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1.
Saint-Hilaire Pascal von Praun Christoph Stolte Etzard Alonso Gustavo Benz Arnold O. Gross Thomas 《Solar physics》2002,210(1-2):143-164
The RHESSI Experimental Data Center (HEDC) at ETH Zürich aims to facilitate the use of RHESSI data. It explores new ways to
speed up browsing and selecting events such as solar flares. HEDC provides pre-processed data for on-line use and allows basic
data processing remotely over the Internet. In this article, we describe the functionality and contents of HEDC, as well as
first experiences by users. HEDC can be accessed at http://www.hedc.ethz.ch. Additional graphical material and color versions of most figures are available on the CD-ROM accompanying this volume.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022413302246 相似文献
2.
The RHESSI Spectrometer 总被引:2,自引:0,他引:2
Smith D.M. Lin R.P. Turin P. Curtis D.W. Primbsch J.H. Campbell R.D. Abiad R. Schroeder P. Cork C.P. Hull E.L. Landis D.A. Madden N.W. Malone D. Pehl R.H. Raudorf T. Sangsingkeow P. Boyle R. Banks I.S. Shirey K. Schwartz Richard 《Solar physics》2002,210(1-2):33-60
RHESSI observes solar photons over three orders of magnitude in energy (3 keV to 17 MeV) with a single instrument: a set of
nine cryogenically cooled coaxial germanium detectors. With their extremely high energy resolution, RHESSI can resolve the
line shape of every known solar gamma-ray line except the neutron capture line at 2.223 MeV. High resolution also allows clean
separation of thermal and non-thermal hard X-rays and the accurate measurement of even extremely steep power-law spectra.
Detector segmentation, fast signal processing, and two sets of movable attenuators allow RHESSI to make high-quality spectra
and images of flares across seven orders of magnitude in intensity. Here we describe the configuration and operation of the
RHESSI spectrometer, show early results on in-flight performance, and discuss the principles of spectroscopic data analysis
used by the RHESSI software. 相似文献
3.
Schwartz R.A. Csillaghy A. Tolbert A.K. Hurford G.J. Mc Tiernan J. Zarro D. 《Solar physics》2002,210(1-2):165-191
The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) performs imaging spectroscopy of the Sun with high spatial
and spectral resolution from 3 keV to 17 MeV using indirect Fourier-transform techniques. We review the rationale behind the
RHESSI data analysis software, and explain the underlying structure of the software tools. Our goal was to make the large
data set available within weeks after the RHESSI launch, and to make it possible for any member of the scientific community
to analyze it easily. This paper describes the requirements for the software and explores our decisions to use the SolarSoftWare
and Interactive Data Language programming packages, to support both Windows and Unix platforms, and to use object-oriented
programming. We also describe how the data are rapidly disseminated and how ancillary data sets are used to enhance the RHESSI
science. Finally, we give a schematic overview of some of the data flow through the high-level analysis tools. More information
on the data and analysis procedures can be found at the RHESSI Data Center website, http://hesperia.gsfc.nasa.gov/rhessidatacenter.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022444531435 相似文献
4.
M. Focardi E. Pace M. Farina A. M. Di Giorgio J. Colomé Ferrer I. Ribas C. Sierra Roig L. Gesa Bote J. C. Morales J. Amiaux C. Cara J. L. Augurés E. Pascale G. Morgante V. Da Deppo M. Pancrazzi V. Noce S. Pezzuto M. Frericks F. Zwart G. Bishop K. Middleton P. Eccleston G. Micela G. Tinetti 《Experimental Astronomy》2018,45(1):1-20
In this paper we present the electromagnetic modeling and beam pattern measurements of a 16-elements ultra wideband sparse random test array for the low frequency instrument of the Square Kilometer Array telescope. We discuss the importance of a small array test platform for the development of technologies and techniques towards the final telescope, highlighting the most relevant aspects of its design. We also describe the electromagnetic simulations and modeling work as well as the embedded-element and array pattern measurements using an Unmanned Aerial Vehicle system. The latter are helpful both for the validation of the models and the design as well as for the future instrumental calibration of the telescope thanks to the stable, accurate and strong radio frequency signal transmitted by the UAV. At this stage of the design, these measurements have shown a general agreement between experimental results and numerical data and have revealed the localized effect of un-calibrated cable lengths in the inner side-lobes of the array pattern. 相似文献
5.
