共查询到20条相似文献,搜索用时 25 毫秒
1.
Deborah L. Domingue Patrick L. Koehn Rosemary M. Killen Ann L. Sprague Menelaos Sarantos Andrew F. Cheng Eric T. Bradley William E. McClintock 《Space Science Reviews》2007,131(1-4):161-186
The existence of a surface-bounded exosphere about Mercury was discovered through the Mariner 10 airglow and occultation experiments.
Most of what is currently known or understood about this very tenuous atmosphere, however, comes from ground-based telescopic
observations. It is likely that only a subset of the exospheric constituents have been identified, but their variable abundance
with location, time, and space weather events demonstrate that Mercury’s exosphere is part of a complex system involving the
planet’s surface, magnetosphere, and the surrounding space environment (the solar wind and interplanetary magnetic field).
This paper reviews the current hypotheses and supporting observations concerning the processes that form and support the exosphere.
The outstanding questions and issues regarding Mercury’s exosphere stem from our current lack of knowledge concerning the
surface composition, the magnetic field behavior within the local space environment, and the character of the local space
environment. 相似文献
2.
Because of its chemical and radiative properties, atmospheric ozone constitutes a key element of the Earth’s climate system.
Absorption of sunlight by ozone in the ultraviolet wavelength range is responsible for stratospheric heating, and determines
the temperature structure of the middle atmosphere. Changes in middle atmospheric ozone concentrations result in an altered
radiative input to the troposphere and to the Earth’s surface, with implications on the energy balance and the chemical composition
of the lower atmosphere. Although a wide range of ground- and satellite-based measurements of its integrated content and of
its vertical distribution have been performed since several decades, a number of uncertainties still remain as to the response
of middle atmospheric ozone to changes in solar irradiance over decadal time scales. This paper presents an overview of achieved
findings, including a discussion of commonly applied data analysis methods and of their implication for the obtained results.
We suggest that because it does not imply least-squares fitting of prescribed periodic or proxy data functions into the considered
times series, time-domain analysis provides a more reliable method than multiple regression analysis for extracting decadal-scale
signals from observational ozone datasets. Applied to decadal ground-based observations, time-domain analysis indicates an
average middle atmospheric ozone increase of the order of 2% from solar minimum to solar maximum, which is in reasonable agreement
with model results. 相似文献
3.
M.-L Chanin 《Space Science Reviews》2006,125(1-4):261-272
In the last 45 years I have studied the thermal structure of the atmosphere from the thermosphere down to the stratosphere,
and found evidence of its variability in relationship with the change of solar irradiation during the 11-year solar cycle.
I would review, in the light of recent model results, the measurements which I had made since the 1960s and which, for some
of them, did not find any explanation at the time of their publication. The data were obtained by two different techniques,
rockets and lidars and correspond to different regions of the atmosphere from the upper thermosphere to the stratosphere.
The expectation was until recently that the atmosphere should be warmed by an increase of solar flux in the course of the
solar cycle due to the increase of UV flux. It has been shown to be the case in the tropical stratosphere and at all latitudes
in the upper thermosphere. But, at high and mid latitudes and at other altitudes, the reverse situation was found to exist
and, until recently, this cooling observed in parts of the atmosphere with increasing solar flux had never been simulated
by models. In addition to reviewing our own data, the paper will present recent results using other dataset which support
our observations. It is only recently that we succeeded with a model able to tune the forcing by planetary waves at the tropopause
level and thus reproduce such behaviour. 相似文献
4.
G. Rottman 《Space Science Reviews》2006,125(1-4):39-51
The Sun’s electromagnetic radiation powers our solar system. In the case of the Earth it heats the lands and ocean, maintains
our atmosphere, generates clouds, and cycles water. For other planets and minor bodies, similar and appropriate physical processes
occur, also powered by the Sun. The Sun varies on all time scales and a precise knowledge of the Sun's irradiance and its
variation is essential to our understanding of environments and physical conditions throughout our solar system. Measurements
of solar irradiance and its variation can only be made from space, and almost thirty years of observation have now established
that the total solar irradiance (TSI) varies by only 0.1 to 0.3%, while certain portions of the solar spectrum, the ultraviolet
for example, vary by orders of magnitude more. This paper provides an overview of TSI observations and of spectral irradiance
observations from the ultraviolet to the near infrared. 相似文献
5.
