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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Transient Oscillations Near the Dayside Open-Closed Boundary: Evidence of Magnetopause Surface Mode?
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Transient Oscillations Near the Dayside Open-Closed Boundary: Evidence of Magnetopause Surface Mode?

机译：暂停振荡附近的云台开放式边界：磁档表面模式的证据？

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Geomagnetic pulsations in Pc5-6 band (~3-20 min) are persistent feature of ULF activity at dayside high latitudes. Magnetopause surface eigenmodes may be suggested as potential mechanism of these pulsations. One might expect the ground response of these modes to be near ionospheric projection of the open-closed field line boundary (OCB). Using data from instruments located at Svalbard we study transient geomagnetic response to impulsive "intrusion" of magnetosheath plasma into the dayside magnetosphere. These intrusions are triggered by modest changes of interplanetary magnetic field to southward, and observed as sudden shifts of equatorward red aurora boundary to lower latitudes and green line emission intensification. Each auroral disturbance is accompanied by burst of ~1.7-2.0-mHz geomagnetic pulsations. Near-cusp latitudinal structure of ULF pulsations is compared with instant location of equatorward boundary of the red aurora, assumed to be a proxy of the OCB. Optical OCB latitude has been identified using data from the meridian scanning photometer. The latitudinal maximum of the transient geomagnetic response tends to be located near disturbed OCB proxy, within the error ~1°-2° of the photometer and magnetometer methods. Recorded transient pulsations may be associated with the ground image of the magnetopause surface mode harmonic. Theoretical consideration indicates that after an initial excitation, surface large-scale mode converts into localized Alfvén oscillations and thus can exist for limited time only. Therefore, MHD surface modes in realistic inhomogeneous plasma cannot be considered in isolation, but as a combined system of modes with discrete and continuous spectra with irreversible transformation between them.
机译：PC5-6频段（〜3-20分钟）的地磁脉动是MSTINE高纬度的ULF活动的持续特征。可以建议磁档表面特征模块作为这些脉动的潜在机制。人们可能期望这些模式的地面响应靠近开孔场线边界（OCB）的电离层投影。使用位于Svalbard的仪器中的数据我们研究了瞬时的地磁响应，以磁性池等离子体的脉冲“入侵”进入天晶磁层。这些侵入是通过跨境磁场到向南的适度变化触发，并且观察到赤道红色极光边界的突然移位，以降低纬度和绿线发射强度。每个极光扰动都伴随着突发的〜1.7-2.0-mHz的地磁脉动。将ULF脉动的近CUSP纬度结构与红色铁晕的赤道边界的即时位置进行比较，假设是OCB的代理。已经使用来自子午线扫描光度计的数据识别光学OCB纬度。瞬态地磁响应的纬度最大值倾向于位于令人不安的OCB代理附近，在光度计和磁力计方法的误差〜1°-2°内。记录的瞬态脉动可以与磁页面曲面模式谐波的地面图像相关联。理论考虑表明，在初始激励之后，表面大规模模式转换为局部的Alfvén振荡，因此可以仅存在限制时间。因此，逼真的不均匀等离子体中的MHD表面模式不能被隔离地考虑，而是作为具有离散和连续光谱的模式的组合系统，在它们之间具有不可逆的变换。

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