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Found 10 entries in the Bibliography.

Showing entries from 1 through 10

2006

Global thermosphere-ionosphere response to onset of 20 November 2003 magnetic storm

Crowley, G.; Hackert, C.; Meier, R.; Strickland, D.; Paxton, L.; Pi, X.; Mannucci, A.; Christensen, A.; Morrison, D.; Bust, G.; Roble, R.; Curtis, N.; Wene, G.;

Published by: Journal of Geophysical Research Published on: Jan-01-2006

YEAR: 2006 DOI: 10.1029/2005JA011518

Effect of IMF By on thermospheric composition at high and middle latitudes: 2. Data comparisons

Immel, Thomas; Crowley, Geoff; Hackert, Chris; Craven, John; Roble, Ray;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2006 DOI:

Effect of IMF BY on thermospheric composition at high and middle latitudes: 1. Numerical experiments

Magnetic storms and their effects on the thermosphere and ionosphere have been studied for many years, yet there are many aspects of the thermospheric and ionospheric responses that are not understood. The purpose of this paper is to show how the high-latitude composition depends on the sign of the IMF BY component, using controlled simulations with a global first principles model. Because the high-latitude convection and neutral wind systems are strongly controlled by the IMF BY component, it seems likely that the compositional response that is driven by high-latitude forcing should also be sensitive to the BY component. To date, no first-principles modeling has been performed to test the idea of IMF BY effects on composition. Numerical experiments using model simulations provide insight into this important scientific question, since the thermospheric compositional response to the convection patterns for different IMF BZ and BY can be studied in isolation in a model. In this paper we use a first-principles model to determine the effect of the IMF BY component on the compositional response of the high-latitude thermosphere. We show for the first time that a clockwise rotation of the potential pattern resulting from a change from BY-negative to BY-positive drives a corresponding rotation in the wind, neutral density, and composition distributions. BY control of thermospheric composition has been invoked in the literature to explain an apparent variability in the effectiveness of auroral activity in causing thermospheric storm effects at middle latitudes, as observed in global images of the far-ultraviolet (FUV) OI 130.4-nm emission from the DE-1 auroral imager. However, the effect in the simulations presented here is opposite from that suggested by earlier work based on DE data, indicating another explanation must be sought for the DE results. These simulations are highly relevant for interpreting data being provided by more modern UV imaging instruments on the DMSP, TIMED, and IMAGE satellites.

Crowley, G.; Immel, T.; Hackert, C.; Craven, J.; Roble, R.;

Published by: Journal of Geophysical Research: Space Physics Published on:

YEAR: 2006 DOI: https://doi.org/10.1029/2005JA011371

composition; thermospheric

2005

First look at the 20 November 2003 superstorm with TIMED/GUVI: Comparisons with a thermospheric global circulation model

The NASA TIMED/GUVI experiment obtained unprecedented far ultraviolet images of thermospheric composition and temperature during the intense geomagnetic storm on 20\textendash21 November 2003. Geographic maps of the atomic oxygen to molecular nitrogen column density ratio show severe depletions that extend to the equator near the peak of the storm. This ratio is a key indicator of how the thermospheric composition is disrupted at high latitudes and how the perturbed air moves globally as a result of dynamical forcing. For example, migrating regions of low oxygen-to-nitrogen air are invariably found to correlate with high thermospheric temperatures. As well, GUVI obtained altitudinal-latitudinal (limb) images of temperature and composition, which show how the disturbances vary at different heights. The ASPEN thermospheric global circulation model was used to test our understanding of these remarkable images. The resulting simulations of thermospheric response show good agreement with GUVI data prior to the peak of the storm on 20 November. During the peak and recovery phases, serious discrepancies between data and model are seen. Although this initial attempt to model the storm is encouraging, much more detailed analysis is required, especially of the high-latitude inputs. The GUVI images demonstrate that far ultraviolet imaging is becoming a crucial component of space weather research and development.

Meier, R.; Crowley, G.; Strickland, D.; Christensen, A.; Paxton, L.; Morrison, D.; Hackert, C.;

Published by: Journal of Geophysical Research Published on: 09/2005

YEAR: 2005 DOI: 10.1029/2004JA010990

dayglow; geomagnetic storm; GUVI; remote sensing; thermospheric composition; TIMED

Thermospheric density structures over the polar regions observed with CHAMP

Schlegel, Kristian; Lühr, Hermann; St-Maurice, J-P; Crowley, Geoff; Hackert, Chris;

Published by: Published on:

YEAR: 2005 DOI:

Violent Sun-Earth Connection Events of October-November 2003-A09S41-First look at the 20 November 2003 superstorm with TIMED/GUVI: Comparisons with a thertnospheric global

Meier, RR; Crowley, G; Strickland, DJ; Christensen, AB; Paxton, LJ; Morrison, D; Hackert, CL;

Published by: Journal of Geophysical Research-Part A-Space Physics Published on:

YEAR: 2005 DOI: