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1.
S.R. Prabhakaran Nayar V. Sanalkumaran Nair V.N. Radhika K. Revathy 《Solar physics》2001,201(2):405-417
The solar wind plasma exhibits many features of the solar surface passed on to the interplanetary medium as temporal variations
due to the solar rotation. The yearly average values of solar wind velocity, and geomagnetic index A
p during 1965–1999 were found to exhibit long period evolution. They were found to peak around the declining phase of each
solar cycle. While the solar wind velocity peaks around the second half of the declining phase, the IMF field strength increases
around the first half of the declining phase of each solar cycle. The power spectrum of these parameters shows peaks around
37-day, 30-day, 27-day, 13.5-day, 9-day, and 7-day periods. The temporal evolution of the power spectrum of the solar wind
plasma parameters and the geomagnetic activity index A
p are also studied in detail and presented with the help of contour graphs. These studies indicate that the strength of the
quasi-periodicities in the interplanetary medium evolves with time. 相似文献
2.
The distribution of the shocks in the heliosphere and their characteristic variations are investigated using Ulysses observations. The jumps in solar wind velocity, IMF magnitude, and proton density across the shocks and discontinuities are
evaluated and used to characterize them. The distribution of these discontinuities with respect to heliolatitude ± 80° and
with radial distance 1 to 5 AU are analyzed during solar minimum and solar maximum to understand their global behavior. It
is noticed that the jumps in solar wind parameters associated with shocks and discontinuities are more prominent during the
second orbit of Ulysses, which coincided with the maximum phase of solar activity. 相似文献
3.
The aim of the present study is to investigate the lineaments of Kolli hills of Tamil Nadu State for which CARTOSAT-1 satellite’s DEM output has been made use of. The extracted lineaments were analysed using ArcGIS and Rockworks software. The total number and length of lineaments are 523 and 943.81 km, respectively. Shorter lineaments constitute about 3/4th of the total number of lineaments. The density of the lineaments varies from 0 to 7.41 km/km2, and areas of very high to high density are restricted to the south central, central and north eastern parts, and these areas reflect the high degree of rock fracturing and shearing which makes these areas unsuitable for the construction of dams and reservoirs. However, these areas could be targeted for groundwater exploitation as they possess higher groundwater potential. The lineaments are oriented in diverse directions. However, those orienting in ENEWSW, NE-SW and NW-SE are predominating followed by those oriented in sub E-W and sub N-S directions. These orientations corroborate with results of previous regional studies and with orientations of prominent geological structures and features of the study area. Distinct variation in the predominant orientations of lineaments of varied sizes is observed, while the shorter ones are oriented in either NW-SE or NNW-SSE directions, the longer ones are oriented in either NE-SW or ENE-WSW. A comparative analysis of lineament datasets of the eight azimuth angles and the final lineament map underlines the need to extract lineaments from various azimuth angles to get a reliable picture about the lineaments. 相似文献
4.
The solar wind velocity near Earth shows systematic structure in and around the heliospheric current sheet. The solar wind velocity measurements at IMF sector boundary crossings at 1 AU during 1972–1977 have been used to infer the azimuthal structure of the solar wind velocity in the current sheet. We found that the solar wind velocity in the in-ecliptic portion of the current sheet varies from longitude to longitude, where it originates from the corona. Also, the yearly average value of solar wind velocity in the HCS is found to vary with the phase of the solar cycle; with a maximum value around 1974. TheK-corona brightness on the source surface corresponding to the IMF sector boundary crossings during the period of study also shows a similar but opposite pattern of variation when the data are averaged over a long period. However, this relation is not observed when we considered them individually. So, we conclude that there exists a longitudinal variation of solar wind velocity in the heliospheric current sheet. 相似文献
5.
Wavelet Analysis of solar,solar wind and geomagnetic parameters 总被引：3，自引：0，他引：3
The sunspot number, solar wind plasma, interplanetary magnetic field, and geomagnetic activity index A
p have been analyzed using a wavelet technique to look for the presence of periods and the temporal evolution of these periods. The global wavelet spectra of these parameters, which provide information about the temporal average strength of quasi periods, exhibit the presence of a variety of prominent quasi periods around 16 years, 10.6 years, 9.6 years, 5.5 years, 1.3 years, 180 days, 154 days, 27 days, and 14 days. The wavelet spectra of sunspot number during 1873–2000, geomagnetic activity index A
p during 1932–2000, and solar wind velocity and interplanetary magnetic field during 1964–2000 indicate that their spectral power evolves with time. In general, the power of the oscillations with a period of less than one year evolves rapidly with the phase of the solar cycle with their peak values changing from one cycle to the next. The temporal evolution of wavelet power in R
z, v
sw, n, B
y, B
z, |B|, and A
p for each of the prominent quasi periods is studied in detail. 相似文献
6.
