R. H. Varney's research while affiliated with University of California, Los Angeles and other places

Publications (90)

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In this study, we report observations made by filtered (557.7 and 630.0 nm) All-Sky Imagers located at Poker Flat, Alaska alongside Poker Flat Incoherent Scatter Radar data for an event observed on 5 February 2017. Together, the data indicate ion upflow in the vicinity of pulsating aurora. Additionally, the data show a strong 630.0 nm (red-line) au...
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Plasmaspheric hiss can cause energetic electron precipitation from the magnetosphere to the Earth's upper atmosphere and affect the ionospheric electron density profiles. In this study, we use Arase satellite measurements in the dayside plasmasphere to model the electron precipitation and the resultant ionospheric response, and compare the results...
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Quantification of energetic electron precipitation caused by wave‐particle interactions is fundamentally important to understand the cycle of particle energization and loss of the radiation belts. One important way to determine how well the wave‐particle interaction models predict losses through pitch‐angle scattering into the atmospheric loss cone...
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Plain Language Summary The Sporadic‐E layer (Es layer) is a globally common phenomenon, which is comprehensively and unceasingly studied in decades by using the observation measurements and numerical simulations. The remarkable agreements on the characteristics and generation mechanisms of Es layer at middle latitudes have then been almost achieved...
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We report one of the first comprehensive ground‐based investigations of energy transfer rates in the E‐region ionosphere compared relative to geomagnetic activity, seasonal effects, and solar activity level using nearly continuously sampled data collected with the Poker Flat Incoherent Scatter Radar (PFISR) between 2010 and 2019. We quantified the...
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We present measurements of the equatorial topside ionosphere above Jicamarca made during extremely low solar flux conditions during the deep solar minimum of 2019–2020. Measurements were made in October, 2019, February, 2020, and September, 2020. The main features observed are a large and extended decrease in noontime temperatures unlike that seen...
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This study exploits the volumetric sampling capabilities of the Resolute Bay Incoherent Scatter Radar (RISR‐N) in collaboration with all‐sky imagery and in situ measurements to examine the interplay between cold plasma transport and auroral precipitation during a high‐latitude lobe reconnection event on the dawn side. Solar wind IMF preceding the e...
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Joule heating deposits a significant amount of energy into the high‐latitude ionosphere and is an important factor in many magnetosphere‐ionosphere‐thermosphere coupling processes. We consider the relationship between localized temperature enhancements in polar cap measured with the Resolute Bay Incoherent Scatter Radar‐North (RISR‐N) and the orien...
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We use the Geospace Environment Model of Ion‐Neutral Interactions (GEMINI) to create three‐dimensional, time‐dependent simulations of auroral ionospheric parameters in the localized, several 100 km region surrounding auroral arcs observed during a winter 2017 sounding rocket campaign, resolving three‐dimensional features of fine‐scale (km) flow str...
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We use simultaneous auroral imaging, radar flows, and total electron content (TEC) measurements over Alaska to examine whether there is a direct connection of large-scale traveling ionospheric disturbances (LSTIDs) to auroral streamers and associated flow channels having significant ground magnetic decreases. Observations from seven nights with cle...
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We present new results using data collected by the Poker Flat Incoherent Scatter Radar (PFISR) of energy transfer rates, which include the effects from neutral winds in the high latitude E‐region ionosphere‐thermosphere (IT) during Fall 2015. The purpose of our investigation is to understand the magnetic local time (MLT) dependence of the peak ener...
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In this study, we present the results of an inversion of ionospheric phase scintillation data to characterize the plasma density irregularity parameters for the structures associated with a series of Polar Cap Patches. The parameter estimates obtained during the inversion suggests that the irregularities associated with Polar Cap Patches are predom...
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This work conducts a focused study of subauroral ion-neutral coupling processes and midlatitude ionospheric/thermospheric responses in North America during a minor but quite geoeffective storm on September 27–28, 2019 under deep solar minimum conditions. Several prominent storm-time disturbances and associated electrodynamics/dynamics were identifi...
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We present high‐resolution Resolute Bay Incoherent Scatter Radar (RISR) measurements in the cusp region during an IMF southward turning. The simultaneous RISR‐N and RISR‐C operation provided 3‐D observations of the dayside polar region, and offered an opportunity to identify the cusp dynamics and polar cap patch formation. Associated with the IMF s...
