TY - JOUR

T1 - Dynamical response of the magnetotail to changes of the solar wind direction

T2 - an MHD modeling perspective

AU - Sergeev, V. A.

AU - Tsyganenko, N. A.

AU - Angelopoulos, V.

PY - 2008

Y1 - 2008

N2 - We performed global MHD simulations to investigatethe magnetotail response to the solar wind directionalchanges (Vz-variations). These changes, although small,cause significant variations of the neutral sheet shape and locationeven in the near and middle tail regions. They displaya complicated temporal response, in which 60 to 80% of the final shift of the neutral sheet in Z direction occurs within first 10–15 min (less for faster solar wind), whereas a much longer time (exceeding half hour) is required to reacha new equilibrium. The asymptotic equilibrium shape of the simulated neutral sheet is consistent with predictions of Tsyganenko-Fairfield (2004) empirical model. To visualize a physical origin of the north-south tail motion we comparedthe values of the total pressure in the northern and southern tail lobes and found a considerable difference (10–15% for only 6 change of the solar wind direction used in the simulation). That difference builds up during the passage of the solar wind directional discontinuity and is responsible for the vertical shift of the neutral sheet, although some pressure difference remains in the near tail even near the new equilibrium. Surprisingly, at a given tailward distance, the responsewas found to be first initiated in the tail center (the “leader effect”), rather than near the flanks, which can be explained by the wave propagation in the tail, and which may have interesting implications for the substorm triggering studies. Thepresent results have serious implications for the data-basedmodeling, as they place constraints on the accuracy of tailmagnetic configurations to be derived for specific events usingdata of multi-spacecraft missions, e.g. such as THEMIS.

AB - We performed global MHD simulations to investigatethe magnetotail response to the solar wind directionalchanges (Vz-variations). These changes, although small,cause significant variations of the neutral sheet shape and locationeven in the near and middle tail regions. They displaya complicated temporal response, in which 60 to 80% of the final shift of the neutral sheet in Z direction occurs within first 10–15 min (less for faster solar wind), whereas a much longer time (exceeding half hour) is required to reacha new equilibrium. The asymptotic equilibrium shape of the simulated neutral sheet is consistent with predictions of Tsyganenko-Fairfield (2004) empirical model. To visualize a physical origin of the north-south tail motion we comparedthe values of the total pressure in the northern and southern tail lobes and found a considerable difference (10–15% for only 6 change of the solar wind direction used in the simulation). That difference builds up during the passage of the solar wind directional discontinuity and is responsible for the vertical shift of the neutral sheet, although some pressure difference remains in the near tail even near the new equilibrium. Surprisingly, at a given tailward distance, the responsewas found to be first initiated in the tail center (the “leader effect”), rather than near the flanks, which can be explained by the wave propagation in the tail, and which may have interesting implications for the substorm triggering studies. Thepresent results have serious implications for the data-basedmodeling, as they place constraints on the accuracy of tailmagnetic configurations to be derived for specific events usingdata of multi-spacecraft missions, e.g. such as THEMIS.

KW - magnetospheric physics

KW - magnetospheric configuration and dynamics

KW - magnetotail

KW - solar wind-magnetosphere interactions

KW - magnetosphere

KW - magnetotail

KW - solar wind

U2 - 10.5194/angeo-26-2395-2008

DO - 10.5194/angeo-26-2395-2008

M3 - статья

VL - 26

SP - 2395

EP - 2402

JO - Annales Geophysicae

JF - Annales Geophysicae

SN - 0992-7689

IS - 8

ER -