Magnetosheath Interaction with the High Latitude Magnetopause     

S. Savin  A. Skalsky  L. Zelenyi  L. Avanov  N. Borodkova  S. Klimov  V. Lutsenko  E. Panov  S. Romanov  V. Smirnov  YU. Yermolaev  P. Song  E. Amata  G. Consolini  T. A. Fritz  J. Buechner  B. Nikutowski  J. Blecki  C. Farrugia  N. Maynard  J. Pickett  J. A. Sauvaud  J. L. Rauch  J. G. Trotignon  Y. Khotyaintsev  K. Stasiewicz 《Surveys in Geophysics》2005,26(1-3):95-133

We present both statistical and case studies of magnetosheath interaction with the high-latitude magnetopause on the basis of Interball-1 and other ISTP spacecraft data. We discuss those data along with recently published results on the topology of cusp-magnetosheath transition and the roles of nonlinear disturbances in mass and energy transfer across the high-latitude magnetopause. For sunward dipole tilts, a cusp throat is magnetically open for direct interaction with the incident flow that results in the creation of a turbulent boundary layer (TBL) over an indented magnetopause and downstream of the cusp. For antisunward tilts, the cusp throat is closed by a smooth magnetopause; demagnetized ‘plasma balls’ (with scale ∼ few R_E, an occurrence rate of ∼25% and trapped energetic particles) present a major magnetosheath plasma channel just inside the cusp. The flow interacts with the ‘plasma balls’ via reflected waves, which trigger a chaotization of up to 40% of the upstream kinetic energy. These waves propagate upstream of the TBL and initiate amplification of the existing magnetosheath waves and their cascade-like decays during downstream passage throughout the TBL. The most striking feature of the nonlinear interaction is the appearance of magnetosonic jets, accelerated up to an Alfvenic Mach number of 3. The characteristic impulsive local momentum loss is followed by decelerated Alfvenic flows and modulated by the TBL waves; momentum balance is conserved only on time scales of the Alfvenic flows (1/f_A ∼12 min). Wave trains at f_A∼1.3 mHz are capable of synchronizing interactions throughout the outer and inner boundary layers. The sonic/Alfvenic flows, bounded by current sheets, control the TBL spectral shape and result in non-Gaussian statistical characteristics of the disturbances, indicating the fluctuation intermittency. We suggest that the multi-scale TBL processes play at least a comparable role to that of macro-reconnection (remote from or in the cusp) in solar wind energy transformation and population of the magnetosphere by the magnetosheath plasma. Secondary micro-reconnection constitutes a necessary chain at the small-scale (∼ion gyroradius) edge of the TBL cascades. The thick TBL transforms the flow energy, including deceleration and heating of the flow in the open throat, ‘plasma ball’ and the region downstream of the cusp.  相似文献   

Spatial and Temporal Cusp Structures Observed by Multiple Spacecraft and Ground Based Observations     

K. J. Trattner  S. A. Fuselier  T. K. Yeoman  C. Carlson  W. K. Peterson  A. Korth  H. Reme  J. A. Sauvaud  N. Dubouloz 《Surveys in Geophysics》2005,26(1-3):281-305

Downward precipitating ions in the cusp regularly exhibit sudden changes in ion energy distributions, forming distinctive structures that can be used to study the temporal/spatial nature of reconnection at the magnetopause. When observed simultaneously with the Polar, FAST, and Interball satellites, such cusp structures revealed remarkably similar features. These similar features could be observed for up to several hours during stable solar wind conditions. Their similarities led to the conclusion that large-scale cusp structures are spatial structures related to global ionospheric convection patterns created by magnetic merging and not the result of temporal variations in reconnection parameters. The launch of the Cluster fleet allows cusp structures to be studied in great detail and during changing solar wind conditions using three spacecraft with identical plasma and field instrumentation. In addition, Cluster cusp measurements are linked with ionospheric convection cells by combining the satellite observations with SuperDARN radar observations that are used to derive the convection patterns in the ionosphere. The combination of satellite observations with ground-based observations during variable solar wind conditions shows that large-scale cusp structures can be either spatial or temporal. Cusp structures can be described as spatial features observed by satellites crossing into spatially separated flux tubes. Cusp structures can also be observed as poleward-traveling (temporal) features within the same convection cell, most probably caused by variations in the reconnection rate at the magnetopause.  相似文献   

Low-Frequency Plasma Waves in the Outer Polar CUSP: A Review of Observations from Prognoz 8, Interball 1, Magion 4, and Cluster     

J. Blecki  R. Wronowski  S. Savin  N. Cornilleau-Wehrlin  M. Parrot  Z. Nemecek  J. Safrankova  O. Santolik  K. Kudela  J-A. Sauvaud 《Surveys in Geophysics》2005,26(1-3):177-191

