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Abstracts (see programme)
All abstracts are ordered alphabetically
according to the first author.
- Arnold, N., Space Plasma Influences on Climate
- Bochnicek, J. and J. Lastovicka, Impact of geomagnetic storms
on the lower atmosphere at middle latitudes
- Füllekrug, M., Remote sensing and characterization of
oceanic/african lightning and sprites in their meteorological and lower
ionospheric conductivity environment
- Inan, U. S., Lightning-driven electrodynamic effects in
near-Earth space
- Kartalev, M. and V. Papitashvili, A new approach in studying
effects of ionospheric currents in the global electric circuit
- Kudela, K., On relations of cosmic rays to space weather
- Makarova, L. N. and A. V. Shirochkov, Impact of the solar
wind variations on the processes in the middle latitude lower atmosphere
- Mareev, E. A. and S. V. Anisimov, Monitoring of global,
regional and local perturbations of the atmospheric electric circuit as
displayed in short-period pulsations and coherent structures of
atmospheric electric field.
- Mareev, E. A., V. Yu. Trakhtengerts, D. I. Iudin, A. E. Sorokin,
E. I. Smirnova, S. S. Davydenko, and N. A. Bogatov, Modeling of
electrical structure of thunderclouds and mesoscale convective systems
as connected to initiation of intra-cloud, cloud-to-ground and
high-altitude discharge phenomena.
- Parrot, M., The micro-satellite DEMETER
- Price, C., M. Asfur, W. Lyons, and Th. Nelson, Geolocating
sprites using an improved ELF/VLF method
- Price, C. and M. Asfur, Lightning and climate: the water
vapor connection
- Kim, V. P., S. A. Pulinets, and V. V. Hegai, The model of
enhanced ionization layers in midlatitude nighttime D-region of
ionosphere in the presence of anomalous electric fields.
- Sátori, G., B. Zieger, and J. Bór, Areal
variation of the worldwide thunderstorm activity as shown by Schumann
resonances
- Shirochkov, A. V., L. N. Makarova, and V. A. Ul'ev, A model
evaluation of the ozone density changes caused by various types of
corpuscular radiation
- Todd, M. C. and D. R. Kniveton, Changes in cloud cover
associated with Forbush decreases of galactic cosmic rays
- Troshichev, O. A., L. V. Egorova, and V. Ya. Vovk, Influence of
the solar wind variations on temperature in the southern polar cap
troposphere
- Tulunay, Y., E. Tulunay, and E. T. Senalp, The trough based
neural network model of the foF2 values
- Y. Yair, C. Price, Z. Levin, A. Devir, B. Ziv, and M. Moalem,
MEIDEX: An opportunity for coordinated global measurements of TLE from
the space shuttle and ground stations
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Space Plasma Influences on Climate
Neil Arnold
Observations of the interaction between the Sun's and the Earth's
atmospheres have been available from the earliest times from aurora.
What has been less well understood is how space plasma may also
influence the climate system at lower altitudes. We present some of the
latest numerical model results that indicate significant non-linear
coupling between the middle and upper atmospheres in the winter due to
the transport of heat and momentum. In collaboration with a number of
groups in the UK and the Danish Meteorological Institute we are
developing a micro-satellite mission to investigate these processes in
more detail.
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Impact of geomagnetic storms on the lower atmosphere at middle
latitudes
Josef Bochnicek(1) and Jan Lastovicka(2)
- Geophysical Institute, Bocni II, 14131 Prague, Czech Republic
- Institute of Atmospheric Physics, Bocni II, 14131 Prague, Czech
Republic
We propose a new project of the above title. Its objective is to
clarify better the observational pattern of geomagnetic storms/activity
effects on the lower atmosphere (troposphere and lowermost stratosphere)
at the extratropical Northern Hemisphere, to make observational
constraints to various suggested mechanisms, and to construct
'scenarios' (or mechanisms). We particularly expect to broaden the
results to include not only temperatures and pressure, but also wind
fields and maybe other parameters. The role of galactic cosmic rays in
geomagnetic storm effects will be further tested observationally. The
project is based on analysis of existing and future meteorological
(temperature, pressure, wind fields northward of 20N) and ozonesounding
(ozone profiles) data from international network. Particularly winter
periods will be studied based on case studies and their statistics. We
hope this effort allows construct observational constraints to test
various suggested mechanisms, as e.g. cloudness variability,
electrofreezing and electroscavenging, role of planetary waves, role of
ozone changes. The project belongs to Group 1 by 10% and Group 2 by 90%.
Participation of other scientists from Group 2 is welcome.
