Department of Physics and Astronomy

University of Mississippi

Events

  • Tue
    21
    Feb
    2017
    4:00 pmLewis Hall 101

    Maarten Buijsman
    Division of Marine Science
    University of Southern Mississippi

    The Equatorial Pacific "Graveyard" for Semidiurnal Internal Tides: Incoherence or Dissipation?

    The jets in the equatorial Pacific Ocean of a realistically-forced global circulation model with a horizontal resolution of 1/12.5 degree yield a strong loss of phase coherence in semidiurnal internal tides that propagate equatorward from the French Polynesian Islands and Hawaii. This loss of coherence is determined with a baroclinic energy analysis, in which the semidiurnal-band terms are separated into coherent, incoherent, and cross terms. For time scales longer than a year the coherent energy flux approaches zero values at the equator, while the total flux is 500 W/m. The time-variability of the incoherent energy flux is compared with phase speed variability computed with the Taylor-Goldstein equations. The variability of monthly-mean Taylor-Goldstein phase speeds agrees well with the phase speed variability inferred from steric sea surface height phases extracted with a plane-wave fit technique. On monthly time scales, the loss of phase coherence in the equatorward beams from the French Polynesian Islands is attributed to the time variability in the sheared background flow associated with the jets and tropical instability waves. On an annual time scale, the effect of stratification variability is of equal or greater importance than the background flow is to the loss of coherence. The model simulation suggests that low-frequency jets do not noticeably enhance the dissipation of the internal tide, but merely decohere and scatter it. Thus, the apparent demise of coherent internal tides seen in satellite altimetry maps of the equatorial Pacific may be due to incoherence rather than dissipation.

  • Mon
    27
    Feb
    2017
    Thu
    02
    Mar
    2017
    9:00 a.m. - 5:00 p.m.Yerby Conference Center, University of Mississippi

    The “Strong Gravity and Binary Dynamics with Gravitational Wave Observations” workshop convenes Feb. 27 to March 2 in the Yerby Conference Center. The event is supported in part by Emanuele Berti’s National Science Foundation CAREER Award and by a Marie Sklodowska-Curie Research and Innovation Staff Exchange Action network, funded by the European Union’s FP7 program.

    “This network supports exchanges of gravity researchers among the participating nodes,” said Berti, associate professor of physics and astronomy. “In addition to Ole Miss, there are five nodes in Europe, one in in Japan and one in Canada. A dozen researchers will visit campus for a month before and after the workshop.”

    About 50 scientists representing some 30 research agencies and institutions of higher learning are scheduled to attend. Researchers will discuss several topics in the newborn field of gravitational-wave astronomy, including the astrophysics of compact binary populations, spin measurements in compact binaries, strong-field tests of Einstein’s theory of general relativity and how to look for hints of new gravitational physics beyond Einstein’s theory.

    For more about the workshop, visit http://www.phy.olemiss.edu/StronGBaD/. For more about the Department of Physics and Astronomy, go to http://physics.olemiss.edu/.

    Also see the article from Inside Ole Miss.