scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Impacts of solar disturbances on the heliosphere and magnetosphere
Wang Chi
State Key Laboratory of Space Weather, Chinese Academy of Sciences
Interplanetary disturbances, including interplanetary shocks and ICMEs, disturbance not only
the magnetosphere-ionosphere system but also the heliosphere. This talk will be divided into
two parts, the first part will discuss the impacts of solar disturbances on the heliosphere. We
present a multi-fluid MHD model, which takes into account the effects of pickup ions, to
describe the solar wind in the outer heliosphere, since the solar wind in the outer heliosphere
is fundamentally different from that in the inner heliosphere, with the influence of the local
interstellar source becomes significant. Using observations from multiple spacecraft
distributed throughout the heliosphere, we traced the propagation of ICMEs and their driven
shocks from 1 AU to the location of Voyager 2. The Bastille Day, 2000 event and April 2001
event are modeled in detail.
Interplanetary (IP) shocks disturb the magnetosphere-ionosphere system resulting in
geosynchronous magnetic field changes and sudden impulses observed by ground-based
magnetometers. We perform a statistical survey of geospace magnetic field responses to IP
shocks. The magnitude of the geosynchronous magnetic field (dBz) responses to IP shocks
depends strongly on local time, which peaks near the noon meridian, however the relative
magnitude of the responses depends only weakly on local time. Negative responses (where
dBz is negative) were sometimes observed in the nightside of the magnetosphere even though
the IP shocks always caused increases in the solar wind dynamic pressure. The 3D global
MHD simulations reproduce the main characters of the observations. The dBz at the
geosynchronous orbit near local noon and the amplitude of sudden impulses (dSYM-H) on the
ground are highly correlated. We show that sudden impulses (SIs) can be used to estimate key
parameters at L1 point and geosynchronous orbit, including the change of square-root the
solar wind dynamic pressure across the shock, and the associated geosynchronous magnetic
field changes near the sub-solar region. Empirical formulae deduced from observations can be
used to estimate certain IP shock characteristics and geosynchronous magnetic field changes
from observed sudden impulse data observed on the ground with prediction efficiency as high
as 89%.