Hurford G.J. Schmahl E.J. Schwartz R.A. Conway A.J. Aschwanden M.J. Csillaghy A. Dennis B.R. Johns-Krull C. Krucker S. Lin R.P. McTiernan J. Metcalf T.R. Sato J. Smith D.M. 《Solar physics》2002,210(1-2):61-86
The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) observes solar hard X-rays and gamma-rays from 3 keV to
17 MeV with spatial resolution as high as 2.3 arc sec. Instead of focusing optics, imaging is based on nine rotating modulation
collimators that time-modulate the incident flux as the spacecraft rotates. Starting from the arrival time of individual photons,
ground-based software then uses the modulated signals to reconstruct images of the source. The purpose of this paper is to
convey both an intuitive feel and the mathematical basis for this imaging process. Following a review of the relevant hardware,
the imaging principles and the basic back-projection method are described, along with their relation to Fourier transforms.
Several specific algorithms (Clean, MEM, Pixons and Forward-Fitting) applicable to RHESSI imaging are briefly described. The
characteristic strengths and weaknesses of this type of imaging are summarized. 相似文献
6.
We present the first in-depth statistical survey of flare source heights observed by RHESSI. Flares were found using a flare-finding
algorithm designed to search the 6 – 10 keV count-rate when RHESSI’s full sensitivity was available in order to find the smallest
events (Christe et al. in Astrophys. J.
677, 1385, 2008). Between March 2002 and March 2007, a total of 25 006 events were found. Source locations were determined in the 4 – 10 keV,
10 – 15 keV, and 15 – 30 keV energy ranges for each event. In order to extract the height distribution from the observed projected
source positions, a forward-fit model was developed with an assumed source height distribution where height is measured from
the photosphere. We find that the best flare height distribution is given by g(h)∝exp (−h/λ) where λ=6.1±0.3 Mm is the scale height. A power-law height distribution with a negative power-law index, γ=3.1±0.1 is also consistent with the data. Interpreted as thermal loop-top sources, these heights are compared to loops generated
by a potential-field model (PFSS). The measured flare heights distribution are found to be much steeper than the potential-field
loop height distribution, which may be a signature of the flare energization process. 相似文献
7.
High-resolution solar hard X-ray imaging on the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) spacecraft is
achieved by a set of rotating modulation collimators. The interpretation of the observed time-modulated X-ray flux in terms
of high-resolution, accurately located images requires continuous, arc-minute roll aspect, which at present is provided by
the `Photo-Multiplier Tube Roll Aspect System' (PMTRAS). This paper describes the PMTRAS operating principles, hardware implementation,
calibration, performance and data analysis approach, with emphasis on its effect on RHESSI imaging. 相似文献
8.
Past analyses of flare hard X-ray (HXR) spectra have largely ignored the effect of nonuniform ionization along the electron
paths in the thick-target model, though it is very significant for well-resolved spectra. The inverse problem (photon spectrum
to electron injection spectrum F
0(E
0)) is disturbingly non-unique. However, we show that it is relatively simple to allow for the effect in forward fitting of
parametric models of F
0(E
0)) and provide an expression to evaluate it for the usual single power-law form of F
0(E
0)).The expression involves the column depth N
* of the transition region in the flare loop as one of the parameters so data fitting can enable derivation of N
* (and its evaporative evolution) as part of the fitting procedure. The fit to RHESSI data on four flares for a single power
law F
0(E
0)) is much improved when ionization structure is included compared to when the usual fully ionized approximation is used.
This removes the need, in these events at least, to invoke broken power laws, or other forms, of the acceleration spectrum
F
0(E
0)) to explain the observed photon spectrum 相似文献
9.