Planetary upper atmospheres-coexisting thermospheres and ionospheres-form an important boundary between the planet itself
and interplanetary space. The solar wind and radiation from the Sun may react with the upper atmosphere directly, as in the
case of Venus. If the planet has a magnetic field, however, such interactions are mediated by the magnetosphere, as in the
case of the Earth. All of the Solar System’s giant planets have magnetic fields of various strengths, and interactions with
their space environments are thus mediated by their respective magnetospheres. This article concentrates on the consequences
of magnetosphere-atmosphere interactions for the physical conditions of the thermosphere and ionosphere. In particular, we
wish to highlight important new considerations concerning the energy balance in the upper atmosphere of Jupiter and Saturn,
and the role that coupling between the ionosphere and thermosphere may play in establishing and regulating energy flows and
temperatures there. This article also compares the auroral activity of Earth, Jupiter, Saturn and Uranus. The Earth’s behaviour
is controlled, externally, by the solar wind. But Jupiter’s is determined by the co-rotation or otherwise of the equatorial
plasmasheet, which is internal to the planet’s magnetosphere. Despite being rapid rotators, like Jupiter, Saturn and Uranus
appear to have auroral emissions that are mainly under solar (wind) control. For Jupiter and Saturn, it is shown that Joule
heating and “frictional” effects, due to ion-neutral coupling can produce large amounts of energy that may account for their
high exospheric temperatures. 相似文献
6.
A. Ohmura 《Space Science Reviews》2006,125(1-4):111-128
The variation of global radiation (sum of direct solar and diffuse sky radiation) at the Earth’s surface is examined based
on pyranometer measurements at about 400~sites. The period of the study covers in general the last 50 years. For Europe the
study is extended to the beginning of observations in the 1920s and 1930s. Global radiation generally increased in Europe
from the 1920s to the 1950s. After the late 1950s and early 1960s global radiation began to decrease in most areas of the
world at a mean rate of 0.7 Wm−2a−1 until 1980s, thereafter 75%; of the stations showed a recovery at a mean rate of 0.7 Wm−2a−1. All stations in the Polar region, which are far from aerosol sources, also show this pattern of change. At the remaining
25% of the stations the decrease has continued to present. These regions are a part of China, most of India, and Central Africa.
Both during the declining and recovering phases global radiation observed under the cloudless condition also followed the
same tendency, indicating the simultaneous and parallel changes of aerosol and cloud conditions. Long-term observations of
total zenith transmittance of the atmosphere indicate a decrease in transmittance to the mid 1980s and an increase after this
period. Since the brighter and darker periods correspond to relatively warmer and colder periods, the present study offers
the possibility to quantitatively evaluate the mutual relationships between the solar irradiance, atmospheric transmittance,
cloud conditions and air temperature. 相似文献
7.
MESSENGER: Exploring Mercury’s Magnetosphere 总被引:1,自引:0,他引:1
James A. Slavin Stamatios M. Krimigis Mario H. Acuña Brian J. Anderson Daniel N. Baker Patrick L. Koehn Haje Korth Stefano Livi Barry H. Mauk Sean C. Solomon Thomas H. Zurbuchen 《Space Science Reviews》2007,131(1-4):133-160
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury offers our first opportunity
to explore this planet’s miniature magnetosphere since the brief flybys of Mariner 10. Mercury’s magnetosphere is unique in
many respects. The magnetosphere of Mercury is among the smallest in the solar system; its magnetic field typically stands
off the solar wind only ∼1000 to 2000 km above the surface. For this reason there are no closed drift paths for energetic
particles and, hence, no radiation belts. Magnetic reconnection at the dayside magnetopause may erode the subsolar magnetosphere,
allowing solar wind ions to impact directly the regolith. Inductive currents in Mercury’s interior may act to modify the solar
wind interaction by resisting changes due to solar wind pressure variations. Indeed, observations of these induction effects
may be an important source of information on the state of Mercury’s interior. In addition, Mercury’s magnetosphere is the
only one with its defining magnetic flux tubes rooted beneath the solid surface as opposed to an atmosphere with a conductive
ionospheric layer. This lack of an ionosphere is probably the underlying reason for the brevity of the very intense, but short-lived,
∼1–2 min, substorm-like energetic particle events observed by Mariner 10 during its first traversal of Mercury’s magnetic
tail. Because of Mercury’s proximity to the sun, 0.3–0.5 AU, this magnetosphere experiences the most extreme driving forces
in the solar system. All of these factors are expected to produce complicated interactions involving the exchange and recycling
of neutrals and ions among the solar wind, magnetosphere, and regolith. The electrodynamics of Mercury’s magnetosphere are
expected to be equally complex, with strong forcing by the solar wind, magnetic reconnection, and pick-up of planetary ions
all playing roles in the generation of field-aligned electric currents. However, these field-aligned currents do not close
in an ionosphere, but in some other manner. In addition to the insights into magnetospheric physics offered by study of the
solar wind–Mercury system, quantitative specification of the “external” magnetic field generated by magnetospheric currents
is necessary for accurate determination of the strength and multi-polar decomposition of Mercury’s intrinsic magnetic field.
