TRESPASS SPRING 1996 SCHEDULE

DATE	SPEAKER	AFFILIATION	TOPIC
1/18/96	Nancy Crooker	Boston University	Big Picture: The Sun As A Source Of The Solar Wind And IMF: A Tutorial
1/25/96	Bryan Tinsley	U. of Texas at Dallas and LANL	Solar Wind Influence On The Global Electric Circuit And Relationship To Weather And Climate Change
2/1/96	Jules Aarons	Boston University	Big Picture: Trans-Ionospheric Radio Propagation-A Personal Path
2/8/96	Victor J. Pizzo	NOAA/SEC	Global Magnetic Structure Of The Quasi-Steady Solar Wind
2/15/96	George Siscoe	Boston University	Big Picture: Global Coherence Of The Magnetosphere
2/22/96	Ed Cliver	USAF Phillips Laboratory	Changing Paradigms In Solar-Terrestrial Physics
2/29/96	John Belcher	MIT	The Solar Wind And The Outer Heliosphere
3/7/96	SPRING BREAK	NO TRESPASSING
3/14/96	Michael Mendillo	Boston University	Big Picture: Ionospheric Physics Approaches The Millenium
3/21/96	Geoff Reeves	Los Alamos National Lab	The Michelin Guide To The Geosynchronous Energetic Particle Environment
3/28/96	Harlan Spence	Boston University	Big Picture: "The Magnetosphere from Pole to Pole" or "A Day in the Life of POLAR"
4/4/96	Jeff Hughes	Boston University	Big Picture: On The Magnetosphere
4/11/96	Marvin Geller	SUNY/Stony Brook	Some Recent UARS Research On Polar Stratospheric Chemistry And Mesosphere-Lower-Thermosphere Dynamics
4/18/96	Robert E. Johnson	University of Virginia	Plasma Bombardment Of The Icy Moons In The Outer Solar System
4/25/96	Supriya Chakrabarti	Boston University	Big Picture: UV Observations in Space Physics and Astrophysics: Challenges and Rewards
5/2/96	Robert Kerr	Boston University	Big Picture: Reconciling Observations With Geocoronal Theory: Implications For The Earth's Hydrogen Budget
5/9/96	Theodore Fritz	Boston University	Big Picture: Prelim: Significant New Results From ISTP/GGS

DESCRIPTION

Nancy Crooker

Date: 1/18/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

The Sun As A Source Of The Solar Wind And IMF: A Tutorial

WEB SITE
EMAIL: crooker@buasta.bu.edu
Telephone: 508-443-8559

Bryan Tinsley

Date: 1/25/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: University of Texas at Dallas and Los Alamos National Laboratory

Solar Wind Influence On The Global Electric Circuit And Relationship To Weather And Climate Change

The solar wind modulates the distribution of air-earth current density in the global electric circuit by several mechanisms:

Variations in the energy spectrum of the galactic cosmic ray flux during the 9-12 year solar cycle and during Forbush decreases, affecting the latitude distribution of atmospheric conductivity;
Changes in ionospheric potential at high magnetic latitudes, associated with ionospheric plasma convection and Interplanetary Magnetic Field changes;
A mechanism possibly involving changes in relativistic electron precipitation at mid latitudes, and related to solar wind velocity and IMF changes.

The measured atmospheric electrical responses are several times larger than can be accounted for theoretically. There are six independent data sets that relate changes in tropospheric dynamics to the above measured air-earth current density changes, on the decadal and daily timescales for northern and southern high latitude winters and the tropics. A hypothetical cloud microphysical mechanism will be discussed.

EMAIL:
Telephone: 214-883-2838

Jules Aarons

Date: 2/1/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

Trans-Ionospheric Radio Propagation-A Personal Path

For 50 years there have been radio scintillation observations in many regions of the earth. Using these observations, the author attempts a brief history of ionospheric fading studies from sources beyond the upper atmosphere. Variability of the energy from discrete radio stars was first noted in 1946 by UK and Australian scientists; relatively quickly they realized that the fluctuations were due to the scattering from irregularities at heights of 100 to over 400 km in the ionosphere. With the advent of satellite transmissions, irregularity development from various areas of the globe were studied. Phenomena which were identified included the discovery of the equatorial anomaly region as the primary source of microwave scintillation, polar cap effects as a function of sunspot cycle, and new means of characterizing auroral irregularities. In years of high solar flux, observations from polar and equatorial regions will experience deep fading at frequencies ranging from 150 MHz to 1600 MHz. Experiences will be recounted with using the scintillation data bank from global observatories to stave off some proposed systems. Fading of radio signals from satellites still plays a role in evaluating operational and proposed system effectiveness. The relevance of these studies to Global Positioning System users and users of proposed systems such as Iridium will be discussed.

