SOLAR-FLARES - GEOEFFECTIVENESS AND THE POSSIBILITY OF A NEW CLASSIFICATION

In this paper it is shown that, according to the parameter of X-ray (λ = 1-8 A ̊) emission ∮ = Im · τ2 (Im being a maximum of flux in the impulse of X-ray emission, and τ the time-width of the impulse at the Im/3-level), flares can be divided into three classes: weak (∮ < 7 in 106 W m-2 h2 units); moderate (7 ≤ ∮ ≤ 35); and strong (∮ > 35). In this case: (a) weak flares are never sources of SSC ; (b) shock waves from moderate flares propagate along the heliospheric current sheet (HCS) because outside the HCS the conditions for their excitation do not seem to be satisfied ; and (c) strong flares are able to excite shock waves outside the HCS as well. It is shown that the character of excitation of shock waves in the HCS substantially depends on the flares' location with respect to the neutral line on the Sun. It is concluded that the parameter ∮ can form the basis for a classification of geoeffectiveness of flares. © 1990.