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We have taken a key step in evaluating the importance of ionospheric outflows relative to electrodynamic coupling in the thermosphere’s impact on geospace dynamics. We isolated the thermosphere’s material influence and suppressed electrodynamic feedback in whole geospace simulations by imposing a time‐constant ionospheric conductance in the ionosph...
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Measurements of plasma lines by the Arecibo incoherent scatter radar are known to have sharp striations in power, varying with the plasma frequency and magnetic aspect angle of the radar beam. We explain these power striations as the manifestation of a suprathermal electron population with peaks in energy at approximately 15, 25, and 45 eV. These e...
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About 40 years after the discovery of the substorm, auroral observations were used to propose that substorm onset was triggered in the inner plasmas sheet (equatorward portion of the auroral oval) by an intrusion of the low entropy plasma by plasma sheet flow channels. Longitudinal localization makes such flow channels difficult to observe with spa...
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Longitudinal expansion of brightening of the substorm onset arc likely represents longitudinal expansion of the substorm onset instability. We used Poker Flat radar campaign auroral observations to identify seven substorm onsets seen east or west of the radar that expanded into the radar field‐of‐view. The radar observations were used to show flows...
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During magnetospheric substorms, high‐latitude ionospheric plasma convection is known to change dramatically. How upper thermospheric winds change, however, has not been well understood, and conflicting conclusions have been reported. Here, we study the effect of substorms on high‐latitude upper thermospheric winds by taking advantage of a chain of...
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Ion upflow in the F region and topside ionosphere can greatly influence the ion density and fluxes at higher altitudes and thus has significant impact on ion outflow. We investigated the statistical characteristics of ion upflow and downflow using a 3‐year (2011–2013) data set from the Poker Flat Incoherent Scatter Radar (PFISR). Ion upflow is twic...
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Thermal ion retarding potential analyzers (RPAs) are used to measure in situ auroral ionospheric plasma parameters. This article analyzes data from a low-resource RPA in order to quantify the capability of the sensor. The RPA collects a sigmoidal current–voltage (I–V) curve, which depends on a non-linear combination of Maxwellian plasma parameters,...
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We investigate a significant duskside ionospheric density modulation in the Pc5 frequency band and related spatial structures during the storm on 28 May 2017. We take advantage of 3‐D ionospheric observations by the PFISR and simultaneous magnetospheric in situ observations. Inversion of the density suggests that the Pc5 pulsations modulated precip...
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The extreme substorm event on 5 April 2010 (THEMIS AL = −2,700 nT, called supersubstorm) was investigated to examine its driving processes, the aurora current system responsible for the supersubstorm, and the magnetosphere‐ionosphere‐thermosphere (M‐I‐T) responses. An interplanetary shock created shock aurora, but the shock was not a direct driver...
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Scintillation in the polar cap ionosphere is observed with a Coherent Electromagnetic Radio Tomography (CERTO) receiver while the Resolute Bay Incoherent Scatter Radars (RISR) provide background plasma conditions in a 3D volume. We interpret fluctuations in the very high frequency (VHF) and ultrahigh frequency (UHF) signal associated with mid‐scale...
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Global Circulation Models (GCMs) for the ionosphere-thermosphere system (I-T) traditionally use empirical models to specify upper boundary conditions to represent solar wind and magnetospheric drivers. However, the magnetosphere, ionosphere and thermosphere systems are coupled on different spatial and temporal scales. During increased levels of geo...
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HIWIND (High altitude Interferometer WIND experiment) is a balloon‐borne Fabry Perot interferometer for daytime thermospheric wind observations. In this paper, we examine the summer polar cap thermospheric winds observed by HIWIND with the RISR‐C (Resolute Incoherent Scatter Radar‐Canada) observed ion drifts and electron densities. We also perform...
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The Rocket Investigation of Current Closure in the Ionosphere (RICCI) sounding rocket mission concept will use the novel deployment of multiple CubeSats as miniature sub-payloads to obtain the first direct in-situ measurement of ionospheric closure currents. These ionospheric currents are critical to understanding the nature of atmosphere-ionospher...
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In this study, we present a bottomside model representation to be used by the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM). This model features a new approach to modeling the bottomside electron density; namely, instead of modelling electron density directly, E-CHAIM models the altitude profile of the scale thickness of a single botto...
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Some existing auroral data products are insufficient for ionospheric simulation input on subkilometer spatial scales and high (second) time resolution near the boundaries of arc structures. Ideally, two-dimensional data maps of the relevant parameters over these small scales would provide models with constraining inputs. Available in situ data have...
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Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates be...
