Browsing by Author "Lohani, N. K."

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Heating of solar coronal loops by phase-mising
(2011-07-06) Lohani, N. K.; Lalan, Prasad
This paper present an analytical method for the heating of solar coronal loops by phase-mixing. We also discuss herewith the non-linear mode of phase mixing by Alfven waves. Under typical coronal heating conditions by ohmic dissipation clue to phase-mixing can provide magnetic energy on a time scale comparable with the coronal radiative time. For large Lundquist number, it is possible that phase-mixing can attain a hot coronal loop. We introduce two model of loops; i.e., flat symmetric loop model and cylindrical symmetric loop model. The magnetic field assumed to be static and associated with only in inhomogeneities plasma density. The solution under initial boundary condition and the ohmic dissipation have been discussed.
Nanoflares as a possible coronal heating agent
(2005-05-01) Lalan, Prasad; Lohani, N. K.
We present the concept of coronal heating by nanoﬂares and the characteristics of active regions which result presumbly from a series of discrete events of various energies analogeus to a large number of more or less random heating agents. The ﬂare associated with small impulsive events of magnetic energy dissipation is from 5 x 1023 to 1025 ergs, called nanoﬂares and it is treated as heating agents. The analysis of these agents are represented by a power law distribution as a function of their energies with a negative slope of 2. We discuss the physical characteristics of nanoﬂare heating process in respect of power law distribution and formulate the coronal luminosity. We estimate the coronal radiation energy and generation rate by nanoﬂares.
On tripolar magnetic reconnection and coronal heating
(2011-07-05) Pandey, Kumud; Narain, Udit; Lohani, N. K.
Using recent data for the photosphere-chromosphere region of the solar atmosphere the magnetic reconnection in tripolar geometry has been investi- gated through the procedure of Sturrock (1999). Particular attention has been given to the width of the reconnecting region, wave number of the rapidly growing tearing mode, island length scales, frequency of MHD ﬂuctuations, tearing mode growth rate, energy dissipation rate and minimum magnetic ﬁeld strength required to heat chromospheric plasma to coronal temperatures. It is found that small length scales are formed in the upper chromosphere. The maximum growth rate of tearing mode instability coincides with the peak in the energy dissipation rate both of which occur in the upper chromo- sphere at the same height. It is realized that the distribution of magnetic ﬁeld with height is essential for a better understanding of the coronal heating problem.