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Remote sensing and characterization of oceanic/african lightning and
sprites in their meteorological and lower ionospheric conductivity
environment
Martin Füllekrug
Institut für Geophysik, Feldbergstr.47, D-60323 Frankfurt/Main,
Germany
Extremely low-frequency magnetic field disturbances from intense
positive lightning discharges are compared to the convective cloud cover
in central Africa, derived from infrared brightness temperatures
recorded on board the geostationary satellite Meteosat during April
1998. The mean diurnal variation of the lightning charge moment is well
correlated with the mean diurnal variation of the cloud cover at 11.5 km
height and constrains the mean lightning channel length. The daily
integrated positive cloud to ground charge transfer exhibits a
pronounced day to day variability which is well correlated with the
cloud cover at 15.5 km height, related to the charging of the
thundercloud 4 hours prior to the maximum cloud to ground charge
transfer. The cloud cover area is used to calculate an effective cloud
volume which is related to the cloud to ground charge transfer via the
charge density. This charge density is used to estimate promising
locations for optical sprite observations in the central Congo basin and
Cameroon with 69 sprite occurrences during an average night.
The electrodynamic properties of intense oceanic lightning discharges
are compared to intense continental lightning discharges. Particularly
intense negative lightning discharges with absolute charge moments >2 kC
km occur more often over the oceans than over the continents during
April 1998. Intense continental lightning discharges with negative and
positive polarity and intense positive oceanic lightning discharges
mainly occur in the late evening associated with mesoscale convection.
The number of intense negative oceanic lightning discharges increases in
the early morning hours, probably associated with the resurgence of
mesoscale oceanic convection in coastal areas. The day to day
variability of intense negative oceanic lightning discharges exhibits a
five day periodicity, possibly related to planetary waves. These results
strongly suggest that intense negative oceanic lightning discharges may
produce mesospheric breakdown and oceanic sprites.
The wave propagation speed of seven spherical electromagnetic
resonance frequencies in the atmosphere is experimentally determined
from twelve years monitoring of natural magnetic field variations in the
frequency range 5-50 Hz at Arrival Heights, Antarctica. The derived
magnetic field spectra are classified with respect to solar short wave
radiation variability determined from the sun's radio flux at 2.8 GHz
near Ottawa, Canada. The wave propagation speed exhibits a deviation of
1 % associated with quiet and disturbed solar conditions. This
modulation of the wave propagation constant can be explained with a 2.5
km height variability of a global average two scale height ionospheric
conductivity profile.
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LIGHTNING-DRIVEN ELECTRODYNAMIC EFFECTS IN NEAR-EARTH SPACE
Umran S. Inan
Space, Telecommunications and Radioscience (STAR) Laboratory Stanford
University, Stanford, California
A fascinating menagerie of complex phenomena have been uncovered
during the past decade that collectively indicate that tropospheric
thunderstorms and lightning discharges are strongly coupled
(electrodynamically) to the overlying upper atmospheric regions, ranging
from the mesosphere to the lower ionosphere and extending to the
radiation belts. Lightning discharges occurring at cloud altitudes (<20
km) affect the upper atmosphere at altitudes >40 km either via the
release of intense electromagnetic pulses (EMPs) and/or the production
of intense quasi-static electric (QE) fields at mesospheric altitudes.
An average lightning discharge radiates an EMP of ~20 GW peak power,
which propagates though the ionosphere and couples into the radiation
belts, heating and ionizing the former and precipitating trapped
energetic electrons from the latter. In addition, lightning discharges
often produce intense transient QE fields of up to ~1 kV/m at 40-80 km
altitudes, which for positive cloud-to-ground (CG) discharges is
directed downwards, and which can thus avalanche accelerate
upward-driven runaway MeV electron beams, producing brief (~1 ms)
flashes of gamma radiation, both in the hemisphere of the parent
lightning and in the conjugate hemisphere, and possibly contributing to
the population of trapped radiation belt particles. A spectacular
manifestation of these intense fields is the so-called 'Sprites', large
luminous discharges which appear in the altitude range of ~40 km to 90
km. Sprites are produced by the heating of ambient electrons in the
mesosphere and lower ionosphere by the intense QE fields which
temporarily (for a few to tens of milliseconds) exist at high altitudes
following intense lightning flashes. The so-called 'Elves' are optical
flashes which last much shorter (<1 ms) than sprites, and are typically
limited to 80-95 km altitude, being produced by the heating, ionization,
and optical emissions due to the EMPs radiated by both positive and
negative lightning discharges. A brief background and a discussion of
recent results will be provided.
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A new approach in studying effects of ionospheric currents in the
global electric circuit
Monio Kartalev(1) and Vladimir Papitashvili(2)
- Institute of Mechanics, Bulgarian Academy of Sciences, Sofia,
Bulgaria
- Space Physics Research Laboratory, University of Michigan, Ann
Arbor, MI, U.S.A.
A new numerical model of global ionospheric electrostatic potentials
(GIEP) has been recently developed and discussed [http://geospace.nat.bg; Kartalev et al.,
2001;]. This model utilizes (as outer parameters) the experimental
distributions of field-aligned currents or electric potentials high
latitudes http://www.sprl.umich.edu/mist/limie.html; Papitashvili and Rich,
2001; Papitashvili et al., 2001]. In the GIEP model, we took into
account diurnal and seasonal effects by using realistic 3-D
distributions of ionospheric conductivities from 85 to 400 km altitudes
provided by the semi-empirical models IRI and MSIS. A new essential
feature in the GIEP model is its ability to describe (in several
differently chosen approaches) a mutual influence of the conjugate
(northern and southern) ionospheres. The model provides 2-D global
ionospheric electric potential distributions separately (but
self-consistently) for each hemisphere assuming the equipotential
geomagnetic field lines. These results permit considering not only the
cross-polar potential drop over the northern and southern polar caps,
but also the "global potential drop" over middle and low latitudes.
