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Rocket measurements of nitric oxide density profile in upper atmosphere with scanning ultraviolet spectrometers aboard Nike-Apache rocket vehicle
The effects on the upper dayside Venus ionosphere of a slow increase in solar wind dynamic pressure are simulated numerically with a one-dimensional (spherically symmetric) Lagrangian hydrodynamical code. The simulation is started with an extended ionosphere in pressure equilibrium with the solar wind at the ionopause. The pressure at the ionopause is gradually increased to five times the initial pressure with rise times of 5, 15, and 30 min. It is found that, for rise times greater than about 10 min, the compression of the ionopause is nearly adiabatic, with the ionopause moving downward at velocities of approximately 1-2 km/sec until it reaches a maximally compressed state, at which time the motion reverses. For short rise times the compression produces a shock wave similar to that occurring in the case of a sudden increase in pressure. The global implications of these processes are discussed within the context of Pioneer Venus observations and future theoretical work on this problem is outlined.
At 23:08 UT on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude (338 krn) during its second flyby of Venus en route to its 201 1 orbit insertion at Mercury. Whereas no measurements were collected during MESSENGER'S first Venus flyby in October 2006, the Magnetometer (MAG) and the Energetic Particle and Plasma Spectrometer (EPPS) operated successfully throughout this second encounter. Venus provides the solar system's best example to date of a solar wind - ionosphere planetary interaction. Pioneer Venus Orbiter measurements have shown that this interaction affects the upper atmosphere and ionosphere down to altitudes of - 150 km. Here we present an initial overview of the MESSENGER observations during the - 4 hrs that the spacecraft spent within 10 planet radii of Venus and, together with Venus Express measurements, examine the influence of solar wind plasma and interplanetary magnetic field conditions on the solar wind interaction at solar minimum.
During a Martian dust storm, the lower atmosphere is heated locally. Due to dynamical effects, the upper atmosphere and ionosphere can be lifted upward on a global scale by approximately 10 km. The connections between lower atmospheric dust events and associated ionospheric responses are poorly understood due to limited observations. Here, we present MAVEN Radio Occultation Science Experiment (ROSE) observations of ionospheric peak altitude during dust events in 2018 and 2016. In June 2018, a planet-encircling dust event arose from the Acidalia storm track in the northern hemisphere. Ionospheric peak altitudes at around 20°S were normal in ROSE egress observations on 19 June and 22 June and then 10–15 km higher on 26 June and thereafter. Ionospheric peak altitudes at around 50°N were also elevated in ROSE ingress observations, which began on 17 June. This suggests that the ionospheric peak altitude was affected by the dust event in the northern hemisphere before the southern hemisphere. We also observe evidence that smaller dust storms can trigger ionospheric responses: In July–October 2016, ionospheric peak altitudes at solar zenith angles of 54–70° and latitudes of 50–80°S were 20 km higher than expected. These observations were acquired during a modest “A storm” during a year without a global dust storm.
Electron density distribution in upper f-region
An overview of a Mars Aeronomy Explorer (MAX) mission design study performed at NASA's Jet Propulsion Laboratory is presented herein. The mission design consists of ten micro-spacecraft orbiters launched on a Delta IV to Mars polar orbit to determine the spatial, diurnal and seasonal variation of the constituents of the Martian upper atmosphere and ionosphere over the course of one Martian year. The spacecraft are designed to allow penetration of the upper atmosphere to at least 90 km. This property coupled with orbit precession will yield knowledge of the nature of the solar wind interaction with Mars, the influence of the Mars crustal magnetic field on ionospheric processes, and the measurement of present thermal and nonthermal escape rates of atmospheric constituents. The mission design incorporates alternative design paradigms that are more appropriate for-and in some cases motivate-distributed micro-spacecraft. These design paradigms are not defined by a simple set of rules, but rather a way of thinking about the function of instruments, mission reliability/risk, and cost in a systemic framework.
The interaction of superthermal electrons, including both magnetospheric electrons and photoelectrons, with the upper atmosphere and ionosphere of Titan, is studied using a two stream electron transport code. Ionization rates, electron heating rates, and airglow emission rates are calculated. Results of a one dimensional model of the ionosphere of Titan, which includes both photoionization and ionization by magnetospheric electrons, are presented. Preliminary calculations of ionospheric ion outflow down the wake (or tail) of Titan, for time periods when the wake region is illuminated by the Sun, are made.
