values. These results are compared in detail with those reported from low, middle and high latitudes including model and discussed in the light of current knowledge of mesospheric turbulence.

A Model for the Sounding Rocket Measurement on an Ionospheric E-F Valley at the Hainan Low Latitude Station

To understand the physics of an ionospheric E-F valley, a new overlapping three-Chapman-layer model is developed to interpret the sounding rocket measurement in the morning (sunrise) on May 7, 2011 at the Hainan low latitude ionospheric observation station (19.5°N, 109.1°E). From our model, the valley width, depth and height are 43.0 km, 62.9% and 121.0 km, respectively. From the sounding rocket observation, the valley width, depth and height are 42.2 km, 47.0% and 123.5 km, respectively. The model results are well consistent with the sounding rocket observation. The observed E-F valley at Hainan station is very wide and deep, and rapid development of the photochemical process in the ionosphere should be the underlying reason.

An Unscheduled Journey: From Cosmic Rays into Cosmic X-Rays

My research career began with cosmic-ray physics. Invited to the Netherlands, I was engaged in the measurement of cosmic-ray electrons. In parallel, we began balloon observations of the cosmic X-ray background. Coming back to Nagoya, we carried out rocket observations of soft X-rays with a thin polypropylene window. Since moving to the Institute of Space and Aeronautical Science (ISAS: later reorganized to the Institute of Space and Astronautical Science), I have been involved in several astronomical satellite programs, in particular X-ray astronomy missions. The main features and major results of those programs are mentioned. Features characteristic of the Japanese space program and the specific roles of ISAS are explained.

Observing earth’s sodium and atomic oxygen dayglow emissions 1This article is part of a Special Issue that honours the work of Dr. Donald M. Hunten FRSC who passed away in December 2010 after a very illustrious career.

The observation of sodium emission in the twilight upper atmosphere was the leading edge of the study of metals in the upper atmosphere, and its quantitative measurement and analysis were pioneered by Donald M. Hunten. He extended these early observations into the daytime, the sodium dayglow, including rocket observations of this phenomenon. More than fifty years later the amount of information on this subject has grown enormously through LIDAR observations, laboratory measurements, and extensive modeling. The author’s participation in those early measurements inspired him to undertake observations of the atomic oxygen dayglow, first from the ground, and then from orbit with the WINDII instrument on NASA’s Upper Atmosphere Research Satellite. The parallels between the Na and O dayglows are described and reviewed, including in particular the methods of observation. Very recent results on the atomic oxygen O(1S) dayglow are presented, showing the influence of the DE3 nonmigrating tide reaching from the troposphere to 250 km altitude in the thermosphere.

Amplitudes of electron cyclotron waves transmitted in the ionosphere

[1] During the two-point sounding rocket experiment Observations of Electric-field Distributions in the Ionospheric Plasma–A Unique Strategy-C (OEDIPUS-C, hereinafter OC), Bernstein or electron cyclotron waves (ECWs) were transmitted over magnetic field-aligned emitter-receiver separations of hundreds of meters. Signals were observed at harmonic frequencies mfc of the electron cyclotron frequency fc, where m was 2, 3, and 4, fc ≈ 1.3 MHz, and the electron plasma frequency was less than half of fc. The electric fields at 2fc radiated by the emitting dipoles have been computed from the inhomogeneous Helmholtz wave equation. Using the full hot plasma theory to evaluate the dielectric tensor, a Green's function has been derived, based partly on numerical inversion and facilitated by some simplifications made possible by the given frequency and plasma parameters. Under the assumption of straight-line rays, it is found that the computed absolute voltage levels induced on the receiving dipoles are of the same order of magnitude as the observed levels. The electric field E radiation patterns at 2fc are found to be highly elongated along the direction of the Earth's magnetic induction field B. The component of E perpendicular to B, the radial or ρ component, is much stronger than the other two components in a cylindrical coordinate system. The prediction of strong radial E magnitudes along ray directions very close to B is consistent with the OC observations. These results enlarge our appreciation of distinct characteristics of ECW radiation and propagation that may improve understanding of the role of these electrostatic waves in ionospheric dynamics.

Sounding rocket study of two sequential auroral poleward boundary intensifications

[1] The Cascades-2 sounding rocket was launched on 20 March 2009 at 11:04:00 UT from the Poker Flat Research Range in Alaska, and flew across a series of poleward boundary intensifications (PBIs). The rocket initially crosses a diffuse arc, then crosses the equatorward extent of one PBI (a streamer), and finally crosses the initiation of a separate PBI before entering the polar cap. Each of the crossings have fundamentally different in situ electron energy and pitch angle structure, and different ground optics images of visible aurora. It is found that the diffuse arc has a quasi-static acceleration mechanism, and the intensification at the poleward boundary has an Alfvenic acceleration mechanism. The streamer shows characteristics of both types of acceleration. PFISR data provide ionospheric context for the rocket observations. Three THEMIS satellites in close conjunction with the rocket foot point show earthward flows and slight dipolarizations in the magnetotail associated with the in situ observations of PBI activity. An important goal of the Cascades-2 study is to bring together the different observational communities (rocket, ground cameras, ground radar, satellite) with the same case study. The Cascades-2 experiment is the first sounding rocket observation of a PBI sequence, enabling a detailed investigation of the electron signatures and optical aurora associated with various stages of a PBI sequence as it evolves from an Alfvenic to a more quasi-static structure.

Further sounding rocket observations of structured whistler mode auroral emissions

Two recent sounding rockets were launched into active auroral substorms from Poker Flat, Alaska: CHARM on 27 February 2007 and SIERRA on 14 January 2002. Both payloads included HF wave receivers. As previously reported, the SIERRA HF receiver recorded short‐lived, periodic, time‐dispersed features at 200–600 kHz (“stripes”), in which high‐frequency components precede low frequencies, leading to a nearly linear frequency‐time signature. These features coincided with a region identified as Alfvénic and dominated by suprathermal electron bursts and 10–110 eV downward going ions poleward of the main inverted V auroral arc. The CHARM experiment, using different electric field sensors, confirmed the occurrence of the stripe features with characteristics similar to those observed with SIERRA. The most promising mechanism to explain stripes is a cyclotron resonance between downgoing Z mode waves and upgoing electron conics in the topside ionosphere at altitudes of 3000–5000 km. These electron conics resonate with successively lower‐frequency waves as they ascend, leading to emissions in which lower frequencies are delayed relative to higher frequencies; detailed modeling reproduces even fairly subtle nonlinear features of the stripes’ frequency‐time signature. The resulting structured Z mode waves then convert to whistler mode waves, which propagate to rocket altitudes. Previous simulations have shown that electron conics can be generated by Alfvénic acceleration and retain the periodicity of the driving Alfvén wave. If this acceleration could be driven by Alfvén waves at the frequency of the periodicity of the stripes, it could explain this periodicity and would be consistent with their correlation with an Alfvénic region.

Observations of mesospheric ice particles from the ALWIN radar and SOFIE

Ice particles near the polar summer mesopause are observed visually, by radar, and using various remote and in-situ techniques. This study investigates concurrent radar observations from the ALOMAR wind (ALWIN) radar and measurements from the Solar Occultation For Ice Experiment (SOFIE) onboard the Aeronomy of Ice in the Mesosphere (AIM) satellite. Mesospheric ice observations from radar are known as polar mesosphere summer echoes (PMSE), while satellite observations of these particles are referred to as polar mesospheric clouds (PMC). Comparisons of concurrent SOFIE and ALWIN observations indicate that PMC and PMSE are different manifestations of the same ice layer. The vertical extent of the ice layer is similar in the ALWIN and SOFIE records, with the primary difference that the PMSE signal peaks about 2km higher than the PMC signal. SOFIE observations of ice particle size and concentration are used to test simple empirical proxies for PMSE which have previously been suggested based on a small number of rocket observations and microphysical modeling.

Macro–micro interlocked simulation algorithm: an exemplification for aurora arc evolution

Using an innovative holistic simulation algorithm that can self-consistently treat a system that evolves as cooperation between macroscopic and microscopic processes, the evolution of a colorful aurora arc is beautifully reproduced as the result of cooperation between the global field-aligned feedback instability of the coupled magnetosphere–ionosphere system and the ensuing microscopic ion-acoustic instability that generates electric double layers and accelerates aurora electrons. These results are in agreement with rocket and satellite observations. This shows that the proposed holistic algorithm could be a reliable tool to reveal complex real dramatic events and become, in the near future, a viable scientifically secure prediction tool for natural disasters such as earthquakes, landslides and floods caused by typhoons.

A study on the low‐latitude daytime E region plasma irregularities using coordinated VHF radar, rocket‐borne, and ionosonde observations

In this paper we study the off‐electrojet low‐latitude daytime E region plasma irregularities using first multi‐instrument observations in India made during July 2004 by the MST radar from Gadanki (13.5°N, 79.2°E, magnetic latitude 6.4°N), Langmuir probe on board the RH‐300 Mk II rocket, and ionosonde from Sriharikota (13.6°N, 80.2°E, magnetic latitude 6.4°N). Radar echoes were confined to altitudes below 105 km and were observed in the form of a descending echoing layer with the descent rate of 1 km/h. Virtual height of the E layer, as observed by ionosonde, shows identical descending behavior. A detailed analysis based on the radar and ionosonde observations shows that the radar echoes are related to the range spread in the ionogram. Rocket observations made on 23 July 2004 revealed weak plasma irregularities with scale sizes more than 100 m and no noticeable irregularity at shorter scales. The spectral slope of the irregularities observed by the rocket probe is found to be −4 for scales in between 1 km and 100 m. During the rocket launch, radar did not detect any echo conforming that the small‐scale irregularities were not present. Examination of concurrent observations of neutral wind made by TIMED Doppler interferometry suggests that zonal wind plays a crucial role in forming electron density layers, which become unstable via the gradient drift instability with background electric field or/and zonal neutral wind generating low‐latitude E region plasma irregularities.