Another set of outer (to GIEP model) parameters can be specified by an
additional system of atmospheric vertical electric currents applied to
the lower ionospheric boundary. Therefore, the global electric circuit
can be affected by variations in the magnetospheric field-aligned
currents applied to the upper ionosphere boundary in the polar regions.
Performance of the GIEP model is demonstrated in a way when the
"internally-driven" (due to the interhemispheric potential difference)
electric currents (permitted to flow between both hemispheres along
geomagnetic field lines) are supposed to be equal at every pair of the
conjugate points. We examined correlations between the diurnal/seasonal
variations of observed high-latitude near-surface vertical electric
fields and the modeled global potential distributions for specified
conditions and times. Our analysis shows that these variations of
near-surface electric fields may correlate better with the global
potentials rather than with the cross-polar potentials.
References:
Kartalev, M. D., V. O. Papitashvili, V. I. Keremidarska, K. G.
Grigorov, and D. K. Romanov, Global distributions of ionospheric
electric potentials for variable IMF conditions: Climatology and
near-real time specification, Proc. Euro Conf. Solar Cycle and Space
Weather, Vico Equense, Italy, 24-29 September 2001, ESA Publ. 477, in
press, 2001.
Papitashvili, V. O., and F. J. Rich, High-latitude ionospheric
convection models derived from DMSP ion drift observations and
parameterized by the IMF strength and direction, revised for J. Geophys.
Res., October 2001.
Papitashvili, V. O., F. Christiansen, and T. Neubert, A new model of
field-aligned currents derived from high-precision satellite magnetic
field data, revised for Geophys. Res. Lett., November 2001.
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On Relations of Cosmic Rays to Space Weather
Karel Kudela
Institute of Experimental Physics, Slovak Acad. Sci.,
Watsonova 47, 043 53 Kosice, Slovakia
Based on recent publications a review of the links between the ground
based cosmic ray measurements and space weather research is presented.
The direct relations include the interaction of high energy particles
with the materials of the airplanes, satellites, atmosphere and living
cells. The ground level effects of the solar flares and their impact on
airplanes are illustrated for the event on April 15, 2001. The indirect
relations include the interactions of cosmic rays with IMF
inhomogenities in interplanetary space. The cosmic ray anisotropy
measured by the networks of neutron monitors and muon telescopes
indicate the possible precursors of geomagnetic storms. Importance of
cutoff reductions for the entry of cosmic rays into the magnetosphere at
medium and low latitudes is shown for the storm on March 31, 2001.
Relevance of cosmic ray measurements in real time for the purposes of
SPECIAL II network is discussed.
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Impact of the solar wind variations on the processes in the middle
latitude lower atmosphere
Makarova L.N and Shirochkov A.V.
Arctic and Antarctic Research Institute, St.-Petersburg, 199397
Russia
The data of the multiparameter atmospheric measurements at Wank
Mountain in Bavarian Alps (47.30°N; 11.09°E; elevation 1780 m)
made during 1972 - 1983 were analysed. Detailed information contained in
these data gives a rare opportunity to explore the internal atmospheric
processes which cause the atmosphere response to impact of the external
disturbing forces. Among the latter factors the solar insolation is
assumed to be the main or even the sole source of energy responsible for
atmosphere behavior. In this study we explored the atmosphere response
to variations of the solar wind energy. Influence of this source of
energy affecting the middle atmosphere behavior has not been considered
so far.
The main results of this study could be formulated as following:
- Magnitude of atmospheric electric field measured at Wank station
crucially depends on the solar wind dynamic pressure and IMF structure:
the more the solar wind dynamic pressure the less the magnitude of the
electric field.
- Relative humidity in the atmosphere increases with the electric
field enhancement and, correspondingly, decreases with the solar wind
dynamic pressure increase.
- Atmospheric temperature as expected, increases with the solar
dynamic pressure enhancement and decreases with humidity enhancement.
- The solar proton fluxes themselves do not produce any notable effect
in middle latitude atmosphere during the solar proton events.
- All the above-mentioned effects could be explained in frame work of
a modified version of the global electric circuit with external EMF
generator driving by the solar wind energy. Electric field produced by
the currents in this circuit is directed against corrotation electric
field of the Earth. Therefore a residual electric field in the middle
latitudes decreases with the solar wind dynamic pressure enhancement.
- The results of this study confirm our previous finding that the
solar wind energy affects the atmospheric behavior in global scale.