MESSENGER’s highly capable instrumentation and broad orbital coverage will greatly advance our understanding of both the origin
of Mercury’s magnetic field and the acceleration of charged particles in small magnetospheres. In this article, we review
what is known about Mercury’s magnetosphere and describe the MESSENGER science team’s strategy for obtaining answers to the
outstanding science questions surrounding the interaction of the solar wind with Mercury and its small, but dynamic, magnetosphere. 相似文献
8.
The record of dynamical structure reveals a systematic variation that operates coherently with the 11-yr variation of UV irradiance.
Involving periods shorter than 5 years, the systematic variation reflects the influence of the QBO on the polar-night vortex.
It has the same basic structure as interannual changes associated with the residual mean circulation of the stratosphere.
A signature of the solar cycle also appears in the direct correlation to solar flux, as recovered through regression of the
entire monthly record. That signature, however, is sharply enhanced around solstice, when the residual circulation is active,
and during extremal phases of the QBO. In the tropics, the solar signature follows, throughout the year, from a decadal modulation
in the frequency of the QBO. The modulation is manifested to either side of the QBO’s mean frequency, in two spectral peaks
where the QBO dwells: one at (24 months)−1, reflecting a Biennial Oscillation (BO), and another at (36 months)-1. Intrinsic to the QBO, those peaks are separated from its mean frequency by ∼11 years−1.Through the QBO’s residual circulation, the decadal modulation introduces anomalies in the subtropics, with symmetry about
the equator. Accompanying anomalous temperature in the subtropics is a stronger signature over the winter pole. Discovered
by Labitzke and van Loon 1988, that solar signature reflects anomalous downwelling of the Brewer-Dobson circulation. It is
shown to follow through the BO, which is intrinsic to the QBO and its modulation of the polar-night vortex. 相似文献
9.
Wiesław M. Macek 《Space Science Reviews》2006,122(1-4):329-337
The question of multifractality is of great importance because it allows us to investigate interplanetary hydromagnetic turbulence.
The multifractal spectrum has been investigated with Voyager (magnetic field) data in the outer heliosphere and with Helios
(plasma) data in the inner heliosphere. We use the Grassberger and Procaccia method that allows calculation of the generalized
dimensions of the solar wind attractor in the phase space directly from the cleaned experimental signal. We analyze time series
of plasma parameters of the low-speed streams of the solar wind measured in situ by Helios in the inner heliosphere. The resulting spectrum of dimensions shows a multifractal structure of the solar wind
attractor. In order to quantify that multifractality, we use a simple analytical model of the dynamical system. Namely, we
consider the generalized self-similar baker’s map with two parameters describing uniform compression and natural invariant
measure on the attractor of the system. The action of this map exhibits stretching and folding properties leading to sensitive
dependence on initial conditions. The obtained solar wind singularity spectrum is consistent with that for the multifractal
measure on the weighted baker’s map. 相似文献
10.
Robert J. Rutten 《Space Science Reviews》1998,85(1-2):269-280
This “rapporteur” report discusses the solar photosphere and low chromosphere in the context of chemical composition studies.
The highly dynamical nature of the photosphere does not seem to jeopardize precise determination of solar abundances in classical
fashion. It is still an open question how the highly dynamical nature of the low chromosphere contributes to first ionization
potential (FIP) fractionation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
11.