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WEB SITE
EMAIL: aarons@buasta.bu.edu
Telephone: 617-353-2639

Victor J. Pizzo

Date: 2/8/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: NOAA/Space Environment Center

Global Magnetic Structure Of The Quasi-Steady Solar Wind

3-D MHD simulations of global, tilted-dipole solar wind flow patterns are analyzed to investigate the large-scale distribution of the interplanetary magnetic field. In the model, flow conditions near the Sun are chosen to provide a reasonable match to the interplanetary configuration prevailing during the recent north-south polar passage by Ulysses, i.e., a streamer belt inclined 10-30 degrees to the solar equator and speeds ranging from 325-800 km/s. Field lines all across the stream pattern are traced from 1 to 5 AU and beyond by following the motion of marker particles embedded in the flow. It is found that those field lines threading the core of the interaction region are subject to significant latitudinal and relative longitudinal displacement over this range of heliocentric distance. Thus, observations taken at a fixed latitude in the inner solar system sample, over the course of a solar rotation, field lines which connect to a range of latitudes in the outer heliosphere. Maps of the field line displacements are presented to help visualize these connections. The correspondence between this idealized picture and Ulysses observations of the global solar wind magnetic structure will be addressed.

EMAIL: vpizzo@vulcan.sel.noaa.gov
Telephone: 303-497-6608

George Siscoe

Date: 2/15/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

Global Coherence Of The Magnetosphere

Outline
I. Context:
  1. Era of BIG PICTURES
       ISTP-GEM-Space Weather
  2. Why models--plural?
       Field in pre-paradigmatic phase (Kennel point)
  3. Types of models
       Analogy to model rockets
  4. Advantage of consumer perspective
       True vs. false -> useful vs. unuseful
  5. Conflicts of interest
       The speaker is not disinterested
II. Content
  1. Desirable features in magnetospheric models
       A. Two-part chassis: head and tail
       B. External ventilation, magnetically semi-permeable
       C. Superstructure in force balance with solar wind
       D. IMF driven global convection with independent
          head and tail regulation
E. Seamless structural and electrical connection
          between mantle and LLBL
  2. Assembly: Parts list and suppliers
       A. Superstructure
            New design innovation: Independent current sheet &
            plasma sheet suspension
       B. Generator: Tailward convection
            Mantle, LLBL: Standard parts, recent splicing
       C. Loads: Earthward convection
            Magnetosphere-ionosphere coupling: Basic parts
            Magnetic storm rated: RCM standard
            Substorm rated: New design implementation of
                            current disruption activator
III. Assessment
  1. Strengths
       A. Superstructure, generator, and loads all integrated
          into a tight, neat electromechanical unit--
          a minimalist's dream
       B. Serviceable in most high energy applications
  2. Weaknesses
       A. Doesn't do well for northward IMF
       B. Missing cusp currents
       C. Missing explicit merging physics & geometry
       D. No role for ionospheric particles
  3. Markets
       A. The need for markets to advance models
       B. Need to foster and develop further the
          synoptic science market
       C. Ditto for the space weather market

WEB SITE
EMAIL: siscoe@buasta.bu.edu
Telephone: 617-353-7423

Ed Cliver

Date: 2/22/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: United States Air Force Phillips Laboratory

