Search

Abstract: The interaction of the Earth''s magnetosphere with the solar wind is a fundamental problem in space plasma physics. Sudden changes in the Interplanetary Magnetic Field (IMF)/solar wind conditions, e.g., coronal mass ejections (CMEs), solar energetic particles (SEPs), and interplanetary shocks, provide excellent opportunities to study the complex response of the Earth''s magnetosphere and ionosphere to the solar wind. The interaction of solar wind discontinuities with the magnetosphere includes several phases, including interaction with the bow shock, propagation in the magnetosheath, interaction with the magnetopause, transmission into the magnetosphere and the ionosphere. The studies of magnetospheric phenomena in conjunction with solar wind discontinuities are tractable from at least two obvious vantage points: First, unlike other magnetospheric phenomena, e.g., substorms, the specific energy source for the solar wind discontinuity related magnetospheric phenomena is clear. Second, the response of the magnetospheric system to solar wind discontinuities usually yield a significant and easily identified electromagnetic signal. Thus, there is no temporal ambiguity for the solar wind discontinuity related phenomena. [Copyright &y& Elsevier]

Abstract: On April 21, 2001 an interplanetary CME started to interact with the magnetosphere when CLUSTER spacecraft were travelling in the cusp region. This interaction produced a strong magnetic storm (D st =103nT) at Earth. Cusp proton aurora was caused by the leading phase of the CME. Cusp proton aurora generally appear during northward IMF, this paper demonstrates that they can also be triggered during southward IMF when the reverse convection has been generated by an IMF dominated Y component. The location of the cusp proton aurora shifted about 30° from dawnside to duskside when IMF B y changed from −10 to 5nT. The requirement to produce proton cusp aurora seems to be a reverse convection in the cusp region instead of the northward IMF (not only northward IMF, but IMF B y is also an important parameter!). [Copyright &y& Elsevier]

Bursty energetic electron events with energies of about 20–400 keV have been observed in the cusp region when the CLUSTER S/C were travelling outbound on 5 April 2001. These electron events are characterized by strong impulsive increases in the flux whereas energetic ions (>30 keV) show no obvious changes. The enhanced energetic electron flux is more than 10 times higher than the background level whereas the energetic ions show no significant changes. The bursts of energetic electrons occurred mainly in the time interval when the northward IMF had a significant By component and were associated with the rotation of the local Bz (bi-polar signature) and with a dramatic change of the plasma flow (<30 keV) from tailward to dawnward. These bursts of electrons are well confined in a small scale flux rope structure as implied by the magnetic field and plasma measurements. Energetic electrons were flowing dawnward from the cusp region along (but anti-parallel to) the magnetic field. No stable energetic electron flux that indicates the cusp has a general open field line geometry has been observed. The spike-like electron bursts could be explained by energetic electrons leaking out of the magnetosphere into the cusp when the flux ropes are formed by a transient reconnection in the cusp stagnation region. Further, we propose that the flux ropes are most likely formed in dawn (dusk) side of the cusp region during northward IMF with a significant positive (negative) By component. [Copyright &y& Elsevier]

Abstract: The role of electrons during the shock-induced chorus intensification observed by THEMIS D on 19 November 2007 is investigated in detail. First, the electrons are accelerated through the local betatron acceleration and radial diffusion, which are primarily in the perpendicular direction and result in the positive anisotropy () of electrons; then they are scattered through the pitch-angle diffusion, during which the electron energies are partially transferred to amplify the chorus. In the case of interest, the energy loss is more efficient for the lower-energy (15keV) electrons because they have larger density gradient along the diffusion curves. The energetic electrons act as the intermediate in this scenario. They transfer the energies carried by the interplanetary shock to the chorus. The energetic electrons injected from magnetotail are not observed; they have no contributions to the energy source in this event. [Copyright &y& Elsevier]

