In Future Directions in Aeronomy
Special Session
SA41C: Future Directions in Aeronomy
I
HR: 10:05h
AN: SA41C-02 INVITED
TI: Problems and Issues in Solar System Aeronomic
Modeling
AU: * Bougher, S W
EM: sbougher at lpl.arizona.edu
AF: Lunar and Planetary Laboratory, University of Arizona, Tucson,
AZ 85721 United States
AU: Muller-Wodarg, I C
EM: ingo at apg.ph.ucl.ac.uk
AF: Atmospheric Physics Laboratory, University College London, London,
United Kingdom
AB: The comparative approach to planetary aeronomy is becoming increasingly
fruitful as new information from various planet atmospheres is assimilated.
Various planetary thermospheric observations and modeling over the past
35-years provide a useful platform for addressing similar upper atmosphere
processes (thermal, dynamical, chemical) in various planetary settings.
Planetary upper atmospheres can be roughly catagorized as those imbedded
in their own planetary magnetosphere (e.g. Earth and Jupiter) and those
that are not (e.g. Venus, Mars, Titan). This distinction determines the
different thermospheric heating mechanisms that generally dominate for
magnetic (auroral and Joule heating) and non-magnetic (solar EUV/UV heating)
bodies. In addition, other basic features of the structure and dynamics
of the Venus, Earth, Mars, Jupiter and Titan thermospheres can be understood
by examining the implications of their fundamental planetary parameters
(e.g. radius, gravity, heliocentric distance, rotation rate). The present
maturity of available Venus and Earth planetary databases (and the promise
for Mars) as well as numerical modeling capabilities permit us to compare
the thermospheres of Venus, Earth, and Mars using well tested and individually
validated three-dimensional (3-D) thermospheric general circulation models
(TGCMs). Recently developed Jupiter and Titan TGCMs also reveal unique
characteristics of their thermospheric winds and structures that data have
yet to confirm. We present sample TGCM simulations that capture the physics
of these 5-thermospheres. Clearly, our geocentric perspective when applied
to other planet atmospheres is initially helpful. However, investigations
must be revised as new planetary data and model simulations combine to
challenge our understanding of aeronomic processes in new planetary environments.
DE: 3369 Thermospheric dynamics (0358)
DE: 5409 Atmospheres--structure and dynamics
DE: 5707 Atmospheres--structure and dynamics
DE: 6207 Comparative planetology
SC: SA
MN: 2001 AGU Fall Meeting
HR: 11:20h
AN: SA41C-07 INVITED
TI: Challenges in Solar System Ionospheres
AU: * Mendillo, M
EM: mendillo at bu.edu
AF: Center For Space Physics, Boston University, 725 Commonwealth Ave.,
Boston, MA 02215 United States
AB: The solar system contains a robust set of ionospheres among its
nine planets, many moons and comets. If one sets aside the transient atmospheres/ionospheres
of comets, and those of larger bodies with tenuous surface-boundary-exospheres
(e.g., Mercury, Moon, Europa, etc.), plus the under-sampled Pluto, then
10 case studies exist for detailed study and comparison (Venus, Earth,
Mars, Jupiter & Io, Saturn & Titan, Uranus, and Neptune & Triton).
The ionospheres of these bodies define the full range of natural processes
that govern plasma environments in our solar system, and indeed for extra-solar-system
planets: (a) photo-chemical mechanisms, (b) energetic (auroral) ionization
sources, (c) mesospheric/thermospheric tides, winds and waves, (d) electrodynamics,
and (e) solar wind impact and/or shielding by a magnetosphere. This brief
review will summarize and compare the dominant production, loss and transport
mechanisms thought to occur at each site. Major uncertainties are, surprisingly,
not due entirely to remoteness of the bodies being studied.
DE: 2400 IONOSPHERE
SC: SA
MN: 2001 AGU Fall Meeting
SA42A: Future Directions in Aeronomy
II
HR: 13:30h
AN: SA42A-01 INVITED
TI: Role of Auroral Science in Solar System
Aeronomy
AU: * Galand, M
EM: mgaland at bu.edu
AF: Center for Space Physics / Boston University, 725 Commonwealth
Avenue, Boston, MA 02215 United States
AU: Chakrabarti, S
EM: supc at bu.edu
AF: Center for Space Physics / Boston University, 725 Commonwealth
Avenue, Boston, MA 02215 United States
AB: Auroral science constitutes a fundamental component of geophysical
research and is expanding to an increasing number of solar system bodies
with improving observation capabilities and modeling tools over the last
decades. For this talk we define aurora as any optical manifestation -
from gamma-rays to infra-red - of the interaction of extra-atmospheric
energetic electrons, ions, and neutrals with an atmosphere. The aurora
is extremely valuable for remote-sensing of atmospheric constituents, of
magnetic field configuration, of plasma interactions, and of energy sources.
The diversity of atmospheres and plasma sources encountered in the solar
system makes it ideal for comparative auroral studies. We will illustrate
the variety in solar system aurorae through the example of X-ray emissions
on the Earth, Jupiter, and some comets. Such an approach should lead us
to further understanding of processes and interactions taking place in
solar system bodies.
