Mass Spectrometer And Incoherent Scatter Research Articles

Data‐Driven Inference of Thermosphere Composition During Solar Minimum Conditions

AbstractMass density variations can deviate from the expected behavior caused by temperature due to changes in the composition. Such deviations can be especially significant during solar minimum conditions. Model‐data differences are typically resolved through temperature corrections while overlooking the role of errors in lower boundary composition. In this work, we use a data‐driven methodology to simultaneously estimate thermosphere composition and temperature contributions to model‐data differences. The methodology uses modal decomposition to extract high‐dimensional, reduced order basis functions for the covariance of the neutral thermospheric species and temperature. The extracted basis functions are combined with CHAllenging Minisatellite Payload and Gravity Recovery And Climate Experiment mass density measurements using a nonlinear least squares solver. We demonstrate the methodology using the Naval Research Laboratory's empirical Mass Spectrometer and Incoherent Scatter (MSIS) model to derive the high‐dimensional basis functions. We characterize and quantify the contribution of temperature and lower boundary effects with oxygen and helium since the two species have a direct impact on drag and orbit prediction through gas‐surface interactions and mass density. We analyze the month of December in 2008, based on the work of Thayer et al. (2012), and estimate that lower boundary composition errors contribute approximately 50% of the model‐data differences.

Estimation of Mesospheric Densities at Low Latitudes Using the Kunming Meteor Radar Together With SABER Temperatures

AbstractNeutral mesospheric densities at a low latitude have been derived during April 2011 to December 2014 using data from the Kunming meteor radar in China (25.6°N, 103.8°E). The daily mean density at 90 km was estimated using the ambipolar diffusion coefficients from the meteor radar and temperatures from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument. The seasonal variations of the meteor radar‐derived density are consistent with the density from the Mass Spectrometer and Incoherent Scatter (MSIS) model, show a dominant annual variation, with a maximum during winter, and a minimum during summer. A simple linear model was used to separate the effects of atmospheric density and the meteor velocity on the meteor radar peak detection height. We find that a 1 km/s difference in the vertical meteor velocity yields a change of approximately 0.42 km in peak height. The strong correlation between the meteor radar density and the velocity‐corrected peak height indicates that the meteor radar density estimates accurately reflect changes in neutral atmospheric density and that meteor peak detection heights, when adjusted for meteoroid velocity, can serve as a convenient tool for measuring density variations around the mesopause. A comparison of the ambipolar diffusion coefficient and peak height observed simultaneously by two co‐located meteor radars indicates that the relative errors of the daily mean ambipolar diffusion coefficient and peak height should be less than 5% and 6%, respectively, and that the absolute error of the peak height is less than 0.2 km.

Data Analysis of Upper Atmosphere Temperature Detected by Sounding Rockets in China

AbstractSounding rockets launched by China have collected data on the upper atmosphere for nearly 50 years. In this work, the data accuracy and variable characteristics of upper atmosphere temperature data, gathered at heights of 20–60 km over Jiuquan, China, during 1974–2014, were analyzed. The relative accuracy of sounding rocket temperature data was determined by comparing the data with Mass Spectrometer and Incoherent Scatter (MSIS) model data by season, and with Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) from the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite by year. The sounding rocket temperature data showed differences from MSIS in every season, with the minimum difference occurring in summer, the next smallest difference in winter, and the maximum difference occurring in autumn. The sounding rocket data showed smaller differences from the SABER data, although the deviation still fluctuated depending on the date and hour of the observations. In addition, the temperature distributions of the temperature profiles were examined at different times at the same heights. By linearly fitting the mean temperature profiles of each season, the statistical characteristics of the temperature changes with height were explored.

Remote sensing of neutral temperatures in the Earth's thermosphere using the Lyman‐Birge‐Hopfield bands of N2: Comparisons with satellite drag data

This paper presents remotely sensed neutral temperatures obtained from ultraviolet observations and compares them with temperatures from the NRLMSISE‐00 version of the Mass Spectrometer and Incoherent Scatter (MSIS) model (unconstrained and constrained to match the total densities from satellite drag). Latitudinal profiles of the temperatures in the Earth's thermosphere are obtained by inversion of high‐resolution (∼1.3 Å) observations of the (1,1) and (5,4) Lyman‐Birge‐Hopfield (LBH) bands of N2. The spectra are from the High resolution Ionospheric and Thermospheric Spectrograph (HITS) instrument aboard the Advanced Research and Global Observation Satellite (ARGOS). The results indicate that on each day examined there was consistency between the remotely sensed thermospheric temperatures, the densities from coincident satellite drag measurements at adjacent altitudes, and the NRLMSISE‐00 model.

