[IGPP Everyone] Space Physics Seminar, Fri. 1/18, 3:30pm: "Characteristics of Reconnection Sites and Fast Flows in an MHD Simulation" (R. McPherron, EPSS)

[Emmanuel V. Masongsong]

SPACE PHYSICS SEMINAR 
DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES 
DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES 
UNIVERSITY OF CALIFORNIA, LOS ANGELES 
(AOS M275C, EPSS M288C) 

Characteristics of Reconnection Sites and Fast Flows in an MHD Simulation 

Robert McPherron 
UCLA EPSS 

The near-Earth neutral line model for substorms that emerge from quiet conditions postulates that the onset of dayside reconnection leads to a growth phase during which a sequence of changes in the magnetotail cause plasma sheet thinning and the sudden onset of tail reconnection. Fast earthward flows from the reconnection site lead to plasma and magnetic field pileup at the inner edge of the plasma sheet, the formation of a current wedge, and auroral expansion. Fast tailward flows carry flux ropes away from the Earth. An MHD simulation of an active interval containing an obvious auroral expansion produces onsets in the simulated AL and midlatitude positive bay (MPB) indices within several minutes of the observed onset. However the simulation does not support the model of a quiet growth phase followed by a sudden onset of reconnection. Instead x-lines and fast flows are continuously present throughout the entire substorm. We have used image processing techniques to characterize the properties of the x-lines and the fast flows they generate. During the growth phase the number of x-lines and their total length increase as their locations move closer to the Earth and towards dusk. The earthward fast flows generated by these x-lines increase in length and area as their centroids move closer to the Earth and dusk. The location of the leading edge of the fast flow coming closest to the Earth also approaches the Earth during growth phase. At the simulated onset the fast flow channel rapidly begins to deposit magnetic flux close to the Earth. At this time the behavior of the x-lines and flow channels are reversed becoming fewer in number, length and further from the Earth. The noses of flow channels move away from the Earth. If the simulation is correct in its representation of the behavior of x-lines during the growth phase then it is difficult to understand why there is no evidence of continuous activity projected to the ionosphere as aurora. 

Friday, January 18 , 2019 
Room 6704 Geology 
3:30 - 5:00 PM 

In Charge: 
V. Angelopoulos 

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