ICS-13 Abstract View

 

On the origin of plasma sheet reconfiguration during the substorm growth phase
Gordeev, E., evgeniy_gordeev@yahoo.com (1)
Sergeev, V., victor40sergeev@gmail.com (1)
Merkin, V., Slava.Merkin@jhuapl.edu (2)
Kuznetsova, M., maria.m.kuznetsova@nasa.gov (3)
Recently Hsieh and Otto [2014] suggested that transport of the closed magnetic flux to the dayside reconnection region may be the key process which controls the reconfiguration of magnetotail during the substorm growth phase (GP). To test their suggestion we investigated the origin of the near-Earth plasma sheet evolution during the GP using the Lyon-Fedder-Mobarry global MHD model, which (among community-available models hosted at CCMC) is most closely resemble the generic substorm-like behavior [Gordeev et al., 2017]. We confirm that magnetotail reconfiguration is essentially a 3D process which cannot be fully described based on 2D-like tail evolution powered by magnetic flux loading into the lobes. We found that near-Earth return convection strength on the nightside is directly related to the intensity of dayside reconnection, which causes the formation of anti-sunward azimuthal pressure gradients that force plasma to flow towards the dayside magnetopause. This near-Earth part of global convection develops immediately after the onset of dayside reconnection and reaches a quasi-steady level in 10 - 15 minutes. Its magnitude exceeds the total sunward flux transport in the midtail plasma sheet at X≈ -20 RE by an order of magnitude, causing significant amount (0.1 - 0.2 GWb) of closed magnetic flux to be removed from the near Earth plasma sheet during moderate GP. In that region the Bz depletion and current sheet thinning are closely related to each other, and the local Jy(Bz) relationship in the simulations matches reasonably well the power law expression found in the plasma sheet in the same distance [Artemyev et al., 2016], indicating the similar way of system evolution. In summary, global simulations confirm quantitatively that near-Earth return convection is primarily responsible for the severe depletion of the closed magnetic flux in the plasma sheet, major tail stretching and current sheet thinning in the near magnetotail at r<15 RE during the GP of substorm.
(1) Department of Earth's Physics, Saint Petersburg State University, Saint-Petersburg, Russia
(2) Applied Physics Laboratory, John Hopkins University, Laurel, MD, USA
(3) NASA Goddard Space Flight Center, Greenbelt, MD, USA