Global modeling of Pi 2 pulsations

Abstract

Abstract. A numerical model of Pi 2 disturbances in the magnetosphere is developed. The model of the magnetosphere is the same as one previously used for the study of Pc 5 pulsations. It is semicylindrical with field lines being semicircular arcs and longitude measured parallel to the axis. The model magnetosphere is excited by a source on the boundary which is limited both in time and in longitude. The disturbance is then a superposition of modes corresponding to all the azimuthal wave numbers excited by the source. The computations show that a global oscillation is excited and that there can be a significant signal on the dayside at low latitudes. The role of the plasmasphere in producing a low-latitude response is important. Because of the simplifications of the model the most important aspect of the calculations is the qualitative understanding that they supply. Nevertheless, quite good quantitative agreement with observation is obtained. The calculations support earlier suggestions about the response of the magnetosphere to the initiation of the substorm current wedge.

Relationship between the Pi2 pulsations and the localized impulsive current associated with the current disruption in the magnetosphere

“…All previous theoretical/numerical studies assumed the initial driving perturbation as the externally-charged electric field at the magnetopause boundary (Pekrides et al, 1997) or a wave impinging on the plasmasphere (Itonaga et al, 1997a,b;Lee, 1998;Lee and Kim, 1999). Therefore, the current disruption model (e.g., Yumoto, 1990) has not been explicitly treated in previous numerical/theoretical studies of the Pi2 pulsation.…”

“…In order to examine the plasmasphere virtual resonance, several theoretical studies have investigated the magnetospheric response of the MHD impulse (Allan et al, 1986;Lee, 1996Lee, , 1998Pekrides et al, 1997;Itonaga et al, 1997a,b;Lee and Kim, 1999). Pekrides et al (1997) presented a 3D numerical simulation of MHD wave propagation in a cylindrical magnetosphere model with the plasmasphere structure. They obtained the plasmasphere virtual resonance oscillation, as well as the magnetosphere bounded mode oscillation.…”

“…Recently, the propagation and generation mechanism of the Pi2 pulsations in middle and low latitudes and in the inner magnetosphere has been studied extensively via observational methods (Yeoman and Orr, 1989;Yumoto, 1989, 1991;Yumoto, 1990;Yumoto et al, 1989Yumoto et al, , 1990Takahashi, 1994;Takahashi et al, 1992Takahashi et al, , 1995Takahashi et al, , 1999Osaki et al, 1998). In response to these observations, theoretical/numerical studies on the behavior of low-latitude MHD waves have been carried out (Allan et al, 1986;Lee, 1996Lee, , 1998Pekrides et al, 1997;Itonaga et al, 1997a,b;Lee and Kim, 1999). Yeoman and Orr (1989) manifested from mid-latitude Pi2 observations that a 180…”

Propagation property of transient MHD impulses in the Magnetosphere‐Ionosphere System: The 2D model of the Pi2 pulsation

“…The magnetosphere model is essentially the same as that used by Fujita et al (2000) except that the equatorial VA is calculated using the plasma density model presented by Pekrides et al (1997) We also check invariance of the results by using several values of the time step (At).…”

Near-equatorial Pi2 and Pc3 waves observed by CHAMP and on SAMBA/MAGDAS stations

“…However, because of its large horizontal scale, even an evanescent fast mode can convey significant wave energy towards the Earth. Commonly, the earthward propagation of compressional fast mode was described in the frameworks of 1D (Pekrides et al, 1997;Matsuoka et al, 1997) or 2D (Allan et al, 1996) models. In reality, the spatial distribution of wave power is determined by the diffraction of an incident large-scale FMS mode on a relatively small conductive sphere (Earth).…”