Mission timetables, spacecraft, scientific objectives, and payloads of the two mission, Orbiter and Multiprobe, planned for launch and encounter with Venus during the 1978 Venus mission opportunity are described. Basically, the Orbiter mission has the goal of global mapping of the clouds, atmosphere and ionosphere of Venus by remote sensing and radio occultation, global studies by in situ measurements of the upper atmosphere and ionosphere and solar wind-ionosphere interaction region, and determination of gravitational field harmonics from perturbations of the spacecraft orbit. The Multiprobe mission will study the nature and composition of the clouds, the structure of the atmosphere, the circulation pattern, and the characteristics of the planetary environmental interaction with the solar wind.
This document is a final report on research activities and accomplishments that occurred during the funding period of 10-1-90 through 1-30-94. The focus of our interdisciplinary investigation during the Dynamics Explorer Mission was on the complex coupling processes that tap the magnetic-storm energy, stored in the ring current particle reservoir, and transport this energy into the subauroral, midlatitude and even equatorial ionospheric regions. The transport of energy through the inner magnetosphere and into the underlying ionospheric regions is a critical element in our understanding of the impact of solar and magnetic disturbances on upper atmospheric and ionospheric regions equatorward of the auroral zone.
We can extend robustly the radio occultation data record by 6 years (+60%) by developing a singlefrequency processing method for GPS/MET data. We will produce a calibrated data set with profile-byprofile data characterization to determine robust upper bounds on ionospheric bias. Part of an effort to produce a calibrated RO data set addressing other key error sources such as upper boundary initialization. Planned: AIRS-GPS water vapor cross validation (water vapor climatology and trends).
At Venus the interaction of the shocked solar wind and cold planetary ions takes place in the dayside mantle. The shocked solar wind is a warm, drifting Maxwellian plasma whereas the planetary plasma is cold; the plasma in the mantle is strongly magnetized. The coexistence of these two populations is unstable, and it leads to wave excitations that organize the energy and momentum exchange between the shocked solar wind and the plasma of planetary origin. The source of the free energy is the solar wind. The intensive wave activity seen in the 100 Hz channel of the wave instrument onboard the Pioneer-Venus Orbiter in the dayside mantle region of Venus can be identified as almost electrostatic VLF waves excited by the kinetic branch of the modified two-stream lower hybrid instability. The waves interact with the particles, and the planetary plasma is heated and accelerated outside the ionosphere, close to its upper boundary. This way solar wind scavenges the ionosphere, and planetary ions leave the planetary magnetosphere. A portion of the wave energy is capable of penetrating directly into the ionosphere and heating it.
The conclusion of Mahajan et al. (1992) that 'the existence of O(+) as dominant at (Venusian) ionopause altitudes in excess of 500-1000 km can only be explained if atomic oxygen is the major neutral constituent' is argued to be incorrect. It is suggested that at a transition region of about 200 km, thermal atomic oxygen is the dominant neutral gas, and hot oxygen is a minor species; thus the O(+) to H(+) ratio at high altitudes is not an indicator of the presence of hot oxygen at these altitudes. A 1D model for H(+) and O(+) appropriate for the dayside ionosphere of Venus shows that within hot atomic oxygen density values from 1000 to 10 exp 6/ cu cm at 150 km, the calculated H(+) and O(+) densities did not change in any meaningful way, because the hot oxygen population remained a minor neutral constituent below 200 km, which is the approximate height of the transition between chemical and diffusive equilibrium conditions for the ions.
The original interest in an ionosphere on Jupiter was generated by the discovery of strong radio-frequency emissions at approximately 20 MHz which were thought to be plasma frequencies associated with Jupiter's ionosphere. The ionosphere of Jupiter provides a means to couple the magnetosphere to the atmosphere by virtue of its high conductivity and collisional interaction with the neutral atmosphere. The Pioneer and Voyager have provided direct measurements of profiles of electron concentration at selected locations on Jupiter. Attention is given to basic principles regarding the characteristics of the Jovian ionosphere, the ionization sources, aspects of ion recombination, ion chemistry, observations of Jupiter's ionosphere, the structure of Jupiter's upper atmosphere, and questions of ionospheric modeling. On the basis of the Pioneer and Voyager observations it appears that Jupiter's ionosphere and thermosphere undergo significant solar cycle changes.