-
Monitoring of global, regional and local perturbations of the
atmospheric electric circuit as displayed in short-period pulsations and
coherent structures of atmospheric electric field
E.A.Mareev(1) and S.V.Anisimov(2)
- Institute of Applied Physics, Russian Academy of Science, Department
of Plasma Physics and Electronics, 46 Ulyanov str., 603950 Nizhny
Novgorod, Russia
- Borok Geophysical Observatory, Russian Academy of Sciences, Borok,
Yaroslavl, 152742. Russia
The remote sensing of the electric field is necessary for global
circuit characterization, thunderstorm electrification study, testing of
different theories in the field. Short-period pulsations
(10-3 - 1 Hz) of the electric field represent an integral
part of atmospheric electric processes found to be important to
recognize global components of atmospheric electric circuit activity
[Ruhnke et al., 1983] and serve as a sensitive indicator of the boundary
layer dynamics, particularly the convective processes and cloud
generation. The authors of this project have developed a new method of
structural-temporal analysis for these pulsations and applied it to the
study of structures of electric field and space charge [Anisimov et al.,
1994]. This analysis allowed us to derive particular information on the
formation and evolution of aeroelectric structures (AES) and develop a
model of aeroelectric structures formation taking into account the
occurrence of convective cells with respective turbulent air and space
charge density distribution, as well as the cooperative
electro-aerodynamic effects in a system of bipolar ions, generated by
cosmic rays and radioactivity, and aerosol particles in the terrestrial
electric field [Anisimov et al., 1999].
Recent investigations [Anisimov and Mareev, 2001] show that these
pulsations at frequencies 10-2 - 10-1 Hz have a
power-law spectrum during fair weather and fog, while the origins of
space charge structures in the surface layer are different under
different meteorological and geophysical conditions. Revealing a
connection of aeroelectric spectra and coherent aeroelectric structures
generation to the meteorological parameters and geophysical conditions
allows us to promote monitoring of local, global and regional-scale
perturbations of the atmospheric electric circuit by means of short
period electric field pulsation analysis. The extensive further
researches of AES with greater space between the field sensors will be
undertaken; the respective database of ground-based electric field and
electric current measurements will be created and theoretically
analysed. Research of mechanisms of pulsation spectra formation will be
continued, including the contribution of convective mechanism. A method
of structural-temporal analysis for electric field pulsations is
used.
Stages of study: 1)parameterization of aeroelectric structures in the
boundary layer; 2) theory of AES generation development; 3) search for
universal spectra of electric field short-period pulsations; 4)
theoretical analysis of spectra; 5) simultaneous measurements and
spectra analysis of temperature and electric field pulsation; 6)
parameterization of convective mechanism for aeroelectric structure
formation and evolution, and its global circuit and climate
implications.
REFERENCES:
Anisimov, S.V. and E.A.Mareev, Aeroelectrical structures in the
atmosphere, Doklady Akademy of Sciences, 371, 1, 101-104, 2000.
Anisimov, S.V., E.A. Mareev and S.S. Bakastov, On the generation and
evolution of aeroelectric structures in the surface layer, J.Geophys.
Res., 104, D12, 14359-14367, 1999.
Anisimov, S.V., E.A.Mareev, N.M.Shikhova and E.M.Dmitriev, Mechanisms
for the formation of electric field pulsation spectra in the
near-surface atmosphere, Radiophysics and Quantum Electronics, 44, 7,
562-577, 2001.
Anisimov, S.V., S.S.Bakastov and E.A.Mareev, Spatiotemporal
structures of electric field and space charge in the surface atmospheric
layer, J. Geophys. Res., 99, 10603-10610, 1994.
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Modeling of electrical structure of thunderclouds and mesoscale
convective systems as connected to initiation of intra-cloud,
cloud-to-ground and high-altitude discharge phenomena
E.A.Mareev, V.Yu.Trakhtengerts, D.I.Iudin, A.E.Sorokin,
E.I.Smirnova, S.S.Davydenko, N.A.Bogatov
Institute of Applied Physics, Russian Academy of Science, Department
of Plasma Physics and Electronics, 46 Ulyanov str., 603950 Nizhny
Novgorod, Russia
Recent studies gave evidence of connection of intra-cloud,
cloud-to-ground and high-altitude discharge initiation to the actual
structure of the space charge and electrical field in thunderstorms and
mesoscale convective systems (MCS), including multi-layer charge
structure of MCS. In particular [Huang et al., 1999] suggested that
different types of space charge structures, leading to positive ground
flashes, could result in sprite or elve generation respectively. Many
results now support the point by Williams [1998] on the positive charge
resevoir for sprite-producing lightning. This point is confirmed also by
recently obtained theoretical results [Smirnova et al., 2000] on the
modeling of lightning generated electric field transitional processes
over thunderclouds. A common way to improve modeling of thunderstorm
electric structure is the increase of complexity taking into account
different charging mechanisms, their different parametrizations and
actual cloud dynamics patterns [MacGorman and Rust, 1998]. The authors
of this project are developing a supplementary approach, based on the
search of main characteristic structural elements of electrification
dynamics. In the framework of such an approach we have modeled
particularly: fine-scale electrical stratification of the cloud as a
result of instability in a multi-flow system of charged particles
[Trakhtengerts, 1989; Mareev et al., 1999]; a branched nonstationary
conducting network (drainage system) gathering the macroscopic space
charge during lightning inception stage [Iudin et al., 1998, 2000];
electric field and current evolution as a solution of a nonlinear
diffusion equation for the field strength in a cloud [Mareev and
Sorokin, 1999]; runaway electron avalanche [Smirnova et al., 2001]. We
have elaborated also the principles of laboratory modeling for the
multi-flow system of ionised air and highly charged aerosol particles,
and started with the design of a set-up for this experiment [Mareev et
al., 1996].
