TRESPASS FALL 1996 SCHEDULE

Date SPEAKER AFFILIATION TOPIC
9/19/96 Leslie Young Boston University Gravity Waves and the Galileo Spaceprobe
9/26/96 Roger Yelle Boston University Exploring the Solar System with Spacecraft: Scientific Problems and Plans for Cassini, DS1/NMP, and Campollion/Rosetta
10/3/96 Alan Rodger British Antarctic Survey Mountains and Valleys in the High Latitude F Region Ionosphere
10/10/96 Jack Gosling Los Alamos National Laboratory An Interplanetary View of Mass Ejections from the Sun
10/17/96 John Steinberg M.I.T. The Lunar Wake as seen by WIND
10/24/96 Jim Vickers Boston University An Evaluation of EUV Remote Sensing of the Ionosphere
10/31/96 Nelson Maynard Mission Research Corporation On Substorms in the Geotail
11/7/96 David Sibeck John Hopkins University Applied Physics Laboratory FTE's and the onset of Merging
11/14/96 Harlan Spence Boston Univerity "Fresh Insights on `Old' Magnetospheric Physics: New Results from the ISTP Program"
11/21/96 Stefano Livi Max Planck Institut fuer Aeronomie Solar wind access to the mid-Altitude Magnetosphere: Polar/CAMMICE MICS Observations
11/28/96 THANKSGIVING BREAK - -
12/5/96 - No Seminar -
12/12/96 AGU Practice Talks - -





DESCRIPTION



Leslie Young
Date: 9/19/96
Time: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

Gravity Waves and the Galileo Spaceprobe

The Atmospheric Structure Instrument on the Galileo spacecraft measured the temperature of Jupiter's atmosphere from a few nanobars to a few bars. Long-wavelength temperature oscillations are seen throughout the stratosphere and lower thermosphere. These are newly-discovered waves: the smaller waves seen in Jupiter's thermal profile from stellar occultations were not detected above the homopause. I will discuss the behavior of gravity waves in Jupiter's upper atmosphere, and the effect they have on Jupiter's thermal structure.
Jim Vickers
Date: 10/24/96
Time:3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

An Evaluation of EUV Remote Sensing of the Ionosphere

Abstract:
The extreme ultraviolet (EUV) dayglow spectrum of the Earth contains several emission features of O+, the dominant ion in the F2 region of the ionosphere. The brightest O+ feature is the allowed triplet transition occurring at 83.4 nm. Production of this triplet occurs predominantly in the lower thermosphere through photoionization of atomic oxygen. Some of the 83.4 nm photons escape the optically-thin lower thermosphere and travel upward into the optically-thick F2 region, where they resonantly scatter with O+ ions before escaping from the region or becoming absorbed by the neutral atmosphere. This research presents an evaluation of the EUV remote sensing of the ionosphere using the OII 83.4 nm emission triplet; specifically, it addresses how accurately the ionospheric profile can be inferred through optical techniques. The research is broken into an experimental section, in which the solar EUV irradiance is measured from space using a novel gas ionization technique, and a theoretical section, in which a new matrix-based radiative transfer (RT) model is developed that allows for the inversion of ionospheric densities from measurements of the OII 83.4 nm radiation field. The subjects are closely related as results show that simultaneous and accurate measurements of the solar EUV irradiance and the 83.4 nm radiation field are required to accurately invert ionospheric profiles. The assumptions that are made in the inversion process - and their implications - are discussed in terms of the retrieved ionospheric profiles. A method is presented for calculating the perceived inversion accuracy in the presence of measurement uncertainties. A thorough discussion is made of the errors affecting the inversion routine. Examples are presented using modeled data and 83.4 nm data from the STP 78-1 spectrometer. Results indicate that an inversion accuracy of 50% can be achieved.

Name: Stefano Livi
Date: 11/21/96
Time: 3:45 p.m. in CAS 500
Affilitation: Max Planck Institut fuer Aeronomie

Solar wind access to the mid-Altitude Magnetosphere: Polar/CAMMICE MICS Observations


Abstract:
On May 29, 1996, the Polar spacecraft appeared to cross into an extended cusp or magnetosheath region. The region was characterized by intense fluxes of ions in the energy range 1-10 keV that had solar wind like ion composition and angular distributions that showed evidence of flows. These ion data are combined with energetic proton observations from Polar and plasma observations from the HEO 95-034 and DMSP satellites to examine the spatial extent and plasma characteristics of this region. The ion composition is consistent with expected solar wind composition. The combined spacecraft observations indicate a considerablespatial extent for the observed region, which may be produced by northward IMF interacting with the northern cusp.