Abstract
On the basis of the Solar Maximum Mission observations, Švestka (Solar Phys. 121, 399, 1989) introduced a new class of flares, the so-called flare hybrids. When they start, they look like typical compact flares (phase 1), but later on, they look like flares with arcades of magnetic loops (phase 2). We summarize the characteristic features of flare hybrids in soft and hard X-rays as well as in the extreme ultraviolet; these features allow us to distinguish flare hybrids from other flares. In this article, additional energy release or long plasma cooling timescales are suggested as possible causes of phase 2. We estimate the frequency of flare hybrids, and study the magnetic configurations favorable for flare hybrid occurrence. Flare hybrids appear to be quite frequent, and the difference between the lengths of magnetic loops in the two interacting loop systems seem to be a crucial parameter for determining their characteristics.
Highlights
There are no two identical flares, but it is useful to classify flares following some schemes
The most commonly accepted classification was introduced by Pallavicini, Serio, and Vaiana (1977) based on soft X-ray images obtained by the S-054 experiment onboard Skylab
Soft X-Rays In Figure 1 we present an example of the flare hybrid, SOL1992-11-05T06:22 (M2.0), observed by the Soft X-ray Telescope (SXT: Tsuneta et al, 1991) onboard the Yohkoh satellite
Summary
There are no two identical flares, but it is useful to classify flares following some schemes. The authors proposed two separate classes of events, namely compact flares (class 1) and flares occurring in large and diffuse systems of loops (class 2). They found that the separation is supported by the different values of several physical parameters such as height, volume, energy density, and characteristic times of rise, decay, and duration. They perceived that flares of class 1 are located very low in active regions and, in contrast to flares of class 2, do not appear to be associated with coronal mass ejections (CMEs) and prominence eruptions or activations.
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