Longitudinal variability of thermospheric zonal winds near dawn and dusk

Understanding the morphology and dynamics of the thermosphere is key to understanding the Earth’s upper atmosphere as a whole. Thermospheric winds play an important role in this process by transporting momentum and energy and affecting the composition, dynamics and morphology of not only the thermosphere but also of the ionosphere. The general morphology of the winds has been well established over the past decades, but we are only starting to understand its variability. In this process the lower atmosphere plays an important role due to direct penetration of waves from the lower atmosphere into the ionosphere/thermosphere, secondary waves generated on the way, or internal feedback mechanisms in the coupled ionosphere-thermosphere system. Therefore, knowledge about thermospheric variability and its causes is critical for an improved understanding of the global ionosphere-thermosphere system and its coupling to the lower atmosphere. We have used low-to mid-latitude zonal wind observations obtained by the Gravity Field and Steady-State Ocean Explorer (GOCE) satellite near 260 km altitude during geomagnetically quiet times to investigate the interannual and spatial zonal wind variability near dawn and dusk, during December solstice. The temporal and spatial variability is presented as a variation about the zonal mean values and decomposed into its underlying wavenumbers using a Fourier analysis. The obtained wave features are compared between different years and clear interannual changes are observed in the individual wave components, which appear to align with changes in the solar flux but do not correlate with variations in either El Niño Southern Oscillation or the Quasi Biennial Oscillation. The obtained wave features are compared and contrasted with results from the Climatological Tidal Model of the Thermosphere (CTMT) and revealed a very good agreement between CTMT and the 2009 and 2010 December GOCE zonal wind perturbations at dawn. However, during dusk, the CTMT zonal wind perturbations and in particular the zonal wave-1 component show significant differences with those observed by GOCE

OPAL CubeSat Data Analysis Model

Understanding the Earth’s lower thermosphere (altitude range 9 km -140km) is of growing interest for many areas of research within the space weather community. The NSF sponsored OPAL (Optical Profiling of the Atmospheric Limb) mission is designed to measure temperature profile by observing the integrated line of sight of the day-time O2 A-band (~760nm) emissions on the limb. The OPAL instrument has an altitude resolution of 1.03km from 80-160km flown on a 3U CubeSat, and is expected to be launched from the ISS (International Space Station) (~400km altitude). We have developed a model of OPAL’s position and attitude of its optical system to investigate the instrument’s ability to detect space weather signatures i.e. solar storms and gravity waves) in the lower thermosphere temperature data. Models of the flight, line- of-sight, and atmospheric O2 A-band emission are used to simulate the expected output of the OPAL instrument. The simulated emission will be used in an inversion method to obtain the altitudinal temperature profile in the lower thermosphere to test our ability to resolve the input parameters of the lower thermospheric model

Climatology of Plasmaspheric Total Electron Content Obtained From Jason 1 Satellite

We used more than 40 million total electron content (TEC) measurements obtained from the GPS TurboRogue Space Receiver receiver on board the Jason 1 satellite in order to investigate the global morphology of the plasmaspheric TEC (pTEC) including the variations with local time, latitude, longitude, season, solar cycle, and geomagnetic activity. The pTEC corresponds to the total electron content between Jason 1 (1336 km) and GPS (20,200 km) satellite altitudes. The pTEC data were collected during the 7 year period from January 2002 to December 2008. It was found that pTEC increases by about 10–30% from low to high solar flux conditions with the largest variations occurring at low latitudes for equinox. During low solar flux condition, pTEC is largely independent of geomagnetic activity. However, it slightly decreases with increasing geomagnetic activity at low latitudes during high solar flux. The seasonal variations such as the annual and semiannual anomalies in the ionosphere also exist in the low-latitude plasmasphere. In particular, the American sector (around 300°E) shows strong annual asymmetry in the plasmaspheric density, being larger in December than in June solstice

Spatial and temporal correlations of thermospheric zonal winds from GOCE satellite observations