DE: 2455 Particle precipitation
DE: 5464 Remote sensing
DE: 5757 Remote sensing
DE: 6207 Comparative planetology
SC: SA
MN: 2001 AGU Fall Meeting
HR: 13:45h
AN: SA42A-02
TI: Planetary Atmospheres: Decadal Survey
of Priorities for 2003-2013
AU: * Huestis, D L
EM: david.huestis at sri.com
AF: Molecular Physics Laboratory, SRI International, Menlo Park, CA
94025 United States
AU: Bougher, S W
EM: sbougher at lpl.arizona.edu
AF: Lunar and Planetary Laboratory, University of Arizona, Tucson,
AZ 85721 United States
AB: At the request of NASA, the NAS/NRC Space Science Board and its
Committee on Planetary and Lunar Exploration have organized a community
assessment of the scientific priorities of the U.S. planetary science
research programs. Community response to this initiative is being
coordinated by the Division for Planetary Science of the American
Astronomical Society. We will present a description of the progress
made by the Planetary Atmospheres Community Panel, which has the difficult
mission of summarizing current knowledge, identifying key science
questions, and recommending research priorities and actions needed
to create and maintain future capabilities. A comparative approach
is clearly valuable in identifying the issues of greatest importance
and in making recommendations that are likely to be implemented. We
wish to attract broad participation in the survey process and to solicit
input about key research needs. The needs are divided into the broad
categories of (1) Comparative Understanding, (2) Observations, (3)
Modeling, (4) Laboratory and Theory, and (5) Future Capabilities.
Let us know about your opinions, interests, and recommendations by
electronic mail, by posting at the AAS Web site, or at the AGU Meeting.
UR:http://www.nationalacademies.org/ssb/ssefrontpage.html
http://www.aas.org/~dps/decadal/
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
SC: SA
MN: 2001 AGU Fall Meeting
HR: 14:15h
AN: SA42A-04 INVITED
TI: Planetary Aeronomy with Large Telescopes
AU: * Slanger, T G
EM: tom.slanger at sri.com
AF: SRI International, 333 Ravenswood Ave., Menlo Park, CA 94025 United
States
AU: Huestis, D L
EM: david.huestis at sri.com
AF: SRI International, 333 Ravenswood Ave., Menlo Park, CA 94025 United
States
AU: Cosby, P C
EM: philip.cosby at sri.com
AF: SRI International, 333 Ravenswood Ave., Menlo Park, CA 94025 United
States
AU: Chanover, N J
EM: nchanove at nmsu.edu
AF: Astronomy Dept., New Mexico State University, Box 30001/MSC 4500,
Las Cruces, NM 88003 United States
AB: Much can be done with ground-based telescopes to explore planetary
atmospheres, including our own. Over the last four years, we have
been using the Keck telescope on Mauna Kea, both in a direct and an
indirect manner, to make observations of the terrestrial nightglow
and the nightglow of Venus. The spectrographs on the Keck I and II
telescopes are very fast echelle systems, and during normal operations
they generate so-called sky spectra. To astronomers these are necessary
evils - to be subtracted from their target spectra - but to aeronomers
they are the best available nightglow spectra in terms of spectral
coverage, simultaneity of recording, and spectral resolution. Co-added
ASCII files of the Keck nightglow spectra are available on the Web.
The use of large telescopes to view planetary atmospheres is an under-used
technique, particularly when it comes to Venus and Mars. Since the
Venera 9/10 orbiters circled Venus in 1975 there have been no spectroscopic
measurements of the planet in the visible spectral region until 1999.
At that time we observed Venus for eight minutes with the Keck I telescope,
and discovered the oxygen green line, with a comparable intensity
(150 R) to the terrestrial value. In a follow-up measurement at the
APO telescope in 2001, relatively strong molecular oxygen emission
(Herzberg II) was seen, but no green line. Such variability is not
presently explicable, particularly when the molecular emission is
not simultaneously extinguished, and points out the importance of
viewing Venus from some terrestrial observatory at every apparition.
In the case of Mars, ground-based viewing is considerably more difficult,
since the dark fraction of the planetary disc is never greater than
15\%. Observations with the Hubble telescope are more likely to be
successful. We gratefully acknowledge support from the NASA Planetary
Astronomy program.
UR: http://www-mpl.sri.com/NVAO/download/Osterbrock.html
DE: 0310 Airglow and aurora
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 0394 Instruments and techniques
DE: 5405 Atmospheres--composition and chemistry
DE: 6295 Venus
SC: SA
MN: 2001 AGU Fall Meeting
HR: 14:45h
AN: SA42A-06 INVITED
TI: Wave Coupling in the Atmospheres of Earth,
Mars and Venus: A Comparative Planetary Perspective
AU: * Forbes, J M
EM: forbes at zeke.colorado.edu
AF: University of Colorado, Department of Aerospace Engineering Sciences
UBC 429, Boulder, CO 80309-0429 United States
AU: * Forbes, J M
EM: forbes at zeke.colorado.edu
AF: Boston University, Center for Space Physics 725 Commonwealth Avenue,
Boston, MA 02215 United States
AB: Planetary atmospheres are rotating stratified fluids, and thus
support a variety of wave motions. Waves often represent an important mechanism
for transporting energy and momentum from one point to another in an atmosphere.
Gravity or buoyancy waves are excited in lower atmospheres by flow over
topography, convective activity, and shear instabilities. Periodic absorption
of solar radiation forces thermal tides at subharmonics of a solar day.
Longer-period waves can be excited by instabilities in the mean flow, by
temporal variations in convective activity (latent heating), and sometimes
arise as resonant atmospheric oscillations. Many waves are capable of propagating
to higher altitudes where they undergo dissipation and deposit heat and
momentum into the mean flow. There exists a degree of similarity between
the types of waves that exist in the atmospheres of the so-called terrestrial
planets, Earth, Mars and Venus, and how waves serve to determine the mean
structures and variability of these planetary atmospheres. The purpose
of this review is to form a comparative planetary perspective on the role
of waves in determining the thermal and wind structures of the atmospheres
of the terrestrial planets from the surface through the thermosphere. Outstanding
questions and strategies for their resolution in the foreseeable future
are formulated.