A multiyear (2002–2006) climatology of O/N2 in the lower thermosphere from TIMED GUVI and ground‐based photometer observations

The Mass Spectrometer and Incoherent Scatter (MSIS) series of models has been a standard for specification and prediction of conditions in the Earth's thermosphere. One aspect of the model that has not been well validated is its predictions of the lower thermospheric compositional response to varying periodic and transient solar and geomagnetic forcings. Here we compare the predictions by the NRLMSIS model over the years 2002 to 2006 for column O/N2 with GUVI satellite (daytime) observations at a fixed longitude of the Poker Flat Research Range in central Alaska. NRLMSIS predictions are also compared with nightside auroral O/N2 observations obtained from ground‐based photometric measurements from central Alaska. While there is often good agreement between the GUVI and NRLMSIS O/N2 at high latitudes, there are also times during large geomagnetic storms when there is some disagreement with the largest occurring at midlatitudes. The 9‐day periodicity, first described in 2007 and attributed to high‐speed solar wind streams, is present in the model at all latitudes but is quite weak in the observations below 55N latitude. Away from high‐latitudes, these differences may exist because the NRLMSIS O/N2 dependence on ap forces nonperiodic contributions contained in the NRLMSIS database to give a periodic response when ap is varied periodically. While the nighttime observations show considerable agreement with NRLMSIS they are much more variable than predicted by the model. This variability suggests that there are significant local effects in the auroral zone that are not captured by the model.

Neutral temperatures in the lower thermosphere from N2 Lyman‐Birge‐Hopfield (LBH) band profiles

Measurements of the neutral temperature in the lower thermosphere, using high resolution (0.13 nm) N2 Lyman‐Birge‐Hopfield (LBH) band emissions are presented. The data were taken by the High‐resolution Ionospheric and Thermospheric Spectrograph (HITS) instrument aboard the Advanced Research and Global Observation Satellite (ARGOS). By fitting the LBH band profiles, temperatures in the thermosphere between ∼150 and 270 km have been retrieved. Temperatures retrieved for three geomagnetically quiet days, 28–30 July 2001 are consistent with temperatures from the Mass Spectrometer and Incoherent Scatter (MSIS) model.

Antarctic mesospheric temperature estimation using the Davis mesosphere‐stratosphere‐troposphere radar

This paper presents the first Antarctic meteor radar temperature estimates. These temperatures have been derived from meteor diffusion coefficients using two techniques: pressure model and temperature gradient model. The temperatures are compared with a temperature model derived using colocated OH spectrometer measurements and Northern Hemisphere rocket observations. Pressure model temperatures derived using rocket‐derived pressures show good agreement with the temperature model, while those derived using Mass Spectrometer and Incoherent Scatter (MSIS) and CIRA model pressures show good agreement in winter but poor agreement in summer. This confirms previous studies suggesting the unreliability of high‐latitude CIRA pressures. The temperature gradient model temperatures show good agreement with the temperature model but show larger fluctuations than the pressure model temperatures. Meteor temperature estimates made during the Southern delta‐Aquarids meteor shower are shown to be biased, suggesting that care should be taken in applying meteor temperature estimation during meteor showers. On the basis of our results we recommend the use of the pressure model technique at all sites, subject to determination of an appropriate pressure model.

Ion and neutral density variations during ionospheric storms in September 1974: Comparison of measurement and models