Rocket observations of two distinct types of dispersive features of auroral HF waves

[1] Two dispersive auroral HF emissions have been observed on two sounding rockets 5 years apart, employing different sensors with different effective antenna lengths and payload orientations. Both the SIERRA and CHARM rockets were launched to ∼735 km over active auroral substorms from Poker Flat, Alaska. On both flights, two distinct types of dispersed features occurred, each of which exhibited a frequency-time structure characterized by an impulsive signal at one end of the frequency range, with progressively greater dispersion as the emission frequency approached a bounding frequency from either above or below. The first type of emissions, called “swishers,” occurred in the frequency range 1200–1500 kHz, with a characteristic signature whereby the signal is progressively more delayed as its frequency approaches a lower bound from above. The second type of emissions, called “hooks,” were observed in the frequency range 600–1100 kHz and were progressively more delayed as their frequency approached an upper bound from below. Qualitatively, hooks and swishers might both be explained purely by wave propagation: As the wave frequency approaches the lower cutoff of the Langmuir, O-mode, or Z-mode (in the case of swishers) or the upper cutoff of the whistler mode (in the case of hooks), the group velocity becomes small and the signals are delayed. In the case of hooks, ray-tracing calculations support this explanation by showing that wave dispersion can explain the observed signature, if the emission originates on the whistler mode resonance cone on the 60° invariant field line. In the case of swishers, ray-tracing calculations suggest that wave dispersion alone cannot explain the observed signature for any possible mode.

An Overview of the Space-based Observations for Upper Atmospheric Research

The upper atmospheric research is of importance both in understanding the global change and the sun-earth connection and in applications of near space weather.It aims to understand and model the dynamical,chemical and radiative processes and their interactions in the upper atmosphere.The ground-based,high altitude aircraft,stratospheric balloon,rocket,and space-based observations have provided many data about the dynamical,thermal and chemical structures and variations in the upper atmosphere.This article will give an overview about the space-based observations which play an essential role in the upper atmosphere researches.Past,current and near future satellite missions and remote sensors for upper atmospheric observation and some important scientific results are summarized.

Solar cycle minimum measurements of the solar extreme ultraviolet spectral irradiance on 14 April 2008

[1] NASA sounding rocket 36.240 was launched from White Sands Missile Range in New Mexico on 14 April 2008. The primary instrument in this payload was the prototype extreme ultraviolet (EUV) Variability Experiment (EVE). The Multiple EUV Grating Spectrograph (MEGS) channels of EVE measure the solar irradiance from 6 to 106 nm at 0.1 nm spectral resolution. While the main purpose of this rocket flight is to provide the fifth underflight calibration for the Solar EUV Experiment (SEE), the importance of this rocket observation is the first observation of the solar EUV irradiance at high spectral resolution during solar cycle minimum conditions. The higher spectral resolution measurements will help resolve outstanding concerns about the previous solar soft X-ray irradiance results made with broadband photometers shortward of 27 nm, and the measurements provide the most accurate reference for the solar cycle minimum as part of the international Whole Heliosphere Interval (WHI) campaign.

The ECOMA 2007 campaign: rocket observations and numerical modelling of aerosol particle charging and plasma depletion in a PMSE/NLC layer

Abstract. The ECOMA series of rocket payloads use a set of aerosol particle, plasma, and optical instruments to study the properties of aerosol particles and their interaction with the ambient plasma environment in the polar mesopause region. In August 2007 the ECOMA-3 payload was launched into a region with Polar Mesosphere Summer Echoes (PMSE) and noctilucent clouds (NLC). An electron depletion was detected in a broad region between 83 and 88 km, coincident with enhanced density of negatively charged aerosol particles. We also find evidence for positive ion depletion in the same region. Charge neutrality requires that a population of positively charged particles smaller than 2 nm and with a density of at least 2×108 m−3 must also have been present in the layer, undetected by the instruments. A numerical model for the charging of aerosol particles and their interaction with the ambient plasma is used to analyse the results, showing that high aerosol particle densities are required in order to explain the observed ion density depletion. The model also shows that a very high photoionisation rate is required for the particles smaller than 2 nm to become positively charged, indicating that these may have a lower work function than pure water ice.

Solar Irradiance Reference Spectra (SIRS) for the 2008 Whole Heliosphere Interval (WHI)

The IHY2007 Whole Heliosphere Interval (WHI) for solar Carrington Rotation 2068 (20 March to 16 April 2008) has been very successful in obtaining a wide variety of solar, heliospheric, and planetary observations during times of solar cycle minimum conditions. One of these efforts is the generation of solar irradiance reference spectra (SIRS) from 0.1 nm to 2400 nm using a combination of satellite and sounding rocket observations. These reference spectra include daily satellite observations from TIMED Solar Extreme ultraviolet Experiment (SEE) and Solar Radiation and Climate Experiment (SORCE) instruments. The extreme ultraviolet range is also improved with higher spectral resolution observations using the prototype SDO Extreme ultraviolet Variability Experiment (EVE) aboard a sounding rocket launched on 14 April 2008. The SIRS result is an important accomplishment in that it is the first data set to have simultaneous measurements over the full spectral coverage up to 2400 nm during solar cycle minimum conditions.