No abstract

In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown bath analytically and numerically that the toraidicity not only breaks up the shear AlfvSn continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the contincim gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed.

Ideal and resistive HHD equations for the shear Alfven waves are studied in a low-fj toroidal model by employing the high-n ballooning formalism. The ion sound effects are neglected. For an infinite shear slab, the ideal HHD model gives rise to a continuous spectrum of real frequencies and discrete eigenmodes (Alfven-Landau modes) with complex frequencies. With toroidal coupling effects due to nonuniform toroidal magnetic field, the continuum is broken up into small continuum bands and new discrete toroidal eigenmodes can exist inside the continuum gaps. Unstable ballooning eigenmodes are also introduced by the bad curvature when $ > 0 C. The* resistivity (r\) can be considered perturbatively for the ideal modes. In addition, four branches of resistive modes are induced by the resistivity: (1) Resistive entropy modes which are stable with frequencies going to zero with resistivity as n 1^3 , (2) Tearing modes which are stable (A' < 0) with frequencies approaching zero as H ' , (3) Resistive periodic shear Alfven waves which approach the finite frequency end points of the continuum bands as ti » an<^ (*) Resistive ballooning modes which are purely growing with growth rate proportional to ^1/3^2/3 a3 n + o and 8+0. DISTRIBUTION OF THIS DOCUMENT IS UMTEO * = i(i(+,e,6) exp[i x

An observational relationship has been well established among magnetic reconnection, high-energy flare emissions and the rising motion of erupting flux ropes. In this paper, we verify that the rate of magnetic reconnection in the low corona is temporally correlated with the evolution of flare nonthermal emissions in hard X-rays and microwaves, all reaching their peak values during the rising phase of the soft X-ray emission. In addition, however, our new observations reveal a temporal correlation between the magnetic reconnection rate and the directly observed acceleration of the accompanying coronal mass ejection (CME) and filament in the low corona, thus establishing a correlation with the rising flux rope. These results are obtained by examining two well-observed two-ribbon flare events, for which we have good measurements of the rise motion of filament eruption and CMEs associated with the flares. By measuring the magnetic flux swept through by flare ribbons as they separate in the lower atmosphere, we infer the magnetic reconnection rate in terms of the reconnection electric field E rec inside the reconnecting current sheet (RCS) and the rate of magnetic flux convected into the diffusion region. For the X1.6 flare event, the inferred E rec is~5.8 V cm À1 and the peak mass acceleration is 3 km s À2 , while for the M1.0 flare event E rec is~0.5 V cm À1 and the peak mass acceleration is 0.2-0.4 km s À2 .