The beam cyclotron instability and electron acoustic instability, driven by cross-tail current and inhomogeneity in density and magnetic field, are found to be unstable in the earth's magnetic tail region. The anomalous resistivities due to these instabilities are found to be of the order of (Ωe being the electron gyro frequency). It is also suggested that the non-linear saturation of the beam cyclotron instability may lead to conditions favourable for exciting ion acoustic instability. 相似文献
7.
Sabu Prabhakaran Subeesh Meethale Puthukkottu George Jenson Vilayil Anilkumar Narayana Pillai Ravichandran Muthalagu 《Ocean Dynamics》2021,71(4):391-409
Ocean Dynamics - The Seychelles-Chagos Thermocline Ridge (SCTR) is a key region which plays a major role in various regional climatic processes at all time scales. The vertical mixing at the base... 相似文献
8.
Ecologically relevant estimates of seasonal variability in nitrogen uptake and allocation in two species of temperate seagrasses were obtained using in situ isotope-labelling approach. Significantly higher uptake rates of ammonium by leaves, roots and epiphytes of Amphibolis than Posidonia were observed. Overall, root uptake rates were lower than other components. Effect of season was not significant for leaves, roots or epiphytes of the two species. However, plankton uptake varied seasonally with higher rates in winter (0.98 mg N g−1 DW h−1). In contrast, nitrate uptake rates for various components were significantly affected by seasons. Uptake rates by plankton were highest ranging from 0.003 mg N g−1 DW h−1 (summer, Amphibolis) to 0.69 mg N g−1 DW h−1 (winter, Posidonia). Uptake of nitrate by roots was negligible. Biotic uptake rates for nitrate were an order of magnitude slower than ammonium, demonstrating an affinity for ammonium over nitrate as a preferred inorganic nitrogen source. Adelaide coastal waters have lost over 5000 ha of seagrasses, much of this attributed to nutrient inputs from wastewater, industrial and stormwater. Managing these inputs into future requires better understanding of the fate of nutrients, particularly biological uptake. This study attempts to quantify uptake rates of nitrogen by seagrasses. 相似文献
9.
Increased human habitation has led to a 30 to 50-fold increase in nutrient loads to the coastal waters of Adelaide, resulting in the loss of over 5000 ha of seagrass meadows. The rate of loss since the 1940s has been irregular, averaging 85 ha yr(-1), marked by a substantial peak between 1971 and 1977. A modelling approach allowed comparison of the annual input with the annual uptake rates for the different biotic components in the seagrass bed. In 2005, the estimated uptake of ammonium (465 t yr(-1)) and nitrate (3.04 t yr(-1)) by the seagrass and associated epiphytes in the Adelaide region accounted for 31% of the ammonium and <1% of the nitrate that is currently discharged into the coastal waters. Environment Improvement Programs, such as the one implemented in 1996, may reduce the total nitrogen loads to 700 t yr(-1), possibly stemming further losses and facilitating recolonisation of new seagrass. 相似文献
10.
D. Prabhakaran T. Kannadasan C. Ahmed Basha 《International Journal of Environmental Science and Technology》2009,6(3):491-498
Electro oxidation processes are developed throughout the world for ambient temperature destruction of organic wastes. Several of these processes are based on mediated electrochemical oxidation. This article presents the experimental results of electro chemical study based on mediated electrochemical oxidation process conducted for synthetic organic ion exchange resin materials. Investigation was carried out using the traditional noble metal oxide coated anode, ruthenium oxide-titanium and the mediator used for the experiment was ferrous sulphate, with sodium chloride as supporting electrolyte. The concentration of sodium chloride was maintained at 5, 8, 12 gm/L. The experiment was carried out in batch recirculation reactor with varied current densities for various flow rates. The study highlighted that in batch reactor set up the best effect of total organic content reduction was found to occur at 3.75 A/dm2 with flow rate of 20 L/h. The simulated studies were carried out for different volumes of effluent and current densities. A graphical analysis was made between the experimental and simulated values and it was found that both the values are very close. 相似文献