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The role of the bow shock in solar wind-magnetosphere coupling
R. E. Lopez, V. G. Merkin,J. G. Lyon
Annales Geophysicae (ANGEO) , 2011,
Abstract: In this paper we examine the role of the bow shock in coupling solar wind energy to the magnetosphere using global magnetohydrodynamic simulations of the solar wind-magnetosphere interaction with southward IMF. During typical solar wind conditions, there are two significant dynamo currents in the magnetospheric system, one in the high-latitude mantle region tailward of the cusp and the other in the bow shock. As the magnitude of the (southward) IMF increases and the solar wind becomes a low Mach number flow, there is a significant change in solar wind-magnetosphere coupling. The high-latitude magnetopause dynamo becomes insignificant compared to the bow shock and a large load appears right outside the magnetopause. This leaves the bow shock current as the only substantial dynamo current in the system, and the only place where a significant amount of mechanical energy is extracted from the solar wind. That energy appears primarily as electromagnetic energy, and the Poynting flux generated at the bow shock feeds energy back into the plasma, reaccelerating it to solar wind speeds. Some small fraction of that Poynting flux is directed into the magnetosphere, supplying the energy needed for magnetospheric dynamics. Thus during periods when the solar wind flow has a low Mach number, the main dynamo in the solar wind-magnetosphere system is the bow shock.
Different magnetospheric modes: solar wind driving and coupling efficiency
N. Partamies, T. I. Pulkkinen, R. L. McPherron, K. McWilliams, C. R. Bryant, E. Tanskanen, H. J. Singer, G. D. Reeves,M. F. Thomsen
Annales Geophysicae (ANGEO) , 2009,
Abstract: This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC) intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential), particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to) the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY). Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading–unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations) during geomagnetically active conditions.
The effect of upstream turbulence and its anisotropy on the efficiency of solar wind – magnetosphere coupling
D. Jankovi ová, Z. V r s,J. imkanin
Nonlinear Processes in Geophysics (NPG) , 2008,
Abstract: The importance of space weather and its forecasting is growing as interest in studying geoeffective processes in the Sun – solar wind – magnetosphere – ionosphere coupled system is increasing. This paper introduces the proper selection criteria for solar wind magnetic turbulence events during duskward electric field and southward Bz driven geomagnetic storms. Two measures for the strength of solar wind fluctuations were investigated: the standard deviations of magnetic field components and a proxy for the so-called Shebalin anisotropy angles. These measures were compared to the strength of geomagnetic storms obtained from a SYM-H index time series. We found a weak correlation between standard deviation of interplanetary magnetic field GSM component Bz and SYM-H index, and a strong correlation between Shebalin anisotropy angle and the SYM-H index, which can be the result of an increase of probability of magnetic reconnection in fluctuating magnetic fields.
Study of the solar wind coupling to the time difference horizontal geomagnetic field
J. M Vaquero
Annales Geophysicae (ANGEO) , 2005,
Abstract: In this short contribution the use of different sunspot numbers for the estimation of past solar and upper atmosphere conditions from historical and modern auroral observations realised by Schr der et al. (2004) is analysed. Moreover, some comments are made on the relationships between mean annual visual observations of the auroras at middle latitudes of Europe and the mean annual sunspot number during 1780–1829. Keywords. Atmospheric composition and structure (Airglow and aurora) – Magnetospheric physics (Auroral phenomena, solar wind-magnetosphere interactions) – History of geophysics (Solar-planetary relationship)
Study of the solar wind-magnetosphere coupling on different time scales  [PDF]
Badruddin,O. P. M. Aslam
Physics , 2013, DOI: 10.1016/j.pss.2013.06.006
Abstract: Solar wind-magnetosphere coupling, its causes and consequences have been studied for the last several decades. However, the assessment of continuously changing behaviour of the sun, plasma and field flows in the interplanetary space and their influence on geomagnetic activity is still a subject of intense research. Search for the best possible coupling function is also important for space weather prediction. We utilize four geomagnetic indices (ap, aa, AE and Dst) as parameters of geomagnetic activity level in the earth's magnetosphere. In addition to these indices, we utilize various solar wind plasma and field parameters for the corresponding periods. We analyse the geomagnetic activity and plasma/field parameters at yearly, half-yearly, 27-day, daily, 3-hourly, and hourly time resolutions. Regression analysis using geomagnetic and solar wind data of different time resolutions, over a continuous long period, and at different phases of solar activity (increasing including maximum/decreasing including minimum) led us to suggest that two parameters BV/1000 (mV/m) and BV2 (mV/s) are highly correlated with the all four geomagnetic activity indices not only at any particular time scale but at different time scales. It probably suggests for some role of the fluctuations/variations in interplanetary electric potential, its spacial variation [i.e., interplanetary electric field BV (mV/m)] and/or time variation [BV2 (mV/s)], in influencing the reconnection rate.
