Space Science Division Naval Research Laboratory Washington

Washington, Washington, United States

Space Science Division Naval Research Laboratory Washington

Washington, Washington, United States

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Hervig M.E.,GATS, Inc. | Bardeen C.G.,U.S. National Center for Atmospheric Research | Siskind D.E.,Space Science Division Naval Research Laboratory Washington | Mills M.J.,U.S. National Center for Atmospheric Research | Stockwell R.,GATS, Inc.
Geophysical Research Letters | Year: 2017

Meteoric smoke has traditionally been understood as a passive tracer which follows the global mesospheric circulation. Smoke extinction measured by the Solar Occultation For Ice Experiment, however, shows that while this is true in the middle to upper mesosphere (pressure <~0.2hPa), it is not true near the stratopause. Here the expected winter increase begins 3months earlier than in models. We suggest that the autumn extinction increase is due to H2SO4 condensing above the nominal stratospheric aerosol layer (~5hPa). This is possible due to lowering of the H2SO4 saturation vapor pressure when the acid is neutralized through combination with meteoric metals. The appearance of neutralized H2SO4 aerosol in autumn is associated with the seasonal decrease in temperature. The combination of meteoric smoke and neutralized H2SO4 aerosols explains the observations and supports previous suggestions that H2SO4 could condense above the nominal stratospheric sulfate layer. © 2017. American Geophysical Union. All Rights Reserved.


Dymond K.F.,Space Science Division Naval Research Laboratory Washington | Budzien S.A.,Space Science Division Naval Research Laboratory Washington | Hei M.A.,Praxis Inc.
Radio Science | Year: 2017

We present and discuss two algorithms of the class known as Image Space Reconstruction Algorithms (ISRAs) that we are applying to the solution of large-scale ionospheric tomography problems. ISRAs have several desirable features that make them useful for ionospheric tomography. In addition to producing nonnegative solutions, ISRAs are amenable to sparse-matrix formulations and are fast, stable, and robust. We present the results of our studies of two types of ISRA: the Least Squares Positive Definite and the Richardson-Lucy algorithms. We compare their performance to the Multiplicative Algebraic Reconstruction and Conjugate Gradient Least Squares algorithms. We then discuss the use of regularization in these algorithms and present our new approach based on regularization to a partial differential equation. ©2017. American Geophysical Union.


Dymond K.F.,Space Science Division Naval Research Laboratory Washington | Coker C.,Space Science Division Naval Research Laboratory Washington | Metzler C.,Space Science Division Naval Research Laboratory Washington | Mcdonald S.E.,Space Science Division Naval Research Laboratory Washington
Radio Science | Year: 2017

We report the results of a model validation study that assessed how well several ionospheric models captured the slant total electron content, especially at low latitudes near the equatorial ionization anomaly, where horizontal and vertical density gradients are large. We assessed NeQuick, IRI-2007, IRI-2012, SAMI-3, and the Utah State University version of the Global Assimilation of Ionospheric Measurements (GAIM) model. We used slant total electron content measurements made by the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) constellation during 5 May to 20 June 2012 to test GAIM, NeQuick, IRI-2007, and IRI-2012 and during 1 October 2011 to 31 December 2011 to test SAMI-3, as the SAMI-3 model runs were not available for the 2012 time frame. We found that the GAIM data assimilation model showed the lowest biases, although all of the models typically agreed with the COSMIC measurements to ~8% in the worst case. One area of concern with all of the models was that the mean percentage difference between the COSMIC measurements and the calculated total electron content (TEC) showed significant scatter, >15% at the 1 sigma level; this was attributed to all of the models not capturing the density gradients near the equatorial ionization anomaly (EIA). All of the models underestimated the topside electron density and thus also the ionospheric slab thickness. Since ionospheric models are often validated using near-vertical TEC measurements and the vertical TEC is the product of the electron density at the F region peak and the slab thickness, our results suggest that the peak density values in the models may be too high. Published 2017. This article is a US Government work and is in the public domain in the United States of America.


Sassi F.,Space Science Division Naval Research Laboratory Washington | Liu H.-L.,High Altitude Observatory | Emmert J.T.,Space Science Division Naval Research Laboratory Washington
Journal of Geophysical Research A: Space Physics | Year: 2016

The effects of breaking of traveling, planetary scale Rossby waves (TPWs) in the lower thermosphere are investigated with respect to the mixing of neutral constituents. We use numerical simulations of the Whole Atmosphere Community Climate Model, eXtended version, whose meteorology below 92km is constrained by atmospheric specifications obtained from operational weather forecast/data assimilation system. The Fourier spectra show that the amplitude of TPWs with periods between 3 and 10days are statistically significant in some years; the amplitude and phase of the band-pass filtered behavior is consistent with the behavior of the 5day wave. A wavelet analysis using the S-transform shows that large variations with periods between 3 and 10days can occur in relatively narrow temporal windows (20-30days) during boreal winter. The momentum flux entering the lower thermosphere during the times of TPW amplification is shown to be large, and the amplifications of the TPWs in the thermosphere are not always associated with stratospheric sudden warming. The subtropical zonal accelerations are consistent with Rossby wave encountering a surf zone at low latitudes, resulting in wave breaking. The zonal acceleration is shown to be associated with a meridional diffusion, which is largest in the lower thermosphere where the wave activity and the wave breaking are also large. The ultimate effect on neutral density and composition is a meridional, down-gradient mixing; although this horizontal diffusion is largest below 110km, the effects on the composition are amplified with increasing altitude, due to the diffusive separation of the thermosphere. © 2016. American Geophysical Union. All Rights Reserved.