DE: 3384 Waves and tides
SC: SA
MN: 2001 AGU Fall Meeting
HR: 15:20h
AN: SA42A-07
TI: The Application of General Circulation
Models to the upper Atmospheres of Titan and Triton
AU: * Mueller-Wodarg, I C
EM: i.mueller-wodarg at ucl.ac.uk
AF: Atmospheric Physics Laboratory, University COllege London, 67-73
Riding House Street, London, W1P 7PP United Kingdom
AU: * Mueller-Wodarg, I C
EM: i.mueller-wodarg at ucl.ac.uk
AF: Center for Space Physics, Boston University, 725, Commonwealth
Avenue, Boston, MA 02215 United States
AU: Yelle, R V
EM: yelle at bohr.phy.nau.edu
AF: Department of Physics and Astronomy, Northern Arizona University,
Flagstaff, Flagstaff, AZ 86011 United States
AU: Mendillo, M
EM: mendillo at bu.edu
AF: Center for Space Physics, Boston University, 725, Commonwealth
Avenue, Boston, MA 02215 United States
AU: Aylward, A D
EM: alan at apg.ph.ucl.ac.uk
AF: Atmospheric Physics Laboratory, University COllege London, 67-73
Riding House Street, London, W1P 7PP United Kingdom
AB: General Circulation Models (GCM's) have been used very successfully
over the past 25 years to reproduce observations in the terrestrial coupled
thermosphere-ionosphere system and considerably helped us in understanding
the complex physics controlling its large-scale behavior. Similar models
have been developed for other planets, such as Mars, Venus, Jupiter and,
most recently, the moons Titan and Triton.We will present simulations for
Titan and Triton, comparing their characteristics with those found on Earth
and identifying as well as explaining the differences. Our Titan simulations
have already helped in extending our largely one-dimensional knowledge
from Voyager observations to a global 3-dimensional picture and for the
first time evaluating the global dynamics driven by solar heating. The
GCM for Titan thus serves as an important tool in conjunction with forthcoming
Cassini observations in helping us to understand the neutral and charged
upper atmosphere of Saturn's largely unexplored moon.
DE: 6007 Atmospheres--structure and dynamics
DE: 6207 Comparative planetology
DE: 6280 Saturnian satellites
SC: SA
MN: 2001 AGU Fall Meeting
HR: 15:50h
AN: SA42A-09
TI: Meteoric Material - One of the Least Explored
Components of Planetary Atmospheres
AU: Moses, J I
EM: moses at lpi.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Blvd, Houston, TX
77058 United States
AU: * Grebowsky, J M
EM: u5jmg at lepvax.gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, Laboratory for Extraterrestrial
Physics Code 695 Greenbelt Road, Greenbelt, MD 20771 United States
AU: Pesnell, W D
EM: Pesnell at NomadResearch.com
AF: Nomad Research, Inc., 795 Scarborough Court, Arnold, MD 21012 United
States
AU: Weisman, A L
EM: frisbee2468 at hotmail.com
AF: River Hill High School, 13849 Russell Zep Drive, Clarkesville,
MD 21029 United States
AB: Interplanetary dust particles (IDPs) continuously impact all the
planets and their satellites in the solar system. In all planetary atmospheres
IDPs leave their imprint as aerosols or smoke particles that are left behind
when the IDPs do not ablate completely or when the ablated vapors recondense.
In addition, in all atmospheres they produce ionization layers comprised
of metallic ions, predominantly Mg${}^{+}$ and Fe${}^{+}$. On Earth the
metal ions are frequently measured to be the dominant positively charged
species in low-latitude ionospheric layers. Theoretical models provide
evidence that such layers exist at Venus, Mars, Jupiter, Saturn, Neptune
and Saturn's moon Titan. Even the sparse atmosphere of Triton may be lit
up by meteors. Spacecraft radio occultation measurements reveal low altitude,
narrow ionosphere layers at each of the giant planets. These narrow features
appear to be consistent with the presence of metallic ions that have been
compressed by electrodynamic processes as on Earth. Observations at Mars
and Venus do not show clear evidence of such layers. The IDPs also deposit
nonmetal neutral species in the ablation process. For the inner planets
these species blend unnoticed into the atmosphere, but for the outer planets
they can lead to persistent amounts of water vapor and carbon dioxide.
Although many measurements are available for the Earth, measurements of
the IDP distributions and their atmospheric signatures at other planets
are in their initial stages at the present time. Modeling efforts are still
qualitative as the chemical reaction rates for many of the ablated gases
are not established. Most of our knowledge of long lasting IDP atmospheric
effects is derived from what we know about Earth, for which our understanding
is still far from complete. This component of all atmospheres must be treated
as a key factor in all planetary atmospheric aeronomy systems.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 2129 Interplanetary dust
DE: 2419 Ion chemistry and composition (0335)
SC: SA
MN: 2001 AGU Fall Meeting
HR: 16:05h
AN: SA42A-10
TI: Auroral Spectra as a Tool for Detecting
Extra-Terrestrial Life
AU: * Akasofu, S
EM: sakasofu at iarc.uaf.edu
AF: International Arctic Research Center, University of Alaska P.O.
Box 7340, Fairbanks, AK 99775-7340 United States
AU: Lummerzheim, D
EM: lumm at gi.alaska.edu
AF: Geophysical Institute, University of Alaska P.O. Box 7320, Fairbanks,
AK 99775-7320 United States
AU: Frey, H U
EM: hfrey at ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley,
CA 94720-7540 United States
AB: One of the most prominent emissions from the aurora is the greenish-white
light from oxygen atoms, while the Jovian aurora contains atomic hydrogen
emissions. The oxygen emission, the so-called "green line" (557.7 nm),
of the terrestrial aurora, arises mostly from the fact that plants release
abundant free oxygen into the atmosphere by the photosynthesis process.
