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1.
Polar coronal holes (PCHs) trace the magnetic variability of the Sun throughout the solar cycle. Their size and evolution have been studied as proxies for the global magnetic field. We present measurements of the PCH areas from 1996 through 2010, derived from an updated perimeter-tracing method and two synoptic-map methods. The perimeter-tracing method detects PCH boundaries along the solar limb, using full-disk images from the SOlar and Heliospheric Observatory/Extreme ultraviolet Imaging Telescope (SOHO/EIT). One synoptic-map method uses the line-of-sight magnetic field from the SOHO/Michelson Doppler Imager (MDI) to determine the unipolarity boundaries near the poles. The other method applies thresholding techniques to synoptic maps created from EUV image data from EIT. The results from all three methods suggest that the solar maxima and minima of the two hemispheres are out of phase. The maximum PCH area, averaged over the methods in each hemisphere, is approximately 6 % during both solar minima spanned by the data (between Solar Cycles 22/23 and 23/24). The northern PCH area began a declining trend in 2010, suggesting a downturn toward the maximum of Solar Cycle 24 in that hemisphere, while the southern hole remained large throughout 2010. 相似文献
2.
We searched for solar neutrons using the data collected by six detectors from the International Network of Solar Neutron Telescopes and one Neutron Monitor between January 2010 and December 2014. We considered the peak time of the X-ray intensity of thirty five ≥ X1.0 class flares detected by GOES satellite as the most probable production time of solar neutrons. We prepared a light-curve of the solar neutron telescopes and the neutron monitor for each flare, spanning ± 3 h from the peak time of GOES. Based on these light curves, we performed a statistical analysis for each flare. Setting a significance level at greater than 3σ, we report that no statistically significant signals due to solar neutrons were found. Therefore, upper limits are determined by the background level and solar angle of these thirty five solar flares. Our calculation assumed a power-law neutron energy spectrum and an impulsive emission profile at the Sun. The estimated upper limits of the neutron emission are consistent within the order of magnitude of the successful detections of solar neutrons made in solar cycle 23. 相似文献
3.
P. Kaufmann F. M. Strauss J. E. R. Costa B. R. Dennis A. Kiplinger K. J. Frost L. E. Orwig 《Solar physics》1983,84(1-2):311-319
Simultaneous microwave and X-ray observations are presented for a solar flare detected on May 8, 1980 starting at 19:37 UT. The X-ray observations were made with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission and covered the energy range from 28–490 keV with a time resolution of 10 ms. The microwave observations were made with the 5 and 45 foot antennas at the Itapetinga Radio Observatory at frequencies of 7 and 22 GHz, with time resolutions of 100 ms and 1 ms, respectively. Detailed correlation analysis of the different time profiles of the event show that the major impulsive peaks in the X-ray flux preceded the corresponding microwave peaks at 22 GHz by about 240 ms. For this particular burst the 22 GHz peaks preceded the 7 GHz by about 1.5 s. Observed delays of the microwave peaks are too large for a simple electron beam model but they can be reconciled with the speeds of shock waves in a thermal model. 相似文献
4.
Pierre Kaufmann Rogério Marcon André Abrantes Emilio C. Bortolucci Luis Olavo T. Fernandes Grigory I. Kropotov Amauri S. Kudaka Nelson Machado Adolfo Marun Valery Nikolaev Alexandre Silva Claudemir S. da Silva Alexander Timofeevsky 《Experimental Astronomy》2014,37(3):579-598
The search for the still unrevealed spectral shape of the mysterious THz solar flare emissions is one of the current most challenging research issues. The concept, fabrication and performance of a double THz photometer system, named SOLAR-T, is presented. Its innovative optical setup allows observations of the full solar disk and the detection of small burst transients at the same time. The detecting system was constructed to observe solar flare THz emissions on board of stratospheric balloons. The system has been integrated to data acquisition and telemetry modules for this application. SOLAR-T uses two Golay cell detectors preceded by low-pass filters made of rough surface primary mirrors and membranes, 3 and 7 THz band-pass filters, and choppers. Its photometers can detect small solar bursts (tens of solar flux units) with sub second time resolution. Tests have been conducted to confirm the entire system performance, on ambient and low pressure and temperature conditions. An artificial Sun setup was developed to simulate performance on actual observations. The experiment is planned to be on board of two long-duration stratospheric balloon flights over Antarctica and Russia in 2014–2016. 相似文献
5.
