The Mars Ion and Neutral Particle Analyzer (MINPA) is one of the three scientific instruments onboard the Tianwen-1 orbiter to investigate the Martian space environment. During Tianwen-1’s transfer orbit to Mars, the MINPA was switched on to measure the solar wind ions. Here, we present the first results of the MINPA observations in the solar wind. During cruise, nearly half of the MINPA ion field-of-view (FOV) was blocked by the lander capsule; thus only the solar-wind ions with azimuthal speeds pointing towards the unblocked FOV sectors could be detected. We perform a detailed comparison of the MINPA’s solar wind observations with data from Earth-based missions when MINPA reached its count-rate peak, finding a general consistency of the ion moments between them. The blocking effect due to the lander is evaluated quantitatively under varying solar-wind velocity conditions. Despite the blocking effect, the MINPA’s solar wind measurements during the transfer orbit suggest a good performance.
We present preliminary results of a new global Magnetohydrodynamics (MHD) simulation model of the Jovian magnetosphere. The model incorporates mass loading from Jupiter's satellite Io, the planet's fast corotation, and electrostatic coupling between its magnetosphere and ionosphere (M-I coupling). The basic configuration of the Jovian magnetosphere including the equatorial plasma flow pattern, the corotation enforcement current system, and the field aligned currents (FACs) in the ionosphere are presented under an antiparallel interplanetary magnetic field (IMF) condition. The simulation model results for equatorial density and pressure profiles are consistent with results from data-based empirical models. It is also found that there are similarities between the FACs distribution in the ionosphere and the observed aurora features, showing the potential application of the simple ionospheric model to the complicated M-I coupling. This model will help deepen our understanding of the global dynamics of the Jovian magnetosphere.
We report multi-spacecraft observations of ULF waves from Van Allen Probes (RBSP), Magnetospheric Multiscale (MMS), Time History of Events and Macroscale Interactions during Substorm (THEMIS), and Geostationary Operational Environmental Satellites (GOES). On August 31, 2015, global-scale poloidal waves were observed in data from RBSP-B, GOES and THEMIS from L=4 to L=8 over a wide range of magnetic local time (MLT). The polarization states varied towards purely poloidal polarity. In two consecutive orbits over 18 hours, RBSP-A and RBSP-B recorded gradual variation of the polarization states of the poloidal waves; the ratio (|Ba|/|Br|) decreased from 0.82 to 0.13. After the variation of polarization states, the poloidal ULF waves became very purely poloidal waves, localized in both L and MLT. We identify the poloidal wave as second harmonic mode with a large azimuthal wave number (m) of –232. From RBSP particle measurements we find evidence that the high-m poloidal waves during the polarization variations were powered by inward radial gradients and bump-on-tail ion distributions through the N=1 drift-bounce resonance. Most of the time, the dominant free energy source was inward radial gradients, compared with the positive gradient in the energy distribution of the bump-on-tail ion distributions.