A clue to the trigger for both the type III solar radioburst and the solar flare

✍ Scribed by E. R. Priest; J. Heyvaerts

• Publisher: Springer
• Year: 1974
• Tongue: English
• Weight: 490 KB
• Volume: 36
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00151212

✦ Synopsis

Recent observations of 'neutral line absorbing features' in the solar atmosphere may give an important clue to the mechanism whereby both type III solar radiobursts and solar flares are triggered. It is suggested that as new satellite magnetic flux emerges at the edge of an active region in an area of opposite polarity a neutral sheet builds up between the new and old flux. When the sheet has a length of about a megametre its thermal insulation from the surrounding plasma is effective enough for a thermal instability to occur. The resulting compression and inflow of plasma is observed in H~ on the disc as a neutral line absorbing feature. Furthermore, the electric field of the accompanying collisionless tearing mode instability in a thin slab near the centre of the sheet exceeds the runaway field; it may therefore accelerate electrons to high enough energies to produce the type III burst which usually occurs at the same time as the absorbing feature. Perhaps the flare which sometimes ensues is triggered when the quasi-equilibrium state is destroyed by the development of turbulence in the neutral sheet.