Models of the upper atmospheres of Mars and Venus were constructed using Viking and Pioneer Venus data. The neutral densities, with the exception of NO, N(4S), N(2D) and N(2P) were taken from the measured values, along with the neutral, ion, and electron temperatures. Using solar fluxes and relevant cross sections, the production rates of ions and neutral fragments by photo and electron impact processes were computed. These production rates were combined with chemical production rates and loss along with one dimensional transport eddy diffusion, molecular and ambi polar diffusion, and thermal diffusion, to determine the densities of ions and odd nitrogen species. Preliminary calculations show that the chemistry of metastables and doubly ionized species is important in the ionospheres of Mars and Venus. Production of N(+) in metastable reactions is particularly important, and it explains the discrepancy between the measurements of earlier models. Production of CO(+) is also affected. Reactions of O(++) and O(+)(2D) with N2 have important consequences for the escape rate of atomic nitrogen from the Martian atmosphere.
We have simulated plasma transport processes in the presence of a quasi-two-dimensional current filament, that generated kV potential structure in the auroral region. The simulation consists of a set of one-dimensional flux tube simulations with different imposed time-dependent, field-aligned currents. The model uses the 16 moment system of equations and simultaneously solves coupled continuity and momentum equations and equations describing the transport along the magnetic field lines of parallel and perpendicular thermal energy and heat flows for each species. The lower end of the simulation is at an altitude of 800 km, in the collisional topside ionosphere, while the upper end is at 10 R(sub E) in the magnetosphere. The plasma consists of hot electrons and protons of magnetospheric origin and low-energy electrons, protons, and oxygen ions of ionospheric origin. The dynamical interaction of the individual current filaments with ionospheric and magnetospheric plasma generates a potential structure in the horizontal direction and kilovolt field-aligned potential drops along the field lines. The side-by-side display exhibits the evolution of the implied potential structure in the horizontial direction. In the presence of this potential structure and parallel electric field ionospheric plasma density is depleted and velocity is reduced, while density enhancement and increased velocity is observed in magnetospheric plasma. The ionospheric and magnetospheric electron temperatures increase below 2 R(sub E) due to magnetic mirror force on converging geomagnetic field lines. The primary cross-field motion produced by the horizontal E field (E x B drift) is perpendicular to both of the significant spatial directions and is thus ignorable in this geometry. The effects of other cross-field drift processes are discussed. The simulation thus provides insight into the dynamical evolution of two-dimensional potential structures driven by an imposed finite width, field-aligned current profile.
This paper presents Dynamic Explorer data on the plasma coupling between the plasmasphere and ionosphere. DE 1 measurements of ion composition and temperatures at 1.4-3.5 R(F) in the plasmasphere were combined with DE-2 measurements of ion composition and electron and ion temperatures in the upper F region/topside ionosphere, closely spaced in universal and local time for cases in the November 6-11, 1981 period. The observations are compared directly with the field-line interhemispheric plasma (FLIP) model calculations of altitudinal ion density and temperature profiles. It was found that, when the FLIP model permitted fractional trapping of ionospheric photoelectrons and consequent plasmaspheric heating, good agreement with the observations was obtained.
Natural and man-made events like earthquakes and nuclear explosions launch atmospheric gravity waves (AGW) into the atmosphere. Since the particle density decreases exponentially with height, the gravity waves increase exponentially in amplitude as they propagate toward the upper atmosphere and ionosphere. As atmospheric gravity waves approach the ionospheric heights, the neutral particles carried by gravity waves collide with electrons and ions, setting these particles in motion. This motion of charged particles manifests itself by wave-like fluctuations and disturbances that are known as traveling ionospheric disturbances (TID). The perturbation in the total electron content due to TID's is derived analytically from first principles. Using the tilted dipole magnetic field approximation and a Chapman layer distribution for the electron density, the variations of the total electron content versus the line-of-sight direction are numerically analyzed. The temporal variation associated with the total electron content measurements due to AGW's can be used as a means of detecting characteristics of the gravity waves. As an example, detection of tsunami generated earthquakes from their associated atmospheric gravity waves using the Global Positioning System is simulated.
The large thermospheric infrared radiance enhancements observed from the TIMED/SABER experiment during recent solar storms provide an exciting opportunity to study the influence of solar-geomagnetic disturbances on the upper atmosphere and ionosphere. In particular, nighttime enhancements of 4.3 um emission, due to vibrational excitation and radiative emission by NO+, provide an excellent proxy to study and analyze the response of the ionospheric E-region to auroral electron dosing and storm-time enhancements to the E-region electron density. In this paper we give a status report of on-going work on model and data analysis methodologies of deriving NO+ 4.3 um volume emission rates, a proxy for the storm-time E-region response, and the approach for deriving an empirical storm-time correction to International Reference Ionosphere (IRI) E-region NO+ and electron densities.