Observations of solar flare transition zone plasmas from the solar maximum mission

Journal Article · Mon Feb 01 04:00:00 EST 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159640· OSTI ID:5234596

Cheng, C; Bruner, E C; Tandbert-Hanssen, E; Woodgate, B E; Shine, R A; Kenny, P J; Henze, W; Poletto, G

We present observations of the 1980 April 8 flare in the Si IV 1401 A lines, obtained with the Ultraviolet Spectrometer and Polarimeter on Solar Maximum Mission. We have studied the spatial and temporal evolution of the Si IV. O IV intensity, density, and mass motions in the preflare and flare transition zone plasmas. The density is determined from the observed intensity ratio between the Si IV resonance line and the O IV intersystem line, and this diagnostic method is discussed in detail. The principal results are as follows: (1) The UV flare observed in the Si IV and O IV lines is unambiguously identified as occurring in a low-lying preexisting transition zone loop. The loop spanned the magnetic neutral line which separated a larger leader spot and a newly emerged isolated spot of opposite polarity. (2) At the onset of the flare, the easternmost footpoint, which are anchored in an isolated spot region of high longtidunal magnetic field gradient, suddenly showed impulsive brightening.This flaring kernel previously had been inconspicuous. (3) The density of the transition zone plasma at a temperature of approx.10/sup 5/ k at the flaring footpoint increased an order of magnitude from its preflare value of 2 x 10/sup 11/ cm/sup -3/ to 3 x 10/sup 12/ cm/sup -3/ during the impulsive brightening. (4) The large intensity and density increases in the flaring kernel were associated with a downward mass motion with a velocity of approx.20 km s/sup -1/. The other part of the loop remained relatively stationary. (5) The emission from the high temperature flare plama, as observed in the soft x-ray Fe XXV lines, was concentrated in a cloud overlying the whole Si IV/O IV loop, indicating that the flare energy was released in a low-lying loop or loops, including the observed Si IV/O IV loop. The released flare energy was transported by way of large-scale connecting field lines to other parts of the active region, producing the hot plasma and H..cap alpha.. kernels observed near the trailing spot.

• Research Organization: NASA Marshall Space Flight Center (now at E. O. Hulbert Center for Space Research, Navala Research Laboratory
• OSTI ID: 5234596
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 253:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHARGED PARTICLES
EMISSION
FUNCTIONS
IONS
MAGNETIC FIELDS
OXYGEN IONS
PLASMA
SILICON IONS
SOLAR ACTIVITY
SOLAR FLARES
SOLAR X-RAY BURSTS
SPECTRA
SPECTRAL FUNCTIONS
ULTRAVIOLET SPECTRA