Abstract Neutrals ejected from Io's atmosphere are the source of many important structures of the jovian magnetosphere: they feed giant neutral clouds, which extend along Io's orbit and nebulae, which extend beyond 500 jovian radii. The neutral loss rate is casually claimed to be ∼1 ton/s, but the processes leading to this loss, their quantitative estimates, and the speed and direction of the ejected neutrals are poorly constrained. In this study, we focus on neutrals ejected by physical chemistry processes resulting from the interaction of the torus plasma interacting with the atmosphere. These processes include electron‐impact dissociative‐ionization and dissociation, symmetrical and asymmetrical charge exchange and ion recombination. Our approach is based on a prescribed atmospheric distribution of SO 2 , SO, S and O. We combine an MHD code to compute the plasma flow into the atmosphere and a Multi‐Species Physical Chemistry code to compute the plasma properties (electrons, SO 2 + , SO + , S + , S ++ , S +++ , O + , O ++ densities and temperatures) and reaction rates along flowlines. In this article, we focus on reactions that specifically produce neutrals and compute their ejection rates, their velocity distribution and ejection direction. Using simplifying assumptions about the atmosphere, the flow and properties of the torus plasma, we provide an upper limit of the neutrals lost by physical chemistry processes ∼1 ton/s, with a velocity distribution specific for each reaction ranging from 0 to 120 km/s. The dominant processes are in the order of importance: molecular ion charge exchange, electron‐impact dissociation and molecular ion dissociative‐recombination, the last of which is prevalent in Io's wake.
Abstract Under appropriate conditions, the activity of phosphofructokinase of skeletal muscle from frog and mouse is extremely sensitive to small changes in pH in the physiological range, a low pH decreasing the affinity of the enzyme for fructose 6-phosphate. It is concluded that shifts in intracellular pH are important in the regulation of phosphofructokinase, but that this effect makes interpretation of data from intact muscle quite difficult.
AbstractAuroral particle precipitation is the main source of ionization on the nightside, making it a critical factor in geospace physics. This magnetosphere‐ionosphere linkage directly contributes to, even controls, the nonlinear feedback within this coupled system. One study has dominated our understanding of this connection, presenting a pair of equations relating auroral particle precipitation to ionospheric Pedersen and Hall conductance, the famous Robinson formulas. This Commentary examines the history of the development and usage of the Robinson formulas and the recent studies exploring corrections and expansions to it. The conclusion is that more work needs to be done; the space physics research community should take up the task to develop improvements and enhancements to better quantify the connection of auroral precipitation to ionospheric conductance.
AbstractObservations of Saturn's magnetic field from July 2004 to December 2016 have been combined to allow a numerical calculation of ∇ × B throughout the magnetosphere, thus permitting the first global mapping of Saturn's currents in three dimensions. The azimuthal ring current Jϕ dominates the magnetospheric currents, peaking near the orbit of the moon Rhea and having a total magnitude of over 10 mega‐Amperes integrated within the L‐shell of Titan. In meridional cross section, the ring current has a teardrop shape rather than a block shape. Jϕ also has a noticeable local time asymmetry, being the largest in the midnight and dawn sectors. The meridional currents Jρ and Jz are smaller than the ring current by an order of magnitude; they flow radially outward near the equator and return at higher latitudes in a looping pattern reminiscent of Hadley cell atmospheric convection. There are two such loops: one in the northern hemisphere and one in the south, flowing in opposing directions. In the noon sector, a strong Jz current may indicate the dayside cusp.