Thus, the green line shows that plant life exists on Earth. It was recently
reported that Upsilon Andromedae, has three planets. This star is a solar-type
star. This discovery and many others in recent years are significant because
they show the planetary system, like the solar system, is not quite unique.
It is expected that a number of stars are accompanied by several planets,
and it may not be too long before the aurora on such planets can be discovered.
One possible way to detect plant life on such planets is to examine their
auroral emissions. If the strong line emission at 557.7 nm and other UV/EUV
emissions from oxygen can be detected among other emissions in the planetary
aurora, the possibility of the presence of plant life is high. Further,
if plant life exists, animal life, whether lower or higher, can also exist
there. The Earth-like auroral processes leading to the oxygen emissions
require, in addition to plant life, both stellar wind and planetary magnetism.
It is highly probable that solar-type stars have stellar wind. If such
a planet does not have a strong dipole-like magnetic field, the stellar
wind can cause atmospheric glow in which the oxygen emissions may be present.
In any case, if the oxygen emissions are detected in the planetary auroral
spectra, the possibility of plant life there is high. The dissociation
of CO2 can also release oxygen. However, if the condition of the planets
is similar to that of the Earth, its contribution is very small. It is
expected that auroral science will evolve in a variety of ways in the future.
It is suggested that the subject dealt with here is such an example. It
is hoped that auroral science could contribute to search for extra-terrestrial
life, one of the ultimate human endeavors.
DE: 0310 Airglow and aurora
DE: 2407 Auroral ionosphere (2704)
DE: 2459 Planetary ionospheres (5435, 5729, 6026, 6027, 6028)
SC: SA
MN: 2001 AGU Fall Meeting
SA51A: Future Directions in Aeronomy
III
HR: 0830h
AN: SA51A-0758
TI: Science goals of the Planet-C mission
AU: * Imamura, T
EM: ima at bochan.ted.isas.ac.jp
AF: The Institute of Space and Astronautical Science, 3-1-1, Yoshinodai,
Sagamihara, 229-8510 Japan
AU: Nakamura, M
EM: mnakamur at eps.s.u-tokyo.ac.jp
AF: The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku , Tokyo, 113-0033
Japan
AB: The primary goal of the Planet-C mission is to reveal the mechanism
of the super-rotation. In the Venus atmosphere, a fast westward wind prevails
at all latitudes. The wind speed increases with height from the ground
surface to the cloud top (70 km). Since eddy viscosity transports momentum
downward, there must be a mechanism which transports momentum upward to
maintain the wind system. Possible mechanisms are: the combination of meridional
circulation and horizontal viscosity (Gierasch mechanism); thermal tides
which are excited in the cloud layer and propagate downward; and equatorial
Kelvin waves which are excited in the lower atmosphere and propagate upward.
Clues to the mystery will be found by the global 3-D observation from the
orbiter. If the Gierasch mechanism is valid, large-scale horizontal disturbances
which transport angular momentum equatorward will be detected by the tracking
of near-IR cloud features around 50 km. Vertical structures of such disturbances
will be inferred from the combination of images in the near-IR, mid-IR
and UV covering altitudes from 35 to 70 km. The propagation of thermal
tides or Kelvin waves will be detected not only by such imaging observations,
but also by the temperature sounding with radio occultation. The vertical
resolution of radio occultation (1 km) is suitable for visualizing the
vertical propagation of such waves. The variation of the mean wind speed
will be correlated with the activity of above-mentioned planetary-scale
eddies: such a correlation will also be an important clue if observed.
Meso-scale dynamics in the cloud layer, and their influences on the upper
atmosphere dynamics, are also important issues. Development and decay of
convective cells or gravity waves will be visualized by a continuous multi-wavelength
observation of clouds. Lightning detection will also give clues to the
convective activity in the cloud layer. The propagation of gravity waves
from the cloud level to the thermosphere will be detected by radio occultation
and airglow imaging. The momentum deposition by such gravity waves may
affects the subsolar-to-antisolar circulation in the thermosphere. The
intensity of airglow in the antisolar region is observed as an indicator
of the downward velocity in the descending branch of the circulation.
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3384 Waves and tides
DE: 5707 Atmospheres--structure and dynamics
DE: 5757 Remote sensing
DE: 6295 Venus
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0759
TI: Japan's Venus meteorological satellite:
Planet-C
AU: * Nakamura, M
EM: mnakamur at eps.s.u-tokyo.ac.jp
AF: Earth and Planetary Sciences, the University of Tokyo, 7-3-1, Hongo,
Bunkyo-ku, Tokyo, 113-0033 Japan
AU: Imamura, T
EM: ima at bochan.ted.isas.ac.jp
AF: the Institute of Space and Astronautical Science, 3-1-1, Yoshinodai,
Sagamihara, Kanagawa, 229-8510 Japan
AB: The Institute of Space and Astronautical Science, Japan, will launch
the Venus meteorological satellite, Planet-C, in 2007. It will start its
operation in mid 2009. In order to understand the driving force of the
intriguing Venusian wind system called super-rotation, we will observe
waves and eddies of wide spectral ranges and evaluate their contributions
to momentum transport. For this purpose, we will build 4 imaging cameras
with high spatial resolution covering UV (280, 360nm), near-IR (1.0, 1.7,
2.3, 2.4um) and long-IR (9-11um). We will also build a lightning imager.
