Abstract
Abstract. In a recent paper, Treumann and Baumjohann (2011) propose that the contribution of dust particles to the solar wind dynamic pressure can cause large compressions of the Earth's magnetopause and suggest that this occurs when Earth encounters meteoroid streams. In this paper we estimate the contribution from charged dust particles to the solar wind dynamical pressure, and we exclude that the dust associated to meteoroid streams can influence the extension of the magnetopause according to the proposed model. A sufficient coupling to the solar wind is only expected for so-called nanodust. However, the dynamic pressure of the nanodust is orders of magnitudes below that of the solar wind, making it unlikely that its variation can be observed in displacements of the magnetopause. We also discuss the equation that the authors use for estimating the extension of the Earth's magnetopause, and conclude that this is not applicable due to the large gyroradius of the nanodust. We finally note that an influence of dust on the extension of a magnetosphere might be quite possible in other astrophysical systems and based on other processes.
Highlights
The Earth’s magnetopause plays an important role for the complex interactions between the Earth’s magnetosphere and the Sun and the interplanetary medium
Many of them are parameterized by the solar wind dynamic pressure and the north– south component of the interplanetary magnetic field (IMF) (Safrankovaet al., 2002)
We suggest that it is not reasonable to assume that Earthorbit-crossing meteoroid streams can influence the extension of the magnetopause as suggested by Treumann and Baumjohann (2011), nor does any other dust component in the solar wind
Summary
The Earth’s magnetopause plays an important role for the complex interactions between the Earth’s magnetosphere and the Sun and the interplanetary medium. Many of them are parameterized by the solar wind dynamic pressure and the north– south component of the interplanetary magnetic field (IMF) (Safrankovaet al., 2002). The five spacecraft of the THEMIS mission have observed around 6500 magnetopause crossings, and these data were used to investigate the dependence of the magnetopause location on the angle between the interplanetary magnetic field and solar wind velocity vectors (i.e. IMF cone angle) (Dusik et al, 2010). While the presence of dust particles is not frequently discussed in the context of the planetary magnetospheres, the influence of interstellar dust dynamic pressure is considered by Holzer (1989), for instance, when describing the extension of the heliosphere.
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