Long-period magnetospheric-ionospheric perturbations during northward interplanetary magnetic field

• Published in: Journal of Geophysical Research: Space Physics
• Main Authors: Huang, Chao-Song, Sofko, G J, Koustov, V, A, Macdougall, J W, Greenwald, R, A, Ruohoniemi, J, J, Villain, Jean-Pierre, J, Lester, M, M, Watermann, J., Papitashvili, V, O, Hughes, J.W.
• Other Authors: University of Saskatchewan Saskatoon (U of S), Department of Electrical Engineering, University of Western Ontario (UWO), Johns Hopkins University Applied Physics Laboratory Laurel, MD (APL), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales Paris (CNES), University of Leicester, Danish Meteorological Institute (DMI), Space Physics Research Laboratory Ann Arbor (SPRL), University of Michigan Ann Arbor, University of Michigan System-University of Michigan System, Center for Space Physics Boston (CSP), Boston University Boston (BU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2001
• Subjects: TAIL; HF RADAR OBSERVATIONS; HIGH-LATITUDE CONVECTION; MAGNETOTAIL; SOLAR-WIND; DYNAMICS; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph]; Iceland
• Online Access: https://insu.hal.science/insu-01558983; https://insu.hal.science/insu-01558983/document; https://insu.hal.science/insu-01558983/file/Huang_et_al-2001-Journal_of_Geophysical_Research__Space_Physics_%281978-2012%29.pdf; https://doi.org/10.1029/2000JA900192

International audience In this paper we present observations of long-period magnetospheric-ionospheric perturbations during northward interplanetary magnetic field (IMF). On November 10-11, 1998, the IMF was northward for 29 hours. The solar wind and IMF parameters were relatively steady. After the IMF had been northward for 14 hours, strong ionospheric velocity (or electric field) perturbations were observed by the Iceland West HF radar in the postmidnight/dawn sector. The velocity perturbations showed periods in the range 50-60 min, with a mean value-54 min. The Super Dual Auroral Radar Network observed periodic changes of nightside ionospheric convection. For each cycle a large-scale convection cell formed around 0200 magnetic local time (MLT) near magnetic latitude 70 ø and grew for-30 min. The convection cell then moved eastward with a mean velocity of-l.4 km s-•. The final position of the cell focus was around 0600 MLT near magnetic latitude 77 ø. Ground magnetometers recorded weak magnetic perturbations with periods 50-60 min in both the premidnight and postmidnight sectors. The GOES 8 satellite also observed magnetospheric magnetic field perturbations with similar periods at L-6 on the nightside. The satellite and the key radars which observed the convection oscillations are nearly magnetically conjugate, so the good temporal correlation between the satellite and radar data indicates that the magnetospheric and ionospheric perturbations have a common source. We propose that the magnetospheric-ionospheric perturbations originated within the magnetosphere. The transformation of the magnetospheric tail from an extended to a more dipolar shape during northward IMF is associated with 40-60 min period global tail oscillations which ultimately result in the generation of field-aligned currents and nightside ionospheric convection vortices near X=-10 Re. If the proposed mechanism is correct, it will be possible to infer the magnetospheric cavity shape from the measured periodicity of the tail oscillations ...