We establish limits on the total radiant energy of solar flares during the period 1980 February – November, using the solar-constant monitor (ACRIM) on board the Solar Maximum Mission. Typical limits amount to 6 × 1029 erg/s for a 32-second integration time, with 5σ statistical significance, for an impulsive emission; for a gradual component, about 4 × 1032 ergs total radiant energy. The limits lie about an order of magnitude higher than the total radiant energy estimated from the various known emission components, suggesting that no heretofore unknown dominant component of flare radiation exists. 相似文献
6.
This paper reviews the electric field environment of the Moon. Lunar surface electric potentials are reported as follows: Solar Wind - Dayside: øo + 10 to + 18 V Solar Wind - Terminator: øo ç ? 10 to ? 100 V Electron and ion densities in the plasma sheath adjacent to each surface potential regime are evaluated and the corresponding Debye length estimated. The electric fields are then approximated by the surface potential over the Debye length. The results are: Solar Wind - Dayside: Eo ? 10 V m?1 outward Solar Wind - Terminator: Eo ç 1 to 10 V m?1 inward These fields are all at least 3 orders of magnitude higher than the pervasive solar wind electric field; however they are confined to within a few tens of meters of the lunar surface. 相似文献
7.
8.
High resolution spectra of the coronal emission line Fe xiv at 530.3 nm obtained at the 30 May 1965 total solar eclipse are analyzed and interpreted. Deconvolution techniques that preserve the line intensity vs wavelength profile shape are developed to obtain further resolution improvement. The west limb coronal enhancement is determined to have temperatures less than 3 MK and turbulent velocities of ～25 km s-1 decreasing with altitude. Temperature gradients provide evidence for marginal solar wind flow from this enhancement. Above the quiet photosphere in the southwest quadrant the comparison of line and continuum intensities and consideration of line width suggest to us the coronal region is filled with inhomogeneous plasma, dense enough in localized regions to maintain collisional excitation. Solar wind flow from this region obtains when turbulent velocities are assumed to contribute to the line broadening. We identify this region as a coronal hole and suggest that coronal material is heated by the quiet photosphere below. 相似文献
9.
D. J. Forrest E. L. Chupp J. M. Ryan M. L. Cherry I. U. Gleske C. Reppin K. Pinkau E. Rieger G. Kanbach R. L. Kinzer G. Share W. N. Johnson J. D. Kurfess 《Solar physics》1980,65(1):15-23
The Solar Maximum Mission Gamma Ray Experiment (SMM GRE) utilizes an actively shielded, multicrystal scintillation spectrometer to measure the flux of solar gamma rays. The instrument provides a 476-channel pulse height spectrum (with energy resolution of 7% at 662 keV) every 16.38 s over the energy range 0.3–9 MeV. Higher time resolution (2 s) is available in three windows between 3.5 and 6.5 MeV to study prompt gamma ray line emission at 4.4 and 6.1 MeV. Gamma ray spectral analysis can be extended to 15 MeV on command. Photons in the energy band from 300–350 keV are recorded with a time resolution of 64 ms. A high energy configuration also gives the spectrum of photons in the energy range from 10–100 MeV and the flux of neutrons 20 MeV. Both have a time resolution of 2 s. Auxiliary X-ray detectors will provide spectra with 1-sec time resolution over the energy range of 10–140 keV. The instrument is designed to measure the intensity, energy, and Doppler shift of narrow gamma ray lines as well as the intensity of extremely broadened lines and the photon continuum. The main objective is to use this time and spectral information from both nuclear gamma ray lines and the photon continuum in a direct study of the dynamics of the solar flare/particle acceleration phenomena. 相似文献
10.
D. F. Webb M. M. Bisi C. A. de Koning C. J. Farrugia B. V. Jackson L. K. Jian N. Lugaz K. Marubashi C. Möstl E. P. Romashets B. E. Wood H.-S. Yu 《Solar physics》2014,289(11):4173-4208
A distinct magnetic cloud (MC) was observed in-situ at the Solar TErrestrial RElations Observatory (STEREO)-B on 20?–?21 January 2010. About three days earlier, on 17 January, a bright flare and coronal mass ejection (CME) were clearly observed by STEREO-B, which suggests that this was the progenitor of the MC. However, the in-situ speed of the event, several earlier weaker events, heliospheric imaging, and a longitude mismatch with the STEREO-B spacecraft made this interpretation unlikely. We searched for other possible solar eruptions that could have caused the MC and found a faint filament eruption and the associated CME on 14?–?15 January as the likely solar source event. We were able to confirm this source by using coronal imaging from the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/EUVI and COR and Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronograph (LASCO) telescopes and heliospheric imaging from the Solar Mass Ejection Imager (SMEI) and the STEREO/Heliospheric Imager instruments. We use several empirical models to understand the three-dimensional geometry and propagation of the CME, analyze the in-situ characteristics of the associated ICME, and investigate the characteristics of the MC by comparing four independent flux-rope model fits with the launch observations and magnetic-field orientations. The geometry and orientations of the CME from the heliospheric-density reconstructions and the in-situ modeling are remarkably consistent. Lastly, this event demonstrates that a careful analysis of all aspects of the development and evolution of a CME is necessary to correctly identify the solar counterpart of an ICME/MC. 相似文献
11.
The Total Solar Irradiance Monitor (TSIM) instrument is designed to perform daily observations of total solar irradiance (TSI) in space on the Chinese FY-3A and FY-3B satellites. Three absolute radiometers are constructed for the TSIM to achieve measurements with traceability to SI with an absolute accuracy better than 550 ppm. The absolute radiometers are implemented based on the principle of electrical substitution. The design of the absolute radiometers and their electrical system, operation modes in space, and uncertainty evaluation are described. A method for calculating the electrical power in the observation and reference phases is proposed to maintain the primary cavity at a nearly constant temperature. 相似文献
12.
Alan L. Kiplinger B. R. Dennis A. Gordon Emslie K. J. Frost L. E. Orwig 《Solar physics》1983,86(1-2):239-240
We present the results of a search for fast spikes in 5483 hard X-ray solar flares as observed with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission (SMM). Hundreds of fast spikes with durations of less than 1 second have been detected at time resolutions of 128 ms and 10 ms. Fast spikes have been detected with rise and decay times as short as 20 ms and with widths as short at 45 ms that represent the fastest hard X-ray variations yet seen from the Sun. The observations of such fast variations place new constraints on the physical nature of the source. 相似文献
13.
J. T. Gosling E. Hildner R. M. Macqueen R. H. Munro A. I. Poland C. L. Ross 《Solar physics》1975,40(2):439-448
Numerous mass ejections from the Sun have been detected with orbiting coronagraphs. Here for the first time we document and discuss the direct association of a coronagraph observed mass ejection, which followed a 2B flare, with a large interplanetary shock wave disturbance observed at 1 AU. Estimates of the mass (2.4 × 1016 g) and energy content (1.1 × 1032 erg) of the coronal disturbance are in reasonably good agreement with estimates of the mass and energy content of the solar wind disturbance at 1 AU. The energy estimates as well as the transit time of the disturbance are also in good agreement with numerical models of shock wave propagation in the solar wind. 相似文献
14.
Flare activity was observed near the limb with two coronagraphs at the Norikura Solar Observatory and the Soft X-ray Crystal Spectrometer (SOX) aboard HINOTORI. A prominence activation occurred and then Hα brightenings were seen on the disk near the prominence. The prominence became very bright and its electron density increased to 1012.8 cm?3 in 1/2 hour. Loop prominence systems appeared above the Hα brightenings about half an hour after the onset of the flare, and were observed in the coronal lines CaXV 5694Å, FeXIV 5303Å, and FeX 6374Å. Shifted and asymmetric profiles of the emission line of 5303Å were sometimes observed, and turbulent phenomena occurred even in the thermal phase. The energy release site of the flare at the onset would be lower than 20 000 km above the solar limb. 相似文献
15.
The hydrodynamic response of confined magnetic structures to strong heating perturbations is investigated by means of a timedependent one-dimensional code which incorporates the energy, momentum and mass conservation equations. The entire atmospheric structure from the chromosphere to the corona is taken into account. The results of model calculations are compared with observations of flares obtained with the X-Ray Polychromator experiment on the Solar Maximum Mission. 相似文献
16.
P. B. Jones 《Astrophysics and Space Science》1975,33(1):215-230
The magnetic distortion is estimated for neutron stars in which the matter in the interior consists of superfluid neutrons and superconducting protons. For type II proton superconductivity, the arrangement of magnetic flux in a two-dimensional lattice of quantized fluxoids and the kinetic energy of the supercurrent carriers cause some components of the spatially averaged stress tensor for field and superconductor to be several orders of magnitude greater than the components of the Max-well stress tensor for a uniform distribution of the same magnetic flux. It is shown that for the Crab pulsar PSR 0531+21, which is considered to have the greater part of its mass in the form of superfluid neutrons and superconducting protons, the magnetic distortion is almost certainly more important than the clastic energy of the outer shell in determining the departure of the inertia tensor from its spherically symmetric form. With the assumption that internal and external magnetic fields have the same symmetry axis, the external field dipole moment of the Crab pulsar is predicted to be approximately perpendicular to the spin direction, in agreement with a number of published interpretations of observational data. 相似文献
17.
18.
It is proposed that the solar flare phenomenon can be understood as a manifestation of the electrodynamic coupling process of the photosphere-chromosphere-corona system as a whole. The system is coupled by electric currents, flowing along (both upward and downward) and across the magnetic field lines, powered by the dynamo process driven by the neutral wind in the photosphere and the lower chromosphere. A self-consistent formulation of the proposed coupling system is given. It is shown in particular that the coupling system can generate and dissipate the power of 1029 erg s#X2212;1 and the total energy of 1032 erg during a typical life time (103 s) of solar flares. The energy consumptions include Joule heat production, acceleration of current-carrying particles along field lines, magnetic energy storage and kinetic energy of plasma convection. The particle acceleration arises from the development of field-aligned potential drops of 10–150 kV due to the loss-cone constriction effect along the upward field-aligned currents, causing optical, X-ray and radio emissions. The total number of precipitating electrons during a flare is shown to be of order 1037–1038. 相似文献
19.
N. R. Sheeley Jr. 《Solar physics》1967,1(2):171-179
Spectrograms, obtained during moments of good seeing with the high spatial resolution afforded by the 80-cm solar image at the Kitt Peak National Observatory, show the following:
- (1)Magnetic fields of several hundred gauss occur in tiny areas easily as small as 500 km in extent in regions of the solar surface sometimes well removed from areas of sunspot activity. 相似文献
20.
In earlier works we introduced and tested a nonlinear force-free (NLFF) method designed to self-consistently calculate the coronal free magnetic energy and the relative magnetic helicity budgets of observed solar magnetic structures. In principle, the method requires only a single, photospheric or low-chromospheric, vector magnetogram of a quiet-Sun patch or an active region and performs calculations without three-dimensional magnetic and velocity-field information. In this work we strictly validate this method using three-dimensional coronal magnetic fields. Benchmarking employs both synthetic, three-dimensional magnetohydrodynamic simulations and nonlinear force-free field extrapolations of the active-region solar corona. Our time-efficient NLFF method provides budgets that differ from those of more demanding semi-analytical methods by a factor of approximately three, at most. This difference is expected to come from the physical concept and the construction of the method. Temporal correlations show more discrepancies that are, however, soundly improved for more complex, massive active regions, reaching correlation coefficients on the order of, or exceeding, 0.9. In conclusion, we argue that our NLFF method can be reliably used for a routine and fast calculation of the free magnetic energy and relative magnetic helicity budgets in targeted parts of the solar magnetized corona. As explained in this article and in previous works, this is an asset that can lead to valuable insight into the physics and triggering of solar eruptions. 相似文献