This paper examines the ability of the field line interhemispheric plasma (FLIP) physical ionospheric model to reproduce the O+, NO+, O2+, and N2+ ion densities, and nitric oxide density in the ionosphere and thermosphere over Australia in September 1974. The study includes ionospheric electron density data from Australian ionosonde stations as well as ion and neutral density composition data from elliptical orbits of the Atmosphere Explorer‐C (AE‐C) satellite. The mass spectrometer and incoherent scatter (MSIS) neutral atmosphere model accurately reproduces the O and N2 densities during quiet periods in September 1974, and this enables the FLIP model to also accurately reproduce the measured ion and NO densities as well as ion and electron temperatures during quiet periods. However, the MSIS model produces poor results during the disturbed period of 15 and 16 September because it underestimates the increase in neutral temperature by several hundred degrees and the depletion of the O column density by a factor of 2. When the measured neutral densities are used in the FLIP model instead of MSIS densities, there is fair agreement between the measured and modeled O+, O2+, and NO+ densities above 200 km on 15 September, but the FLIP model overestimates the O2+ density below 200 km. The FLIP model is also in fair agreement with the NmF2 from the ionosonde and reproduces the measured O+ density on 16 September but severely overestimates the satellite measured O2+ and NO+ densities at all altitudes. As found in previous studies, the FLIP model was able to accurately reproduce a positive ionospheric storm that occurred during this period. An important result to emerge from this study is the observation that even during these severely disturbed periods the altitude distributions of the measured O and N2 densities can be reasonably well represented by hydrostatic equilibrium profiles. This suggests that the basic philosophy of the MSIS model remains intact and that it should be possible to improve the MSIS model storm behavior just by improving the specification of the neutral boundary densities and the exospheric temperature. The assumption of hydrostatic equilibrium also simplifies the task of deducing neutral composition from remote sensing.

IRI related data and model services at NSSDC

Abstract NASA's National Space Science Data Center (NSSDC) provides internet access to a large number of space physics data sets and models. We will review and explain the different products and services that might be of interest to the IRI community. Data can be obtained directly through anonymous ftp or through the SPyCAT WWW interface to a large volume of space physics data on juke-box type mass storage devices. A newly developed WWW system, the ATMOWeb, provides browse and sub-setting capabilities for selected atmospheric and thermospheric data. NSSDC maintains an archive of space physics models that includes a subset of ionospheric models. The model software can be retrieved via anonymous ftp. A selection of the most frequently requested models can be run on-line through special WWW interfaces. Currently supported models include the International Reference Ionosphere (IRI), the Mass Spectrometer and Incoherent Scatter (MSIS) atmospheric model, the International Geomagnetic Reference Field (IGRF) and the AE-8/AP-8 radiation belt models. In this article special emphasis will be given to the IRI interface and its various input/output options. Several new options and a Java-based plotting capability were recently added to the Web interface.

Two day wave induced variations in the oxygen green line volume emission rate: WINDII observations

Variations in the oxygen green line emission rate (at 5577 Å) which correspond to a two day wave signature were observed from January 20 to January 30, 1993 by the Wind Imaging Interferometer (WINDII) on the Upper Atmosphere Research Satellite (UARS). The latitude and height extent of these emission variations are summarized. From the volume emission rate data, fields of oxygen mixing ratio using Mass Spectrometer and Incoherent Scatter (MSIS) model data as the background atmosphere were calculated. Analyses of the mixing ratio fields show the variations of emission rate to be primarily the result (to first order) of vertical motions associated with the quasi two day wave (QTDW), not mixing events associated with wave breaking. The mean peak‐to‐peak amplitude of the vertical displacement is of the order of 1 km although at times this amplitude is as much as 4 km. The phase of the mixing ratio variations approaches the two day wave zonal wind phase above 100 km as is expected from simple considerations of the phase relationships associated with planetary waves and the lifetime of atomic oxygen.

F2 peak electron density at Millstone Hill and Hobart: Comparison of theory and measurement at solar maximum

