TY - JOUR
T1 - Substorm-time magnetic field perturbations in the polar magnetosphere
T2 - POLAR observations
AU - Kawano, H.
AU - Le, G.
AU - Russell, C. T.
AU - Rostoker, G.
AU - Brittnacher, M. J.
AU - Parks, G. K.
N1 - Funding Information:
Acknowledgments. The CANOPUS instrument array was constructed and is maintained and operated by the Canadian Space Agency for the Canadian scientific community. We appreciate K. Ogilvie for the data from WIND Solar Wind Experiment. We also appreciate R. Lepping for the data from Wind Magnetic Field Investigation. We also appreciate S. Ohtani for his comments on this paper. G. Le and C. T. Russell were supported by the National Aeronautics and Space Administration (NASA) under research grant NAG5-7721. This work was partly supported by the Japan Society for the Promotion of Science under Grant-in-Aid for Scientific Research 13740286.
PY - 2002
Y1 - 2002
N2 - We present a case study of substorm-time magnetic field perturbations in the high-altitude polar magnetosphere, corresponding to the polar lobe, using data from the POLAR spacecraft together with ground-based CANOPUS observations and WIND solar-wind observations. The substorm of this paper had a clear growth phase and one clear major expansion onset, enabling an unmistakable comparison of the substorm timings and those of the magnetic field perturbations observed by POLAR. During the growth phase, the magnetic field strength (Btotal) increased and the flaring angle of the field line decreased at POLAR: They are ascribed to the pileup of magnetic field lines over the polar magnetosphere and to the braking effect of the ionosphere on the tailward motion of the piled-up field lines, respectively. For ∼28 min after the expansion onset, Btotal at POLAR did not decrease toward its pre-substorm value, in contrast to past tail-lobe observations where Btotal decreased during the expansion phase. This absence of the field-decrease signature in the polar lobe for ∼28 min, reported for the first time in this paper, could be ascribed to dipolarization/ compression of the inner magnetosphere during the expansion phase, cancelling the field-decreasing effect.
AB - We present a case study of substorm-time magnetic field perturbations in the high-altitude polar magnetosphere, corresponding to the polar lobe, using data from the POLAR spacecraft together with ground-based CANOPUS observations and WIND solar-wind observations. The substorm of this paper had a clear growth phase and one clear major expansion onset, enabling an unmistakable comparison of the substorm timings and those of the magnetic field perturbations observed by POLAR. During the growth phase, the magnetic field strength (Btotal) increased and the flaring angle of the field line decreased at POLAR: They are ascribed to the pileup of magnetic field lines over the polar magnetosphere and to the braking effect of the ionosphere on the tailward motion of the piled-up field lines, respectively. For ∼28 min after the expansion onset, Btotal at POLAR did not decrease toward its pre-substorm value, in contrast to past tail-lobe observations where Btotal decreased during the expansion phase. This absence of the field-decrease signature in the polar lobe for ∼28 min, reported for the first time in this paper, could be ascribed to dipolarization/ compression of the inner magnetosphere during the expansion phase, cancelling the field-decreasing effect.
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U2 - 10.1186/BF03352444
DO - 10.1186/BF03352444
M3 - Article
AN - SCOPUS:20644464588
VL - 54
SP - 963
EP - 971
JO - Earth, Planets and Space
JF - Earth, Planets and Space
SN - 1343-8832
IS - 10
ER -