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101.
Suresh Chandra 《Astrophysics and Space Science》1983,96(2):455-456
The investigation of Alamet al. (1979), of the temperature distribution in spherically-symmetric transition region and inner corona, appears to be in error. 相似文献
102.
103.
We carried out simultaneous measurements of drop size distribution (DSD) and stable oxygen and hydrogen isotopic compositions (??18O and ??D) of rain at the National Atmospheric Research Laboratory (NARL), Gadanki (13.5°N, 79.2°E), southern India, during September?COctober 2006, with the aim of understanding microphysical processes leading to rain formation. The MST radar at NARL was operated continuously during rain events, while rain samples were collected at very short time intervals (<1?h), to capture small changes (>0.2?? and >2??) in their ??18O and ??D. The slope of the local meteoric water line (??D?C??18O line), was 8.07?±?0.47, similar to that of global meteoric water line, confirming that the precipitation occurred under isotopic equilibrium, and was unaffected by some anomalous process; further, the evaporation of rain drops at the cloud base was insignificant. Whenever the isotopic variations were larger during a rain event (>2??) there was a significant negative correlation between the ??18O and DSD. The possible explanation is that larger drops are mostly associated with convective rather than stratiform rain, and 18O (and D) depletion in convective rain is relatively more. Bin-resolved microphysical models incorporating water isotopologues could benefit by considering drop size spectra, which could improve the match with stable isotope observations of precipitation. 相似文献
104.
We present the results obtained by a detailed study of the extragalactic Z source LMC X-2, using broad-band Suzaku data and a large (∼750 ks) data set obtained with the proportional counter array (PCA) onboard the Rossi X-ray Timing Experiment ( RXTE ). The PCA data allow the study of the complete spectral evolution along the horizontal, normal and flaring branches of the Z track. Comparison with previous studies shows that the details of spectral evolution (like the variation of Comptonizing electron temperature) are similar to those of GX 17+2 but unlike those of Cyg X-2 and GX 349+2. This suggests that Z sources are a heterogeneous group, with perhaps LMC X-2 and GX 17+2 being members of a subclass. However, non-monotonic evolution of the Compton y parameter seems to be generic to all sources. The broad-band Suzaku data reveal that the case in which the additional soft component of the source is modelled as disc blackbody emission is strongly preferred over the one where it is taken to be a blackbody spectrum. This component, as well as the temperature of seed photons, does not vary when the source goes into flaring mode, and the entire variation can be ascribed to the Comptonizing cloud. The bolometric unabsorbed luminosity of the source is constrained to be ∼2.23 × 1038 erg s−1 , which, if the source is Eddington-limited, implies a neutron star mass of 1.6 M⊙ . We discuss the implications of these results. 相似文献
105.
Navin Chandra Joshi Neeraj Singh Bankoti Seema Pande Bimal Pande Kavita Pandey 《Solar physics》2009,260(2):451-463
In this article we present the results of a study of the spatial distribution and asymmetry of solar active prominences (SAP)
for the period 1996 through 2007 (solar cycle 23). For more meaningful statistical analysis we analyzed the distribution and
asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR, DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The North – South (N – S) latitudinal distribution
shows that the SAP events are most prolific in the 21° to 30° slice in the Northern and Southern Hemispheres; the East – West
(E – W) longitudinal distribution study shows that the SAP events are most prolific (best observable) in the 81° to 90° slice
in the Eastern and Western Hemispheres. It was found that the SAP activity during this cycle is low compared to previous solar
cycles. The present study indicates that during the rising phase of the cycle the number of SAP events are roughly equal in
the Northern and Southern Hemispheres. However, activity in the Southern Hemisphere has been dominant since 1999. Our statistical
study shows that the N – S asymmetry is more significant then the E – W asymmetry. 相似文献
106.
