Heat balance for the high-temperature component of a solar flare

• Published in: Solar physics Vol. 84; no. 1-2; pp. 189 - 203
• Main Author: Duijveman, Andr
• Format: Journal Article
• Language: English
• Published: 01.04.1983
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/BF00157456

Shortly after the occurrence of the impulsive spikes of the two-ribbon flare of May 21, 1980, a temperature analysis of the X-ray-emitting flare plasma showed the presence of a low-temperature component [n=15 x 10 super(1) super(0) cm super(-) super(3) ; T=20 x 10 super(6) K] and a high-temperature component [n=2 x 10 super(1) super(0) cm super(-) super(3) ; T=40 x 10 super(6) K]. The mean free path of an electron in the hot component is comparable to the size of the source ( identical with 10 super(4) km). Heat losses from the hot source can, therefore, not be described with classical formulas. Theoretical arguments show that, most likely, the electron-to-ion-temperature ratio, T sub(e) /T sub(i) , in the hot plasma is close to unity. This implies the presence of a hot ion component (T sub(i) identical with 40 x 10 super(6) K). Under these conditions (T sub(e) identical with T sub(i) ), heat flux limitation by electrostatic turbulence is ineffective. However, reduction of the heat flux is still possible because of the breakdown of classical theory. It is demonstrated that only nonclassical current dissipation processes can sustain a hot source against cooling by a saturated heat flux. Investigation of the collisionality as a function of position along a magnetic loop shows that the breakdown of classical theory should be expected to occur first near the base of the loop. The author concludes that the newly discovered hot source is important for the energy budget of the flare, even if the heat losses are considerably reduced. It is estimated that, for the May 21, 1980, flare, similar to 10 super(3) super(1) ergs were necessary to maintain the hot source against heat losses over the time period that it was observed ( identical with 10 min).