Multiscale behavior and fractional kinetics from the data of solar wind - magnetosphere coupling  [PDF]
G. M. Zaslavsky,P. N. Guzdar,M. Edelman,M. I. Sitnov,A. S. Sharma
Physics , 2005,
Abstract: Multiscale phenomena are ubiquitous in nature as well in laboratories. A broad range of interacting space and time scales determines the dynamics of many systems which are inherently multiscale. In most research disciplines multiscale phenomena are not only prominent, but also they have often played the dominant role. In the solar wind - magnetosphere interaction, multiscale features coexist along with the global or coherent features. Underlying these phenomena are the mathematical and theoretical approaches such as phase transitions, turbulence, self-organization, fractional kinetics, percolation, etc. The fractional kinetic equations provide a suitable mathematical framework for multiscale behavior. In the fractional kinetic equations the multiscale nature is described through fractional derivatives and the solutions of these equations yield non-convergent moments, showing strong multiscale behavior. Using a L\'{e}vy-flights approach, we analyze the data of the magnetosphere and the solar wind. Based on this analysis we propose a model of the multiscale features and compare it with the solutions of diffusion type equations. The equation with fractional spatial derivative shows strong multiscale behavior with divergent moments. On the other hand the equation with space dependent diffusion coefficients yield convergent moments, indicating Gaussian type solutions and absence of long tails typically associated with multiscale behavior.
Fluctuations in the interplanetary electric potential and energy coupling between the solar-wind and the magnetosphere  [PDF]
Badruddin,O. P. M. Aslam
Physics , 2013,
Abstract: We utilize solar rotation average geomagnetic index ap and various solar wind plasma and field parameters for four solar cycles 20-23. We perform analysis to search for a best possible coupling function at 27-day time resolution. Regression analysis using these data at different phases of solar activity (increasing including maximum/decreasing including minimum) led us to suggest that the time variation of interplanetary electric potential is a better coupling function for solar wind-magnetosphere coupling. We suspect that a faster rate of change in interplanetary electric potential at the magnetopause might enhance the reconnection rate and energy transfer from the solar wind into the magnetosphere. The possible mechanism that involves the interplanetary potential fluctuations in influencing the solar wind-magnetosphere coupling is being investigated.
Coupling the solar dynamo and the corona: wind properties, mass and momentum losses during an activity cycle  [PDF]
Rui F. Pinto,Allan Sacha Brun,Laurène Jouve,Roland Grappin
Physics , 2011, DOI: 10.1088/0004-637X/737/2/72
Abstract: We study the connections between the sun's convection zone and the evolution of the solar wind and corona. We let the magnetic fields generated by a 2.5D axisymmetric kinematic dynamo code (STELEM) evolve in a 2.5D axisymmetric coronal isothermal MHD code (DIP). The computations cover an 11 year activity cycle. The solar wind's asymptotic velocity varies in latitude and in time in good agreement with the available observations. The magnetic polarity reversal happens at different paces at different coronal heights. Overall sun's mass loss rate, momentum flux and magnetic braking torque vary considerably throughout the cycle. This cyclic modulation is determined by the latitudinal distribution of the sources of open flux and solar wind and the geometry of the Alfv\'en surface. Wind sources and braking torque application zones also vary accordingly.