The angular distribution of electrons accelerated in solar flares is a key parameter in the understanding of the acceleration and propagation mechanisms that occur there. However, the anisotropy of energetic electrons is still a poorly known quantity, with observational studies producing evidence for an isotropic distribution and theoretical models mainly considering the strongly beamed case. We use the effect of photospheric albedo to infer the pitch-angle distribution of X-ray emitting electrons using Hard X-ray data from RHESSI. A bi-directional approximation is applied and a regularised inversion is performed for eight large flare events to deduce the electron spectra in both downward (towards the photosphere) and upward (away from the photosphere) directions. The electron spectra and the electron anisotropy ratios are calculated for a broad energy range, from about ten up to ~?300 keV, near the peak of the flares. The variation of electron anisotropy over short periods of time lasting 4, 8 and 16 seconds near the impulsive peak has been examined. The results show little evidence for strong anisotropy and the mean electron flux spectra are consistent with the isotropic electron distribution. The 3σ level uncertainties, although energy and event dependent, are found to suggest that anisotropic distribution with anisotropy larger than ~?three are not consistent with the hard X-ray data. At energies above 150?–?200 keV, the uncertainties are larger and thus the possible electron anisotropies could be larger. 相似文献
10.
José F. Gómez Joaquín Trapero Carmen Morales Verónica Orozco Jerry Edelstein Eric Korpela Michael Lampton 《Astrophysics and Space Science》2001,276(1):233-238
EURD (EspectrógrafoUltravioleta extremo para la Radiación Difusa) is one of thescientific instruments on board MINISAT 01. EURD is a spectrograph withvery high sensitivity and spectral resolution ( 5 Å), designed to obtain extremeultraviolet ( 350-1100 Å) spectra of diffuse radiation.We outline the processing of EURD data, and how we obtain informationfrom these data on the scientific goals of the mission: hot interstellarmedium, neutrino decay line, nightglow emission, and early-type stars. 相似文献
11.
This paper presents the methods of soil parameter estimation from neutron probing data that are used when processing the data from the DAN experiment on the Martian surface. We discuss the data preprocessing steps that enable us to compare experimental data to a Monte-Carlo numerical model, algorithms used to estimate equivalent water and chlorine content for standard soil composition and to dynamically analyse the soil parameters in non-standard cases. We also provide the water and chlorine content estimates and compare them with the SAM experiment data. 相似文献
12.
《Solar physics》2002,210(1-2):3-32
RHESSI is the sixth in the NASA line of Small Explorer (SMEX) missions and the first managed in the Principal Investigator
mode, where the PI is responsible for all aspects of the mission except the launch vehicle. RHESSI is designed to investigate
particle acceleration and energy release in solar flares, through imaging and spectroscopy of hard X-ray/gamma-ray continua
emitted by energetic electrons, and of gamma-ray lines produced by energetic ions. The single instrument consists of an imager,
made up of nine bi-grid rotating modulation collimators (RMCs), in front of a spectrometer with nine cryogenically-cooled
germanium detectors (GeDs), one behind each RMC. It provides the first high-resolution hard X-ray imaging spectroscopy, the
first high-resolution gamma-ray line spectroscopy, and the first imaging above 100 keV including the first imaging of gamma-ray
lines. The spatial resolution is as fine as ∼ 2.3 arc sec with a full-Sun (≳ 1°) field of view, and the spectral resolution
is ∼ 1–10 keV FWHM over the energy range from soft X-rays (3 keV) to gamma-rays (17 MeV). An automated shutter system allows
a wide dynamic range (>107) of flare intensities to be handled without instrument saturation. Data for every photon is stored in a solid-state memory
and telemetered to the ground, thus allowing for versatile data analysis keyed to specific science objectives. The spin-stabilized
(∼ 15 rpm) spacecraft is Sun-pointing to within ∼ 0.2° and operates autonomously. RHESSI was launched on 5 February 2002,
into a nearly circular, 38° inclination, 600-km altitude orbit and began observations a week later. The mission is operated
from Berkeley using a dedicated 11-m antenna for telemetry reception and command uplinks. All data and analysis software are
made freely and immediately available to the scientific community.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022428818870 相似文献
13.
We present an analysis of hard X-ray imaging observations from one of the first solar flares observed with the Reuven Ramaty
High-Energy Solar Spectroscopic Imager (RHESSI) spacecraft, launched on 5 February 2002. The data were obtained from the 22
February 2002, 11:06 UT flare, which occurred close to the northwest limb. Thanks to the high energy resolution of the germanium-cooled
hard X-ray detectors on RHESSI we can measure the flare source positions with a high accuracy as a function of energy. Using
a forward-fitting algorithm for image reconstruction, we find a systematic decrease in the altitudes of the source centroids
z(ε) as a function of increasing hard X-ray energy ε, as expected in the thick-target bremsstrahlung model of Brown. The altitude
of hard X-ray emission as a function of photon energy ε can be characterized by a power-law function in the ε=15–50 keV energy
range, viz., z(ε)≈2.3(ε/20 keV)−1.3 Mm. Based on a purely collisional 1-D thick-target model, this height dependence can be inverted into a chromospheric density
model n(z), as derived in Paper I, which follows the power-law function n
e(z)=1.25×1013(z/1 Mm)−2.5 cm−3. This density is comparable with models based on optical/UV spectrometry in the chromospheric height range of h≲1000 km, suggesting that the collisional thick-target model is a reasonable first approximation to hard X-ray footpoint sources.
At h≈1000–2500 km, the hard X-ray based density model, however, is more consistent with the `spicular extended-chromosphere model' inferred from radio sub-mm observations, than with standard models based on hydrostatic equilibrium. At coronal heights,
h≈2.5–12.4 Mm, the average flare loop density inferred from RHESSI is comparable with values from hydrodynamic simulations
of flare chromospheric evaporation, soft X-ray, and radio-based measurements, but below the upper limits set by filling-factor
insensitive iron line pairs. 相似文献
14.
太阳耀斑中硬X射线(HXR)光子谱的低能变平过去一般认为是由于耀斑中非热电子的低能截止造成的,但现在也有作者认为耀斑光子与下层大气的逆康普顿散射(albedo效应)或者其他作用也能够使得HXR光子谱出现低能变平的情形.采用Gan etal.(2001,2002)中提出的求非热电子低能截止的方法,统计分析了Ramaty High EnergySolar Spectroscopy Imager(RHESSI)卫星在2002--2005年间观测的100个耀斑,发现经albedo校正,有18个耀斑的HXR光子谱可以利用单幂律谱来拟合,在80个可以用双幂律谱来拟合HXR光子谱的耀斑中,有21个耀斑可以直接用单幂律电子谱加一个低能截止来解释.低能截止范围为20-50keV,平均值约为30keV.同时也分析了耀斑光子谱特征的其他可能解释. 相似文献
15.
《天文和天体物理学研究(英文版)》2016,(11)
White-light(WL) flares have been observed and studied for more than a century since their first discovery. However, some fundamental physics behind the brilliant emission remains highly controversial.One of the important facts in addressing the flare energetics is the spatio-temporal correlation between the WL emission and the hard X-ray(HXR) radiation, presumably suggesting that energetic electrons are the energy sources. In this study, we present a statistical analysis of 25 strong flares(≥M5) observed simultaneously by the Helioseismic and Magnetic Imager(HMI), on board the Solar Dynamics Observatory(SDO),and the Reuven Ramaty High Energy Solar Spectroscopic Imager(RHESSI). Among these events, WL emission was detected by SDO/HMI in 13 flares, associated with HXR emission. To quantitatively describe the strength of WL emission, equivalent area(EA) is defined as the integrated contrast enhancement over the entire flaring area. Our results show that the EA is inversely proportional to the HXR power-law index,indicating that stronger WL emission tends to be associated with a larger population of high energy electrons. However, no obvious correlation is found between WL emission and flux of non-thermal electrons at50 ke V. For the other group of 13 flares without detectable WL emission, the HXR spectra are softer(larger power-law index) than those flares with WL emission, especially for the X-class flares in this group. 相似文献
16.
