The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on SolarProbe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review.

The objective of this paper is to explore the application of a six-component overset grid to solar wind simulation with a three-dimensional (3D) Solar-InterPlanetary Conservation Element/Solution Element MHD model. The essential focus of our numerical model is devoted to dealing with: (1) the singularity and mesh convergence near the poles via the use of the six-component grid system, (2) the ∇ · B constraint error via an easy-to-use cleaning procedure by a fast multigrid Poisson solver, (3) the Courant-Friedrichs-Levy number disparity via the Courant-number insensitive method, (4) the time integration by multiple time stepping, and (5) the time-dependent boundary condition at the subsonic region by limiting the mass flux escaping through the solar surface. In order to produce fast and slow plasma streams of the solar wind, we include the volumetric heating source terms and momentum addition by involving the topological effect of the magnetic field expansion factor f S and the minimum angular distance θ b (at the photosphere) between an open field foot point and its nearest coronal hole boundary. These considerations can help us easily code the existing program, conveniently carry out the parallel implementation, efficiently shorten the computation time, greatly enhance the accuracy of the numerical solution, and reasonably produce the structured solar wind. The numerical study for the 3D steady-state background solar wind during Carrington rotation 1911 from the Sun to Earth is chosen to show the above-mentioned merits. Our numerical results have demonstrated overall good agreements in the solar corona with the Large Angle and Spectrometric Coronagraph on board the Solar and Heliospheric Observatory satellite and at 1 AU with WIND observations.

Abstract. We investigate the dynamical relationships between a coronal flux rope, a streamer, a coronal mass ejection (CME), and a magnetic cloud by using observations from the satellites of the International Solar-Terrestrial Physics observatories together with a streamer and flux rope interaction model . This is the first physical description of the evolution of a CME related to a flux rope in a streamer near the Sun to a magnetic cloud at 1 AU. The distinctive physical configuration of the model is based on a theoretical suggestion [Low, 1994] and observations [Hundhausen, 1993] that the magnetic structure of a streamer with an embedded cavity provides favorable condition for launch of a CME. We explore this physical scenario by identifying a flux rope as the cavity and using a fully self-consistent numerical simulation to illustrate the dynamical process of evolution of the flux rope/CME into a magnetic cloud. The simulation results are then compared to solar and interplanetary data from the wellobserved Sun-Earth connection event of January 6-12, 1997. The data used for this analysis were collected chiefly by the Solar and Heliospheric Observatory (SOHO) LargeAngle and Spectrometric Coronagraph Experiment coronagraph and the solar wind particle and field sensors on the Wind spacecraft, but ground-based solar data were used as well. Because we have detailed observations of the same disturbance both at the Sun (SOHO) and at 1 AU (Wind), this event gives us an unusual opportunity to test the magnetohydrodynamic methodology and to learn about the physical processes of the SunEarth connection. In this study we show that when the flux rope rises (owing to increasing axial current, as assumed here, or to some other mechanism), it disrupts the streamer-flux rope system, thus launching a coronal mass ejection. The flux rope then escapes from the streamer and evolves to become a magnetic cloud, as expected, in interplanetary space. The CME is a visible feature moving ahead of the flux rope. The model also predicts a fast-mode shock in front of the magnetic cloud, as observed. IntroductionA magnetic cloud is an interplanetary structure defined by (1) strong magnetic fields, (2) a smooth rotation of the magnetic field direction as it moves past the spacecraft at 1 AU, ] have studied physical processes for the initiation of CMEs using both analytical and numerical simulation models, but these models are limited to the corona.In these coronal mass ejection models several initiation mechanisms are explored. For example, Linker and Mikid [1995] have used photospheric shear as a driving mechanism for streamer disruption to launch a CME by using a resistive magnetohydrodynamic model, but the initial streamer had no flux rope embedded in it. Their result showed that it took 500 hours for a photospheric shear speed of 0.94 km s-• to initiate a CME. Recently, Wu and Guo [1997b] also tested the shearing motion for CME initiation using a model of a flux rope suspended inside a streamer as suggested by Low [1994, 1997] and simil...

Abstract. For the sets of magnetic clo•ds studied in this workwe have shown the existence of a relationship between their peak magnetic field strength and peak velocity values, with a clear tendency that, clouds which move at, higher speeds also possess higher core magnetic field strengths. This result suggests a possible intrinsic property of magnetic clouds and also implies a geophysical consequence. The relatively low field strengths at low velocities is pres•mably the cause of the lack of intense storms during low speed e. jecta. There is also an indication that, this type of behavior is peculiar for magnetic clouds, whereas other types of non cloud-driver gas events do not, seem to show a similar relationship, at least, for the data studied in this paper. We suggest that, a field/speed relationship for magnetic clouds, as that obtained in our present study, could be associated with the cloud release and acceleration mechanism a.t the sun.Since for magnetic clouds the total field tyically has a substantial southward component, B•, our results in,ply that the interplanetary dawn-dusk electric field, given by v x Bs (where v is the cloud's velocity), is enhanced by both factors. Therefore, the consequent magnetospheric energization (that is governed by this electric field) becomes more efficient for the occurrence of magnetic storms.

[1] Numerical studies of the interplanetary ''multiple magnetic clouds (Multi-MC)'' are performed by a 2.5-dimensional ideal magnetohydrodynamic (MHD) model in the heliospheric meridional plane. Both slow MC1 and fast MC2 are initially emerged along the heliospheric equator, one after another with different time intervals. The coupling of two MCs could be considered as the comprehensive interaction between two systems, each comprising of an MC body and its driven shock. The MC2-driven shock and MC2 body are successively involved into interaction with MC1 body. The momentum is transferred from MC2 to MC1. After the passage of MC2-driven shock front, magnetic field lines in MC1 medium previously compressed by MC2-driven shock are prevented from being restored by the MC2 body pushing. MC1 body undergoes the most violent compression from the ambient solar wind ahead, continuous penetration of MC2-driven shock through MC1 body, and persistent pushing of MC2 body at MC1 tail boundary. As the evolution proceeds, the MC1 body suffers from larger and larger compression, and its original vulnerable magnetic elasticity becomes stiffer and stiffer. So there exists a maximum compressibility of Multi-MC when the accumulated elasticity can balance the external compression. This cutoff limit of compressibility mainly decides the maximally available geoeffectiveness of Multi-MC because the geoeffectiveness enhancement of MCs interacting is ascribed to the compression. Particularly, the greatest geoeffectiveness is excited among all combinations of each MC helicity, if magnetic field lines in the interacting region of Multi-MC are all southward. Multi-MC completes its final evolutionary stage when the MC2-driven shock is merged with MC1-driven shock into a stronger compound shock. With respect to Multi-MC geoeffectiveness, the evolution stage is a dominant factor, whereas the collision intensity is a subordinate one. The magnetic elasticity, magnetic helicity of each MC, and compression between each other are the key physical factors for the formation, propagation, evolution, and resulting geoeffectiveness of interplanetary Multi-MC.Citation: Xiong, M., H. Zheng, S. T. Wu, Y. Wang, and S. Wang (2007), Magnetohydrodynamic simulation of the interaction between two interplanetary magnetic clouds and its consequent geoeffectiveness,