This paper presents a review of the most interesting observations of low-frequency plasma waves together with plasma particles which were made by the Interball 1, Magion 4 and Prognoz 8 satellites in the outer polar cusp. Accelerated plasma particles, hot electron populations and very strong wave activity, particularly at low frequencies, are observed. A detailed study of the wave spectra together with the distribution function for electrons indicate the correlation between the presence of lower-hybrid waves and the population of the particles with higher energy than in the surrounding space. These experimental facts suggest that strong coupling between waves and particles is responsible for plasma heating. During polar cusp crossings by Interball 1 and Prognoz 8, FFT analysis of the wave form indicates many bursts of ULF emissions in both electric and magnetic components. These waves have highly non-stationary characteristics. To study the dynamics of changes in the spectral characteristics of the waves wavelet analysis has been used. Nonlinear interactions are studied using bispectral methods of analysis. This presentation gives the results of such an analysis for selected cusp crossings at different altitudes. An example of wave activity registered by the STAFF instrument onboard the CLUSTER spacecraft in the polar cusp is also presented.  相似文献   

Temporal Evolution of the Solar-Wind Electron Core Density at Solar Minimum by Correlating SWEA Measurements from STEREO A and B     

A. Opitz  J.-A. Sauvaud  A. Fedorov  P. Wurz  J. G. Luhmann  B. Lavraud  C. T. Russell  P. Kellogg  C. Briand  P. Henri  D. M. Malaspina  P. Louarn  D. W. Curtis  E. Penou  R. Karrer  A. B. Galvin  D. E. Larson  I. Dandouras  P. Schroeder 《Solar physics》2010,266(2):369-377

The twin STEREO spacecraft provide a unique tool to study the temporal evolution of the solar-wind properties in the ecliptic since their longitudinal separation increases with time. We derive the characteristic temporal variations at ～?1 AU between two different plasma parcels ejected from the same solar source by excluding the spatial variations from our datasets. As part of the onboard IMPACT instrument suite, the SWEA electron experiment provides the solar-wind electron core density at two different heliospheric vantage points. We analyze these density datasets between March and August 2007 and find typical solar minimum conditions. After adjusting for the theoretical time lag between the two spacecraft, we compare the two density datasets. We find that their correlation decreases as the time difference increases between two ejections. The correlation coefficient is about 0.80 for a time lag of a half day and 0.65 for two days. These correlation coefficients from the electron core density are somewhat lower than the ones from the proton bulk velocity obtained in an earlier study, though they are still high enough to consider the solar wind as persistent after two days. These quantitative results reflect the variability of the solar-wind properties in space and time, and they might serve as input for solar-wind models.  相似文献   

High-energy electron detection onboard DEMETER: The IDP spectrometer, description and first results on the inner belt   总被引：6，自引：0，他引：6  

J.A. Sauvaud  T. Moreau  R. Maggiolo  C. Jacquey  J. Coutelier  E. Penou 《Planetary and Space Science》2006,54(5):502-511

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Mass composition of the escaping plasma at Mars     

E. Carlsson  A. Fedorov  E. Budnik  H. Gunell  J.-A. Sauvaud  Y. Futaana  H. Andersson  J.D. Winningham  J.R. Sharber  A.J. Coates  D.O. Kataria  H. Koskinen  P. Riihelä  J. Kozyra  E. Roelof  S. Livi  K.C. Hsieh  M. Grande  J.-J. Thocaven  S. Orsini  M. Maggi  P. Bochsler  J. Woch  K. Asamura 《Icarus》2006,182(2):320-328

Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO⁺₂/O⁺ and O⁺₂/O⁺. The following ratios averaged over all events and energies were identified: CO⁺₂/O⁺ = 0.2 and O⁺₂/O⁺ = 0.9. The values measured are significantly higher, by a factor of 10 for O⁺₂/O⁺, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O⁺, followed by O⁺₂ and CO⁺₂. We estimate the loss of CO⁺₂ to be by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.  相似文献   

Multispacecraft Observations of Magnetic Clouds and Their Solar Origins between 19 and 23 May 2007     

E. K. J. Kilpua  P. C. Liewer  C. Farrugia  J. G. Luhmann  C. Möstl  Y. Li  Y. Liu  B. J. Lynch  C. T. Russell  A. Vourlidas  M. H. Acuna  A. B. Galvin  D. Larson  J. A. Sauvaud 《Solar physics》2009,254(2):325-344

