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21.
Sriharsha Madhavan Junqiang Sun Xiaoxiong Xiong 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(10):3059-3071
Dust detection using remotely sensed measurements has been one of the challenging problems encountered by atmospheric scientists. MODerate Resolution Imaging Spectroradiometer (MODIS) on the Terra (T) and Aqua (A) platforms have been a versatile sensor for well over 21 and 18 years respectively, and have been extremely useful in the retrieval of aerosol information over the entire globe. The MODIS radiances from the Level 1B in general are expected to be within 5% accuracy in the reflective wavelengths and within 1% in the thermal emissive wavelengths. In this paper, we evaluate the sensitivity of previously developed dust detection technique based on thermal emissive wavelengths, which correspond to MODIS bands 20, 29, 31, and 32 respectively. The Thermal Emissive Dust Index (TEDI) performed very comparably to the traditional Aerosol Optical Thickness (AOT) retrievals by MODIS reflective channels. Since the MODIS Thermal Emissive Bands (TEB) are well calibrated on-orbit using a BlackBody (BB) source, the calibration of these long wave infrared bands is quite robust. As A-MODIS continues to perform well beyond its designed lifetime of 6 years, the instrument has undergone various levels of degradation during its mission time. As a consequence, it is imperative to check the impacts of calibration on the higher-level retrievals. In this paper, we rigorously analyze the sensitivity of TEDI due to the impact of calibration by the afore-mentioned TEB. The perturbation of the dominant (linear) calibration term demonstrated the following: first, there was a correlation in the sensitivity of the TEDI due to the uncertainty in the linear calibration term. Based on a perturbation in the linear calibration term for all aforementioned bands over a range of ±5% yielded the TEDI sensitivity to vary from approximately ?3.2% to about ?3.6%. When considering the uncertainty in each individual band significant changes were observed. The least change was observed for the perturbation in the calibration of band 20 with the TEDI sensitivity and the largest sensitivity in TEDI was observed in the perturbation of band 31 calibration. Thus, in the case of TEDI, noticeable sensitivity due to calibration uncertainty was observed in bands 29, 31, and 32, reiterating the importance of the TEB calibration in these bands. Also, the dust detection scheme based on A-MODIS was successfully transferred to the follow-on sensors such as Suomi (SNPP) and NOAA 20 (N20) VIIRS. The results presented in this paper would be extremely helpful in understanding impacts of calibration on the higher-level products for both current and future missions based on the MODIS heritage. Finally, the work also identifies the importance of radiometric fidelity in maintaining the accuracy of the dust detection. Results presented will show drastic improvement of the Saharan dust detection after the reduction of the electronic crosstalk in the 8.5 µm channel of T-MODIS. 相似文献
22.
Mikhail E. Gushchin Sergey V. KorobkovAlexander V. Kostrov Mikhail V. StarodubtsevAskold V. Strikovsky 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Modulation of whistler waves in a plasma with time-dependant magnetic field perturbations was investigated experimentally. The experiments were performed on large “Krot” device, which was specially designed to study space plasma physics phenomena. It is shown that magnetic field variations on the wave propagation path can lead to splitting of initially continuous whistler wave into the sequence of bursts, whose repetition rate corresponds to magnetic field perturbation period. The frequency inside each burst is changing from its front edge to the back edge. Relative shift of the wave frequency can be as large as the relative magnetic disturbance. Distortion of whistler wave frequency spectrum after its passing through magnetically disturbed areas can be used as a diagnostics for low-frequency magnetic field variations. The applicability of our laboratory results to space plasma is discussed. 相似文献
23.
J. G. Trotignon J. L. Michau D. Lagoutte M. Chabassière G. Chalumeau F. Colin P. M. E. Décréau J. Geiswiller P. Gille R. Grard T. Hachemi M. Hamelin A. Eriksson H. Laakso J. P. Lebreton C. Mazelle O. Randriamboarison W. Schmidt A. Smit U. Telljohann P. Zamora 《Space Science Reviews》2007,128(1-4):713-728
The main objective of the Mutual Impedance Probe (MIP), part of the Rosetta Plasma Consortium (RPC), is to measure the electron
density and temperature of Comet 67P/Churyumov-Gerasimenko’s coma, in particular inside the contact surface. Furthermore,
MIP will determine the bulk velocity of the ionised outflowing atmosphere, define the spectral distribution of natural plasma
waves, and monitor dust and gas activities around the nucleus. The MIP instrumentation consists of an electronics board for
signal processing in the 7 kHz to 3.5 MHz range and a sensor unit of two receiving and two transmitting electrodes mounted
on a 1-m long bar. In addition, the Langmuir probe of the RPC/LAP instrument that is at about 4 m from the MIP sensor can
be used as a transmitter (in place of the MIP ones) and MIP as a receiver in order to have access to the density and temperature
of plasmas at higher Debye lengths than those for which the MIP is originally designed. 相似文献
24.
