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1.
From the gyroresonance brightness temperature spectrum of a sunspot, one can determine the magnetic field strength by using the property that microwave brightness is limited above a frequency given by an integer-multiple of the gyrofrequency. In this paper, we use this idea to find the radial distribution of magnetic field at the coronal base of a sunspot in the active region, NOAA 4741. The gyroresonance brightness temperature spectra of this sunspot are obtained from multi-frequency interferometric observations made at the Owens Valley Radio Observatory at 24 frequencies in the range of 4.0–12.4 GHz with spatial resolution 2.2″–6.8″. The main results of present study are summarized as follows: first, by comparison of the coronal magnetic flux deduced from our microwave observation with the photospheric magnetic flux measured by KPNO magnetograms, we show that theo-mode emission must arise predominantly from the second harmonic of the gyrofrequency, while thex-mode arises from the third harmonic. Second, the radial distribution of magnetic fieldsB(r) at the coronal base of this spot (say, 2000–4000 km above the photosphere) can be adequately fitted by $$B(r) = 1420(1 \pm 0.080)\exp \left[ { - \left( {\frac{r}{{11.05''(1 \pm 0.014)}}} \right)^2 } \right]G,$$ wherer is the radial distance from the spot center at coronal base. Third, it is found that coronal magnetic fields originate mostly from the photospheric umbral region. Fourth, although the derived vertical variation of magnetic fields can be approximated roughly by a dipole model with dipole moment 1.6 × 1030 erg G?1 buried at 11000 km below the photosphere, the radial field distribution at coronal heights is found to be more confined than predicted by the dipole model. 相似文献
2.
The objective of this study is to demonstrate that the channel flow routing techniques used in the Soil and Water Assessment Tool (SWAT) can be sometimes inappropriate for runoff simulation in small basins. Simulated hydrographs have a tendency to underestimate peak flows or may send a false signal during the recession periods when SWAT is applied to the Mihocheon Basin in South Korea. This was particularly evident for sub‐basins that had a short travel time of much less than a day. In order to enhance the channel routing module in SWAT, an alternative routing technique in which Manning relationship is combined with a simple channel reach continuity equation is proposed in the present study. The advantage of the proposed routing technique is that parameters are readily available from channel morphological data and that it is applicable to small basins. Through simulations of specific events, this routing module that is incorporated into SWAT is almost free from instability errors and produces realistic flow depths and velocities unlike the original version of SWAT with Muskingum method. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
The modified Soil Conservation Service curve number (CN) method is widely used in long‐term continuous models to predict daily surface runoff. However, it has been shown that this method gives poor results in reproducing peak flows in high rainfall periods. This is because there is an inaccuracy stemming from the model algorithm as it adjusts the daily runoff curve number as a function of soil moisture content at the end of the previous day. This paper proposes an alternative daily based curve number technique that can provide better prediction of daily runoff during the high flow season. The proposed method uses the temporally weighted average curve number (TWA‐CN) to estimate daily surface runoff, while considering the effect of rainfall during a given day as well as the antecedent soil moisture condition. To test the applicability of the TWA‐CN method, it was incorporated with the long‐term, continuous simulation watershed models SWAT and SWAT‐G. Simulations were conducted for the Miho River watershed located in the middle of South Korea. The graphical displays and statistics of the determination coefficient (R2) and the Nash–Sutcliffe model efficiency (NSE) of the observed and simulated daily runoff indicated that the modified SWAT with the TWA‐CN method may provide better runoff prediction (R2 = 0·837, NSE = 0·833) than the original SWAT (R2 = 0·815, NSE = 0·824). Likewise, the determination coefficient (R2 = 0·816) and the Nash–Sutcliffe efficiency (NSE = 0·834) for the modified SWAT‐G are also higher than the original version (R2 = 0·782, NSE = 0·825). It is expected that the improved capability in predicting surface runoff using the suggested CN estimate method will provide a sound contribution to the accurate simulations of water yield. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
4.
We report new properties of solar magnetic fields in a quiet region as found from their magnetic power spectra. The power spectra of network and intranetwork fields (non-network fields) are separately calculated from a Big Bear magnetogram obtained with moderately high spatial resolution of 1.5 arc sec and a high sensitivity reaching 2 Mx cm-2. The effect of seeing on the power spectrum has been corrected using Fried's (1966) Modulation Transfer Function with the seeing parameter determined in our previous analysis of the magnetogram. As a result, it is found that the two-dimensional power spectra of network and non-network fields appear in a form: (
1)
-1 and (
1)
-3.5. Here
0 0.47 Mm-1 for network fields and
0 0.69 Mm-1 for non-network fields, the latter of which corresponds to the size of mesogranulation;
1 3.0 Mm-1 for both, which is about the size of a large granule. The network field spectrum below
0 appears nearly flat, whereas that of non-network fields instead decreases towards lower wave numbers as (
)
1.3. The turnover behavior of magnetic field spectra around
1 coincides with that found for the velocity power spectrum, which may justify the kinetic approach taken in previous theoretical studies of the solar magnetic power spectra. 相似文献
5.
L. G. Kocharov Jeongwoo W. Lee H. Zirin G. A. Kovaltsov I. G. Usoskin K. R. Pyle M. A. Shea D. F. Smart 《Solar physics》1994,155(1):149-170
In this paper, we are primarily concerned with the solar neutron emission during the 1990 May 24 flare, utilizing the counting rate of the Climax neutron monitor and the time profiles of hard X-rays and γ-rays obtained with the GRANAT satellite (Pelaezet al., 1992; Talonet al., 1993; Terekhovet al., 1993). We compare the derived neutron injection function with macroscopic parameters of the flare region as obtained from theHα and microwave observations made at the Big Bear Solar Observatory and the Owens Valley Radio Observatory, respectively. Our results are summarized as follows: (1) to explain the neutron monitor counting rate and 57.5–110 MeV and 2.2 MeV γ-ray time profiles, we consider a two-component neutron injection function,Q(E, t), with the form $$Q(E,t) = N_f {\text{ exp[}} - E/E_f - t/T_f ] + N_s {\text{ exp[}} - E/E_s - t/T_s ],$$ whereN f(s),E f(s), andT f(s) denote number, energy, and decay time of the fast (slow) injection component, respectively. By comparing the calculated neutron counting rate with the observations from the Climax neutron monitor we derive the best-fit parameters asT f ≈ 20 s,E f ≈ 310 MeV,T s ≈ 260 s,E s ≈ 80 MeV, andN f (E > 100 MeV)/N s (E > 100 MeV) ≈ 0.2. (2) From the Hα observations, we find a relatively small loop of length ≈ 2 × 104 km, which may be regarded as the source for the fast-decaying component of γ-rays (57.5–110 MeV) and for the fast component of neutron emission. From microwave visibility and the microwave total power spectrum we postulate the presence of a rather big loop (≈ 2 × 105 km), which we regard as being responsible for the slow-decaying component of the high-energy emission. We show how the neutron and γ-ray emission data can be explained in terms of the macroscopic parameters derived from the Hα and microwave observations. (3) The Hα observations also reveal the presence of a fast mode MHD shock (the Moreton wave) which precedes the microwave peak by 20–30 s and the peak of γ-ray intensity by 40–50 s. From this relative timing and the single-pulsed time profiles of both radiations, we can attribute the whole event as due to a prompt acceleration of both electrons and protons by the shock and subsequent deceleration of the trapped particles while they propagate inside the magnetic loops. 相似文献
6.
We analyze the time variation of microwave spectra and hard X-ray spectra of 1989 March 18, which are obtained from the Solar Array at the Owens Valley Radio Observatory (OVRO) and the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM), respectively. From this observation, it is noted that the hard X-ray spectra gradually soften over 50–200 keV on-and-after the maximum phase while the microwaves at 1–15 GHz show neither a change in spectral shape nor as rapid a decay as hard X-rays. This leads to decoupling of hard X-rays from the microwaves in the decay phase away from their good correlation seen in the initial rise phase. To interpret this observation, we adopt a view that microwave-emitting particles and hard X-ray particles are physically separated in an inhomogeneous magnetic loop, but linked via interactions with the Whistler waves generated during flares. From this viewpoint, it is argued that the observed decoupling of microwaves from hard X-rays may be due to the different ability of each source region to maintain high energy electrons in response to the Whistler waves passing through the entire loop. To demonstrate this possibility, we solve a Fokker-Planck equation that describes evolution of electrons interacting with the Whistler waves, taking into account the variation of Fokker-Planck coefficients with physical quantities of the background medium. The numerical Fokker-Planck solutions are then used to calculate microwave spectra and hard X-ray spectra for agreement with observations. Our model results are as follows: in a stronger field region, the energy loss by electron escape due to scattering by the waves is greatly enhanced resulting in steep particle distributions that reproduce the observed hard X-ray spectra. In a region with weaker fields and lower density, this loss term is reduced allowing high energy electrons to survive longer so that microwaves can be emitted there in excess of hard X-rays during the decay phase of the flare. Our results based on spectral fitting of a flare event are discussed in comparison with previous studies of microwaves and hard X-rays based on either temporal or spatial information. 相似文献
7.
We present observations of four filaments that exhibit large-amplitude periodic mass motion. Observations are obtained using
the high resolution (2″) and high cadence (1 min) Hα telescope system at the Big Bear Solar Observatory (BBSO). The motions
found in these events are along the axis of the filaments, and are associated with the activity of a nearby flare or filament.
The most characteristic properties of these motions are long period (≥ q80 min), large distance (≥ q 4 × 104 km) of mass transport at much higher velocity (≥ q 30 km s−1) than ever detected from filament motions. The velocity, period, dimension and damping timescale measured for these motions
are presented, and discussed to identify the most plausible restoring force and damping mechanism. 相似文献
8.
Seungjin Kim Jeongwoo Lee Seehyung Lee Chang-Sang Cho Jae-Hwan Sa Eui-Chan Jeon 《Environmental Earth Sciences》2014,72(7):2325-2332
While the Intergovernmental Panel on Climate Change classifies coal as anthracite, bituminous coal, and sub-bituminous coal, Korea only distinguishes coal as anthracite and bituminous coal while sub-bituminous coal is considered bituminous coal. As a result, Korea conducted research in the CO2 emission factors of anthracite and bituminous coal, but largely ignored sub-bituminous coal. Therefore, the purpose of this research is to develop the CO2 emission factor of sub-bituminous coal by classifying sub-bituminous coal from resources of bituminous coal activities collected in Korea between 2007 and 2011. The 2007–2011 average carbon content of sub-bituminous coal was analyzed to be 69.63 ± 3.11 %, the average hydrogen content 4.97 ± 0.37 %, the inherent moisture 12.60 ± 4.33 %, the total moisture 21.91 ± 5.45 %, and the dry-based gross calorific value was analyzed to be 5,914 ± 391 kcal/kg; using these analyzed values, the as-received net calorific value was found to be 20.75 ± 7.59 TJ/Gg and the CO2 emission factor was found to be 96,241 ± 4,064 kg/TJ. In addition, the 62.7 million ton amount for the 2009 greenhouse gas emission from sub-bituminous coal as estimated with the analyzed value of this study is an amount that is equivalent to 11.1 % of the 2009 total greenhouse gas emission amount of 564.7 million tons, and this amount is larger than the 9.3 % for the industrial processes sector, 3.3 % for the agricultural sector and 2.5 % for the waste sector. Therefore, it is important to reflect the realities of Korea when estimating the greenhouse gas emission from such sub-bituminous coals. 相似文献
9.
Jeongwoo Lee Chang-Sang Cho Ki-hyup Hong Jae-Hak Jeong Seungjin Kim Eui-Chan Jeon 《Environmental Earth Sciences》2013,70(4):1709-1715
Consumption of primary energy in Korea increased 5.25 % per year over a 10 years span starting in 1990. Korea ranked 8th in primary energy consumption in 2011; coal consumption increased 35 % from 87,827 million tons in 2006–119,321 tons in 2010. Heavy energy-consuming countries consistently conduct research to develop an emission factor of Tier 2 level, reflecting the characteristics of the fuel that they use. To calculate the emission factor of bituminous coal for fuel, this study developed emission factor and calculated emission amount by implementing fuel analysis on bituminous coal consumed in Korea between 2007 and 2009. CO2 emission factor calculated by fuel analysis method is 95,315 kg/TJ, which is 0.75 % higher than the default value suggested by IPCC. The emission amount calculated by using the CO2 emission factor in this study is 231.881 million tons, which has a difference of 1.739 million tons compared to the IPCC default value. 相似文献
10.
Microwave emission from solar active regions at frequencies above 4 GHz is dominated by gyroresonance opacity in strong coronal magnetic fields, which allows us to use radio observations to measure coronal magnetic field strengths. In this paper we demonstrate one powerful consequence of this fact: the ability to identify coronal currents from their signatures in microwave images. Specifically, we compare potential-field (i.e., current-free) extrapolations of photospheric magnetic fields with microwave images and are able to identify regions where the potential extrapolation fails to predict the magnetic field strength required to explain the microwave images. Comparison with photospheric vector magnetic field observations indicates that the location inferred for coronal currents agrees with that implied by the presence of vertical currents in the photosphere. The location, over a neutral line exhibiting strong shear, is also apparently associated with strong heating. 相似文献