This paper compares the observed behavior of the F2 layer of the ionosphere at Millstone Hill and Hobart with calculations from the field line interhemispheric plasma (FLIP) model for solar maximum, solstice conditions in 1990. During the study period the daily F10.7 index varied by more than a factor of 2 (123 to 280), but the 81‐day mean F10.7 (F10.7A) was almost constant near 190. Calculations were performed with and without the effects of vibrationally excited N2 (N2*) which affects the loss rate of atomic oxygen ions. In the case without N2* there is generally good agreement between the model and measurement for the daytime, peak density of the F region (NmF2). Both the model and the measurement show a strong seasonal anomaly with the winter noon densities a factor of 3 to 4 greater than the summer noon densities at Millstone Hill and a factor of 2 greater at Hobart. The seasonal anomaly in the model is caused by changes in the neutral composition as given by the mass spectrometer and incoherent scatter (MSIS) 86 neutral density model. There is generally little or no increase in the observed noon NmF2 as a function of daily F10.7 except at Millstone Hill in winter. In May‐July, where the measured NmF2 shows least dependence on daily F10.7, there is excellent agreement between the model and data. The modeled NmF2 is about 30% less than the measured values at Millstone Hill at the December solstice, but both model and data increase with increasing daily F10.7 index. At Hobart, on the other hand, the model densities are greater than or comparable to the measured densities for the December solstice. This suggests that the differences between model and data are not due to the incorrect solar EUV flux. The effect of including N2* is to worsen the agreement between model and data at Millstone Hill by reducing the summer densities from good agreement to 40% below the data. In winter the N2* effects are much smaller, and the densities are reduced by only 10%. While N2* worsens the model‐data comparison at Millstone Hill, it does bring the model seasonal density ratio into better agreement with the data and also improves the agreement at Hobart. Although the 1990 daytime ionosphere can be well modeled without N2*, it may still be important for high levels of solar and magnetic activity. There is a very close relationship between the height at which peak density occurs hmF2 variation and the NmF2 variation with F10.7 in summer at Millstone Hill. In contrast to the generally good agreement between model and data at noon, the model badly underestimates the density at night at Millstone Hill at all seasons. At Hobart the model reproduces the nighttime density variations well in both winter and summer. The international reference ionosphere (IRI) model generally provides a good representation of the average behavior of noon NmF2 and hmF2 but because the data show a lot of day‐to‐day variability, there are often large differences. The FLIP model is able to reproduce this variability when hmF2 is specified. The IRI model peak densities are better than the FLIP densities at night, but the IRI model does not represent the Millstone Hill summer data very well at night in 1990.

A consideration of atomic oxygen interactions with the Space Station

A computer model is developed in order to calculate fluence for a generalized spacecraft in orbital flight based on mass spectrometer and incoherent scatter (MSIS) measurements of ambient density. The calculations are used to identify criteria for the selection of materials for the construction of an LEO Space Station. The model is generalized such that the surfaces for study can be oriented in any direction with respect to: a body coordinate system fixed to the spacecraft (E surfaces); and a solar inertial coordinate system. A parametric study was performed in order to evaluate the effects of altitude, inclination, and solar activity on atomic oxygen fluence. Values are obtained for samples of Mylar, Kevlar, Kapton, Tedlar, Teflon and sulfone, as well as for some ethylene polymers. The range of values for material reactivities is from 360 microns for ram-facing surfaces to 200 microns for solar power surfaces during each cycle of solar activity. The possibility of improving reactivity by employing certain chemical coatings is also discussed.

A global model of the neutral thermosphere in magnetic coordinates based on AE‐C data

Molecular nitrogen, atomic oxygen, and helium densities obtained from the AE‐C satellite are analyzed in magnetic latitude and magnetic local time coordinates and compared to OGO 6 data for various seasons and magnetic activity levels. A depletion region for atomic oxygen and helium with respect to molecular nitrogen at high magnetic latitudes in the postmidnight magnetic local time sector persists under both high and low solar activity conditions. A global model in magnetic coordinates, patterned after the mass spectrometer and incoherent scatter (MSIS) model, is developed for molecular nitrogen, atomic oxygen, and helium. It is shown to represent the data well, without any residual UT dependence, and with an accuracy comparable to that provided by the more complex MSIS model with longitude terms. The advantage of using magnetic coordinates is that they are more directly related to the major energy inputs and momentum sources in the polar regions than are geographic coordinates and are more convenient to use in studies of high latitude energy deposition processes. This is important for comparison with theoretical models where the number of coordinates is limited.

Nighttime temperatures and ion chemistry from Ogo 6 Plasma measurements

An analysis is presented of ion temperature and concentration data from the retarding potential analyzer on board the Ogo 6 satellite. The investigation is restricted to plasma measurements in the undisturbed nighttime nonpolar ionosphere between 400 and 450 km spanning several months near solstice; under these conditions, observed ion temperatures are assumed to approximate the neutral gas temperature closely. Emphasis is placed upon statistical analyses of all data acquired within small cells of finite width in latitude and day of observation. Physical effects induced by changing solar and geophysical conditions are considered by comparing these average temperatures with the mass spectrometer and incoherent scatter (MSIS) atmospheric model. Measured nighttime temperatures between low summer and middle winter latitudes are, on the average, about 50°K lower in magnitude than those calculated from the model. The MSIS model does, however, provide an excellent representation of the observed long‐term temperature variations. Measured total concentrations of the molecular ions near the equator are larger in magnitude than those calculated according to equilibrium ion chemistry; this difference exceeds current stated uncertainties in either the reaction rates or the supporting neutral composition and suggests that important problems remain in our quantitative understanding of the ion chemistry of the nighttime F region. On the other hand, changes in the equatorial molecular ion concentrations are directly related to similar variations in the observed ion temperatures and in the MSIS neutral atmosphere.

