Influence of He
            ++
            and Shock Geometry on Interplanetary Shocks in the Solar Wind: 2D Hybrid Simulations

Alpha particles (He++) are the most important minor ion species in the solar wind, constituting typically about 5% of the total ion number density. When crossing an interplanetary shock protons and He++ particles are accelerated differently due to their different charge-to-mass ratio. This behavior can produce changes in the velocity distribution function (VDF) for both species in the immediate downstream region generating anisotropy in the temperature which is considered to be the energy source for various phenomena such as ion cyclotron and mirror mode waves for example. How these changes in temperature anisotropy and shock structure depend on the percentage of He++ particles and the geometry of the shock is not completely understood. In this work we perform various 2D local hybrid simulations (particle ions, massless fluid electrons) with similar characteristics (e.g., Mach number) to observed interplanetary shocks for both quasi-parallel and quasi-perpendicular geometries including self-consistently different percentages of He++ particles. We find that the change of the initial &#952;Bn leads to variations of the efficiency with which particles can escape to the upstream region facilitating or not the formation of compressive structures in the magnetic field that will produce increments in perpendicular temperature. The regions where both temperature anisotropy and compressive fluctuations appear tend to be more extended and reach higher values as the He++ content in the simulations increase.

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Cluster observations of sudden impulses in the magnetotail caused by interplanetary shocks and pressure increases

Annales Geophysicae ◽

10.5194/angeo-23-609-2005 ◽

2005 ◽

Vol 23 (2) ◽

pp. 609-624 ◽

Cited By ~ 26

Author(s):

K. E. J. Huttunen ◽

J. Slavin ◽

M. Collier ◽

H. E. J. Koskinen ◽

A. Szabo ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Dynamic Pressure ◽

Solar Wind Speed ◽

Interplanetary Shock ◽

Wind Pressure ◽

Shock Propagation ◽

Interplanetary Shocks ◽

Maximum Variance ◽

The Magnetic Field

Abstract. Sudden impulses (SI) in the tail lobe magnetic field associated with solar wind pressure enhancements are investigated using measurements from Cluster. The magnetic field components during the SIs change in a manner consistent with the assumption that an antisunward moving lateral pressure enhancement compresses the magnetotail axisymmetrically. We found that the maximum variance SI unit vectors were nearly aligned with the associated interplanetary shock normals. For two of the tail lobe SI events during which Cluster was located close to the tail boundary, Cluster observed the inward moving magnetopause. During both events, the spacecraft location changed from the lobe to the magnetospheric boundary layer. During the event on 6 November 2001 the magnetopause was compressed past Cluster. We applied the 2-D Cartesian model developed by collier98 in which a vacuum uniform tail lobe magnetic field is compressed by a step-like pressure increase. The model underestimates the compression of the magnetic field, but it fits the magnetic field maximum variance component well. For events for which we could determine the shock normal orientation, the differences between the observed and calculated shock propagation times from the location of WIND/Geotail to the location of Cluster were small. The propagation speeds of the SIs between the Cluster spacecraft were comparable to the solar wind speed. Our results suggest that the observed tail lobe SIs are due to lateral increases in solar wind dynamic pressure outside the magnetotail boundary.

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Hybrid simulations of preferential heating of heavy ions in the solar wind

10.1063/1.1324324 ◽

2000 ◽

Author(s):

Paulett C. Liewer

Keyword(s):

Solar Wind ◽

Heavy Ions ◽

Hybrid Simulations

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Interaction of the Solar Wind with Weak Obstacles: Hybrid Simulations for Weakly Active Comets and for Mars

Space Science Reviews ◽

10.1007/s11214-006-6218-2 ◽

2006 ◽

Vol 122 (1-4) ◽

pp. 197-208 ◽

Cited By ~ 25

Author(s):

U. Motschmann ◽

E. Kührt

Keyword(s):

Solar Wind ◽

Hybrid Simulations

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Microinstabilities and plasma waves at Near-Sun Solar Wind collisionless Shocks: Predictions for PSP and SO

10.5194/egusphere-egu21-8114 ◽

2021 ◽

Author(s):

Zhongwei Yang ◽

Shuichi Matsukiyo ◽

Huasheng Xie ◽

Fan Guo ◽

Mingzhe Liu ◽

...

Keyword(s):

Solar Wind ◽

Shock Front ◽

Leading Edge ◽

Relativistic Electrons ◽

Interplanetary Shocks ◽

Particle In Cell ◽

Drift Instability ◽

Shock Simulation ◽

Mass Ejection ◽

The Impact

Microinstabilities and waves excited at perpendicular interplanetary shocks in the near-Sun solar wind are investigated by full particle-in-cell simulations. By analyzing the dispersion relation of fluctuating field components directly issued from the shock simulation, we obtain key findings concerning wave excitations at the shock front: (1) at the leading edge of the foot, two types of electrostatic (ES) waves are observed. The relative drift of the reflected ions versus the electrons triggers an electron cyclotron drift instability (ECDI) that excites the first ES wave. Because the bulk velocity of gyro-reflected ions shifts to the direction of the shock front, the resulting ES wave propagates obliquely to the shock normal. Immediately, a fraction of incident electrons are accelerated by this ES wave and a ring-like velocity distribution is generated. They can couple with the hot Maxwellian core and excite the second ES wave around the upper hybrid frequency. (2) From the middle of the foot all the way to the ramp, electrons can couple with both incident and reflected ions. ES waves excited by ECDI in different directions propagate across each other. Electromagnetic (EM) waves (X mode) emitted toward upstream are observed in both regions. They are probably induced by a small fraction of relativistic electrons. The impact of shock front rippling, Mach numbers, and dimensions on the ES wave excitation also will be discussed. Results shed new insight on the mechanism for the occurrence of ES wave excitations and possible EM wave emissions at young coronal mass ejection&#8211;driven shocks in the near-Sun solar wind.

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Theoretical Interpretation of Traveling Interplanetary Phenomena and Their Solar Origins

Symposium - International Astronomical Union ◽

10.1017/s0074180900067966 ◽

1980 ◽

Vol 91 ◽

pp. 443-458 ◽

Cited By ~ 3

Author(s):

S. T. Wu

Keyword(s):

Solar Wind ◽

Wave Propagation ◽

Interplanetary Shock ◽

Theoretical Interpretation ◽

Theoretical Studies ◽

Interplanetary Shocks ◽

Physical Processes ◽

Mathematical Methods ◽

Microscopic Approach ◽

Alternative Approaches

Recent theoretical studies on Traveling Interplanetary Phenomena (TIP) and their relation or presumed relation to their solar origins will be reviewed. An attempt is made to outline the theoretical studies in the context of mathematical methods and physical processes. The following alternative approaches are examined: analytical vs. numerical methods; magnetohydrodynamics vs. hydrodynamics; processes with or without dissipation; continuum (macroscopic) vs. the kinetic (microscopic) approach. In particular, the flare-generated interplanetary shocks are used as examples to illustrate these theoretical studies within the context of TIP. Some emphasis will be placed on MHD wave propagation through the inner corona and its maturity to a fully-developed interplanetary shock. Further, their propagation and the disturbing effects on the solar wind will be considered. Cases concerning the classification and characteristics of blast-produced shocks and long-lasting ejecta are also discussed in the context of numerical simulations.

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