Initial Venus Express magnetic field observations of the Venus bow shock location at solar minimum

Zhang, T.L.; Delva, M.; Baumjohann, W.; Volwerk, M.; Russell, C. T.; Barabash, S.; Balikhin, M. A.; Pope, Simon; Glaßmeier, K.‐H.; Kudela, K.; Wang, Chao; Vörös, Z.; Zambelli, W.

doi:10.1016/j.pss.2007.09.012

Cited by 79 publications

(103 citation statements)

References 10 publications

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“…Fitting the observed bow shock locations for 20 Zhang et al (2008a) found that L ≈ 2.14 and ≈ 0.621, which leads to a terminator distance of R BS,t ≈ 2.14 R V , which is slightly smaller than the value R BS,t ≈ 2.40 R V which was found by Russell et al (1988) for solar maximum conditions using Pioneer Venus Orbiter data, with an eccentricity ≈ 0.609.…”

Section: Bow Shock Locationmentioning

confidence: 69%

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Mirror mode waves in Venus's magnetosheath: solar minimum vs. solar maximum

et al. 2016

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Abstract. The observational rate of mirror mode waves in Venus's magnetosheath for solar maximum conditions is studied and compared with previous results for solar minimum conditions. It is found that the number of mirror mode events is approximately 14 % higher for solar maximum than for solar minimum. A possible cause is the increase in solar UV radiation, ionizing more neutrals from Venus's exosphere and the outward displacement of the bow shock during solar maximum. Also, the solar wind properties (speed, density) differ for solar minimum and maximum. The maximum observational rate, however, over Venus's magnetosheath remains almost the same, with only differences in the distribution along the flow line. This may be caused by the interplay of a decreasing solar wind density and a slightly higher solar wind velocity for this solar maximum. The distribution of strengths of the mirror mode waves is shown to be exponentially falling off, with (almost) the same coefficient for solar maximum and minimum. The plasma conditions in Venus's magnetosheath are different for solar minimum as compared to solar maximum. For solar minimum, mirror mode waves are created directly behind where the bow shock will decay, whereas for solar maximum all created mirror modes can grow.

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Section: Bow Shock Locationmentioning

confidence: 69%

“…In Zhang et al (2008a) the statistical location of the bow shock was determined using the observed crossings of the bow shock into and out of the magnetosheath. The equation for the conic section that was used to describe the bow shock is…”

Section: Bow Shock Locationmentioning

confidence: 99%

Mirror mode waves in Venus's magnetosheath: solar minimum vs. solar maximum

et al. 2016

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“…In the figure, the highlighted regions represent the magnetic field profiles in the upstream and downstream, respectively. In order to test the validity of magnetic coplanarity and MVA methods, a Venusian bow shock model [20] are also used in the paper. The normal components of the magnetic field determined by the three methods are also shown in the bottom panel.…”

Section: The Normal Of Venusian Bow Shockmentioning

confidence: 99%

Comparison between magnetic coplanarity and MVA methods in determining the normal of Venusian bow shock

Lun

Zhang

et al. 2013

Chin. Sci. Bull.

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With the measurements of magnetic field of Venus Express (VEX), magnetic coplanarity and minimum variance analysis (MVA) methods are analyzed and their validity is tested to determine the normal of Venusian bow shocks. It is found that MVA method is the better than magnetic coplanarity, and 95% shock crossings can be accurately determined by the method. However, the occurrence of the shock normal which is not determined accurately by magnetic coplanarity increases with the decrease of the solar zenith angle (SZA). At the same time, compared with quasi-parallel shocks, there is more occurrence of the shock normal which cannot be determined accurately by magnetic coplanarity for quasi-perpendicular shocks. The physics of collisionless shock is a very broad topic in space and astrophysical plasmas [1][2][3]. A shock plays an important role in converting upstream bulk flow energy into downstream thermal energy, across which the plasma speed decreases from super-magnetosonic in the upstream to sub-magnetosonic in the downstream. A controlling factor, which determines the characteristics of a collisionless shock, is the magnetic geometry of the shock, usually described by the angle  Bn between the shock normal and the upstream magnetic field direction. Quasi-parallel ( Bn <45°) and quasiperpendicular shocks ( Bn >45°) have very different internal structure and thermalization processes. A quasi-perpendicular shock has an ion cyclotron scale foot and an overshoot after ramp [4], while low-frequency, large amplitude turbulence is ubiquitous prior to and after quasi-parallel shock. The dissipation mechanism from upstream bulk flow energy into downstream thermal energy is also different between a quasi-parallel and quasi-perpendicular shock. Therefore, determining the normal direction of a shock is the premise to study the characteristics of a shock. A planet bow shock is generated by the interaction between the tenuous, high speed solar wind and the magnetosphere, ionosphere and atmosphere of the planet. In addition, the heated ions created by charge exchange or photoionization of cold neutral atoms, escaping from planetary atmosphere, also play an important role in a planet bow shock [5,6], for example in Venusian bow shock. There are two analysis methods to determine the normal of a shock by single spacecraft observation, i.e. magnetic coplanarity [7][8][9] and minimum variance analysis (MVA) [10][11][12]. In this paper, with the magnetic field data obtained by Venus Express (VEX) spacecraft, we compare magnetic coplanarity and MVA methods in determining the normal of Venusian bow shock.

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“…These atoms are ionised through various processes, picked-up by the solar wind in the form of protons and transported away from the planet. Zhang et al (2008b) used VEX MAG data to study the location and structure of the magnetic barrier at Venus. The magnetic barrier plays the same role as the magnetosphere at planets with a significant intrinsic magnetic field, in that it provides the effective barrier to the solar wind.…”

Section: Slow/thermal Driftmentioning

confidence: 99%

“…The study shows that there is a well defined upper boundary to the magnetic barrier which can be considered as an induced magnetopause. Zhang et al (2008a) used VEX MAG data to study the location of the Venusian bow shock at solar minimum. This study showed that the bow shock is located notably closer to Venus at solar minimum, when compared to studies conducted at solar maximum.…”

Section: Slow/thermal Driftmentioning

confidence: 99%

Exploring planetary magnetic environments using magnetically unclean spacecraft: a systems approach to VEX MAG data analysis

et al. 2011

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Abstract. In situ measurements of the magnetic field are vital to the study of many fundamental problems in planetary research. Therefore the magnetometer experiment is a key element of the payload of Venus Express. In addition to the interaction of the solar wind with Venus, these measurements are crucial for the study of atmospheric escape and detection of lightning. However, the methodology for the magnetic field measurements had to be different to the traditional approach, because Venus Express is not a magnetically clean spacecraft. A technique based on two-point simultaneous measurements of the magnetic field and systems identification software is used to separate the natural magnetic field from the spacecraft generated interference. In this paper an overview of the techniques developed to separate these two field types and the results achieved for 1 Hz Venus Express data are presented. Previous publications suggest that the resulting Venus Express cleaned data is of comparable quality to measurements made from onboard magnetically clean spacecraft (Zhang et al., 2008a, b;Slavin et al., 2009).

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Initial Venus Express magnetic field observations of the Venus bow shock location at solar minimum

Cited by 79 publications

References 10 publications

Mirror mode waves in Venus's magnetosheath: solar minimum vs. solar maximum

Mirror mode waves in Venus's magnetosheath: solar minimum vs. solar maximum

Comparison between magnetic coplanarity and MVA methods in determining the normal of Venusian bow shock

Exploring planetary magnetic environments using magnetically unclean spacecraft: a systems approach to VEX MAG data analysis

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