Near-IR channels observe lower clouds around 50 km altitude and the distribution
of carbon monooxide below clouds, while UV and long-IR channels cover the
cloud top region around 70 km. Multi-wavelength images obtained simultaneously
by these cameras, and temperature profiles by radio occultation will visualize
the 3-D structure of atmospheric disturbance. The satellite has a 3-axis
stabilized attitude control to give the optimum platform for atmospheric
imaging. We select an orbit that allows the angular motion of the satellite
to be approximately synchronized with the westward mean zonal wind for
20 hours around the apogee region (a perigee altitude of 300 km and an
apogee altitude of 13 Venus radii) for continuous observation of each air
parcel with high-spatial resolution. The time scale of atmospheric phenomena
recorded in such continuous data-sets ranges from several minutes to several
months. Such a synchronized orbit will also allow deriving the horizontal
wind field from cloud motions with high accuracy.
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3384 Waves and tides
DE: 5707 Atmospheres--structure and dynamics
DE: 5757 Remote sensing
DE: 6295 Venus
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0760
TI: Ionospheric Variability on Earth and Mars
AU: * Mendillo, M
EM: mendillo at bu.edu
AF: Center for Space Physics, Boston University, 725 Commonwealth Ave.,
Boston, MA 02215 United States
AU: Smith, S
EM: smsm at bu.edu
AF: Center for Space Physics, Boston University, 725 Commonwealth Ave.,
Boston, MA 02215 United States
AU: Martinis, C
EM: martinis at spica.bu.edu
AF: Center for Space Physics, Boston University, 725 Commonwealth Ave.,
Boston, MA 02215 United States
AU: Wilson, J K
EM: jkwilson at bu.edu
AF: Center for Space Physics, Boston University, 725 Commonwealth Ave.,
Boston, MA 02215 United States
AU: Moore, L
EM: moore at bu.edu
AF: Center for Space Physics, Boston University, 725 Commonwealth Ave.,
Boston, MA 02215 United States
AU: Hinson, D P
EM: hinson at nimbus.stanford.edu
AF: Stanford University, Packard Building Rm. 333, 350 Serra Mall,
Stanford, CA 94305-9515 United States
AU: Rishbeth, H
EM: hr at phys.soton.ac.uk
AF: Center for Space Physics, Boston University, 725 Commonwealth Ave.,
Boston, MA 02215 United States
AU: Rishbeth, H
EM: hr at phys.soton.ac.uk
AF: Department of Physics & Astronomy, University of Southampton,
S017 1BJ, Southampton, United Kingdom
AB: The day-to-day variability of an ionosphere arises from a complex
blend of processes: photo-chemistry, neutral-ion coupling, and electrodynamics.
Until recently, the study of ionospheric perturbations has been possible
only on Earth where decades of daily observations have been conducted.
For the terrestrial case, the variability of F-region peak electron density
about a monthly mean is ~ 25\% at most local times, seasons and latitudes,
and ~ 10\% in the E-region. While daily changes in solar photon output
and upward coupling from the neutral atmosphere affect both the E- and
F-regions, geomagnetic activity induced dynamics is a source of variability
confined mostly to the F- region. The radio science experiment onboard
Mars Global Surveyor (MGS) has yielded the first set of electron density
profiles capable of supporting studies of day-to-day variability of an
ionosphere on another planet. For the peak electron density, the MGS variability
patterns suggest $\sim$10\% for samples in December 1998 and March 1999
at early morning hours at high latitudes. At the altitude of the peak electron
density at Mars, photo-chemical equilibrium is the dominant process and
thus the observed variability should be consistent with an E-region-like
terrestrial ionosphere. Under comparable conditions of solar zenith angle
and latitude on Earth, ionosonde records show an E-region variability of
~10\% for the same days as sampled on Mars. A simple E-region model has
been developed to explore the causes of variability seen simultaneously
on Earth and Mars.
DE: 2400 IONOSPHERE
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0761
TI: Mechanisms for IMF penetration into the
ionosphere of Mars and Venus
AU: * Jin, H
EM: jin at stp.isas.ac.jp
AF: Institute of Space and Astronautical Science, 3-1-1 Yoshinodai,
Sagamihara, 229-8510 Japan
AU: Maezawa, K
EM: maezawa at stp.isas.ac.jp
AF: Institute of Space and Astronautical Science, 3-1-1 Yoshinodai,
Sagamihara, 229-8510 Japan
AU: Mukai, T
EM: mukai at stp.isas.ac.jp
AF: Institute of Space and Astronautical Science, 3-1-1 Yoshinodai,
Sagamihara, 229-8510 Japan
AB: Since Mars and Venus do not have a global intrinsic magnetic field,
unlike the earth, the solar wind directly interacts with the ionosphere
of these planets. PVO (Pioneer Venus Orbiter) discovered that the IMF sometimes
penetrates into the Venus ionosphere and recently MGS (Mars Global Surveyor)
also observed the IMF penetration into the Martian ionosphere. The IMF
forms both large-scale and small-scale fields in these ionospheres. The
large-scale field in the ionosphere is one of the major features on both
planets. It is related to the transfer of solar wind momentum and energy
to the ionosphere, and may probably have significant effects on the ionospheric
structures such as plasma density, flows, ion composition and so on. The
large-scale field also affects dynamics of ionospheric plasma, so that
even the amount of atmospheric escape flux may be influenced by it. The
mechanism responsible for the IMF penetration into the ionosphere is, however,
still not clear. According to the PVO observation, it is when dynamic pressure
of the solar wind exceeds thermal pressure of the ionosphere that the large-scale
field is observed in the ionosphere. During that time, the ionopause descends
and thickens. Therefore, we can expect that the IMF penetration may be
related to photochemical reactions and/or magnetic dissipation due to collisions
among charged particles and between charged particles and neutrals in the
lower ionosphere. We discuss the IMF penetration mechanisms that include
these effects, by using a multi-species MHD model.