Erich Becker 《Space Science Reviews》2012,168(1-4):283-314
This review recapitulates the concept of the wave-driven residual circulation in the stratosphere and mesosphere. The residual circulation is defined as the conventional mean meridional circulation corrected by the quasi-linear Stokes drift due to atmospheric waves. Only when the zonal-mean primitive equations are transformed using the residual circulation, they reflect the causality arising from the Eliassen-Palm (EP) theorem. The EP theorem states that the proper wave-mean flow interaction, defined as the EP flux divergence, vanishes for waves that are linear, conservative, and steady. In the real atmosphere, this theorem is violated mainly due to wave breaking and turbulence. The resulting EP flux divergence then drives a residual circulation which causes the observed substantial deviations from some hypothetical radiatively determined state. With regard to this dynamical control we discuss the different contributions of Rossby waves and gravity waves. Recapitulation of Lindzen’s theory of gravity-wave saturation allows us to interpret various phenomena in the upper mesosphere such as interhemispheric coupling or modulations of the gravity-wave driven branch of the residual circulation by solar proton effects and thermal tides. In addition we discuss the relative importance of changes in radiative transfer and tropospheric gravity-wave sources on the long-term temperature trends in the summer mesosphere. 相似文献
12.
Emmanuel Lellouch 《Space Science Reviews》2005,116(1-2):211-224
Our knowledge of Io’s atmosphere has improved dramatically in the last fifteen years, with a wealth of new observational data
at millimeter, UV and IR wavelengths, and the development of numerous models describing its horizontal and vertical structure,
composition, photochemistry and plasma interaction. Io’s atmosphere is dominantly composed of SO2, present mostly at low-tomid
latitudes with column densities of a few 1016 cm−2 and important (factors of 5-10) longitudinal variations. Minor compounds include SO, S2, and NaCl. Sublimation equilibrium with SO2 frost and direct volcanic output coexist to maintain Io’s atmosphere against condensation, photolytic and escape losses. 相似文献
13.
Athena Coustenis 《Space Science Reviews》2005,116(1-2):171-184
The origin and evolution of Titan’s enigmatic atmosphere is reviewed. Starting with the present-day volatile inventory, the
question of what was the original composition on Titan and how a satellite of similar size to other Galilean moons managed
to acquire and hold on to the required material is discussed. In particular the possible sources and sinks of the main mother
molecules (nitrogen, methane and oxygen) are investigated in view of the most recent models and laboratory experiments. The
answers expected to be provided by the instruments aboard the Cassini-Huygens mission to some of the most prominent current
questions regarding Titan’s atmosphere are defined. 相似文献
14.
The response of the lower and middle atmosphere to variations in solar irradiance typical of those observed to take place over the 11-year activity cycle has been investigated. The effects on radiative heating rates of changing total solar irradiance, solar spectral irradiance and two different assumptions concerning stratospheric ozone have been studied with a radiative transfer code. The response in the stratosphere depends on the changes specified in the ozone distribution which is not well known. A general circulation model (GCM) of the atmosphere up to 0.1 mbar (about 65 km) has been used to study the impacts of these changes on the thermodynamical structure. The results in the troposphere are very similar to those reported by Haigh99 using a quite different GCM. In the middle atmosphere the model is able to reproduce quite well the observed seasonal evolution of temperature and wind anomalies. Calculations of radiative forcing due to solar variation are presented. These show that the thermal infrared component of the forcing, due to warming of the stratosphere, is important but suggest a near balance between the longwave and shortwave effects of the increased ozone so that ozone change may not be important for net radiative forcing. However, the structure of the ozone change does affect the detailed temperature response and the spectral composition of the radiation entering the troposphere. 相似文献
15.
