|Description||2018 Fall Graduate Colloquium Series|
Jupiter’s Magnetosphere and Aurorae Observed by the Juno Spacecraft during its First Polar Orbits
On August 5th, 2011 The Juno spacecraft left the confines of earth and began its journey toward the largest gas giant of our solar system. Five years later Nasa received confirmation that the satellite had reached it’s final destination, Jupiter. Juno’s designated capture orbit placed it in prime position to observe the poles of the planet and therefore the aurorae borealis known to take place there. The orbit also included passages through the planet’s intense inner radiation belts. Passing underneath the most sever areas of radiation, the craft came as close as 4,000 kilometers from the cloud tops below. During these transits, Juno gathered information concerning Jupiter’s magnetosphere, high velocity particle impacts on the craft, and the majestic aurorae. This presentation will cover data gathered during the first several of these orbits while discussing the variations of the observed events from their terrestrial analogues.
Connerney, J.E.P., et al. “Jupiter’s Magnetosphere and Aurorae Observed by the Juno Spacecraft during Its First Polar Orbits.” Science, vol. 356, no. 6340, 26 May 2017, pp. 826–832., doi:10.1126/science.aam5928.
Sudip Jang Bahadur Gurung
Enhanced Nonlinear Refractive Index in Epsilon
Near Zero Materials
The optical properties of a medium could be described by the dielectric permittivity (ε) and the refractive index (n), where ε reflects on how the polarization is induced upon application of an electromagnetic wave, while n determines how the optical phase develops as optical wave propagates in the optical medium with associated momentum k and energy ħω. Optical epsilon-near-zero (ENZ) material possesses the permittivity |ε | → 0 and the phase velocity of optical wave becomes very large while the group velocity is slowing down signiﬁcantly, owing to the relation between refractive index and permittivity, . For nonlinear optical processes, the optical Kerr nonlinearity is strongly enhanced in the ENZ spectral range because of the unique optical material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a six-fold increase of the Kerr nonlinear refractive index (n2) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.
Reference: Caspani, L.; Kaipurath, R.; Clerici, M.; Ferrera, M.; Roger, T.; Kim, J.; Kinsey, N.; Pietrzyk, M.; Di Falco, A.; Shalaev, V. M., Enhanced nonlinear refractive index in ε-near-zero materials. Physical review letters 2016, 116 (23), 233901
For more information contact: Dr. Howard Lee, 254-710-2277