We are going:
- to examine noninductive/inductive thunderstorm-charging mechanisms
with regard to the electrical filamentation and electrohydrodynamic
turbulence in a thundercloud, and to perform laboratory modeling of
electrical interaction for multi-flow charged aerosol particles and
weakly ionised air;
- to develop an autowave model of a thunderstorm cloud and reveal a
connection between electrical structure of thunderclouds (gross-scale
and fine-scale) and initiation of intra-cloud, cloud-to-ground and
high-altitude discharge phenomena;
- to develop a theory of electric discharge in a gas of aerosol
particles;
- to model severe storms and mesoscale convective systems in a global
circuit;
- to develop a fractal approach for the quantitative description of
the macroscopic charge gathering within a thundercloud.
The recently elaborated theory of fine structure generation will be
developed in terms of account for different charge transfer mechanism
and application for actual thunderstorm cloud and MCS conditions. The
experimental modelling of the flow instability is based on the creation
of colliding flows of unipolar charged aerosol and unipolar charged air
flow, which form the quasineutral nonequilibrium medium to be favourable
for an instability realization. The results of this experiment will help
to understand the nature of space charge structure formation and
lightning discharge development in thunderstorms.
REFERENCES:
Smirnova E.I., Mareev E.A. and Chugunov Yu.V., Modeling of electric
field transitional processes, Geophys. Res. Lett., V.27, N23. 3833-3836,
2000.
Mareev E.A., Sorokin, A.E. and V.Yu. Trakhtengerts, Effects of
collective charging in a multiflow aerosol plasma, Plasma Physics
Reports, 25, N3, 289-300, 1999.
Mareev, E.A., and A.E.Sorokin, An autowave model of electric field in
a thunderstorm, Radiophysics and Quantum Electronics, 39, 797-814,
2001. Smirnova, E.I., V.E.Semenov and E.A.Mareev, Analytical
model of high-altitude discharge caused by runaway electron avalanche,
JASTP, 2001 (submitted).
Iudin D.I., Trakhtengerts V.Y. Dynamics of electrical discharges in a
thunderstorm cloud. In: Proceedings of Intern. Workshop "Strong
Microwaves in Plasmas". N. Novgorod, 2 - 9 August 1999. Ed. by A.G.
Litvak. V.2, p. 461, 2000.
-
The Micro-satellite DEMETER
M. Parrot
LPCE/CNRS, Orléans, France
The micro-satellite DEMETER (Detection of Electro-Magnetic Emissions
Transmitted from Earthquake Regions) is a low-altitude satellite (< 800
km with a nearly polar orbit to be launched by CNES in 2003. The
scientific objectives of this project are related to the investigation
of ionospheric perturbations due to seismic activity, and to the global
study of the Earth electromagnetic environment. The payload of DEMETER
is composed of several sensors associated to a data processing unit and
a large memory in order to record the information all around the Earth
independently from a telemetry station. DEMETER will measure
electromagnetic waves from DC up to 4 MHz, and plasma parameters. There
are two modes: i) a survey mode to record low bit rate data all around
the Earth, and ii) a burst mode to record high bit rate data above main
seismic regions. The duration of the mission is two years. This poster
will describe the scientific objectives of the project, the payload, the
operations, and the relations with other satellites and ground-based
measurements.
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Geolocating Sprites using an improved ELF/VLF method
Colin Price(1), Mustafa Asfur(1), Walter Lyons(2) and Thomas
Nelson(2)
- Department of Geophysics and Planetary Sciences, Tel Aviv
University, Israel
- Yucca Ridge Field Station, FMA Research, Inc., Fort Collins,
Colorado, U.S.A.
The majority of sprites, the most common of transient luminous events
(TLEs) in the upper atmosphere, are associated with a sub-class of
positive cloud-to-ground lightning flashes (+CGs) whose characteristics
are slowly being revealed. These +CGs produce extremely low frequency
(ELF) and very low frequency (VLF) radiation detectable at great
distances from the parent thunderstorm. During the STEPS field program
in the United States, ELF/VLF transients associated with sprites were
detected in the Negev Desert, Israel, some 11000 km away. Within a
two-hour period on 4 July, 2000, all of the sprites detected optically
in the United States produced detectable ELF transients in Israel. All
of these transients were of positive polarity (representing positive
lightning). Using the VLF data to obtain the azimuth of the transients,
and the ELF data to calculate the distance between the source and
receiver, we remotely determined the position of sprite-forming
lightning events with an average locational error of 184 km (error of
1.6%).