DE: 2437 Ionospheric dynamics
DE: 2780 Solar wind interactions with unmagnetized bodies
DE: 6225 Mars
DE: 6295 Venus
DE: 7843 Numerical simulation studies
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0771
TI: Lightning observation in Venus
AU: Takahashi, Y
EM: yosiyuki at pat.geophys.tohoku.ac.jp
AF: Department of Gephysics, Tohoku University, Aramaki, Aoba-ku, Sendai,
980-8578 Japan
AU: * Takahashi, Y
EM: yukihiro at pat.geophys.tohoku.ac.jp
AF: Department of Gephysics, Tohoku University, Aramaki, Aoba-ku, Sendai,
980-8578 Japan
AB: Lightning discharge is a phenomenon which reflects the dynamics
and material characteristics in the planetary atmosphere. Charge separation
in the thundercloud is considered to be caused mainly by frictions between
ice crystal and hail, which are closely related to atmospheric motion especially
for vertical convection. Recently it is found that the vertical electric
field, which is maintained by the global electric circuit in which the
lightning discharge plays an important role, shows high correlation with
global surface temperature. This fact means that the lightning activity
is an excellent quantitative indicator representing the activity of atmospheric
convection. The recent imaging observations of lightning flash in Jupiter
found a good coincidence between the lightning location and cumulonimbus,
inferred from infrared images, as well as in Earth. From the analogies
it is most probable that also on Venus the lightnings are generated mainly
by the vertical convection and the global observation of lightning might
be a good method to get information on the atmospheric activities and characteristics
of cloud particle in the planet with a good time resolution. Especially,
the lightning observation is expected to be a powerful in analysis of meso-scale
atmospheric phenomena. The lightning in Venus might be similar to sprites
or elves observed in the middle and upper atmosphere of the Earth. Since
the distance between the cloud deck and the ground in Venus is considerably
large (about 45 km) and the atmospheric pressure is quite high, the discharge
from cloud top to the ionosphere may be more probable than cloud to ground
discharge. The existence of Venus lightning has been still under controversy
for almost 20 years regardless of extensive optical and plasma wave observations.
We plan to install a lightning imager (LAC) at the Venus orbiter, which
will be launched in 2007. Scientific targets and design of the instruments
will be presented.
DE: 2435 Ionospheric disturbances
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
DE: 5405 Atmospheres--composition and chemistry
DE: 5462 Polar regions
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0774
TI: Comparative Planetary Aurora: Jupiter,
Saturn, and the Earth
AU: * Clarke, J T
EM: jclarke at bu.edu
AF: Boston University, 725 Commonwealth Ave, Boston, MA 02215 United
States
AB: Detailed observations of the UV aurora from Jupiter and Saturn
have been carried out with the cameras on the Hubble Space Telescope. These
images reveal distinct similarities, and also differences, between the
giant planet auroras and auroral processes on the Earth. In general, the
Earth's aurora are controlled by the interaction of the Earth's magnetic
field with the solar wind, Jupiter's aurora are dominated by internal dynamics
and plasmas, and Saturn presents an intermediate case with features of
each of the other planets. We are learning much more about the outer planets
through comparisons with the in situ measurements now being made by the
Galileo and Cassini spacecraft. The Hubble images will be presented for
comparison with each other, and with other results on the Earth, in this
short overview of the subject. This research has been supported by grant
GO-8657.01-99A from the Space Telescope Science Institute to the University
of Michigan.
UR: http://www.sprl.umich.edu/CassiniHSTJupiterflyby/
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0310 Airglow and aurora
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0775
TI: The Hot Atom Coronae of Venus, Mars and
the Earth: Current Understanding and Challenges
AU: * Paxton, L J
EM: larry.paxton at jhuapl.edu
AF: The Johns Hopkins University, Applied Physics Laboratory 11100
Johns Hopkins Rd., Laurel, MD 20723 United States
AU: Vervack, R J
AF: The Johns Hopkins University, Applied Physics Laboratory 11100
Johns Hopkins Rd., Laurel, MD 20723 United States
AB: The exospheres of the terrestrial planets (Venus, Mars, and the
Earth) are very different in composition and extent as well as the amount
of interaction they experience with the solar wind. In this paper we discuss
new results from the analysis of the Pioneer Venus Orbiter Ultraviolet
Spectrometer data taken over more than a solar cycle. These observations,
in particular those in the atomic oxygen solar resonance line at 130.4
nm, show the response of the planetary ionosphere to changing levels of
solar flux and the degree to which the exosphere varies in density. We
also report a new analysis of data from the ultraviolet spectrometers on
the Mariner Mars missions: these data are nearly thirty years old. We report
the detection of a hot oxygen corona here as well. Hot, or non-thermal,
oxygen in the Earth's atmosphere is much more difficult to observe. Yet
it holds valuable clues to thermospheric processes. We will summarize the
differences between the exospheres of the three terrestrial planets and
what we still may learn from another aeronomical mission to Mars or Venus.