Wei Fengsi Feng Xueshang Guo Jian-shan Fan Quanlin Wu Jian 《Space Science Reviews》2003,107(1-2):327-334
Recent progress in space weather research are briefly presented here from three aspects: establishment or improvement in observation
systems, such as extra-soft X-ray detector and γ-ray detector onboard the spacecraft ‘Shen Zhou 2’, new solar radio broad-band
spectrometer, magnetometer-chain, ionosonde and digisonde–chain, laser-lidar system and VHF radar; partial topic progresses
included in CMEs, multi-streamer structures, evolution of interplanetary magnetic field B
z component, regional properties of traveling ionospheric disturbances, a fully-nonlinear global dynamical model for the middle
and upper atmosphere, and a combined prediction method for geomagnetic disturbances; and space weather activity, such as ‘Meridian
Project’ — a national major scientific project, ‘International Space Weather Meridian Circle Program’ — a suggestion of internationalization
of ‘Meridian Project’, ‘Space Weather Research Plan’ — a major research plan from National Natural Science Foundation of China
(NNSFC) and other space weather activities.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
A coupled climate model is used to explore the regional response of the climate system to solar forcing, with emphasis on
the role of the ocean. It is shown that both the transient and the equilibrium response of surface temperature to changes
in total solar irradiation is smaller over ocean than over land because of the ocean’s large heat capacity and the feedback
involving evaporation. Furthermore, the advection of temperature anomalies and changes in ocean currents have an impact on
the timing and the geographical distribution of the response. Nevertheless, at regional scales, the response to the forcing
is embedded within the large internal variability of the system making the detection and analysis of the forced response difficult.
Furthermore, this forced response could imply both changes in the mean state of the system as well as in its variability. 相似文献
17.
Brian E. Wood 《Space Science Reviews》2006,126(1-4):3-14
Exposure to the solar wind can have significant long term consequences for planetary atmospheres, especially for planets such
as Mars that are not protected by global magnetospheres. Estimating the effects of solar wind exposure requires knowledge
of the history of the solar wind. Much of what we know about the Sun’s past behavior is based on inferences from observations
of young solar-like stars. Stellar analogs of the weak solar wind cannot be detected directly, but the interaction regions
between these winds and the interstellar medium have been detected and used to estimate wind properties. I here review these
observations, with emphasis on what they suggest about the history of the solar wind. 相似文献
18.
Alfvén waves are considered to be viable transporters of the non-thermal energy required to heat the Sun’s quiescent atmosphere. An abundance of recent observations, from state-of-the-art facilities, have reported the existence of Alfvén waves in a range of chromospheric and coronal structures. Here, we review the progress made in disentangling the characteristics of transverse kink and torsional linear magnetohydrodynamic (MHD) waves. We outline the simple, yet powerful theory describing their basic properties in (non-)uniform magnetic structures, which closely resemble the building blocks of the real solar atmosphere. 相似文献
19.
Chang Tom Tam Sunny W.Y. Wu Cheng-Chin Consolini Giuseppe 《Space Science Reviews》2003,107(1-2):425-445
The first definitive observation that provided convincing evidence indicating certain turbulent space plasma processes are
in states of ‘complexity’ was the discovery of the apparent power-law probability distribution of solar flare intensities.
Recent statistical studies of complexity in space plasmas came from the AE index, UVI auroral imagery, and in-situ measurements
related to the dynamics of the plasma sheet in the Earth's magnetotail and the auroral zone.
In this review, we describe a theory of dynamical ‘complexity’ for space plasma systems far from equilibrium. We demonstrate
that the sporadic and localized interactions of magnetic coherent structures are the origin of ‘complexity’ in space plasmas.
Such interactions generate the anomalous diffusion, transport, acceleration, and evolution of the macroscopic states of the
overall dynamical systems.
Several illustrative examples are considered. These include: the dynamical multi- and cross-scale interactions of the macro-and
kinetic coherent structures in a sheared magnetic field geometry, the preferential acceleration of the bursty bulk flows in
the plasma sheet, and the onset of ‘fluctuation induced nonlinear instabilities’ that can lead to magnetic reconfigurations.
The technique of dynamical renormalization group is introduced and applied to the study of two-dimensional intermittent MHD
fluctuations and an analogous modified forest-fire model exhibiting forced and/or self-organized criticality [FSOC] and other
types of topological phase transitions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Recent observational evidence has suggested that variations in solar activity may affect winter stratospheric polar ozone and temperature levels. The paucity of direct sunlight available during this season points strongly to a dynamical mechanism. We have carried out several large ensemble experiments within the middle atmosphere and the coupled middle atmosphere and lower thermosphere to simulate the radiative/dynamical coupling via planetary waves for a range of solar fluxes. In the former case, the model response in the winter stratosphere was linear and of the order of the summer stratopause forcing, whilst in the latter, the level of correlation in the winter stratosphere remained high, but was diluted over a wider volume. The inclusion of the upper atmosphere enhanced the winter polar stratospheric response by a factor of three. 相似文献