Engineering topics

Masson, A.

Publications and source records attributed to Masson, A..

2 records

NASA NTRS2012

Spatial Distribution of Rolled up Kelvin-Helmholtz Vortices at Earth's Dayside and Flank Magnetopause

The Kelvin-Helmholtz Instability (KHI) can drive waves at the magnetopause. These waves can grow to form rolled-up vortices and facilitate transfer of plasma into the magnetosphere. To investigate the persistence and frequency of such waves at the magnetopause we have carried out a survey of all Double Star 1 magnetopause crossings, using a combination of ion and magnetic field measurements. Using criteria originally used in a Geotail study made by Hasegawa et al. (2006) (forthwith referred to as H2006), 17 candidate events were identified from the entire TC-1 mission (covering 623 orbits where the magnetopause was sampled), a majority of which were on the dayside of the terminator. The relationship between density and shear velocity was then investigated, to identify the predicted signature of a rolled up vortex from H2006 and all 17 events exhibited some level of rolled up behavior. The location of the events had a clear dawn-dusk asymmetry, with 12 (71 %) on the post noon, dusk flank suggesting preferential growth in this region.

dawn-dusk asymmetry↗

NASA NTRS2003

Density Irregularities Inside the Plasmasphere: Cluster Observations

The electron density profiles derived from the EFW and WHISPER instruments onboard the four Cluster spacecraft reveal small-scale density irregularities inside the plasmasphere and at its outer boundary, the plasmapause. We review statistics of the plasmapause position and thickness, as well as statistics of these density structures. We focus on a particular plasmasphere crossing on 11 April 2002, with several density irregularities, as well as two plasma tails, observed by Cluster on the legs of the inbound and outbound passes. We derive the density gradient vectors from simultaneous density measurements by the four spacecraft. We determine also the normal velocity of the surface of these irregularities, assuming they are planar boundaries, from the time delays between density structures in the four individual density profiles. These new observations yield novel insights about (1) the dimensions of plasma irregularities across and parallel to magnetic field lines, (2) the dynamics of these small-scale structures, (3) their bulk velocities, and (4) their position and distribution as a function of the magnetic local time (MLT) and the geomagnetic conditions (as determined by Kp).

Darrouzet, F.↗