Interplanetary Coronal Mass Ejections from MAVEN Orbital Observations at Mars

The measurements from the Mars Atmosphere and Volatile EvolutioN spacecraft, in orbit around Mars, are utilized to investigate interplanetary coronal mass ejections (ICMEs) near 1.52 au. We identify 24 ICMEs from 2014 December 6 to 2019 February 21. The ICME list is used to examine the statistical properties of ICMEs. On average, the magnetic field strength of 5.99 nT in ICMEs is higher than that of 5.38 nT for stream interaction regions (SIRs). The density of 5.27 cm−3 for ICMEs is quite comparable to that of 5.17 cm−3 for SIRs, the velocity of 394.7 km s−1 for ICMEs is slightly lower than that of 432.8 km s−1 for SIRs, and the corresponding dynamic pressure of 1.34 nPa for ICMEs is smaller than that of 1.50 nPa for SIRs. Using existing databases of ICMEs at 1 au for the same time period, we compare ICME average properties at 1.52 au with those at 1 au. The averages of the characteristic quantities decrease by a factor of 1.1–1.7 from 1 to 1.52 au. In addition, we analyze an unusual space weather event associated with the ICME on 2015 March 9–10, and propose that the extremely strong dynamic pressure with a maximum of ∼18 nPa on March 8 is caused by the combined effects of the enhanced density inside a heliospheric plasma sheet (HPS), the compression of the HPS by the forward shock, and the high velocity of the sheath ahead of the ICME.

Solar Wind ∼0.15–1.5 keV Electrons around Corotating Interaction Regions at 1 au

Here we present a statistical study of the ∼0.15–1.5 keV suprathermal electrons observed in uncompressed/compressed slow and fast solar wind around 59 corotating interaction regions (CIRs) with good measurements by Wind 3DP from 1995 through 1997. For each of these CIRs, we fit the strahl and halo energy spectra at ∼0.15–1.5 keV to a Kappa function with a Kappa index κ and kinetic temperature T eff. We find that the ∼0.15–1.5 keV strahl electrons behave similarly in both slow and fast wind: the strahl number density n s positively correlates with the solar wind electron temperature T e and interplanetary magnetic field magnitude ∣B∣, while the strahl pitch angle width Θ s decreases with the solar wind speed V sw. These suggest that the strahl electrons are generated by a similar/same process at the Sun in both slow and fast wind that produces these correlations, and the scattering efficiency of strahl in the interplanetary medium (IPM) decreases with V sw. The ∼0.15–1.5 keV halo electrons also behave similarly in both slow and fast wind: the halo parameter positively correlates with the corresponding strahl parameter, and the halo number density n h positively correlates only with T e . These indicate that the halo formation process in the IPM retains most of the strahl properties, but it erases the relationship between n s and ∣B∣. In addition, κ in compressed wind distributes similarly to that in uncompressed wind, for both the strahl and halo. It shows that CIRs at 1 au are not a significant/effective acceleration source for the strahl and halo.

Direct Interaction of ATP7B and LC3B Proteins Suggests a Cooperative Role of Copper Transportation and Autophagy

Macroautophagy/autophagy plays an important role in cellular copper clearance. The means by which the copper metabolism and autophagy pathways interact mechanistically is vastly unexplored. Dysfunctional ATP7B, a copper-transporting ATPase, is involved in the development of monogenic Wilson disease, a disorder characterized by disturbed copper transport. Using in silico prediction, we found that ATP7B contains a number of potential binding sites for LC3, a central protein in the autophagy pathway, the so-called LC3 interaction regions (LIRs). The conserved LIR3, located at the C-terminal end of ATP7B, was found to directly interact with LC3B in vitro. Replacing the two conserved hydrophobic residues W1452 and L1455 of LIR3 significantly reduced interaction. Furthermore, autophagy was induced in normal human hepatocellular carcinoma cells (HepG2) leading to enhanced colocalization of ATP7B and LC3B on the autophagosome membranes. By contrast, HepG2 cells deficient of ATP7B (HepG2 ATP7B−/−) showed autophagy deficiency at elevated copper condition. This phenotype was complemented by heterologous ATP7B expression. These findings suggest a cooperative role of ATP7B and LC3B in autophagy-mediated copper clearance.

Turbulent Magnetogenesis in a Collisionless Plasma

We demonstrate an efficient mechanism for generating magnetic fields in turbulent, collisionless plasmas. By using fully kinetic, particle-in-cell simulations of an initially nonmagnetized plasma, we inspect the genesis of magnetization, in a nonlinear regime. The complex motion is initiated via a Taylor–Green vortex, and the plasma locally develops strong electron temperature anisotropy, due to the strain tensor of the turbulent flow. Subsequently, in a domino effect, the anisotropy triggers a Weibel instability, localized in space. In such active wave–particle interaction regions, the seed magnetic field grows exponentially and spreads to larger scales due to the interaction with the underlying stirring motion. Such a self-feeding process might explain magnetogenesis in a variety of astrophysical plasmas, wherever turbulence is present.

Thermostability-based binding assays reveal complex interplay of cation, substrate and lipid binding in the bacterial DASS transporter, VcINDY.