DE: 0310 Airglow and aurora
DE: 0355 Thermosphere--composition and chemistry
DE: 0358 Thermosphere--energy deposition
DE: 0394 Instruments and techniques
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0776
TI: Hot Oxygen Production and Thermalization
in Planetary Atmospheres
AU: * Shizgal, B D
EM: shizgal at theory.chem.ubc.ca
AF: University of British Columbia, Department of Chemistry, Vancouver,
BC V6T 1Z1 Canada
AU: Kabin, K
EM: kabin at phys.ualberta.ca
AF: University of British Columbia, Department of Chemistry, Vancouver,
BC V6T 1Z1 Canada
AB: There are numerous processes in the atmospheres of the terrestrial
planets which involve the production of energetic atoms with translational
energies considerably above thermal values. These hot atoms can play an
important role in enhanced reaction rates, nonthermal emissions, and in
particular the enhanced nonthermal escape of atmospheric species. In this
talk, we present a new analytical result for the velocity distribution
function of the hot atoms produced by dissociative recombination. Our calculation
takes into account different temperatures of the electrons and ions and
arbitrary dependence of the cross section on the relative velocity of the
colliding particles. We compare this analytic result with previous Monte-Carlo
simulations. We use our result to study the production of hot oxygen atoms
in the upper atmosphere of the terrestrial planets. Thermalization of the
hot oxygen is described using a linearized Boltzmann equation at the altitudes
at which the thermal oxygen is still a dominant species and with a nonlinear
Boltzmann equation at higher altitudes where the hot oxygen becomes the
main component of the atmosphere.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 5407 Atmospheres--evolution
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0777
TI: Gravity Wave-Driven Fluctuations in the
H3+ Emission of Jupiter
AU: * Matcheva, K
EM: Katia.Matcheva at obspm.fr
AF: DESPA, Observatoire de Paris-Meudon, 5 place Jules Janssen, Meudon,
F-92195 France
AU: Drossart, P
EM: Pierre.Drossart at obspm.fr
AF: DESPA, Observatoire de Paris-Meudon, 5 place Jules Janssen, Meudon,
F-92195 France
AU: Raynaud, E
EM: Elisabeth.Raynaud at obspm.fr
AF: DESPA, Observatoire de Paris-Meudon, 5 place Jules Janssen, Meudon,
F-92195 France
AU: Sicardy, B
EM: Bruno.Sicardy at obspm.fr
AF: DESPA, Observatoire de Paris-Meudon, 5 place Jules Janssen, Meudon,
F-92195 France
AU: Widemann, T
EM: Thomas.Widemann at obspm.fr
AF: DESPA, Observatoire de Paris-Meudon, 5 place Jules Janssen, Meudon,
F-92195 France
AB: It is widely recognized that acoustic-gravity waves and atmospheric
tides play a major role in the dynamical coupling of different atmospheric
regions. In the terrestrial atmosphere waves and wave related phenomena
are systematically studied from the ground, air and space. In recent years,
a number of ground-based and spacecraft observations provided us with compelling
evidence for wave activity in the atmospheres of other solar system planets.
Temperature profiles of the upper atmosphere of Jupiter derived from stellar
occultations and in situ measurements (Galileo atmospheric probe) exhibit
small amplitude variations that are interpreted as signatures of propagating
gravity waves. We consider the possibility of using Jupiter's H3+ near-IR
emission as a complementary remote sensing method for studying the horizontal
morphology of the wave activity in Jupiter's atmosphere at ionospheric
heights. Similar to the gravity wave-driven variations in the OH nightglow
in the Earth's atmosphere, the intensity of the jovian H3+ emission can
be modified by a passing wave directly by inducing fluctuations in the
ion temperature and number density, and indirectly by disturbing the local
ion chemistry. We perform numerical simulations of the response of the
H3+ emission to propagating waves using a linear gravity wave model in
a dissipative, nonisothermal atmosphere coupled with a detailed radiative
transfer model of H3+ near-IR emission from an extended atmospheric region.
We investigate the magnitude of the wave impact on the planetary emission
for different values of the wave parameters in a variety of ionospheric
conditions and for different H3+ profiles. Recent observations of the H3+
emission at high sensitivity with the VLT/ISAAC instrument at 3.5 micron
in December 2000 allow us to determine an upper limit on the direct detection
of gravity waves by this method.
DE: 3359 Radiative processes
DE: 3384 Waves and tides
DE: 5707 Atmospheres--structure and dynamics
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0778
TI: Heating of Jupiter's Thermosphere by Dissipating
Acoustic Waves
AU: * Hickey, M P
EM: hickey at hubcap.clemson.edu
AF: Clemson University, Department of Physics and Astronomy 308 Kinard
Laboratory, Clemson, SC 29634-0978 United States
AU: Schubert, G
EM: schubert at ucla.edu
AF: University of California, Los Angeles, Department of Earth and
Space Sciences Institute of Geophysics and Planetary Physics, Los Angeles,
CA 90095-1567 United States
AU: Walterscheid, R L
EM: richard.walterscheid at aero.org
AF: The Aerospace Corporation, Space Science Applications Laboratory,
Los Angeles, CA 90009 United States
AB: Thunderstorms in Jupiter's atmosphere are likely to be prodigious
generators of acoustic waves, as are thunderstorms in Earth's atmosphere.
The contribution of viscous heating to the thermal balance of the thermospheres
of both planets by dissipating acoustic waves is largely unknown. Accordingly,
we have used a numerical model to study the dissipation in Jupiter's thermosphere
of upward propagating acoustic waves. Model simulations are performed for
a range of wave periods and horizontal wavelengths believed to characterize
these acoustic waves. Whereas dissipating gravity waves can cool the upper
atmosphere through the effects of sensible heat flux divergence, it is
found that acoustic waves mainly heat the thermosphere by viscous dissipation.
Though the amplitudes and mechanical energy fluxes of acoustic waves are
poorly constrained in Jupiter's atmosphere, our calculations suggest that
dissipating acoustic waves can locally heat the thermosphere at a significant
rate and might thereby account for the high temperatures of Jupiter's upper
atmosphere.
DE: 0358 Thermosphere--energy deposition
DE: 3384 Waves and tides
SC: SA
MN: 2001 AGU Fall Meeting
HR: 0830h
AN: SA51A-0779
TI: Comparative Studies of Small-Scale Variations
in the Upper Atmospheres of the Planets
AU: * Shinagawa, H
EM: sinagawa at stelab.nagoya-u.ac.jp
AF: STEL/Nagoya University, 3-13 Honohara, Toyokawa, 442-8507 Japan
AB: The planetary ionospheres and thermospheres often show very complicated
structures and dynamics. The ionosphere and the thermosphere are controlled
by a number of variable processes such as solar EUV radiation, interactions
with the solar wind and the magnetosphere, particle precipitation, Joule
heating, and various kinds of waves propagating from the lower atmosphere.