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High-latitude neutral winds often circulate in a two-cell pattern as driven by large-scale auroral forcing. However, auroral forcing also occurs in various types of mesoscale forms (i.e., tens to hundreds of kilometers in space and a few to tens of minutes in time) and contains more energy input over mesoscale than large scale. A question arises as...
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Polar cap “patches” are ~100 to 1,000 km islands of high-density plasma at polar latitudes, which can cause scintillation to communication and navigation signals. An automatic algorithm for patch identification has been developed and applied to the observations from the Resolute Bay Incoherent Scatter Radar-Canada during January to March and Septem...
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In a recent study, Liang et al. (2017, https://doi.org/10.1002/2017JA024127) repeatedly identified strong electron temperature (Te) enhancements when Swarm satellites traversed pulsating auroral patches. In this study, we use joint optical and Poker Flat Incoherent Scatter Radar (PFISR) observations to further investigate the F region plasma signat...
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In this study, we present a topside model representation to be used by the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM). In the process of this, we also present a comprehensive evaluation of the NeQuick's, and by extension the International Reference Ionosphere (IRI)'s, topside electron density model for mid and high latitudes in the...
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The Mahali Global Positioning System (GPS) array (9 receivers, 15--30~km baseline distance) in central Alaska has probed auroral structures in a field aligned direction during a geomagnetic substorm on 07 October, 2015. We present results from a collaborative study of GPS phase scintillation, optical emission brightness and ionospheric density pert...
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In this study, the correlations between the fluxes of precipitating soft electrons in the cusp region and solar wind coupling functions are investigated utilizing the Lyon-Fedder-Mobarry (LFM) global magnetosphere model simulations. We conduct two simulation runs during periods from 20 March 2008 to 16 April 2008 and from 15 December 2014 to 24 Dec...
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An examination of the high latitude performance of the bottomside and topside F-layer parameterizations of the NeQuick electron density model is presented using measurements from high latitude ionosonde and Incoherent Scatter Radar (ISR) facilities. For the bottomside, we present a comparison between modeled and measured B2Bot thickness parameter....
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Sudden commencement (SC) induced by solar wind pressure enhancement can produce significant global impact on the coupled magnetosphere-ionosphere (MI) system, and its effects have been studied extensively using ground magnetometers and coherent scatter radars. However, very limited observations have been reported about the effects of SC on the iono...
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Plasma density cavities are correlated with heavy ion outflow where ions are heated transversely by wave particle interactions (WPIs). This paper presents the first result of a 3D ionospheric fluid model that incorporates plasma temperature anisotropies and a phenomenological treatment of WPIs, leading to transversely accelerated ions (TAIs). It is...
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Based on two northern (Eureka 80.0 N, 85.9 W, MLAT 88, and Resolute, 74.7 N, 94.8 W, MLAT 83) and one southern (Jang Bogo, 74.7S, 164.2E, MLAT 77) polar cap stations, simultaneous thermospheric wind data during the northern (December) and southern (June) winter month were obtained and compared with the NCAR TIEGCM model simulations driven by the We...
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Joint observations of the Rankin Inlet (RKN) and Inuvik Super Dual Auroral Radar Network (SuperDARN) HF radars and Resolute Bay incoherent scatter radar (RISR) are used to assess consistency in their plasma flow velocity measurements. The analysis covers more than 500 h of successful concurrent measurements. We demonstrate that, overall, the radars...
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We present the first simulations of magnetospheric sawtooth oscillations under steady solar wind conditions that are driven internally by heavy ion outflow from a physics-based model. The simulations presented use the multi-fluid Lyon-Fedder-Mobarry (MFLFM) magnetohydrodynamics (MHD) model two-way coupled to the ionosphere/polar wind model (IPWM)....
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We describe a coupled geospace model that includes causally regulated ion outflow from a physics-based ionosphere/polar wind model. The model two-way couples the multi-fluid Lyon-Fedder-Mobarry (MFLFM) magnetohydrodynamics (MHD) model to the ionosphere/polar wind model (IPWM). IPWM includes the H + and O + polar wind as well as a phenomenological t...
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We investigate low-energy (<10 eV) ion upflows (mainly O+) within the cleft ion fountain (CIF) using conjunctions of the Enhanced Polar Outflow Probe (e-POP) satellite, the DMSP F16 satellite, the SuperDARN radar, and the Resolute Bay Incoherent Scatter Radar North (RISR-N). The SEI instrument on board e-POP enables us to derive ion upflow velociti...