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Lightning and Climate: The Water Vapor Connection
Colin Price and Mustafa Asfur
Department of Geophysics and Planetary Sciences Tel Aviv University,
Ramat Aviv, 69978 Israel
The amplitude of future global warming will depend strongly on how
upper tropospheric water vapor (UTWV) changes in response to greenhouse
gas forcings. There are arguments in support of both positive and
negative water vapor feedbacks. To understand these feedbacks it is
necessary to understand how UTWV varies on different spatial and
temporal scales. However, monitoring long-term changes in water vapor is
very difficult, and no single method is in place, or planned, to deal
with this problem. We will present evidence showing the close link
between UTWV variability and global and regional lightning activity.
Continental deep convective storms that transport large amounts of water
vapor into the upper troposphere dominate the variability of global
UTWV, while also being the storms that produce the majority of our
planet's lightning. Furthermore, integrated global lightning activity
can be continuously observed from a single location on the earth's
surface via the Schumann Resonances (SR), an electromagnetic phenomenon
in the atmosphere produced by global lightning. Therefore, observations
of the SR may supply a cheap, convenient method of studying the
long-term variability of global UTWV.
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THE MODEL OF ENHANCED IONIZATION LAYERS IN MIDLATITUDE NIGHTTIME
D-REGION OF IONOSPHERE IN THE PRESENCE OF ANOMALOUS ELECTRIC FIELDS
V.P.Kim, S.A.Pulinets, V.V.Hegai
IZMIRAN, Troitsk, Moscow Region, 142190, RUSSIA
Theoretical model of possible electron density enhancements in the
mid-latitude nighttime D-region ionosphere in the presence of anomalous
atmospheric vertical electric field is presented. Such electric fields
could appear over giant thunderstorm clouds or within the seismoactive
zone few days before the severe earthquake. Electric field penetrating
into ionosphere and magnetosphere creates the ducts of ionization with
perpendicular size of order 300 km. Effective canalization of the
coherent and incoherent VLF emissions takes place. The cyclotron
resonance interaction with the energetic particles of radiative belts
leads to the pitch-angle diffusion of energetic particles, and due to
diffusion the part of the particles fall into the loss-cone and
precipitates into the atmosphere. Our model calculations show that the
nighttime D-region electron density can considerably increase due to
precipitating energetic electrons' ionization of the lower atmosphere.
Horizontal size of perturbed electron density area is about 300 km. The
perturbation effect is expected to be more prominent if a powerful VLF
radiotransmitter operates in the vicinity of an anomalous electric field
zone. In this case a very dense ionization layer of daytime D-layer type
can be formed at altitudes of the upper nighttime mesosphere resulting
in the effect of substantial absorption of HF radiowaves propagating
over the earthquake preparation area. Our calculations are supported by
the experimental measurements of over horizon propagation of VHF FM
broadcast signals in Japan before the strong earthquakes, as well as
amplitude and phase anomalies of Omega transmitter signals over
epicentral zones of forthcoming earthquakes. These effects could be
explained by the formation of enhanced ionization layers in the lower
ionosphere. Such ionization is provided by the precipitating
particles.
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AREAL VARIATION OF THE WORLDWIDE THUNDERSTORM ACTIVITY AS SHOWN BY
SCHUMANN RESONANCES
G. Sátori, B. Zieger and J. Bór
Geodetic and Geophysical Research Institute, Csatkai u. 6-8. H-9401
Sopron, Hungary
Long-term Schumann resonance frequency records at Nagycenk (NCK),
Hungary have been used to determine areal variations of the worlwide
thunderstorm activity on seasonal, annual and interannual time scales.
The daily frequency range (DFR) of Schumann resonances (SR) is the band
in which the resonance frequency shifts up and down during a day. The
DFR is related to the size of the region where the random lightning
discharges are distributed. The wider, the region is, the smaller the
DFR becomes, and vice versa. The mean size (diameter) of thunderstorm
regions can be obtained from the DFR using a calibration curve
charcteristic of the SR station at NCK. Monthly means of source diameter
were determined from May 1993 up to the present. Annual variations with
May-June maxima and November-December minima and semiannual variations
with April and October maxima were extracted with a filtering technique.
The annual areal variation can be explained by the North-South asymmetry
of the land-ocean distribution. The annual and semiannual areal
variations show a clear, long term (decadal) modulation which might be
attributed to a solar-cycle dependence of the worlwide lightning
area.
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A model evaluation of the ozone density changes caused by various types
of corpuscular radiation
Shirochkov A.V., Makarova L.N., Ul'ev V.A.
Arctic and Antarctic Research Institute, St.-Petersburg, 199397
Russia
There are reliable experimental evidences that some strong proton
events (SPE) are accompanied by simultaneous intense precipitation of
the relativistic (E>1 MeV) electron fluxes -so called relativistic
electron precipitation (REP) events. However, the ionospheric and
atmospheric effects caused by such combined geophysical disturbances are
analysed by the usual methods: as the results of impact of the sole
agent -the solar proton fluxes.
