Energy Conversion in the Solar Flare due to
Direct Electric Fields as a Result of the Sheared Magnetic
Reconnection
T. Hirayama (National Astronomical Observatory, Japan)
We propose a new mechanism of the main energy conversion of the
solar flare. Because the rising velocity of a flare inducing
prominence, or a magnetic flux tube is <300km/s, plasmas below it
cannot eject with Alfven velocities of 3000km/s throughout the
early phase of flares, but only with Vz〜100km/s. Hence we need
other than the slow shock mechanism.
When there is a substantial sheared field as expected in every
flare, the main energy conversion region cannot be within a plane
with horizontal x and vertical z-components to the solar surface;
there should be y-components parallel to a long direction of
photospheric magnetic neutral line. Then Gauss law leads non-zero
electric chargess: 4πσ=divE =-div(V×B)/c 〜 By∂Vz/c∂x. Field-
aligned electric fields calculated from the Coulomb law using this
σ is far greater than the Dreicer field (By 〜 Bz 〜 40G and
dx 〜 10^(3-4) km), and accelerate electrons and protons. Due to
large electric fields, incoming horizontal Poynting energy flux in
area Sx are immediately converted to a kinetic energy of electron
beams along the magnetic field in Sz; Vx B^2 Sx/4π= 1/2 me Nbeam
Vbeam^{3} Sz and e.g. Sx/Sz 〜 3. The total flare energy can be
supplied by 10-20keV electrons of 1/2 me Vbeam^{2} and nbeam = 2×
10^7 cm^-3 for Vx = 40km/s. This Vx ensures short time scales of
flares.
Correspondence
Tadashi Hirayama (t-h-hira@parkcity.ne.jp), NAOJ
presentation
poster