Plasma distribution and magnetic field orientation in the Venus near wake: Solar wind control of the nightside ionopause

Abstract. The paper analyses one long-term pass (26 August 2007) of the THEMIS spacecraft across the dayside low-latitude magnetopause. THEMIS B, serving partly as a magnetosheath monitor, observed several changes of the magnetic field that were accompanied by dynamic changes of the magnetopause location and/or the structure of magnetopause layers observed by THEMIS C, D, and E, whereas THEMIS A scanned the inner magnetosphere. We discuss the plasma and the magnetic field data with motivation to identify sources of observed quasiperiodic plasma transients. Such events at the magnetopause are usually attributed to pressure pulses coming from the solar wind, foreshock fluctuations, flux transfer events or surface waves. The presented transient events differ in nature (the magnetopause surface deformation, the low-latitude boundary layer thickening, the crossing of the reconnection site), but we found that all of them are associated with changes of the magnetosheath magnetic field orientation and with enhancements or depressions of the plasma density. Since these features are not observed in the data of upstream monitors, the study emphasizes the role of magnetosheath fluctuations in the solar wind-magnetosphere coupling.

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Magnetopause magnetic barrier parameters in dependence on the solar wind magnetic field orientation

Annales Geophysicae ◽

10.1007/s00585-995-0828-y ◽

1995 ◽

Vol 13 (8) ◽

pp. 828-835 ◽

Cited By ~ 9

Author(s):

M. I. Pudovkin ◽

S. A. Zaitseva ◽

B. P. Besser

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Field Strength ◽

Interplanetary Magnetic Field ◽

Opposite Effect ◽

Field Orientation ◽

Magnetic Field Orientation ◽

Dayside Magnetopause ◽

Solar Wind Magnetic Field ◽

Theoretical Predictions

Abstract. Some theories predict the magnetosheath magnetic field strength will decrease and the density increase just outside the dayside magnetopause as the interplanetary magnetic field turns southward. Two studies have recently reported results which confirm these expectations. In contrast, we briefly review our own theoretical predictions which indicate that precisely the opposite effect is expected. We survey new and previously reported magnetosheath observations and demonstrate that they are consistent with the predictions of our model. The conflicting results indicate a need for further theoretical and observational work.

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Investigating the nature of the link between magnetic field orientation and proton temperature in the solar wind

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936728 ◽

2019 ◽

Vol 632 ◽

pp. A92 ◽

Cited By ~ 1

Author(s):

R. D’Amicis ◽

R. De Marco ◽

R. Bruno ◽

D. Perrone

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Large Scale ◽

Interplanetary Space ◽

Angular Displacement ◽

Local Magnetic Field ◽

Temperature Anisotropy ◽

Field Orientation ◽

Magnetic Field Orientation ◽

Proton Temperature

Solar wind fluctuations are a mixture of propagating disturbances and advected structures that transfer into the interplanetary space the complicated magnetic topology present at the basis of the corona. The large-scale interplanetary magnetic field introduces a preferential direction in the solar wind, which is particularly relevant for both the propagation of the fluctuations and their anisotropy and for the topology of the structures advected by the wind. This paper focusses on a particular link observed between angular displacements of the local magnetic field orientation from the radial direction and values of the proton temperature. In particular, we find that observations by Helios and Wind show a positive correlation between proton temperature and magnetic field orientation. This is especially true within Alfvénic wind characterized by large-amplitude fluctuations of the background field orientation. Moreover, in the case of Wind, we found a robust dependence of the perpendicular component of the proton temperature on the magnetic field angular displacement. We interpret this signature as possibly due to a physical mechanism related to the proton cyclotron resonance. Finally, by simulating the sampling procedure of the proton velocity distribution function (VDF) of an electrostatic analyzer, we show that the observed temperature anisotropy is not due to instrumental effects.

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