The purpose of this study is to try to separate effects of two
simultaneously existing sources of energization of the middle
atmosphere: the solar proton and relativistic electron fluxes and to
evaluate importance of each of them. An event of May, 1992 when intense
SPE was accompanied by significant increase of relativistic (E>2 MeV)
electron precipitation as measured by the GOES-7 detectors. We have used
in this study our original 1D photochemical dynamical model of the
middle atmosphere (altitude range 10-90 km). This model includes the
oxygen, hydrogen, chlorine and bromine component groups which interact
with each other in 150 chemical reactions. The model consists of several
independent which can evaluate numerically the following parameters: a)
atmospheric temperature together with concentration of the main
atmospheric components: O2 and N2; b) rate of ionization by the solar
proton fluxes; c) rate of photodissociation by the solar EUV radiation;
d) concentration of the atmospheric minor components; e) rate of
ionization by the relativistic electron fluxes.
The main results of this study are the following:
- There are solar proton events where simultaneous intense
precipitations relativistic electron fluxes registered.
- Both these ionization agents cause their own ionospheric and
atmospheric effects at altitudes of its maximum penetration into
atmosphere.
- Exact evaluation of the effects of the solar proton and relativistic
electron fluxes is important for correct understanding of the
disturbances in the middle atmosphere.
- Ozone layer in stratosphere (at altitudes of its maximum density)
can be affected only by the solar proton and relativistic electron
fluxes very hard energetic spectra.
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Changes in cloud cover associated with Forbush decreases of galactic
cosmic rays
Martin C. Todd(1) and Dominic R. Kniveton(2)
- Department of Geography, University College London (UCL), 26 Bedford
Way, London, WC1H 0AP Tel. +44 20 7679 4271 Fax. +44 20 7679 4293
- School of Chemistry, Physics and Environmental Science, University
of Sussex, Falmer, Brighton, BN1 9QJ, UK
A controversial issue in climate science is the possible effect of
galactic cosmic ray flux (GCR) on clouds. Here, we present the results
of a study to quantify the relationship between cloud cover and
short-term Forbush decreases (FD) of GCR. FD events represent an
interesting sampling base for GCR/cloud studies given that there are no
known internal modes of climate variability operating with similar
temporal frequency. Using an extensive record of global satellite
derived cloud products from the International Satellite Cloud
Climatology Project (ISCCP) D1 data series, epoch superposition analysis
of a sample of FD events was conducted. Cloud anomalies relative to
conditions prior to FD events were derived at a range of spatial scales
from global, through 5-degree geomagnetic latitude bands to a global
grid with 2.5-degree resolution. Resulting cloud anomalies were tested
for significance using a randomised Monte Carlo experiment. The results
indicate a small but significant (at 0.001% level) decline in the global
proportion of cloud cover (of up to 1.4%) immediately prior to and
following FD events. Analysis of data averaged over geomagnetic latitude
bands reveals that significant cloud anomalies are concentrated in the
high latitudes. These anomalies occur largely in the upper-level cloud,
and are particularly pronounced (up to -30%) over Antarctica. In
contrast, analysis using a sample of FD events associated with solar
proton burst events shows no statistically significant cloud
anomalies.
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INFLUENCE OF THE SOLAR WIND VARIATIONS ON TEMPERATURE IN THE
SOUTHERN POLAR CAP TROPOSPHERE
O.A.Troshichev, L.V.Egorova, V.Ya.Vovk
Arctic and Antarctic Research Institute, St.Petersburg, Russia
Fluxes of galactic cosmic rays altered by solar wind and spikes of
solar cosmic rays are usually examined as one possible mechanism of
solar activity influencing the Earth-s atmosphere. Analysis of wide set
of aerological data from the Antarctic near-pole station Vostok has
shown that atmospheric perturbations in the Southern winter polar region
are better related with interplanetary shocks that always accompany
perturbations in galactic and solar cosmic rays. It is possible that
these effects are most obvious at the Vostok station because: (1) Vostok
station is located at a flat homogeneous plain at height 3.5 km (ice
dome), that is not subjected to local atmospheric vortices; (2)
Circumpolar atmospheric circulation, with alone circle covering the
whole continent, is typical of Antarctica in the winter season, and
Vostok station is close to center of this circle; (3) Vostok station is
not exposed to the direct solar radiation in period of polar night in
winter season; (4) The catabatic type of atmospheric circulation (i.e.
vertical type of circulation) is typical of the central part of
Antarctic, where the stratosphere cold air masses go down to ice dome
and then flow along the dome surface toward the cost. These features
allow the Vostok station location to act like a window into the nature
of the nighttime middle atmosphere where solar influences are stronger
than in the lower atmosphere.