We analyze a series of complex interplanetary events and their solar origins that occurred between 19 and 23 May 2007 using observations by the STEREO and Wind satellites. The analyses demonstrate the new opportunities offered by the STEREO multispacecraft configuration for diagnosing the structure of in situ events and relating them to their solar sources. The investigated period was characterized by two high-speed solar wind streams and magnetic clouds observed in the vicinity of the sector boundary. The observing satellites were separated by a longitudinal distance comparable to the typical radial extent of magnetic clouds at 1 AU (fraction of an AU), and, indeed, clear differences were evident in the records from these spacecraft. Two partial-halo coronal mass ejections (CMEs) were launched from the same active region less than a day apart, the first on 19 May and the second on 20 May 2007. The clear signatures of the magnetic cloud associated with the first CME were observed by STEREO B and Wind while only STEREO A recorded clear signatures of the magnetic cloud associated with the latter CME. Both magnetic clouds appeared to have interacted strongly with the ambient solar wind and the data showed evidence that they were a part of the coronal streamer belt. Wind and STEREO B also recorded a shocklike disturbance propagating inside a magnetic cloud that compressed the field and plasma at the cloud’s trailing portion. The results illustrate how distant multisatellite observations can reveal the complex structure of the extension of the coronal streamer into interplanetary space even during the solar activity minimum. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.  相似文献   

On the Temporal Variability of the “Strahl” and Its Relationship with Solar Wind Characteristics: STEREO SWEA Observations     

P. Louarn  C. Diéval  V. Génot  B. Lavraud  A. Opitz  A. Fedorov  J. A. Sauvaud  D. Larson  A. Galvin  M. H. Acuňa  J. Luhmann 《Solar physics》2009,259(1-2):311-321

The “strahl” is a specific population of the solar wind, constituted by strongly field aligned electrons flowing away from the Sun, with energies >60 eV. Using the Solar Wind Electron Analyzer (SWEA) onboard STEREO, we investigate the short time scale fluctuations of this population. It is shown that its phase space density (PSD) at times presents fluctuations larger than 50% at scales of the order of minutes and less. The fluctuations are particularly strong for periods of a few tens of hours in high-speed streams, following the crossing of the corotating interaction region, when the strahl is also the most collimated in pitch angle. The amplitude of the fluctuations tends to decrease in conjunction with a broadening in pitch angle. Generally, the strongly fluctuating strahl is observed when the magnetic field is also highly perturbed. That SWEA is able to perform a very rapid 3D analysis at a given energy is essential since it can be demonstrated that the observed magnetic turbulence can only marginally perturb the PSD measurements.  相似文献   

Venus express: Highlights of the nominal mission     

D. V. Titov  H. Svedhem  F. W. Taylor  S. Barabash  J. -L. Bertaux  P. Drossart  V. Formisano  B. Häusler  O. Korablev  W. J. Markiewicz  D. Nevejans  M. Pätzold  G. Piccioni  J. -A. Sauvaud  T. L. Zhang  O. Witasse  J. -C. Gerard  A. Fedorov  A. Sanchez-Lavega  J. Helbert  R. Hoofs 《Solar System Research》2009,43(3):185-209

Venus Express is the first European (ESA) mission to the planet Venus. Its main science goal is to carry out a global survey of the atmosphere, the plasma environment, and the surface of Venus from orbit. The payload consists of seven experiments. It includes a powerful suite of remote sensing imagers and spectrometers, instruments for in-situ investigation of the circumplanetary plasma and magnetic field, and a radio science experiment. The spacecraft, based on the Mars Express bus modified for the conditions at Venus, provides a versatile platform for nadir and limb observations as well as solar, stellar, and radio occultations. In April 2006 Venus Express was inserted in an elliptical polar orbit around Venus, with a pericentre height of ～250 km and apocentre distance of ～66000 km and an orbital period of 24 hours. The nominal mission lasted from June 4, 2006 till October 2, 2007, which corresponds to about two Venus sidereal days. Here we present an overview of the main results of the nominal mission, based on a set of papers recently published in Nature, Icarus, Planetary and Space Science, and Geophysical Research Letters.  相似文献   

The Venusian induced magnetosphere: A case study of plasma and magnetic field measurements on the Venus Express mission     

E. Kallio  T.L. Zhang  R. Jarvinen  P. Janhunen  J.-A. Sauvaud  J.-J. Thocaven  H. Andersson  K. Brinkfeldt  M. Holmström  M. Yamauchi  W. Baumjohann  A.J. Coates  D.O. Kataria  K.C. Hsieh  M. Grande  T. Säles  P. Riihelä  N. Krupp  J.G. Luhmann  S. Orsini  A. Mura  M. Maggi  P. Brandt  K. Szego  R.A. Frahm  J.R. Sharber  P. Bochsler 《Planetary and Space Science》2008,56(6):796-801

Plasma and magnetic field measurements made onboard the Venus Express on June 1, 2006, are analyzed and compared with predictions of a global model. It is shown that in the orbit studied, the plasma and magnetic field observations obtained near the North Pole under solar minimum conditions were qualitatively and, in many cases also, quantitatively in agreement with the general picture obtained using a global numerical quasi-neutral hybrid model of the solar wind interaction (HYB-Venus). In instances where the orbit of Venus Express crossed a boundary referred to as the magnetic pileup boundary (MPB), field line tracing supports the suggestion that the MPB separates the region that is magnetically connected to the fluctuating magnetosheath field from a region that is magnetically connected to the induced magnetotail lobes.  相似文献