The latitudinal gradient of nitric oxide in the thermosphere

Theoretical calculations of nitric oxide altitude profiles are made at five different latitudes by using neutral temperatures and composition primarily from the MSIS (mass spectrometer and incoherent scatter) model. The nitric oxide calculated for an altitude of 105 km remains nearly constant with increasing latitude. Observations made by the ultraviolet nitric oxide instrument on the Atmosphere Explorer C satellite show that at low magnetic activity (Ap ≃4), the NO density at 105 km agrees with the theory; however, at moderate levels of activity it increases with latitude. This discrepancy between the theoretical and observed latitudinal gradients of nitric oxide suggests the transport of NO from a high latitude source to lower latitudes. At 200 km the theoretical and observed latitudinal gradients are in reasonable agreement, an indication that the knowledge of the local composition and temperature is sufficient to model nitric oxide at this altitude.

Direct measurements of nighttime thermospheric winds and temperatures, 3. Monthly variations during solar minimum

We used a high-resolution Fabry-Perot spectrometer at Fritz Peak Observatory (39.9°N, 105.5°W) to determine the nighttime variation of thermospheric temperatures and winds from the line profiles and Doppler shifts of the O I 15,867-K (6300 A) line emission. With data obtained during the period April 1975 through March 1976 we examined the variation of the nighttime neutral gas temperature, zonal winds, and meridional winds at F layer heights throughout the year during solar cycle minimum. We compare our observed temperatures to predictions made by the MSIS (mass spectrometer and incoherent scatter) empirical model of neutral temperature and composition in the thermosphere. The calculated nighttime variation of thermospheric temperature is about 100°–150°K lower than measurements for summer and equinox months and about 50°–75°K lower than measurements for winter months. We compare the observed winds to the zonal and meridional winds, which we calculate from a three-dimensional semiempirical dynamic model of the thermosphere by using the pressure gradients specified by the MSIS model. The calculated nighttime winds are in general agreement with observed winds; both reveal a systematic monthly variation during geomagnetic quiet times. The nighttime equatorward meridional winds are greater in summer than in winter. The zonal winds are eastward throughout most of the night during winter; however, as the season progresses toward summer, a transition develops in the early morning hours from eastward to westward winds. This transition occurs earlier in the night as summer approaches. We use model predictions of the diurnal variations of winds and temperatures to calculate diurnal averages of the zonal and meridional wind components over Fritz Peak Observatory. The seasonal variation of these zonal mean values is presented.

A global thermospheric model based on mass spectrometer and incoherent scatter data MSIS, 1. N2density and temperature

Measurements of neutral nitrogen density from mass spectrometers on five satellites (AE-B, Ogo 6, San Marco 3, Aeros A, and AE-C) and neutral temperatures inferred from incoherent scatter measurements at four ground stations are combined to produce a model of thermospheric neutral temperatures and nitrogen densities similar to the Ogo 6 empirical model (Hedin et al., 1974). This global model is designated MSIS (mass spectrometer and incoherent scatter). The global average temperature, the annual temperature variation, lower bound density, and lower bound temperature are discussed. The data set covers the time period from the end of 1965 to mid-1975 and also a wide range of solar activities. Diurnal and semidiurnal variations in lower bound density and temperature are considered, as is magnetic activity.

A global thermospheric model based on mass spectrometer and incoherent scatter data MSIS, 2. Composition

Measurements of O, He, and Ar from neutral gas mass spectrometers on four satellites (Ogo 6, San Marco 3, Aeros A, and AEC-C) and inferred oxygen and hydrogen densities from an ion mass spectrometer on AE-C have been combined with a neutral temperature and nitrogen density model to produce a global model of thermospheric composition in terms of inferred variations at 120 km. The data set covers the time period from mid-1969 to mid-1975. The MSIS (mass spectrometer and incoherent scatter data) model is compared with the Ogo 6 model (Hedin et al., 1974). Ar variations at 120 km tend to be in phase with temperature variations and inverse to the He, O, and H variations.