Changing Paradigms In Solar-Terrestrial Physics

The history of solar-terrestrial physics is reviewed beginning with the recognition by Sabine in 1852 that the then recently discovered 11-yr cycle in sunspots was also present in the record of geomagnetic disturbances. Almost from the start, the lack of detailed correspondence between solar activity and magnetic storms served as an engine to drive further research and provide insights on solar activity. These included Maunder's recognition of the 27-day solar rotation period in the geomagnetic record and Greaves and Newton's study which led to the identification of two distinct types of storms - recurrent and sporadic. During the 1930s and 1940s, the two basic storm types were associated with M-regions and flares, respectively. The M-regions remained mysterious until rocket flights and space missions (OSO and Skylab) during the early 1970s revealed them as coronal holes in the X-ray corona. These same space missions observed for the first time the coronal mass ejections (CMEs) that were recognized early on as the proximate cause of sporadic geomagnetic storms. It was still thought, however, that the flares propelled the CMEs. Over the course of two decades this presumed cause and effect relationship began to unravel resulting in the much discussed paradigm shift from flares to CMEs in solar-terrestrial physics that was both documented and furthered by Jack Gosling's "Solar Flare Myth" paper. Even more recently, a revision has been proposed to the commonly-held view that coronal holes by themselves are the long-sought M-regions.

EMAIL:
Telephone: 617-377-3975

John Belcher

Date: 2/29/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Massachusetts Institute of Technology

The Solar Wind And The Outer Heliospheres

The Voyager mission to the outer solar system has been one of the most successful unmanned space missions in the history of spaceflight. After the last of their planetary encounters in 1989, the two Voyager spacecraft have been headed out of the solar system on a new mission of discovery, the Voyager Interstellar Mission. Although presently well beyond the orbit of Pluto, both the Voyager 1 and 2 spacecraft are still immersed in the solar wind. The solar wind is the expanding outer atmosphere of the Sun, superheated to millions of degrees near the Sun, and as a result, flowing outward from the Sun at high speeds into the distant solar system. This wind from the Sun blows a bubble full of solar material in the surrounding interstellar medium (the interstellar medium is the material between the stars). The bubble itself is called the heliosphere, and the boundary of the bubble (separating solar from interstellar material) is known as the the heliopause. The goal of the Voyager Interstellar Mission is for the Voyager spacecraft to leave regions dominated by the Sun and move for the first time into true interstellar space. The distance to the boundary of interstellar space is thought to be about 100 Astronomical Units (AU). The Voyagers presently are roughly 55 AU from the Sun. The Voyager spacecraft should continue to return data until 2020 AD, at which time they will be more than 100 AU from the Sun, and hopefully making measurements in the local interstellar medium. We discuss present best estimates of the distance to the heliopause, the physical conditions in the outer heliosphere at the present location of the Voyager spacecraft, recent observations from HST bearing on the nature of the shocked interstellar medium beyond the heliopause, and other topics. Recent Voyager 2 solar wind data (a few days from real time) can be viewed on the Web at http://web.mit.edu/space/www/voyager.html

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WEB SITE
EMAIL: jwb@space.mit.edu
Telephone: 617-253-4285

Michael Mendillo

Date: 3/14/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

Ionospheric Physics Approaches The Millenium

By mid-20th Century, it was generally agreed that the ionosphere was definitely non-Chapman-like. Since then, the ionospheric physics community has struggled with the reasons why. This seminar will review the origins of the problems, describe state-of-the-art approaches in observations and modeling, and offer biased views on what is important and what might be achieved in the contexts of pure atmospheric science and applications to Space Weather.

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WEB SITE
EMAIL: mendillo@buasta.bu.edu
Telephone: 617-353-2629

Geoff Reeves

Date: 3/21/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Los Alamos National Laboratory

The Michelin Guide To The Geosynchronous Energetic Particle Environment

This talk will be an overview of the geosynchronous energetic particle environment. Geosynchronous orbit is populated by literally hundreds of commercial and military satellites including the satellites that provide daily weather images. Geosynchronous orbit is also an interesting region of space. It lies in a transition region between the inner magnetosphere that is dominated by the earth's internal magnetic field and the outer magnetosphere that is dominated by the interaction with the solar wind. Some of the processes that affect the energetic particle environment around geosynchronous orbit include solar energetic particle events, relativistic electron enhancements, and the effects of magnetospheric storms and substorms. This handy pocket guide will help you to decide what to see (and what to avoid) if you're ever visiting geosynchronous orbit.