The detail analysis of the Vostok data for 1978-1992 made it possible
to conclude that dramatic changes of the tropospheric temperature
observed in the Southern near-pole region in relation to the
interplanetary shocks are caused by sharp changes of the IMF Bz
component (and, correspondingly, by fluctuations of the interplanetary
electric field) typical of the interplanetary shocks. There is a linear
relationship between the value of IMF Bz changes and ground temperature
at Vostok station: the larger is leap in the southern Bz the stronger is
the warming. The regularity is especially supported by fact that cooling
at Vostok is observed in relation with the northward Bz leaps. The
effect reaches maximum (warming up to 20 degrees in specific events)
within one day and is damped equally quickly. It is particularly
remarkable that the tropospheric temperature also responds to daily
changes of the IMF Bz component, if these changes are considerable.
Linkage between the interplanetary electric field and the temperature
variations observed in the southern polar region is regarded as evidence
of the strong solar wind influence on global electric circuit acting
between the ionosphere and ground.
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The Trough Based Neural Network Model of the foF2 Values
Yurdanur Tulunay(1), Ersin Tulunay(2) and Erdem Turker
Senalp(2)
- Faculty of Aeronautics and Astronautics, Istanbul Technical
University, Istanbul, Turkey
- Dept of Electrical and Electronics Engineering, Middle East Technical
University, Ankara, Turkey
The mid latitude electron density trough has been investigated by
Tulunay extensively since 1968 by using the electron density data returned
by the ARIEL3 and ARIEL4 satellites. In the past years starting with the
COST238: PRIME Action it has been demonstrated that the abrupt gradients
of electron densities in space and time of the trough are directly
reflected foF2.
Thus the performance of HF communications are directly affected. In
this work an attempt has been made for the modelling to quantify the
influence of the ionospheric mid latitude electron density trough on the
ionospheric critical frequency foF2 by using neural networks. Data sets
are used from the ground stations that include observations in the trough
region. It has been demonstrated that the neural net based approaches are
promising in modeling of the ionospheric processes. Data generated by
using statistical relationships obtained by the Ariel4 data are used to
train the neural network. It has been shown with this work that properly
constructed NN-based systems, trained and tested with properly organized
data are promising in modeling the complex nonlinear processes, such as
the influence of the trough on foF2 values.
-
MEIDEX: An Opportunity for Coordinated Global Measurements of TLE from
the Space Shuttle and Ground Stations
Yoav Yair(1,2), Colin Price(1), Zev Levin(1), Adam Devir(1),
Baruch Ziv(1,2), Meir Moalem(1)
- Department of Geophysics and Planetary Sciences, Tel-Aviv University
Tel-Aviv, Israel 69978
- Open University of Israel, 16 Klausner St., Tel-Aviv, Israel 61392
The Mediterranean Israeli Dust Experiment (MEIDEX) will be carried
out from the space shuttle Columbia, scheduled for the STS-107 flight in
summer 2002. The 16 days' mission will be in a 39°-inclination
orbit, passing over the major thunderstorm regions on Earth. The primary
science instrument is a Xybion IMC-201 image-intensified radiometric
camera with 6 narrow band filters, boresighted with a wide-FOV color
video camera. Both cameras are mounted on a single-axis gimbal with a
cross-track scan of ±22°, inside a pressurized canister
sealed with a coated quartz window that is mounted in the shuttle cargo
bay. Data will be recorded in 3 digital VCRs and downlinked to the
ground. During the night part of the orbit there will be dedicated
observations toward the Earth's limb above areas of active
thunderstorms, in an effort to image TLEs from space. Observations will
consist of a continuous recording of the Earth's limb, from the
direction of the dusk terminator towards the night side. While earlier
shuttle flights have succeeded in recording several ionospheric
discharges by using cargo bay video cameras, MEIDEX offers a unique
opportunity to conduct targeted observations with a calibrated,
multispectral instrument. The Xybion camera has a rectangular FOV of
14.04(H) x 10.76 (V) degrees, that covers a volume of 466km (H) x 358km
(V) at the Earth's limb, 1900km away from the shuttle. The spatial
resolution is 665m (H) x 745m (V) per pixel, enabling to resolve some
structural features of TLE. Optical observations from space will be
conducted with the 665nm filter that matches the observed wide peak
centered at 670nm that typifies red sprites, and also with the 380 and
470nm filters to record blue jets. Areas of high convective activity
will be forecast by using global aviation SIG maps, and uplinked to the
crew before the observation. The astronaut will direct the camera toward
areas with lightning activity, observed visually through the windows and
on monitors in the crew cabin. Simultaneously with the optical
observations from space, dedicated ground measurements will be conducted
on a global scale. Two field sites in the Negev Desert in Israel will be
used to collect electromagnetic data in the ELF and VLF frequency range.
Additional ground stations in Germany, Hungary, USA, Antarctica, Chile,
South Africa, Australia, Taiwan and Japan will also record Schumann
Resonance and VLF signals. The coordinated measurements from various
locations on Earth and from space will enable geo-locating and
determining the polarity and charge moment of the parent lightning of
the optically observed TLE. The success of the campaign will further
clarify the global picture of TLE occurrence.
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| Last update: 2002-02-11, 1348 UT, by Th.Ulich, editor [e-mail | homepage]. |
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