Explosive plasma flows in a solar flare

• Published in: The Astrophysical journal Vol. 324; no. 1; pp. 582 - 589
• Main Authors: Zarro, Dominic M., Canfield, Richard C., Metcalf, Thomas R., Strong, Keith T.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS University of Chicago Press 01.01.1988
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Flares, bursts, and related phenomena; Solar Physics; Solar system; Solar corona; Plasma; Plasma flow; Spectral line profile; X ray emission; Solar flare
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/165919

Solar Maximum Mission soft X-ray data and Sacramento Peak Observatory H-alpha observations are combined in a study of the impulsive phase of a solar flare. A blue asymmetry, indicative of upflows, was observed in the coronal Ca XIX line during the soft X-ray rise phase. A red asymmetry, indicative of downflows, was observed simultaneously in chromospheric H-alpha emitted from bright flare kernels during the period of hard X-ray emission. Combining the velocity data with a measurement of coronal electron density, it is shown that the impulsive phase momentum of upflowing soft X-ray-emitting plasma equalled that of the downflowing H-alpha-emitting plasma to within one order of magnitude. In particular, the momentum of the upflowing plasma was 2 x 10 to the 21st g cm/s while that of the downflowing plasma was 7 x 10 to the 21st g cm/s, with a factor of 2 uncertainty on each value. This equality supports the explosive chromospheric evaporation model of solar flares, in which a sudden pressure increase at the footprint of a coronal loop produces oppositely directed flows in the heated plasma.