The ionosphere and the thermosphere are also strongly coupled with each
other through chemical reactions and transfer of momentum and energy via
collisions. Although average or typical global structures of the ionosphere
and thermospheres are understood fairly well, small-scale variations in
the planetary ionospheres and thermospheres have not been fully understood
even at the Earth. Thanks to rapid progress of measurement techniques of
the upper atmosphere from the ground and from satellites, it is now possible
to quantitatively measure the mesoscale dynamics of the terrestrial ionosphere
and thermosphere. Recent observations have suggested that the mesoscale
phenomena might have significant influences on the global structure and
dynamics of the upper atmosphere. Although quality and amount of data of
the upper atmosphere are still not enough to investigate mesoscale phenomena
for Venus and Mars, it is expected that more and better data will be obtained
in the near future. Therefore, it is now a good time to start comparative
studies of the planetary ionospheres and thermospheres. In addition to
observations, it is also important to develop high-resolution ionosphere-thermosphere
models of the planets. In this paper, a few small-scale ionosphere-thermosphere
coupling processes at the planets are reviewed. Numerical models to study
those processes are also presented and discussed.
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2437 Ionospheric dynamics
DE: 2459 Planetary ionospheres (5435, 5729, 6026, 6027, 6028)
DE: 3369 Thermospheric dynamics (0358)
SC: SA
MN: 2001 AGU Fall Meeting
In Follow the Water: The Search
for Habitable Environments in the Solar System: P22B
HR: 1330h
AN: P22B-0553
TI: Toward a Model for Detecting Life on Extrasolar
Planets
AU: * Rye, R
EM: rye at gps.caltech.edu
AF: Caltech, GPS Div., MC 170-25, Pasadena, CA
AU: Storrie-Lombardi, M
AF: JPL, M/S 183-301, Pasadena, CA
AB: The search for life extraterrestrial life has rapidly expanded
during the past several years. In addition to missions to Mars and Europa,
NASA now envisions launching an orbiting telescope, Terrestrial Planet
Finder (TPF), capable of resolving Earth-sized planets around stars as
far away as 50 parsecs within the next 10-15 years. By that time we need
to develop our understanding of the effects of life on such planets in
order to confidently distinguish inhabited planets from barren ones. Our
group is in the process of developing a fully coupled generalized 1-D radiative
transfer-atmospheric chemistry model. Around this core we are building
the Virtual Planetary Laboratory (VPL) to generate synthetic spectra of
hypothetical extrasolar terrestrial planets. Computational modules mimicking
the influence of life on atmospheric chemistry/climate are of central importance
for analyzing data from TPF and related missions. Here we describe our
rationale and initial efforts to parameterize the effects of life using
a Virtual Microbial Community (VMC). At first glance, the task of modeling
hypothetical inhabited planets appears intractable. However, we may assume
that most planets settle into a fairly small number of stable climate/chemistry
regimes during their history. These regimes are maintained by negative
feedback loops. Transitions from one stable solution to another are singularities,
times during which the system is unregulated and may vary wildly. In this
context, life is one of several processes modifying the chemical composition
of a planetary atmosphere, potentially modifying climate. We seek to elucidate
those processes and signatures unique to life and visible from space. The
VMC is a first attempt at quantifying the possible range of effects of
life on the atmosphere of a planet. We start from the presumption that
kinetics and thermodynamics are the same throughout the universe. Given
the remarkable metabolic diversity of life on Earth, we assume that all
available energy sources may be used by biology on detectably colonized
planets. Simple feedback loops such as those governing Lovelock?s famous
Daisyworld or the Walker CO2 feedback, offer starting points for thinking
about global scale feedbacks. Feedbacks in microbial communities, e.g.
those postulated in anaerobic methane oxidation communities, involving
the use of one or more organisms? waste products as nutrients by another,
hint at the local complexity from which we need to scale up. Our first
attempt at bridging this gap involves describing the processes that may
have helped stabilize the Archean climate. Archean biogenic methane production
could have been rapid enough to provide 100s ppm atmospheric CH4. At such
CH4 levels Earth would have remained ice free. Sudden increases in CH4
production might have led to runaway greenhouse conditions. However, if
CH4/CO2 > 1 a UV absorbing aerosol haze should form. UV-labile ammonia
could have accumulated in the atmosphere under the haze, quickly making
rain pH > 7, dramatically slowing chemical weathering on the continents
and interrupting vital phosphate delivery to the oceans. The residence
time of P is ca.10,000 years. Thus, over a time scale of ca.10,000 years
primary productivity dropped sharply. Biogenic methane production, near
the base of the trophic ladder, suffered disproportionately. With little
CH4 production CH4/CO2 fell to < 1. The UV screen and atmospheric NH3
disappeared in a few years. Rain pH dropped. Weathering restarted. Biological
productivity recovered. The above testable scenario serves as an example
of a plausible feedback involving interplay between biological, geochemical,
atmospheric and stellar processes. Feedback loops of this sort will be
central features of the fully realized VMC module for the VPL.
DE: 0325 Evolution of the atmosphere
DE: 1615 Biogeochemical processes (4805)
DE: 4805 Biogeochemical cycles (1615)
DE: 4840 Microbiology
DE: 6207 Comparative planetology
SC: P
MN: 2001 AGU Fall Meeting
u
Related Websites
If you have any questions or comments regarding
the comparative approach as part of the "Future
Directions in Aeronomy" special session at 2001
Fall AGU, feel free to contact:
- Marina Galand (mgaland at bu.edu) and Steve Bougher (sbougher at
lpl.arizona.edu).
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