2005/09/30 by Ryan O. Milligan, R. O. Milligan, P. T. Gallagher +6 · 8 citations
Physics and Astronomy · #Ionosphere and magnetosphere dynamics #Solar and Space Plasma Dynamics #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/500555
published as Astrophys.J.638:L117-L120,2006 · 5 pages, 4 figures, ApJL (In Press)
arxiv created 2005/12/21 · openalex publication_date 2006/01/27 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
Simultaneous observations of explosive chromospheric evaporation are presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager ( RHESSI ) and the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory . For the first time, cospatial imaging and spectroscopy have been used to observe explosive evaporation within a hard X-ray emitting region. RHESSI X-ray images and spectra were used to determine the flux of nonthermal electrons accelerated during the impulsive phase of an M2.2 flare. When we assumed a thick-target model, the injected electron spectrum was found to have a spectral index of ~7.3, a low-energy cutoff of ~20 keV, and a resulting flux of ≥4 × 10 10 ergs cm -2 s -1 . The dynamic response of the atmosphere was determined using CDS spectra; we found a mean upflow velocity of 230 ± 38 km s -1 in Fe XIX (592.23 Å) and associated downflows of 36 ± 16 and 43 ± 22 km s -1 at chromospheric and transition region temperatures, respectively, relative to an averaged quiet-Sun spectra. The errors represent a 1 σ dispersion. The properties of the accelerated electron spectrum and the corresponding evaporative velocities were found to be consistent with the predictions of theory.