Thomas P. Sparn Gary Rottman Thomas N. Woods Brian D. Boyle Richard Kohnert Sean Ryan Randall Davis Robert Fulton William Ochs 《Solar physics》2005,230(1-2):71-89
The Solar Radiation and Climate Experiment, SORCE, is a satellite carrying four scientific instruments that measure the total
solar irradiance and the spectral irradiance from the ultraviolet to the infrared. The instruments were all developed by the
Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder. The spacecraft carrying and accommodating
the instruments was developed by Orbital Sciences Corporation in Dulles, Virginia. It is three-axis stabilized with a control
system to point the instruments at the Sun, as well as the stars for calibration. SORCE was successfully launched from the
Kennedy Space Center in Florida on 25 January 2003 aboard a Pegasus XL rocket. The anticipated lifetime is 5 years, with a
goal of 6 years. SORCE is operated from the Mission Operations Center at LASP where all data are collected, processed, and
distributed. This paper describes the SORCE spacecraft, integration and test, mission operations, and ground data system. 相似文献
17.
Daniel F. Ryan Aidan M. O’Flannagain Markus J. Aschwanden Peter T. Gallagher 《Solar physics》2014,289(7):2547-2563
We test the compatibility and biases of multi-thermal flare DEM (differential emission measure) peak temperatures determined with AIA with those determined by GOES and RHESSI using the isothermal assumption. In a set of 149 M- and X-class flares observed during the first two years of the SDO mission, AIA finds DEM peak temperatures at the time of the peak GOES 1?–?8 Å flux to have an average of T p=12.0±2.9 MK and Gaussian DEM widths of log10(σ T )=0.50±0.13. From GOES observations of the same 149 events, a mean temperature of T p=15.6±2.4 MK is inferred, which is systematically higher by a factor of T GOES/T AIA=1.4±0.4. We demonstrate that this discrepancy results from the isothermal assumption in the inversion of the GOES filter ratio. From isothermal fits to photon spectra at energies of ?≈6?–?12 keV of 61 of these events, RHESSI finds the temperature to be higher still by a factor of T RHESSI/T AIA=1.9±1.0. We find that this is partly a consequence of the isothermal assumption. However, RHESSI is not sensitive to the low-temperature range of the DEM peak, and thus RHESSI samples only the high-temperature tail of the DEM function. This can also contribute to the discrepancy between AIA and RHESSI temperatures. The higher flare temperatures found by GOES and RHESSI imply correspondingly lower emission measures. We conclude that self-consistent flare DEM temperatures and emission measures require simultaneous fitting of EUV (AIA) and soft X-ray (GOES and RHESSI) fluxes. 相似文献
18.
19.
20.
SONG Ye-zhi HUANG Yong HU Xiao-gong LI Pei-jia CAO Jian-feng 《Chinese Astronomy and Astrophysics》2014
It is known that the dynamical orbit determination is the most common way to get the precise orbits of spacecraft. However, it is hard to build up the precise dynamical model of spacecraft sometimes. In order to solve this problem, the technique of the orbit determination with the B-spline approximation method based on the theory of function approximation is presented in this article. In order to verify the effectiveness of this method, simulative orbit determinations in the cases of LEO (Low Earth Orbit), MEO (Medium Earth Orbit), and HEO (Highly Eccentric Orbit) satellites are performed, and it is shown that this method has a reliable accuracy and stable solution. The approach can be performed in both the conventional celestial coordinate system and the conventional terrestrial coordinate system. The spacecraft's position and velocity can be calculated directly with the B-spline approximation method, it needs not to integrate the dynamical equations, nor to calculate the state transfer matrix, thus the burden of calculations in the orbit determination is reduced substantially relative to the dynamical orbit determination method. The technique not only has a certain theoretical significance, but also can serve as a conventional algorithm in the spacecraft orbit determination. 相似文献