Bibliography

Observations of Spatial Variations in O/N ₂ During an Auroral Substorm Using the Multichannel Downlooking Camera on the VISIONS Rocket

At 0821 UT on 7 February 2013, during an auroral substorm, the NASA VISIONS rocket was launched northward from Poker Flat Research Range on a flight to approximately 750-km altitude that terminated in the Arctic Ocean. A subpayload jettisoned on the up leg carried a multichannel optical imager that looked downward and observed the auroral emission through four narrow passband filters. Three of the channels had sufficiently strong signal to allow a measure of the time evolution of the horizontal extent of the electron aurora and changes in the ratio of the column O to the column N₂. These data revealed rather rapid changes in this measure of composition over an area larger than would be expected from the changes expected from particle and Joule heating. Although such rapid large changes have been observed previously, and Christensen et al. (1997, https://doi.org/10.1029/97JA01800) had hypothesized that they were due to enhanced turbulent diffusion, this imaging experiment is the first to show their evolution over a large area. On the down leg the camera was able to see the vertical spatial extent of the auroral emission which is consistent with the decrease in O/N₂ seen in the downlooking data. The change in this ratio with altitude suggests the deposition of an additional number of low-energy electrons that would cause a larger decrease in that ratio at higher altitudes.

Hecht, J.; Clemmons, J.; Conde, M.; Hampton, D.; Michell, R.; Rowland, D.; Pfaff, R.; Walterscheid, R.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 07/2018

YEAR: 2018     DOI: 10.1029/2018JA025288

Ion-neutral coupling during deep solar minimum

The equatorial ionosphere under conditions of deep solar minimum exhibits structuring due to tidal forces. Data from instruments carried by the Communication/Navigation Outage Forecasting System (C/NOFS) which was launched in April 2008 have been analyzed for the first 2 years following launch. The Planar Langmuir Probe (PLP), Ion Velocity Meter (IVM) and Vector Electric Field Investigation (VEFI) all detect periodic structures during the 2008\textendash2010 period which appear to be tides. However when the tidal features detected by these instruments are compared, there are distinctive and significant differences between the observations. Tides in neutral densities measured by the Gravity Recovery and Climate Experiment (GRACE) satellite were also observed during June 2008. In addition, Broad Plasma Decreases (BPDs) appear as a deep absolute minimum in the plasma and neutral density tidal pattern. These are co-located with regions of large downward-directed ion meridional velocities and minima in the zonal drifts, all on the nightside. The region in which BPDs occur coincides with a peak in occurrence rate of dawn depletions in plasma density observed on the Defense Meterological Satellite Program (DMSP) spacecraft, as well as a minimum in radiance detected by UV imagers on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) and IMAGE satellites.

Huang, Cheryl; Roddy, Patrick; Sutton, Eric; Stoneback, Russell; Pfaff, Robert; Gentile, Louise; Delay, Susan;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 10/2013

YEAR: 2013     DOI: 10.1016/j.jastp.2012.11.009

Equatorial ionosphere; Nonmigrating tides; Plasma depletions; thermosphere

Longitudinal differences of ionospheric vertical density distribution and equatorial electrodynamics

Accurate estimation of global vertical distribution of ionospheric and plasmaspheric density as a function of local time, season, and magnetic activity is required to improve the operation of space-based navigation and communication systems. The vertical density distribution, especially at low and equatorial latitudes, is governed by the equatorial electrodynamics that produces a vertical driving force. The vertical structure of the equatorial density distribution can be observed by using tomographic reconstruction techniques on ground-based global positioning system (GPS) total electron content (TEC). Similarly, the vertical drift, which is one of the driving mechanisms that govern equatorial electrodynamics and strongly affect the structure and dynamics of the ionosphere in the low/midlatitude region, can be estimated using ground magnetometer observations. We present tomographically reconstructed density distribution and the corresponding vertical drifts at two different longitudes: the East African and west South American sectors. Chains of GPS stations in the east African and west South American longitudinal sectors, covering the equatorial anomaly region of meridian \~37\textdegreeE and 290\textdegreeE, respectively, are used to reconstruct the vertical density distribution. Similarly, magnetometer sites of African Meridian B-field Education and Research (AMBER) and INTERMAGNET for the east African sector and South American Meridional B-field Array (SAMBA) and Low Latitude Ionospheric Sensor Network (LISN) are used to estimate the vertical drift velocity at two distinct longitudes. The comparison between the reconstructed and Jicamarca Incoherent Scatter Radar (ISR) measured density profiles shows excellent agreement, demonstrating the usefulness of tomographic reconstruction technique in providing the vertical density distribution at different longitudes. Similarly, the comparison between magnetometer estimated vertical drift and other independent drift observation, such as from VEFI onboard Communication/Navigation Outage Forecasting System (C/NOFS) satellite and JULIA radar, is equally promising. The observations at different longitudes suggest that the vertical drift velocities and the vertical density distribution have significant longitudinal differences; especially the equatorial anomaly peaks expand to higher latitudes more in American sector than the African sector, indicating that the vertical drift in the American sector is stronger than the African sector.

Yizengaw, E.; Zesta, E.; Moldwin, M.; Damtie, B.; Mebrahtu, A.; Valladares, C.; Pfaff, R.;

Published by: Journal of Geophysical Research      Published on: 07/2012

YEAR: 2012     DOI: 10.1029/2011JA017454

Tomography; vertical drift

Space-based research into the ionosphere-thermosphere system: The need for greater organization and a plan for achieving it

Clemmons, JH; Crowley, G; Heelis, RA; Mannucci, AJ; Paxton, LJ; Pfaff, RF; Spann, JF;

Published by:       Published on:

YEAR: 2007     DOI:

Implications of Auroral Electron Precipitation During the JOULE Experiment

Slocum, PL; Clemmons, JH; Hecht, JH; Larsen, MF; Pfaff, RF; Steigies, CT; Stenbaek-Nielsen, HC; Strickland, DJ;

Published by:       Published on:

YEAR: 2005     DOI:

The Interaction of Auroral Electron Precipitation with the Thermosphere During the JOULE Experiment

Slocum, PL; Clemmons, JH; Hecht, JH; Pfaff, RF; Steigies, CT; Larsen, MF; Strickland, DJ;

Published by:       Published on:

YEAR: 2004     DOI: