Some problems in coupling solar activity to meteorological phenomena

The development of a theory of coupling of solar activity to meteorological phenomena is hindered by the difficulties of devising a mechanism that can modify the behavior of the troposphere while employing only a negligible amount of energy compared with the energy necessary to drive the normal meteorological system, and determining how such a mechanism can effectively couple some relevant magnetospheric process into the troposphere in such a way as to influence the weather. A clue to the nature of the interaction between the weather and solar activity might be provided by the fact that most solar activity undergoes a definite 11-yr cycle, and meteorological phenomena undergo either no closely correlated variation, an 11-yr variation, or a 22-yr variation

Evidence for short cooling time in the Io plasma torus

We present empirical evidence for a radiative cooling time for the Io plasma torus that is about a factor of ten less than presently accepted values. We show that brightness fluctuations of the torus in the extreme ultraviolet (EUV) at one ansa are uncorrelated with the brightness at the other ansa displaced in time by five hours, either later or earlier. Because the time for a volume of plasma to move from one ansa to the other is only five hours, the cooling time must be less than this transport time in order to wipe out memory of the temperatures between ansae. Most (∼80–85%) of the EUV emission comes from a narrow (presumably ribbon‐like) feature within the torus. The short cooling time we observe is compatible with theoretical estimates if the electron density in the ribbon is ∼10^4/cm^3. The cooling time for the rest of the torus (which radiates the remaining 15–20% of the power) is presumably consistent with the previously derived 20‐hour values. A nearly‐continuous heating in both longitude and time is needed to maintain the EUV visibility of the torus ribbon—a requirement not satisfied by presently available theories

James B. Macelwane Award to Dan McKenzie, Gerald Schubert and Vytenis M. Vasyliunas

To those earth scientists who have followed the revolutionary development of plate tectonics from its dawning, it may come as a surprise that Dan McKenzie can have done so much and still be young enough to qualify for the James B. Macelwane Award. Nonetheless it is so. He was born on February 21, 1941. He received his advanced education at King's College, Cambridge University, and was awarded a B.A. in 1963 and a Ph.D. in 1966. He became a Fellow of the college in 1965. He was fortunate enough to be a student in Edward Bullard's Department of Geodesy and Geophysics just in those exciting years when the validity of sea floor spreading was demonstrated. McKenzie was one of the first to realize the broader implications of the computer fitting of continents by Bullard and others which assumed that the drifting crust is rigid

Trajectory model simulations of ozone (O<sub>3</sub>) and carbon monoxide (CO) in the lower stratosphere

A domain-filling, forward trajectory model originally developed for simulating stratospheric water vapor is used to simulate ozone (O3) and carbon monoxide (CO) in the lower stratosphere. Trajectories are initialized in the upper troposphere, and the circulation is based on reanalysis wind fields. In addition, chemical production and loss rates along trajectories are included using calculations from the Whole Atmosphere Community Climate Model (WACCM). The trajectory model results show good overall agreement with satellite observations from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) in terms of spatial structure and seasonal variability. The trajectory model results also agree well with the Eulerian WACCM simulations. Analysis of the simulated tracers shows that seasonal variations in tropical upwelling exerts strong influence on O3 and CO in the tropical lower stratosphere, and the coupled seasonal cycles provide a useful test of the transport simulations. Interannual variations in the tracers are also closely coupled to changes in upwelling, and the trajectory model can accurately capture and explain observed changes during 2005–2011. This demonstrates the importance of variability in tropical upwelling in forcing chemical changes in the tropical lower stratosphere

Winds, B-Fields, and Magnetotails of Pulsars

We investigate the emission of rotating magnetized neutron stars due to the acceleration and radiation of particles in the relativistic wind and in the magnetotail of the star. We consider that the charged particles are accelerated by driven collisionless reconnection. Outside of the light cylinder, the star's rotation acts to wind up the magnetic field to form a predominantly azimuthal, slowly decreasing with distance, magnetic field of opposite polarity on either side of the equatorial plane normal to the star's rotation axis. The magnetic field annihilates across the equatorial plane with the magnetic energy going to accelerate the charged particles to relativistic energies. For a typical supersonically moving pulsar, the star's wind extends outward to the standoff distance with the interstellar medium. At larger distances, the power output of pulsar's wind $\dot{E}_w$ of electromagnetic field and relativistic particles is {\it redirected and collimated into the magnetotail} of the star. In the magnetotail it is proposed that equipartition is reached between the magnetic energy and the relativistic particle energy. For such conditions, synchrotron radiation from the magnetotails may be a significant fraction of $\dot{E}_w$ for high velocity pulsars. An equation is derived for the radius of the magnetotail $r_m(z^\prime)$ as a function of distance $z^\prime$ from the star. For large distances $z^\prime$, of the order of the distance travelled by the star, we argue that the magnetotail has a `trumpet' shape owing to the slowing down of the magnetotail flow.Comment: 11 pages, 4 figures, accepted for publication in Ap

Spontaneous axisymmetry breaking of Saturn's external magnetic field

Saturn's magnetic field is remarkably axisymmetric. Its dipole axis is inclined by less than 0.2 deg with respect to its rotation axis. Rotationally driven convection of magnetospheric plasma breaks the axisymmetry of its external magnetic field. Field aligned currents transfer angular momentum from the planet to a tongue of outflowing plasma. This transfer slows the rate of rotation of the ionosphere relative to that of the underlying atmosphere. The currents are the source for the non-axisymmetric components of the field. The common rotation rates of these components and Saturn's kilometric radio (SKR) bursts is that of the plasma near the orbit of Enceladus, and by extension the rotation rate in the ionosphere to which this plasma is coupled. That rate tells us nothing about the rotation rate of Saturn's deep interior. Of that we remain ignorant. Magnetic perturbations with magnitudes similar to those observed by Cassini are produced for Mdot ~ 10^4 g/s, a value similar to estimates for the rate of production of plasma from Saturn's E-ring. Enhancement of the SKR occurs in a narrow range of longitudes where the tip of the outgoing plasma stream connects to the auroral ionosphere via field lines that are bowed outwards by currents that supply the plasma's centripetal acceleration. (abridged)Comment: 24 pages, 2 figures, submitted to JGR

Simultaneous, in situ measurements of OH, HO_2, O_3, and H_2O: A test of modeled stratospheric HO_x chemistry

Simultaneous, in situ measurements of OH, HO_2, H_2O, and O_3 from 37–23 km are reported. The partitioning between OH and HO_2 and the total HO_x concentration are compared with expected steady-state values. The ratio of HO_2 to OH varies from less than 2 at 36 km to more than 3 at 25 km; in the lower stratosphere this ratio is nearly a factor of two less than predicted. The data are used to calculate HO_x production and loss rates. The measured HOx mixing ratio is consistent with production dominated by the reaction of O(1D) with H_2O, and loss controlled by NO_y below 28 km and HO_x above 30 km. The steady-state concentration of H_2O_2 is inferred from the measured HO_2 concentration and calculated photolysis rate. The maximum H_2O_2 mixing ratio (at 33 km) is predicted to be less than 0.2 ppb

The Jovian hydrogen bulge: Evidence for co-rotating magnetospheric convection

The hydrogen bulge is a feature in Jupiter's upper atmosphere that co-rotates with the planetary magnetic field (i.e. the hydrogen bulge is fixed in System III coordinates). It is located approximately 180[deg] removed in System III longitude from the active sector, which has been identified as the source region for Jovian decametric radio emission and for release of energetic electrons into interplanetary space. According to the magnetic-anomaly model, the active sector is produced by the effect of the large magnetic anomaly in Jupiter's northern hemisphere. On the basis of the magnetic-anomaly model, it has been theoretically expected for some time that a two-cell magnetospheric convection pattern exists within the Jovian magnetosphere. Because the convection pattern is established by magnetic-anomaly effects of the active sector, the pattern co-rotates with Jupiter. (This is in contrast to the Earth's two-cell convection pattern that is fixed relative to the Sun with the Earth rotating beneath it.) The sense of the convection is to bring hot magnetospheric plasma into the upper atmosphere in the longitude region of the hydrogen bulge. This hot plasma contains electrons with energies of the order of 100keV that dissociate atmospheric molecules to produce the atomic hydrogen that creates the observed longitudinal asymmetry in hydrogen Lyman alpha emission. We regard the existence of the hydrogen bulge as the best evidence available thus far for the reality of the expected co-rotating magnetospheric convection pattern.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24466/1/0000741.pd

A New Model of Jupiter's Magnetic Field from Juno's First Nine Orbits

A spherical harmonic model of the magnetic field of Jupiter is obtained from vector magnetic field observations acquired by the Juno spacecraft during its first nine polar orbits about the planet. Observations acquired during eight of these orbits provide the first truly global coverage of Jupiter's magnetic field with a coarse longitudinal separation of ~45 deg between perijoves. The magnetic field is represented with a degree 20 spherical harmonic model for the planetary ("internal") field, combined with a simple model of the magnetodisc for the field ("external") due to distributed magnetospheric currents. Partial solution of the underdetermined inverse problem using generalized inverse techniques yields a model ("Juno Reference Model through Perijove 9") of the planetary magnetic field with spherical harmonic coefficients well determined through degree and order 10, providing the first detailed view of a planetary dynamo beyond Earth