Winds in the thermosphere play an important role in the transport of momentum and energy in the upper atmosphere and affect the composition, dynamics and morphology of the ionospheric plasma. Although the general morphology of the winds is well understood, we are only starting to understand its variability. During the last decade it has become inherently clear that in addition to solar forcing of the thermosphere, the lower atmosphere also is an important driver of thermospheric variability. Therefore, an understanding of thermospheric variability and its spatial and temporal correlations is critical for an improved understanding of the coupled ionosphere-thermosphere system and the coupling to the lower atmosphere. The Gravity Field and Steady-State Ocean Explorer (GOCE) provided zonal winds near dawn and dusk at an altitude of around 260 km from November 2009 to October 2013. We have used GOCE zonal wind observations from low- to mid-latitudes obtained during geomagnetically quiet times to investigate spatial and temporal correlations in the zonal winds near dawn and dusk. Latitudinal correlations were calculated for the GOCE zonal winds for December solstice separately for each year from 2009 to 2012 and their year-to-year variation was established. Correlations between hemispheric conjugate points were found at mid latitudes during the latter years. Latitudinal correlations for December solstice 2009 and June solstice 2010 were compared and the correlation length was found to be consistently larger in the winter hemisphere during dawn and in the summer hemisphere during dusk. Zonal wind longitudinal/temporal correlations were also determined for December 2009 and 2011 and for June 2010 and found to be periodic in longitude/time. The temporal evolution of the temporal/longitudinal correlations were found to gradually decrease over the course of several days. The maxima in the correlation coefficients were always located in the winter hemisphere during dawn and in the summer hemisphere during dusk. During dawn, the largest contributors to the temporal/longitudinal correlations were found to be nonmigrating tides, whereas during dusk, additional waves appear to play important roles

OPAL CubeSatellite Flight and Line of Sight Integration Modeling

Understanding the lower thermosphere, the range of 90km to 140km above the surface of the Earth, is a growing interest for many areas of research within space weather. The Optical Profiling of the Atmospheric Limb (OPAL) mission is funded by NSF to gather global thermosphere temperatures. OPAL will be able to resolve the temperature profiles through observing day-time emissions of O2 A-band (~760nm) emissions. This is done by using integrated line-of-sight measurements of the A-band through a tangential view of the atmosphere down to 90km. The OPAL instrument is on a 3U CubeSatellite (30cm×10cm×10cm) and is expected to follow the International Space Station (ISS) orbit (~400km altitude). Having an accurate model of the OPAL CubeSatellite’s position and the attitude of its optical system are crucial in checking the instruments’ ability to detect space weather signatures in the temperature data (i.e. solar flares and gravity waves). Using Matlab and Analysis Graphics Inc.’s (AGI) System Tool Kit (STK) for mission modeling and analysis, we will have the proper position of OPAL and its line of sight to combine with other information about the data interpretation and collection

Equatorial Disturbance Dynamo Vertical Plasma Drifts Over Jicamarca: Bi‐Monthly and Solar Cycle Dependence

We use extensive incoherent scatter radar observations from the Jicamarca Radio Observatory to study the local time and bi‐monthly dependence of the equatorial disturbance dynamo vertical plasma drifts on solar flux and geomagnetic activity. We show that the daytime disturbance drifts have generally small magnitudes with largest values before noon and an apparent annual variation. Near dusk, they are downward throughout the year with largest values during the equinoxes and smallest during June solstice. These downward drifts increase strongly with solar flux, and shift to later local times. They also increase with increasing geomagnetically active conditions with no apparent local time shift. The equinoctial evening downward disturbance drifts are larger during the autumnal equinox than during the vernal equinox. The nighttime disturbance drifts are upward and have small seasonal and solar cycle dependence but increase strongly with geomagnetic activity, particularly in the late night sector. Our results are in general agreement with those from previous theoretical and experimental studies, except near dusk where our results show much stronger seasonal and solar cycle dependence

Development of a Physics-Based Reduced State Kalman Filter for the Ionosphere

A physics-based data assimilation model of the ionosphere is under development as the central part of a Department of Defense/Multidisciplinary University Research Initiative (MURI)-funded program called Global Assimilation of Ionospheric Measurements (GAIM). With the significant increase in the number of ionospheric observations that will become available over the next decade, this model will provide a powerful tool toward an improved specification and forecasting of the global ionosphere, with an unprecedented accuracy and reliability. The goal of this effort will be specifications and forecasts on spatial grids that can be global, regional, or local (25 km × 25 km). The specification/forecast will be in the form of three-dimensional electron density distributions from 90 km to geosynchronous altitudes (35,000 km). The main data assimilation in GAIM will be performed by a Kalman filter. In this paper we present a practical method for the implementation of a Kalman filter using a new physics-based ionosphere/plasmasphere model (IPM). This model currently includes 5 ion species (O2 +, N2 +, NO+, O+, and H+) and covers the low and middle latitudes from 90 km to about 20,000 km altitude. A Kalman filter based on approximations of the state error covariance matrix is developed, employing a reduction of the model dimension and a linearization of the physical model. These approximations lead to a dramatic reduction in the computational requirements. To develop and evaluate the performance of the algorithm, we have used an Observation System Simulation Experiment. In this paper, we will initially present the physics-based IPM used in GAIM and demonstrate its use in the reduced state Kalman filter. Initial results of the filter in the South American sector using synthetic measurements are very encouraging and demonstrate the proper performance of the technique