The divalent anionsodium symporter (DASS) family of transporters (SLC13 family in humans) are key regulators of metabolic homeostasis, disruption of which results in protection from diabetes and obesity, and inhibition of liver cancer cell proliferation. Thus, DASS transporter inhibitors are attractive targets in the treatment of chronic, age-related metabolic diseases. The characterisation of several DASS transporters has revealed variation in the substrate selectivity and flexibility in the coupling ion used to power transport. Here, using the model DASS co-transporter, VcINDY from Vibrio cholerae, we have examined the interplay of the three major interactions that occur during transport: the coupling ion, the substrate, and the lipid environment. Using a series of high-throughput thermostability-based interaction assays, we have shown that substrate binding is Na+-dependent; a requirement that is orchestrated through a combination of electrostatic attraction and Na+-induced priming of the binding site architecture. We have identified novel DASS ligands and revealed that ligand binding is dominated by the requirement of two carboxylate groups in the ligand that are precisely distanced to satisfy carboxylate interaction regions of the substrate binding site. We have also identified a complex relationship between substrate and lipid interactions, which suggests a dynamic, regulatory role for lipids in VcINDY’s transport cycle.

Direct Interaction of ATP7B and LC3B Proteins Suggests a Cooperative Role of Copper Transportation and Autophagy

Macroautophagy/autophagy plays an important role in cellular copper clearance. The means by which the copper metabolism and autophagy pathways interact mechanistically is vastly unexplored. Dysfunctional ATP7B, a copper-transporting ATPase, is involved in the development of monogenic Wilson disease, a disorder characterized by disturbed copper transport. Using in silico prediction, we found that ATP7B contains a number of potential binding sites for LC3, a central protein in autophagy pathway, so-called LC3 interaction regions (LIRs). The conserved LIR3, located at the C-terminal end of ATP7B, was found to directly interact with LC3B in vitro. Replacing the two conserved hydrophobic residues W1452 and L1455 of LIR3 significantly reduced interaction. Furthermore, autophagy was induced in normal human hepatocellular carcinoma cells (HepG2) leading to enhanced colocalization of ATP7B and LC3B on the autophagosome membranes. By contrast, HepG2 cells deficient of ATP7B (HepG2 ATP7B-/-) showed autophagy deficiency at elevated copper condition. This phenotype was complemented by heterologous ATP7B expression. These findings suggest a cooperative role of ATP7B and LC3B in autophagy-mediated copper clearance.

Earth-affecting solar transients: a review of progresses in solar cycle 24

This review article summarizes the advancement in the studies of Earth-affecting solar transients in the last decade that encompasses most of solar cycle 24. It is a part of the effort of the International Study of Earth-affecting Solar Transients (ISEST) project, sponsored by the SCOSTEP/VarSITI program (2014–2018). The Sun-Earth is an integrated physical system in which the space environment of the Earth sustains continuous influence from mass, magnetic field, and radiation energy output of the Sun in varying timescales from minutes to millennium. This article addresses short timescale events, from minutes to days that directly cause transient disturbances in the Earth’s space environment and generate intense adverse effects on advanced technological systems of human society. Such transient events largely fall into the following four types: (1) solar flares, (2) coronal mass ejections (CMEs) including their interplanetary counterparts ICMEs, (3) solar energetic particle (SEP) events, and (4) stream interaction regions (SIRs) including corotating interaction regions (CIRs). In the last decade, the unprecedented multi-viewpoint observations of the Sun from space, enabled by STEREO Ahead/Behind spacecraft in combination with a suite of observatories along the Sun-Earth lines, have provided much more accurate and global measurements of the size, speed, propagation direction, and morphology of CMEs in both 3D and over a large volume in the heliosphere. Many CMEs, fast ones, in particular, can be clearly characterized as a two-front (shock front plus ejecta front) and three-part (bright ejecta front, dark cavity, and bright core) structure. Drag-based kinematic models of CMEs are developed to interpret CME propagation in the heliosphere and are applied to predict their arrival times at 1 AU in an efficient manner. Several advanced MHD models have been developed to simulate realistic CME events from the initiation on the Sun until their arrival at 1 AU. Much progress has been made on detailed kinematic and dynamic behaviors of CMEs, including non-radial motion, rotation and deformation of CMEs, CME-CME interaction, and stealth CMEs and problematic ICMEs. The knowledge about SEPs has also been significantly improved. An outlook of how to address critical issues related to Earth-affecting solar transients concludes this article.

Solar Rotation Multiples in Space-Weather Effects

The solar rotation period is the most prominent mid-term periodicity in the temporal behaviour of solar, heliospheric, and geomagnetic parameters. It is also a cause of the repeatedly appearing geomagnetic storms originating from the corotating interaction regions (CIRs). Since geomagnetic CIR-driven storms have a natural periodic character, and geomagnetic storms impact energy infrastructure via geomagnetically induced currents, it is of interest whether this periodic character is also noticeable in the temporal behaviour of electrical-grid failures (EGFs), which, at least to some extent, might be of solar origin.