S.A. Elwakil M.A. Zahran E.K. El-Shewy A.E. Mowafy 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A theoretical investigation has been made for adiabatic positive and negative dust charge fluctuations on the propagation of dust-ion acoustic waves (DIAWs) in a weakly inhomogeneous, collisionless, unmagnetized dusty plasmas consisting of cold positive ions, stationary positively and negatively charged dust particles and isothermal electrons. The reductive perturbation method is employed to reduce the basic set of fluid equations to the variable coefficients Korteweg–de Vries (KdV) equation. Either compressive or rarefactive solitons are shown to exist depending on the critical value of the ion density, which in turn, depends on the inhomogeneous distribution of the ion. The dissipative effects of non-adiabatic dust charge variation has been studied which cause generation of dust ion acoustic shock waves governed by KdV-Burger (KdVB) equation. The results of the present investigation may be applicable to some dusty plasma environments, such as dusty plasma existing in polar mesosphere region. 相似文献
25.
G.S. Lakhina S.V. SinghA.P. Kakad 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A general model for the ion- and electron-acoustic solitons and double layers in a multi-component unmagnetized plasma consisting of background electrons, counter-streaming electron beams and ions is discussed. The model is based on the multi-fluid equations and the Poisson equation, and uses the Sagdeev pseudo-potential techniques. For identical counter-streaming electron beams and depending upon the plasma parameters, three types of solutions, namely, ion-acoustic, slow and fast electron-acoustic soliton/double layer, are possible. Generally, the ion acoustic solitons have positive potentials, slow-electron acoustic solitons have negative potentials and fast electron-acoustic solitons and double layers can have either positive or negative potentials depending on the core electron density. As beam speed is increased, first ion-acoustic and then slow electron-acoustic solitons disappear. At large beam speed, only fast electron-acoustic solitons/double layers survive. The results may be relevant to the observations of the electrostatic solitary waves (ESWs) observed in the Earth’s magnetosphere. 相似文献
26.
An increasing number of high-resolution spacecraft observations provide access to details of energetic electron and ion velocity-space
distribution structures. Since resonant wave-particle interaction processes depend considerably on the distribution function
details, space plasma modeling is of particular interest for studies of a variety of plasma environments as planetary magnetospheres,
the interplanetary medium or solar flares. After summarizing the most popular particle acceleration processes we focus on
wave-powered energization mechanisms induced by Landau interaction and demonstrate from a time-evolutionary scenario that
power-law distributions, highly favored by observations in recent years, are generated resonantly by an Alfvén wave spectrum
and possibly saturate. This process is further stimulated in non-uniform magnetic field configurations where multiple wave
packets at different phase velocities provide the energy source for a continuous acceleration process. Moreover, in this conjunction
we demonstrate that in particular κ-distributions are a consequence of a generalized entropy concept, favored by nonextensive
statistics, which provides the missing link for power-law plasma models from fundamental physics. With regard to in situ space
observations examples are provided illuminating that for non-thermal plasma characteristics the particular structure of the
velocity-space distribution dominates as regulating mechanism for the wave-particle interaction process over effects related
to changes in space plasma parameters.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
27.
Frank Verheest 《Space Science Reviews》1994,68(1-4):109-114
Nonlinear modes are investigated in magnetized dusty plasmas, where the dust dynamics is modelled by a number of cold, highly negatively charged and very massive fluids, besides ordinary electrons and protons. Several low-frequency motions occur which are typical for the dust components, some of them described by model equations such as the derivative nonlinear Schrödinger equation for electromagnetic waves. One can include equilibrium drifts and even fluctuations in the grain charges. Most of the preceding conclusions are relevant for different kinds of astrophysical and heliospheric plasmas. 相似文献
28.
29.
S. Takechi K. Nogami T. Miyachi M. Fujii N. Hasebe T. Iwai S. Sasaki H. Ohashi H. Shibata E. Grün R. Srama N. Okada 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
A cosmic dust monitor for use onboard a spacecraft is currently being developed using a piezoelectric lead zirconate titanate element (PZT). Its characteristics of the PZT sensor is studied by ground-based laboratory impact experiments using hypervelocity particles supplied by a Van de Graaff accelerator. The output signals obtained from the sensor just after the impact appeared to have a waveform that was explicitly related to the particle’s impact velocity. For velocities less than ∼6 km/s, the signal showed an oscillation pattern and the amplitude was proportional to the momentum of the impacting particle. For higher velocities, the signal gradually changed to a single waveform. The rise time of this single waveform was proportional to the particle’s velocity for velocities above ∼6 km/s. The present paper reports on results for the low velocity case and especially discusses the effect of an outer coating of the sensor with a paint, which is used to reduce heating by solar radiation. 相似文献
30.
Gianfranco Vidali Ling Li Joseph E. Roser Ryan Badman 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Silicates constitute an important class of interstellar grain material and are the site of catalytic activities, most notably the formation of molecular hydrogen. Here we report an analysis of experiments conducted in the laboratory to measure the efficiency of formation of molecular hydrogen on amorphous silicates, a realistic analogue of interstellar dust grains. From the measurements, we also obtain the energetics of key processes in the reaction and information on the mechanism of reaction. Comparison with earlier measurements of molecular hydrogen formation on a sample of polycrystalline olivine shows that amorphous materials are more efficient catalysts. 相似文献