X-ray observations of two short but intense solar flares

Journal Article · Sat Mar 31 23:00:00 EST 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168618· OSTI ID:6806635

Nitta, N; Dennis, B R; Kiplinger, A L ^[1]

---

1. NASA, Goddard Space Flight Center, Greenbelt, MD (USA) Maryland Univ., College Park (USA) Colorado Univ., Space Environment Laboratory, Boulder (USA)

This paper presents continuum X-ray spectra of impulsive emission in two short but intense solar flares which have relatively weak soft X-ray emissions, combining data obtained with soft X-ray and hard X-ray spectrometers on board two satellites, the SMM and Hinotori. In both flares, photon spectra of the impulsive component are found to flatten toward low energies, suggesting that a low-energy cutoff of the electron spectrum could be greater than about 50 keV and that the total energy contained in the electrons is significantly less than that usually quoted for a cutoff energy of about 20 keV. Different shapes of the X-ray spectrum at energies below 50 keV in other flares can be attributed to the variety in the relative strength of gradual and impulsive emissions. In one of the two flares, observations with the imager on Hinotori suggest that hard X-ray emission is likely to be associated with loop footpoints. It is argued that contamination by the gradual soft X-ray emission and/or the asymmetry of loops could explain the detection of single sources in the majority of flares that have been imaged in hard X-rays. 67 refs.

• OSTI ID: 6806635
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 353; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
ELECTROMAGNETIC RADIATION
ELECTRON SPECTRA
ELEMENTARY PARTICLES
IMAGES
IONIZING RADIATIONS
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC FIELDS
MASSLESS PARTICLES
PHOTONS
PHOTOSPHERE
RADIATIONS
SOFT X RADIATION
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR FLARES
SPECTRA
X RADIATION
X-RAY SPECTRA