Electricity Generation and Energy Cost Estimation of Large-Scale Wind Turbines in Jarandagh, Iran  [PDF]
Kasra Mohammadi,Ali Mostafaeipour,Yagob Dinpashoh,Nima Pouya
Journal of Energy , 2014, DOI: 10.1155/2014/613681
Abstract: Currently, wind energy utilization is being continuously growing so that it is regarded as a large contender of conventional fossil fuels. This study aimed at evaluating the feasibility of electricity generation using wind energy in Jarandagh situated in Qazvin Province in north-west part of Iran. The potential of wind energy in Jarandagh was investigated by analyzing the measured wind speed data between 2008 and 2009 at 40?m height. The electricity production and economic evaluation of four large-scale wind turbine models for operation at 70?m height were examined. The results showed that Jarandagh enjoys excellent potential for wind energy exploitation in 8 months of the year. The monthly wind power at 70?m height was in the range of 450.28–1661.62?W/m2, and also the annual wind power was 754.40?W/m2. The highest capacity factor was obtained using Suzlon S66/1.25?MW turbine model, while, in terms of electricity generation, Repower MM82/2.05?MW model showed the best performance with total annual energy output of 5705?MWh. The energy cost estimation results convincingly demonstrated that investing on wind farm construction using all nominated turbines is economically feasible and, among all turbines, Suzlon S66/1.25?MW model with energy cost of 0.0357?$/kWh is a better option. 1. Introduction Depletion of fossil fuel, negative effects of CO2 emission, and high price of crude oil are major concerns which influence the motivation and adoption of the renewable energies like wind, solar, geothermal, and so on. Among all renewable energy sources, wind energy, as an abundant source of energy, has the highest annual growing rate of about 30% [1]. The aforementioned problems during the recent year have forced many scientists across the globe to pay more attention to clean energy sources like wind which is environmentally friendly and renewable [2]. It is worthwhile to mention that the economic growth and environmental pressure should be decoupled, as evidenced by international agreements on environmental policy such as the Kyoto Protocol for reducing greenhouse gas emissions [3]. The government plans to install more wind stations in Iran and, therefore, further regions should be explored. Based on Iranian Renewable Energy Organization (SUNA) data, some recent studies indicated that Jarandagh is one of the promising locations for wind power generation [4]. Exploitation of the wind power potential is significant and profitable for the regions, particularly for reducing carbon emission. Nevertheless, reliable data is of great importance for the purpose of wind
Solar wind-magnetosphere coupling functions on timescales of 1 day to 1 year
I. Finch,M. Lockwood
Annales Geophysicae (ANGEO) , 2007,
Abstract: There are no direct observational methods for determining the total rate at which energy is extracted from the solar wind by the magnetosphere. In the absence of such a direct measurement, alternative means of estimating the energy available to drive the magnetospheric system have been developed using different ionospheric and magnetospheric indices as proxies for energy consumption and dissipation and thus the input. The so-called coupling functions are constructed from the parameters of the interplanetary medium, as either theoretical or empirical estimates of energy transfer, and the effectiveness of these coupling functions has been evaluated in terms of their correlation with the chosen index. A number of coupling functions have been studied in the past with various criteria governing event selection and timescale. The present paper contains an exhaustive survey of the correlation between geomagnetic activity and the near-Earth solar wind and two of the planetary indices at a wide variety of timescales. Various combinations of interplanetary parameters are evaluated with careful allowance for the effects of data gaps in the interplanetary data. We show that the theoretical coupling, Pα, function first proposed by Vasyliunas et al. is superior at all timescales from 1-day to 1-year.
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