Abstract: We investigate the coupling between the solar wind and the magnetospheric cusp during the passage of a Corotating Interaction Region (CIR) high-speed stream. A CIR event on 11 January 2002 is selected for this study. We use ACE (Advanced Composition Explorer) and Geotail plasma and magnetic field data for interplanetary solar wind observations and Cluster plasma and magnetic field data for the cusp observations. The response of the solar wind on the polar cusp was studied and made visible with the wavelet and cross-wavelet analysis. During the CIR event we observe significantly enhanced wave power for waves with periods ranging from 15 to 25min (1.1–0.7mHz). Significant cross-correlation power of the ACE and Geotail interplanetary magnetic field (IMF) Bz- and Ey-component and the solar wind Vx-component versus the Cluster cusp H+ density, the thermal temperature and energetic electron flux (50–244keV) were found at the corresponding frequencies. We conclude that the solar wind Alfvén waves affect the magnetospheric dayside cusp density and heat the cusp. We interpret these correlation results as evidence of high-speed solar wind—magnetosphere coupling driven by waves in the solar wind. [ABSTRACT FROM AUTHOR]

Abstract: We have examined the response of ionospheric electric field to the ICME sheath with the coordinated ground- and space-based magnetic measurements during the initial phase of December 14, 2006 storm. The duskward IEF pulses enhanced the westward convection electrojet and the eastward equatorial ionospheric electric field. The in situ magnetic measurements in the vicinity of geosynchronous orbit suggested that the Earth’s magnetosphere was continuously compressed on the dayside and stretched to more tail-like on the nightside, due to the sustained high solar wind dynamic pressure in the sheath region. The compression prevented shielding current from increasing and then caused electric field penetration. [ABSTRACT FROM AUTHOR]

Abstract: We present a method of polar cusp identification using high charge state heavy ions. There is reason to think that these ions would constitute shocked solar wind ions such as doubly charged helium ions, He2+, and multiply charged oxygen ions, O(3−8)+, that appear to have relatively easy access to one or both of the polar cusps essentially at all times. The observations made with the ISTP/POLAR spacecraft were mostly obtained during geomagnetically non-storm times in April 2001 when the spacecraft orbit allowed northern cusp encounters with low trajectory angle between the spacecraft velocity vector and the overall cusp magnetic field orientation. We also show one extended cusp crossing during the modest magnetic storm of April 22, 2001 (with D st ∼−103 nT). It is found that during the study period, 1–10keV high charge state ions are present in the cusp region at virtually all times, during storm or quiet. We also found that what appears to be the interior of the northern polar magnetic cusp region can be rather turbulent both in the local magnetic field direction and in the energetic charged particle kinetic flow characteristics. There is some evidence for temporally varying turbulent acceleration processes, either within the cusp domain itself or in the surrounding magnetosphere. In terms of the present ion observations, there is little to distinguish the dayside low latitude boundary layer (LB) ion signatures from those of the interior of the polar cusp region (high charge state ions, abundant 1–10keV ion fluxes). [Copyright &y& Elsevier]

Abstract: The scientific objectives of an advanced NeUtral Atom Detector Unit (NUADU) designed for the Chinese Double Star Polar Mission, which is scheduled for launch in July 2004, are described. The potential during this mission to realize, hitherto unprecedented, integrated studies of global dynamic magnetospheric processes through combining with NUADU data contemporaneous measurements made aboard the CLUSTER II, IMAGE and TWINS spacecraft is also discussed and a short technical account of NUADU provided. [Copyright &y& Elsevier]

Cold ions of plasmaspheric origin have been observed to abundantly appear in the magnetospheric side of the Earth's magnetopause. These cold ions could affect the magnetic reconnection processes at the magnetopause by changing the Alfvén velocity and the reconnection rate, while they could also be heated in the reconnection layer during the ongoing reconnections. We report in situ observations from a partially crossing of a reconnection layer near the subsolar magnetopause. During this crossing, step-like accelerating processes of the cold ions were clearly observed, suggesting that the inflow cold ions may be separately accelerated by the rotation discontinuity and slow shock inside the reconnection layer., (Copyright © 2018 Science China Press. Published by Elsevier B.V. All rights reserved.)