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WEB SITE
EMAIL: reeves@lanl.gov
Telephone: 505-665-4414

Harlan Spence

Date: 3/28/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

"The Magnetosphere from Pole to Pole" or "A Day in the Life of POLAR"

With the successful launch of the POLAR spacecraft on February 24, 1996, the NASA Global Geospace Science (GGS) program reached its full complement of spacecraft. As the title suggests, the POLAR trajectory samples vast regions of the magnetosphere in one orbit (very approximately one day) and is thus an attractive platform for obtaining a global or "big" picture. The first thirty days of the mission have been filled with great excitement as each of the twelve main science packages have been activated and validated. The data thus far acquired are of extremely high quality and the promise for excellent scientific return is great. On 1 April (!) 1996, the POLAR mission will officially enter the analysis phase. As we enter this new phase of the mission, the GGS Science Team will be combining data from many ancillary sources, both from space and ground, with theory and modeling to unravel the global magnetospheric response to changing solar wind and interplanetary magnetic field conditions. These data will be central to a large portion of CSP research and graduate theses in the coming years. In order to raise group conciousness and to facilitate collaborative studies within the CSP, I will provide an overview of the POLAR mission profile and the POLAR instrumentation, with an emphasis of those data products obtained by the BU energetic charged particle sensor packages (Charge and Mass Magnetospheric Ion Composition Experiment - CAMMICE, and Comprehensive Energetic Particle and Pitch Angle Distribution experiment - CEPPAD). I will outline the science projects that are already underway by our energetic, energetic particle team, and, to the extent possible, promote your interest in new collaborations heretofore unimagined.

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WEB SITE
EMAIL: spence@bu.edu
Telephone: 617-353-7412

Jeff Hughes

Date: 4/4/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

On The Magnetosphere

This is the third in the series of "Big Picture Talks" that focuses on the terrestrial magnetosphere, following the seminars by George Siscoe and Harlan Spence earlier this semester. As a significant fraction of the student audience heard me lecture on the magnetosphere for the whole of last semester, I will take to heart the "broad brush" approach I was asked to adopt, and address myself to how I see my own and my students' current research fitting into the bigger questions that the magnetospheric community is attempting to answer. My approach will complement George Siscoe's in that I am perhaps less radical or more conventional in my view of the state of the discipline. But I will use the opportunity this talk provides to outline, for the benefit of those starting out in research, the many factors that influence how one chooses what research question to pursue. In a subject like magnetospheric physics which is increasingly organising itself into ever larger programs (GGS, GEM, ISTP) the interaction of the individual scientist and the community effort is undergoing a redefination that deserves a reexamination.

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WEB SITE
EMAIL: hughes@buasta.bu.edu
Telephone: 617-353-2471

Marvin Geller

Date: 4/11/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: SUNY/Stony Brook

Some Recent UARS Research On Polar Stratospheric Chemistry And Mesosphere-Lower-Thermosphere Dynamics

"Two research topics using UARS data are described. In the first, measurements verifying the paradigm for polar processing of inactive chlorine species to species that catalytically lead to ozone destruction are discussed. We are able to see polar stratospheric cloud formation, decreases in HCl and ClONO2, and increases in ClO, as are predicted. In the second, a new method for deriving the structure of the diurnal tide in the mesosphere-lower thermosphere region is described. This method may be thought of as a crude data assimilation procedure in that it adjusts the results of a tidal model to UARS/HRDI observations. By these means, we derive the diurnal structure for all variables together with the implied atmospheric disspation."

EMAIL: MGELLER@ccmail.sunysb.edu
Telephone: 516-632-6170

Robert E. Johnson

Date: 4/18/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: University of Virginia

Plasma Bombardment Of The Icy Moons In The Outer Solar System

Many of the icy moons of the giant planets in the outer solar system are bombarded by relatively intense fluxes of ions and electrons. This can cause a change in the optical reflectance of the surface and ejection of atoms and molecules from these surfaces, a process referred to as sputtering. The sputtered particles can form an ambient gas about the object that is often the source of the local plasma, resulting in an interesting feedback process. In this colloquium the physics of the sputtering of ices and its relevance to a number of outer solar system objects will be described: the sputter-produced plasma trapped in Saturn's magnetosphere; the production of an O2 `atmosphere' on Europa; and the production of absorption features, such as SO2 on Europa and O2 and O3 in the icy surface of Ganymede.