Pedatella N.M.,University of Colorado at Boulder | Fang T.-W.,University of Colorado at Boulder | Jin H.,Japan National Institute of Information and Communications Technology | Sassi F.,Space Science Division Naval Research Laboratory Washington | And 4 more authors.
Journal of Geophysical Research A: Space Physics | Year: 2016

A comparison of different model simulations of the ionosphere variability during the 2009 sudden stratosphere warming (SSW) is presented. The focus is on the equatorial and low-latitude ionosphere simulated by the Ground-to-topside model of the Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Model plus Global Ionosphere Plasmasphere (WAM+GIP), and Whole Atmosphere Community Climate Model eXtended version plus Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (WACCMX+TIMEGCM). The simulations are compared with observations of the equatorial vertical plasma drift in the American and Indian longitude sectors, zonal mean F region peak density (NmF2) from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites, and ground-based Global Positioning System (GPS) total electron content (TEC) at 75°W. The model simulations all reproduce the observed morning enhancement and afternoon decrease in the vertical plasma drift, as well as the progression of the anomalies toward later local times over the course of several days. However, notable discrepancies among the simulations are seen in terms of the magnitude of the drift perturbations, and rate of the local time shift. Comparison of the electron densities further reveals that although many of the broad features of the ionosphere variability are captured by the simulations, there are significant differences among the different model simulations, as well as between the simulations and observations. Additional simulations are performed where the neutral atmospheres from four different whole atmosphere models (GAIA, HAMMONIA (Hamburg Model of the Neutral and Ionized Atmosphere), WAM, and WACCMX) provide the lower atmospheric forcing in the TIME-GCM. These simulations demonstrate that different neutral atmospheres, in particular, differences in the solar migrating semidiurnal tide, are partly responsible for the differences in the simulated ionosphere variability in GAIA, WAM+GIP, and WACCMX+TIMEGCM. ©2016. American Geophysical Union.


Share G.H.,University of Maryland College Park | Murphy R.J.,Space Science Division Naval Research Laboratory Washington | Tylka A.J.,NASA | Dennis B.R.,NASA | Ryan J.M.,University of New Hampshire
Journal of Geophysical Research A: Space Physics | Year: 2015

Low-energy (1-10 MeV) neutrons emanating from the Sun provide unique information about accelerated ions with steep energy spectra that may be produced in weak solar flares. However, observation of these solar neutrons can only be made in the inner heliosphere where measurement is difficult due to high background rates from neutrons produced by energetic ions interacting in the spacecraft. These ions can be from solar energetic particle events or produced in passing shocks associated with fast coronal mass ejections. Therefore, it is of the utmost importance that investigators rule out these secondary neutrons before making claims about detecting neutrons from the Sun. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) neutron spectrometer recorded an hour-long neutron transient beginning at 15:45 UTC on 4 June 2011 for which Lawrence et al. (2014) claim there is "strong evidence" that the neutrons were produced by the interaction of ions in the solar atmosphere. We studied this event in detail using data from the MESSENGER neutron spectrometer, gamma ray spectrometer, X-ray Spectrometer, and Energetic Particle Spectrometer and from the particle spectrometers on STEREO A. We demonstrate that the transient neutrons were secondaries produced by energetic ions, probably accelerated by a passing shock, that interacted in the spacecraft. We also identify significant faults with the authors' arguments in favor of a solar neutron origin for the transient. ©2014. American Geophysical Union.


Hervig M.E.,GATS, Inc. | Berger U.,Leibniz Institute of Atmospheric Physics | Siskind D.E.,Space Science Division Naval Research Laboratory Washington
Journal of Geophysical Research: Atmospheres | Year: 2016

