The shape of the Venusian bow shock at solar minimum and maximum: Revisit based on VEX observations

Lun, Shan; Lu, Quanming; Mazelle, C.; Huang, Can; Zhang, Tielong; Wu, Mingyu; Gao, Xinliang; Wang, Shui

doi:10.1016/j.pss.2015.01.004

Cited by 31 publications

(45 citation statements)

References 30 publications

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“…Hence, it is not so surprising that the terminator shock distances observed by VEX are quite different. According to VEX measurements the bow shock is located further out during solar maximum, but the terminator shock distance of 2.14 R V is comparable with the solar minimum value determined by PVO (Shan et al 2015). However, the solar maximum experienced by VEX was very weak, as inferred from the F10.7 flux and sunspot number, and the solar minimum extremely long and weak.…”

Section: Location and Structure Of The Bow Shockmentioning

confidence: 55%

“…However, the solar maximum experienced by VEX was very weak, as inferred from the F10.7 flux and sunspot number, and the solar minimum extremely long and weak. VEX observations show that the terminator shock distance changes from 2.08 to 2.14 R V and the subsolar shock distance from 1.36 to 1.46 R V during the solar cycle in the model used by Shan et al (2015).…”

Section: Location and Structure Of The Bow Shockmentioning

confidence: 99%

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Solar Wind Interaction and Impact on the Venus Atmosphere

et al. 2017

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Venus has intrigued planetary scientists for decades because of its huge contrasts to Earth, in spite of its nickname of "Earth's Twin". Its invisible upper atmosphere and space environment are also part of the larger story of Venus and its evolution. In 60s to 70s, several missions (Venera and Mariner series) explored Venus-solar wind interaction regions. They identified the basic structure of the near-Venus space environment, for example, existence of the bow shock, magnetotail, ionosphere, as well as the lack of the intrinsic magnetic field. A huge leap in knowledge about the solar wind interaction with Venus was made possible by the 14-year long mission, Pioneer Venus Orbiter (PVO), launched in 1978. More recently, ESA's probe, Venus Express (VEX), was inserted into orbit in 2006, operated for 8 years.Owing to its different orbit from that of PVO, VEX made unique measurements in the polar and terminator regions, and probed the near-Venus tail for the first time. The near-tail hosts dynamic processes that lead to plasma energization. These processes in turn lead to the loss of ionospheric ions to space, slowly eroding the Venusian atmosphere. VEX carried an ion spectrometer with a moderate mass-separation capability and the observed ratio of the escaping hydrogen and oxygen ions in the wake indicates the stoichiometric loss of water from Venus. The structure and dynamics of the induced magnetosphere depends on the prevailing solar wind conditions. VEX studied the response of the magnetospheric system on different time scales. A plethora of waves was identified by the magnetometer on VEX; some of them were not previously observed by PVO. Proton cyclotron waves were seen far upstream of the bow shock, mirror mode waves were observed in magnetosheath and whistler mode waves, possibly generated by lightning discharges were frequently seen. VEX also encouraged renewed numerical modeling efforts, including fluid-type of models and particle-fluid hybrid type of models, describing the plasma interaction on scales ranging from ion gyro radius to the entire induced magnetosphere. In this review article, we review what has been found from space physics measurements around Venus (from the solar wind down to the ionopause), with a particular emphasis on updated results since the Venus Express mission. We conclude the article by a short discussion on the remaining open scientific questions and the future of this field.

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Section: Location and Structure Of The Bow Shockmentioning

confidence: 55%

Section: Location and Structure Of The Bow Shockmentioning

confidence: 99%

Solar Wind Interaction and Impact on the Venus Atmosphere

et al. 2017

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“…This is also the reason for the increase in ion cyclotron waves upstream of Venus's bow shock as shown by Delva et al (2015). The increased ionization also causes the bow shock and ionosphere to move outward (Alexander and Russell, 1985;Shan et al, 2015), albeit Slavin et al (1980) argue that charge exchange at low altitudes near the ionopause is causing the shock to move closer at solar minimum. The MM wave effect is to balance magnetic pressure B 2 /2µ 0 and plasma pressure n i k B T ⊥,i , and the instability is driven by the temperature anisotropy of the ions (see Eq.…”

Section: Discussionmentioning

confidence: 97%

“…Delva et al, 2015), and thus the bow shock and ionopause move outward from Venus (e.g. Alexander and Russell, 1985;Shan et al, 2015).…”

Section: Statistical Studymentioning

confidence: 99%

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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“…The statistical results, see Table , also show that there are magnetic north‐south asymmetries in all the regions, and the scales of the magnetic north‐south asymmetries are (0.114 ± 0.056) R V or 5% in the near‐subsolar BS, (0.148 ± 0.107) R V or 7% in the terminator BS, and (0.181 ± 0.106) R V or 9% in the tail BS; here we take the average shock terminator distance as 2.098 R V [ Chai et al , ]. These asymmetries may at least partly account for the large deviation of BS location from the averaged shape recently showed by Shan et al [].…”

Section: Sza‐dependent Asymmetriesmentioning

confidence: 99%

Solar zenith angle‐dependent asymmetries in Venusian bow shock location revealed by Venus Express

et al. 2015

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It has been long known that the Venusian bow shock (BS) location is asymmetric from the observations of the long‐lived Pioneer Venus Orbiter mission. The Venus Express (VEX) mission crossed BS near perpendicularly not only in the terminator region but also in the near‐subsolar and tail regions. Taking the advantage of VEX orbit geometry, we examined a large data set of BS crossings observed during the long‐lasting solar minimum between solar cycles 23 and 24 and found that the Venusian BS asymmetries exhibit dependence of solar zenith angle. In the terminator and tail regions, both the magnetic pole‐equator and north‐south asymmetries are observed in Venusian BS location, which is similar to the Pioneer Venus Orbiter (PVO) observation near terminator. However, in the near‐subsolar region, only the magnetic north‐south is observed; i.e., the BS shape is indented inward over magnetic south pole and bulged outward over magnetic north pole. The absence of the magnetic pole‐equator asymmetry in the near‐subsolar region suggests that the magnetic pole‐equator asymmetry is mainly caused by the asymmetric wave propagation rather than the ion pickup process. The evident magnetic north‐south asymmetry in solar minimum, which is not observed by PVO, suggests that even during the low long‐lasting solar minimum, the ion pickup process is very important in Venusian space environment.

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The shape of the Venusian bow shock at solar minimum and maximum: Revisit based on VEX observations

Cited by 31 publications

References 30 publications

Solar Wind Interaction and Impact on the Venus Atmosphere

Solar Wind Interaction and Impact on the Venus Atmosphere

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

Solar zenith angle‐dependent asymmetries in Venusian bow shock location revealed by Venus Express

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