EMAIL:
Telephone:

Supriya Chakrabarti

Date: 4/25/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

UV Observations in Space Physics and Astrophysics: Challenges and Rewards

UV instrumentation is dififficult and expensive. For space physics and astrophy sics work, one needs to conduct these experiments from space, which complicates matter enormous ly. As a result, this field is rather young and there is room for scientific contribution in many areas. In keeping with the big picture theme, I will review some of the key issues, discuss our co ntribution in various areas and present a biased view of where we should be heading.

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WEB SITE
EMAIL: supc@bu.edu
Telephone: 617-353-7425

Robert Kerr

Date: 5/2/96
Time and Place: 3:45 p.m. in CAS 522
Affiliation: Boston University Center for Space Physics

Reconciling Observations With Geocoronal Theory: Implications For The Earth's Hydrogen Budget

The evaporative interface between planetary atmospheres and interplanetary space, as it pertains to the evolution of planetary atmospheres, has been an historic focus of atmospheric physics. In fact, crystalization of ``aerono' as a sub-field was in large part driven by the complex behavior of hydrogen in the earth's atmosphere. The significant contributors to early theoretical advance in exospheric physics reads as a list of the ``fathers'' of aeronomy, including: Jeans, Chamberlain, Banks, Hunten, Donahue, Meier, and Tinsley, to name a few. Likewise, early efforts to model and measure topside F-region light ion composition were championed by a similarly impressive list including Rishbeth, Evans, Nagy, Moorcraft, Baily, and Holt, to name just a few.

Unfortunately, observational capabilities have lagged far behind the theoretical development. Generally, measurements of the abundances and the dy dictating geocoronal structure have proven to be some of the most observationally challenging for extant aeronomical instrumentation. Proper interpretation of those measurements has proven equally tedious. I report and demonstrate techniques that now provide the densities [H], [O], [H+, [He+], the temperatures T(O), T(H), T(He), Te, T(O+), T(H+), the wind field above and below the F-region peak. and the independent H, H+, and O+ flu. These optical, infrared, and radar techniques can now be performed simultaneously using nested instrumentation at two NSF facilities.

Armed with these capabilities, the solar cycle and semi-diurnal variabilities of atomic hydrogen abundance has been determined. Geocoronal column abundance ab ove 500 km varies by a factor of about two over a solar cycle, with largest abunda nces at solar minimum. Far greater variability would be expected if hydrogen escap e were driven by thermal affects alone. At 2000 km, the solar cycle variability vanishes. Secular varibility correlated to geomagnetic activity is also demonstrated. Mid-latitude exopsheric H abundances can more than double within hours of magn etic storm onset, although precise ehancements and timing appear quite variable. These e nhancements can not be explained by thermal atmospheric expansion alone. Hydrogen airglow data gathered since 1983 also reveal a secular trend that is consistent with an assertion that the impact of increasing methane depostion in the lower atmosphere has propogated throughout the atmosphere in the form of enhanced hydrogenous species concentrations. Recall that the increase in methane depostion mirrors human population growth.

Perturbations of the measured atomic hydrogen velocity distribution (and thus the escape flux) are demonstrably correlated with topside F-region H+ abundance and flux. Large perturbations in the H velocity distribution are associated with wintertime, morning, H+ enhancements and large downward fluxes. These velocity distribution perturbations are sufficient to mask the ``gravitational cooling'' of H with altitude caused by decreasing escape velocity. More importantly, we reveal a diurnal varibility of local hydrogen escape flux throttled by proton abundance and flux.

bullet WEB SITE
EMAIL: kerr@moe.bu.edu
Telephone: 617-353-6139

Theodore Fritz

Date: 5/9/96
Time and Place: 3:45 p.m. in CAS 500
Affiliation: Boston University Center for Space Physics

Significant New Results From ISTP/GGS

The NASA/GGS project is a component of the International Solar Terrestrial Physics or ISTP program which consists of two satellite projects named WIND and POLAR. With the launch of the POLAR satellite on February 24th, the Global Geospace Science project has entered a phase of mission operations and data analysis. This talk with review the history and evolution of the program, its goals, initial results, and the methods and means now in place of achieving further results.

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WEB SITE
EMAIL: fritz@bu.edu
Telephone: 617-353-7446

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