Observations of polar mesospheric clouds (PMC) from the solar backscatter ultraviolet (SBUV) satellite instruments are used to characterize variability and trends from 1979 to 2014. The SBUV PMC record indicates decadal oscillations during the 1980s and 1990s, which are expected to result from the 11year solar cycle. This oscillation is absent in the recent decade, however, and we speculate that solar cycle effects at PMC altitudes during the 1980s and 1990s may have been fortuitously amplified by stratospheric warming due to volcanic eruptions which occurred near solar maximum. SBUV trend results are compared with temperature, water vapor, and PMCs from the Mesospheric Ice Microphysics and Transport (MIMAS) model. Both SBUV and the model indicate positive trends in PMC vertically integrated water content (IWC), which increase toward higher latitudes. Using analysis of Solar Occultation for Ice Experiment (SOFIE) observations, the SBUV IWC trends are expressed in terms of the underlying changes in temperature and water vapor in the upper mesosphere. SBUV indicates cooling trends that increase toward higher latitudes (-0.5±0.2Kdecade-1 at 77°N), consistent with the MIMAS model and scant observations. SBUV indicates increasing water vapor in the Northern Hemisphere upper mesosphere (0.07±0.03ppmvdecade-1 at 77°N, insignificant in the Southern Hemisphere), with values that are consistent with MIMAS but less than expected due to increasing methane. © 2016. American Geophysical Union. All Rights Reserved.


Krall J.,Plasma Physics Division Naval Research Laboratory Washington | Emmert J.T.,Space Science Division Naval Research Laboratory Washington | Sassi F.,Space Science Division Naval Research Laboratory Washington | Mcdonald S.E.,Space Science Division Naval Research Laboratory Washington | Huba J.D.,Plasma Physics Division Naval Research Laboratory Washington
Journal of Geophysical Research A: Space Physics | Year: 2016

Satellite drag data showing significant (20%) short-term variations in atmospheric mass density are presented. These data, along with the Naval Research Laboratory SAMI3 (Sami3 is Also a Model of the Ionosphere) ionosphere/plasmasphere model and the WACCM (Whole Atmosphere Community Climate Model) atmosphere model are used to estimate day-to-day variability in thermosphere composition, thermosphere winds, and exosphere temperatures and the effect of this variability on plasmasphere refilling rates. This assessment is guided by SAMI3 modeling showing that modest (20%) decreases in thermospheric density and exospheric temperature can lead to large (60%) increases in plasmaspheric refilling rates and that changes in the thermospheric wind pattern can have a similar effect. Results suggest that day-to-day variability in thermospheric wind and composition could affect plasmaspheric refilling rates by 50 to 100%. ©2016. American Geophysical Union. All Rights Reserved.


Mcdonald S.E.,Space Science Division Naval Research Laboratory Washington | Sassi F.,Space Science Division Naval Research Laboratory Washington | Mannucci A.J.,Jet Propulsion Laboratory
Space Weather | Year: 2015

We have performed simulations using the Naval Research Laboratory's physics-based model of the ionosphere, Sami3 is A Model of the Ionosphere (SAMI3), to illustrate how neutral wind dynamics is responsible for day-to-day variability of the ionosphere. We have used neutral winds specified from the extended version of the specified dynamics Whole Atmosphere Community Climate Model (SD-WACCM-X), in which meteorology below 92km is constrained by atmospheric specifications from an operational weather forecast model and reanalysis. To assess the realism of the simulations against observations, we have carried out a case study during January-February 2009, a dynamically disturbed time characterized by a sudden stratospheric warming (SSW) commencing 24 January 2009. Model results are compared with total electron content (TEC) from Jet Propulsion Laboratory global ionospheric maps. We show that SAMI3/SD-WACCM-X captures longitudinal variability in the equatorial ionization anomaly associated with nonmigrating tides, with strongest contributions coming from the diurnal eastward wave number 2 (DE2) and DE3. Both migrating and nonmigrating tides contribute to significant day-to-day variability, with TEC varying up to 16%. Our simulation during the SSW period reveals that at the Jicamarca longitude (285°E) on 27 January 2009 nonmigrating tides contribute to an enhancement of the electron density in the morning followed by a decrease in the afternoon. An enhancement of the semidiurnal eastward wave number 2 (SE2) and SE3 nonmigrating tides, likely associated with the appearance of the SSW, suggests that these tides increase the longitudinal variability of the SSW impact on the ionosphere. The conclusion is that realistic meteorology propagating upward from the lower atmosphere influences the dynamo region and reproduces aspects of the observed variability in the ionosphere. ©2015. American Geophysical Union.


Dymond K.F.,Space Science Division Naval Research Laboratory Washington | Budzen S.A.,Space Science Division Naval Research Laboratory Washington | Coker C.,Space Science Division Naval Research Laboratory Washington | Chua D.H.,Space Science Division Naval Research Laboratory Washington
Journal of Geophysical Research A: Space Physics | Year: 2016

The Tiny Ionospheric Photometer (TIP) is an ultraviolet nadir-viewing photometer that flew aboard the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC, also known as FORMOSAT-3), which was launched on 14 April 2006. One TIP flew on each of the six COSMIC/FORMOSAT3 satellites; these compact instruments operated exclusively at nighttime and observed the O I 135.6nm emission that is a signature of the decay of the F region ionosphere and, as such, is a diagnostic of the ionospheric state. We describe the TIP instruments and their on-orbit operation. Additionally, some key science highlights of the mission are presented and discussed.

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