Effects of the interaction and evolution of interplanetary shocks on “background” solar wind speeds

Abstract

[1] Solar wind speed plays an important role in the study of space weather prediction. Some workers have used it for measuring the arrival time of solar disturbances at 1 AU. The purpose of this work is to extend our previous study (Wu et al., 2005c) of some Halloween 2003 events by presenting additional physical effects of multiple shock interactions on the solar wind profile during a complex compound event. In order to achieve this goal, we track a group of specific solar events' plasma and magnetic field output as they propagate into interplanetary space. A one-dimensional, time-dependent adaptive grid MHD code is used to study the evolution and interaction of shocks from Sun through the heliosphere. The MHD simulation results demonstrate that the solar wind speed might increase about %25% after two shocks collide with each other. This kind of interaction can affect the accuracy of the identification of the solar source that causes the interplanetary event (e.g., magnetic cloud, coronal mass ejection, interplanetary shock, or some other interplanetary discontinuity.) In this study we further simulate part of the famous Halloween 2003 events that contain at least four major solar events (flares) during 28 October to 1 November 2003. These major events, simulated by pressure pulses, generated shocks that matched well with ACE (Advanced Composition Explorer) observations as reported by Wu et al. (2005c) in our previous study. The present work presents new details concerning the interplay (such as sunward and antisunward traveling compression and rarefaction waves) between fast forward and fast reverse interplanetary shocks.

Magnetohydrodynamic Fast Shocks and Their Relation to Solar Energetic Particle Event Intensities

“…Note that we will omit consideration of the first SEP event since the first shock event, which is probably responsible for the first SEP event, was not studied by Wu et al (2006). The other SEP events, in our opinion, will provide sufficient evidence for this study.…”

“…Evolution of the flare-associated CME-driven shocks from the surface of the Sun out to 1 AU for the Halloween storm event has been studied and reported by Wu et al (2005Wu et al ( , 2006Wu et al ( , 2007. The simulation used a 1.5D adapted code (Panitchob 1987) to solve numerically a set of governing equations that satisfy the conservation of mass, momentum, and energy for a compressible, non-viscous, perfectly conducting, adiabatic (γ = 5/3) magneto-hydrodynamic fluid in the presence of gravitational forces between the Sun and the solar wind plasma.…”

“…On the other hand, two shocks (one forward and one reverse) can collide and penetrate each other. The strength of the shock can become increasing (FFS2) or decreasing (FFS4) depending on their upstream and downstream solar wind conditions (Wu et al 2006).…”

Relationship between solar energetic oxygen flux and MHD shock mach number

“…The enhancement of oxygen flux was apparently associated with the IP shock driven by the CME event associated with the X17.2 flare. Evolution of the CME and CME-driven shock for this particular event has been studied by Wu et al [17][18][19], using a 1.5D adapted code [20]. The numerical code solves a set of MHD equations for a compressible, non-viscous, perfect conducting magnetohydrodynamic fluid in the presence of gravitational forces (from the Sun only).…”

Beam tracking strategies for fast acquisition of solar wind velocity distribution functions with high energy and angular resolutions

“…The solar wind speed vector can vary by 500 km · s and more in interplanetary coronal mass ejections (e.g. Gosling et al, 1968;Volkmer and Neubauer, 1985;Dryer, 1994;Watari and Detman, 1998;Wu et al, 2016). Such dramatic changes occur over seconds to many 10 minutes.…”