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Sub‐ion magnetic holes are rich in the terrestrial plasma sheet and magnetosheath. Here, we statistically investigate 60 sub‐ion magnetic holes in the solar wind at 1 AU using the high‐resolution data measured by the Magnetospheric Multiscale mission. We find that they are observed with a duration of 0.1 –0.5 s, and the lengths of their cross‐section are ~0.1 –0.6 ion gyroradius. These structures prefer to occur in the slow solar wind with a weak ambient magnetic field strength. They also prefer to occur in the marginally mirror stable or unstable environments. Electron vortices as well as an enhancement of the electron perpendicular temperature and electron fluxes at ~90° pitch angle tend to be observed inside some magnetic holes with a large ambient magnetic field strength. By contrast, there are no clearly observational electron vortices as well as the electron fluxes at ~90° pitch angle inside some magnetic holes with a weak ambient magnetic strength. The current density with a value of ~10 –50 nA/m2 reveals that the corresponding maximum electron velocity is <10 km/s inside some magnetic holes, lower than the level of the observational electron velocity noise, which prevents the detection of the weak electron vortex. We suggest that electron vortices exist inside all the sub‐ion magnetic holes in the solar wind. The generation of these sub‐ion magnetic holes can be explained by the electron magnetohydrodynamics soliton and the electron vortex magnetic hole. Key Points: Electron vortices are a common feature inside the sub‐ion magnetic hole in the solar wind at 1 AUThe magnetic holes prefer to occur in the marginally mirror stable and weak magnetic field strength environments during the slow solar windThe electron magnetohydrodynamics soliton and electron vortex magnetic hole are two potential generation mechanisms of the magnetic hole [ABSTRACT FROM AUTHOR]

Electron vortices are a key element in the sub‐ion magnetic hole. Here, we investigate the electron velocity inside two sub‐ion magnetic holes in the solar wind based on the Magnetospheric Multiscale (MMS) mission. We find that the observational electron velocities inside the magnetic holes are contributed by the combination of the electron diamagnetic (Ve,dia), E × B (Ve,E), magnetic gradient (Ve,▽B) and curvature (Ve,R) drifts. Ve,dia, Ve,▽B, and Ve,R are comparable, while Ve,E is very small inside the hole. The weak Ve,E could result from the electric field approximately perpendicular to the magnetic field inside the structure. The value of Ve,▽B + Ve,R is near 0; thus, Ve,dia is approximately equal to the observational electron velocity. The current density contributed by the electron diamagnetic, magnetic gradient and curvature drift motions is self‐consistent with the magnetic depression inside the hole, suggesting that these three electron drift motions play a crucial role in stabilizing the magnetic hole in the mirror‐stable astrophysical plasma environment. Key Points: Electron vortices exist in the sub‐ion‐scale magnetic holes in the solar windThe electron vortex is mainly contributed by the combination of the electron diamagnetic, magnetic gradient, and curvature driftsThe magnetic gradient and curvature drifts almost cancel each other out; thus, the electron vortex can be explained by the diamagnetic drift [ABSTRACT FROM AUTHOR]

