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Full-Text Articles in Physical Sciences and Mathematics
Dynamics Of Density Cavities Generated By Frictional Heating: Formation, Distortion, And Instability, M. D. Zettergren, J. L. Semeter, H. Dahlgren
Dynamics Of Density Cavities Generated By Frictional Heating: Formation, Distortion, And Instability, M. D. Zettergren, J. L. Semeter, H. Dahlgren
Publications
A simulation study of the generation and evolution of mesoscale density cavities in the polar ionosphere is conducted using a time-dependent, nonlinear, quasi-electrostatic model. The model demonstrates that density cavities, generated by frictional heating, can form in as little as 90 s due to strong electric fields of ∼120 mV/m, which are sometimes observed near auroral zone and polar cap arcs. Asymmetric density cavity features and strong plasma density gradients perpendicular to the geomagnetic field are naturally generated as a consequence of the strong convection and finite extent of the auroral feature. The walls of the auroral density cavities are …
Self-Accleration And Instability Of Gravity Wave Packets: 1. Effects Of Temporal Localization, David C. Fritts, Brian Laughman, Thomas S. Lund, Jonathan B. Snively
Self-Accleration And Instability Of Gravity Wave Packets: 1. Effects Of Temporal Localization, David C. Fritts, Brian Laughman, Thomas S. Lund, Jonathan B. Snively
Publications
"An anelastic numerical model is used to explore the dynamics accompanying the attainment of large amplitudes by gravity waves (GWs) that are localized in altitude and time. GW momentum transport induces mean flow variations accompanying a GW packet that grows exponentially with altitude, is localized in altitude, and induces significant GW phase speed, and phase, variations across the GW packet. These variations arise because the GW occupies the region undergoing accelerations, with the induced phase speed variations referred to as “self-acceleration.” Results presented here reveal that self-acceleration of a GW packet localized in time and altitude ultimately leads to stalling …
Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona, Claire Foullon, Erwin Verwichte, Katariina Nykyri, Markus J. Aschwanden, Iain G. Hannah
Kelvin-Helmholtz Instability Of The Cme Reconnection Outflow Layer In The Low Corona, Claire Foullon, Erwin Verwichte, Katariina Nykyri, Markus J. Aschwanden, Iain G. Hannah
Publications
New capabilities for studying the Sun allow us to image for the first time the magnetic Kelvin–Helmholtz (KH) instability developing at the surface of a fast coronal mass ejecta (CME) less than 150 Mm above the solar surface. We conduct a detailed observational investigation of this phenomenon, observed off the east solar limb on 2010 November 3, in the EUV with SDO/AIA. In conjunction with STEREO-B/EUVI, we derive the CME source surface position. We ascertain the timing and early evolution of the CME outflow leading to the instability onset. We perform image and spectral analysis, exploring the CME plasma structuring …
Observations Of Overturning In The Upper Mesosphere And Lower Thermosphere, M. F. Larsen, Alan Z. Liu, C. S. Gardner, M. C. Kelley, S. Collins, J. Friedman, J. H. Hecht
Observations Of Overturning In The Upper Mesosphere And Lower Thermosphere, M. F. Larsen, Alan Z. Liu, C. S. Gardner, M. C. Kelley, S. Collins, J. Friedman, J. H. Hecht
Physical Sciences - Daytona Beach
A number of observations of the sodium density primarily in the mesosphere and lower thermosphere (but also of the electron density structure) have shown what appears to be overturning or convective roll cells near the transition from the mesosphere to the lower thermosphere. The cells are found in the region between 95 and 105 km and occur near the boundary between the region of lower stability in the mesosphere and the region of higher stability in the lower thermosphere. The vertical scale for the rolls is ~5–6 km, and the timescale is ~1–3 hours. The rolls occur in a region …