A filament disappearance event was observed on 22 May 2008 during our recent campaign JOP 178. The filament, situated in the Southern Hemisphere, showed sinistral chirality consistent with the hemispheric rule. The event was well observed by several observatories, in particular by THEMIS. One day, before the disappearance, Hα observations showed up- and down-flows in adjacent locations along the filament, which suggest plasma motions along twisted flux rope. THEMIS and GONG observations show shearing photospheric motions leading to magnetic flux canceling around barbs. STEREO A, B spacecraft with separation angle 52.4°, showed quite different views of this untwisting flux rope in He ii 304 Å images. Here, we reconstruct the three-dimensional geometry of the filament during its eruption phase using STEREO EUV He ii 304 Å images and find that the filament was highly inclined to the solar normal. The He ii 304 Å movies show individual threads, which oscillate and rise to an altitude of about 120 Mm with apparent velocities of about 100 km?s?1 during the rapid evolution phase. Finally, as the flux rope expands into the corona, the filament disappears by becoming optically thin to undetectable levels. No CME was detected by STEREO, only a faint CME was recorded by LASCO at the beginning of the disappearance phase at 02:00 UT, which could be due to partial filament eruption. Further, STEREO Fe xii 195 Å images showed bright loops beneath the filament prior to the disappearance phase, suggesting magnetic reconnection below the flux rope. 相似文献
107.
108.
Using the Quantum hydrodynamic (QHD) model the modulational instability of electron-acoustic waves (EAWs) has been examined theoretically by deriving a nonlinear Schrodinger equation in a two-electron-populated relativistically degenerate super dense plasma. Through numerical analysis it is shown that the relativistic degeneracy parameter significantly influence the stability conditions and the formation and properties of the envelop solitons. 相似文献
109.
Shantanu Kumar Biswal Santosh Kumar Agarwalla Munesh Chandra Adhikary 《Astrophysics and Space Science》2012,337(2):645-650
Some recent experimental observations have been shown that inclusion of electron collisions damping in inertial Alfvén wave
(IAW) dynamics may be important for laboratory as well as space plasmas. This paper presents the numerical simulation of model
equation governing the nonlinear dynamics of IAW in low-beta plasmas. When the nonlinearity arises due to the ponderomotive
force and Joule heating driven density perturbations, the model equation turns out to be a modified nonlinear Schr?dinger
equation (MNLS). The electron collisions are introduced only in the electron momentum equation. The damped localized structures
of IAW with sidebands are obtained. Also, the effect of collisional damping on power spectra of magnetic fluctuations with
different scaling laws has been studied. These turbulent structures may be responsible for particle acceleration in laboratory
and space plasmas. 相似文献
110.
The pressure-corrected hourly counting rate data of ground-based super neutron monitor stations, situated in different latitudes, have been employed to study the characteristics of the long-term variation of cosmic-ray diurnal anisotropy for a long (44-year) period (1965?–?2008). Some of these super neutron monitors are situated in low latitudes with high cutoff rigidity. Annual averages of the diurnal amplitudes and phases have been obtained for each station. It is found that the amplitude of the diurnal anisotropy varies with a period of one solar activity cycle (11 years), whereas the diurnal phase varies with a period of 22 years (one solar magnetic cycle). The average diurnal amplitudes and phases have also been calculated by grouping the days on the basis of ascending and descending periods of each solar cycle (Cycles 20, 21, 22, and 23). Systematic and significant differences are observed in the characteristics of the diurnal variation between the descending periods of the odd and even solar cycles. The overall vector averages of the descending periods of the even solar cycles (20 and 22) show significantly smaller diurnal amplitudes compared to the vector averages of the descending periods of the odd solar cycles (21 and 23). In contrast, we find a large diurnal phase shift to earlier hours only during the descending periods of even solar cycles (20 and 22), as compared to almost no shift in the diurnal phase during the descending periods of odd solar cycles. Further, the overall vector average diurnal amplitudes of the ascending period of odd and even solar cycles remain invariant from one ascending period to the other, or even between the even and odd solar cycles. However, we do find a significant diurnal phase shift to earlier hours during the ascending periods of odd solar cycles (21 and 23) in comparison to the diurnal phase in the ascending periods of even solar cycles (20 and 22). 相似文献