We investigate the heavy ion density and velocity in the Venusian upper ionosphere near the North Pole, using the Ion Mass Analyzer, a part of the Analyzer of Space Plasmas and Energetic Atoms 4, together with the magnetic field instruments on Venus Express. The measurements were made during June–July 2014, covering the aerobraking campaign with lowered altitude measurements (~130 km). The plasma scale heights are ~15 km below 150‐km altitude and ~200 km at 150–400‐km altitude. A clear trend of dusk‐to‐dawn heavy ion flow across the polar ionosphere was found, with speeds of ~2–10 km/s. In addition, the flow has a significant downward radial velocity component. The flow pattern does not depend on the interplanetary magnetic field directions nor the ionospheric magnetization states. Instead, we suggest a thermal pressure gradient between the equatorial and polar terminator regions, induced by the decrease in density between the regions, as the dominant mechanism driving the ion flow. Plain Language Summary: We have calculated the ion density and velocities in the Venusian polar ionosphere using measurements from the Ion Mass Analyzer on board the Venus Express spacecraft. During June–July 2014 the periapsis was lowered to ~130 km, which allowed for measurements down to low altitudes of the ionosphere near the North Pole. The plasma scale heights are ~15 km below 150‐km altitude and ~200 km at 150–400 km, which is similar to what was found near the equatorial region by the Pioneer Venus mission. In addition, there is a clear trend of dusk‐to‐dawn flow, along the terminator, for the heavy ions. This is surprising, as a general flow from day‐to‐night is expected for the Venusian ionosphere due to the long nights and significant heating of the dayside upper atmosphere. The interplanetary magnetic field direction does not appear to affect the ion flow pattern. Instead, we propose a thermal pressure gradient as the dominant accelerating mechanism, induced by the decrease in density from the equator toward the pole. Key Points: A net dusk‐to‐dawn heavy ion flow across the polar region was found, with high speeds inside the collisional region of the ionosphereThe heavy ion flow pattern does not depend on the external interplanetary field directions or the magnetization state of the upper ionosphereWe suggest a thermal pressure gradient between the polar and equatorial terminator regions as an accelerating mechanism toward the pole [ABSTRACT FROM AUTHOR]

We investigate the characteristics of the magnetic flux rope in the Venusian ionosphere near the terminator observed by the Venus Express while previous works about flux rope by PVO are mainly in the subsolar region. The probability to observe the flux rope becomes larger as solar activity strengthens. A statistical work during solar maximum presents the following characteristics. (1) The flux ropes in the terminator region have a lower spatial occurrence compared with those in the subsolar region, and the spatial occurrence of the flux ropes is also getting smaller when altitude increases. (2) The scale size of the flux rope is larger in the terminator region than that in the subsolar region and becomes larger when altitude increases. (3) In the terminator region, the flux rope appears to have a quasi-horizontal orientation but with some cases can be vertical at low altitude. (4) The flux ropes in high solar zenith angle regions are confirmed to have a lower helicity compared with those in low solar zenith angle regions. [ABSTRACT FROM AUTHOR]

The interaction of CMEs with the solar wind can lead to the formation of interplanetary shocks. Ions accelerated at these shocks contribute to the solar energetic protons observed in the vicinity of the Earth. Recently a joint analysis of Venus Express (VEX) and STEREO data by Russell et al. (2009) have shown that the formation of strong shocks associated with Co-rotating Interaction Regions (CIRs) takes place between the orbits of Venus and the Earth as a result of coalescence of weaker shocks formed earlier. The present study uses VEX and Advanced Composition Explorer (ACE) data in order to analyse shocks associated with CMEs that erupted on 29 and 30 July 2007 during the solar wind conjunction period between Venus and the Earth. For these particular cases it is shown that the above scenario of shock formation proposed for CIRs also takes place for CMEs. Contradiction with shock formation resulting from MHD modelling is explained by inability of classical MHD to account for the role of wave dispersion in the formation of the shock. [ABSTRACT FROM AUTHOR]

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere2,3. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum. [ABSTRACT FROM AUTHOR]

The occurrence of lightning in a planetary atmosphere enables chemical processes to take place that would not occur under standard temperatures and pressures. Although much evidence has been reported for lightning on Venus, some searches have been negative and the existence of lightning has remained controversial. A definitive detection would be the confirmation of electromagnetic, whistler-mode waves propagating from the atmosphere to the ionosphere. Here we report observations of Venus’ ionosphere that reveal strong, circularly polarized, electromagnetic waves with frequencies near 100 Hz. The waves appear as bursts of radiation lasting 0.25 to 0.5 s, and have the expected properties of whistler-mode signals generated by lightning discharges in Venus’ clouds. [ABSTRACT FROM AUTHOR]