Magnetic Field near Venus: Comparison between Solar Cycle 24 and Previous Cycles

• Published in: The Astrophysical journal Vol. 867; no. 2; pp. 129 - 137
• Main Authors: Chang, Qing, Xu, Xiaojun, Zhang, Tielong, Chai, Lihui, Wei, Yong, Xu, Qi
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 10-11-2018; IOP Publishing
• Subjects: Astrophysics; Field strength; Ionosphere; Magnetic fields; Magnetism; Magnetospheric-solar wind relationships; Magnetotails; Pioneer Venus 1 spacecraft; Planetary magnetic fields; Planetary magnetospheres; planets and satellites: individual (Venus); planets and satellites: magnetic fields; planets and satellites: terrestrial planets; Solar activity; Solar cycle; Solar magnetic field; Solar maximum; Solar minimum; Solar wind; Solar wind magnetic fields; Sun: activity; Venus; Venus Express (ESA)
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aae3e7

Solar Cycle 24 has been proven to be the weakest cycle in solar activity in the last century. So far, most of the evidence has been presented near Earth at 1 au. In this study, we statistically studied the magnetic field of the solar wind near Venus and the induced magnetosphere of Venus using Pioneer Venus Orbiter (PVO) and Venus Express (VEX) observations. Our study provides fundamental and comparative results between different solar phases of Solar Cycle 24 at 0.72 au. The solar wind magnetic field strength near Venus shows a strongly correlated variation with solar activities. While the solar wind magnetic field direction, indicated by the Bx component ratio, is almost the same in different solar phases of the same cycle. It is significantly different between Cycle 24 and previous cycles. The magnetic field strength of the Venusian-induced magnetosphere is also closely correlated to solar activities. It is strongest at solar maximum and weakest at solar minimum. Observations from PVO and VEX clearly show that the magnetic barrier of the Venusian-induced magnetosphere is much weaker in Cycle 24 than in previous cycles. But the average magnetic fields of the ionosphere and the magnetotail are stronger in Cycle 24.