Reduction in the intensity of solar X-ray emission in the 2- to 15-keV photon energy range and heating of the solar coro
- PDF / 644,467 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 53 Downloads / 144 Views
E PLASMA
Reduction in the Intensity of Solar Xray Emission in the 2 to 15keV Photon Energy Range and Heating of the Solar Corona I. K. Mirzoeva Space Research Institute, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow, 117997 Russia email: [email protected] Received March 6, 2012; in final form, June 28, 2012
Abstract—The time profiles of the energy spectra of lowintensity flares and the structure of the thermal background of the soft Xray component of solar corona emission over the period of January–February, 2003, are investigated using the data of the RHESSI project. A reduction in the intensity of Xray emission of the solar flares and the corona thermal background in the 2 to 15keV photon energy range is revealed. The RHESSI data are compared with the data from the Interball–Geotail project. A new mechanism of solar corona heating is proposed on the basis of the results obtained. DOI: 10.1134/S1063780X13040077
1. INTRODUCTION The expansion of observation potentialities caused by both the development of the experimental base and the improvement of the measurement accuracy has stimulated interest in studies of lowintensity solar events and the quiet Sun. In particular, the RHESSI Xray spectrometer [1] makes it possible to perform highresolved measurements of the emission of low intensity flares in a broad energy range, as well as to study the thermal background of the solar corona. The RHESSI mission consists of a single spacecraft launched on February 5, 2002, by a Pegasus vehicle to a lowaltitude equatorial orbit inclined by 38° to the Earth’s equator. The lowaltitude equatorial orbit was chosen with the aim to minimize the damage of ger manium detectors by fast charged particles in the Earth’s radiation belts. A spectrometer capable of recording solar flare images in the X and γray energy ranges is mounted onboard the spacecraft. The spectrometer is designed using tungsten and molybdenum grids, which modu late the solar Xray flux, and detectors measuring the energy of each photon. The spacecraft is stabilized by a ~15rpm rotation and allows one to take up to 20 images per second. Highresolution spectroscopy is provided by nine germanium detectors, which record X and γray emission in a broad energy range from 3 keV to 20 MeV. The 1keV resolution makes it possi ble to carefully study specific features of X and γray solar emission.
In this work, the time profiles of the energy spectra of Xray events in the 2 to 15keV photon energy range are analyzed using the data of the RHESSI project [1]. Specific features of the thermal Xray background of the solar corona in the absence of unsteady solar events are also studied. The RHESSI data are compared with the data from the Interball– Geotail project. A new mechanism of solar corona heating is proposed that takes into account partial absorption of radiation from the Sun’s surface by the solar corona plasma in narrow bands of the Xray spectrum. 2. ANALYSIS OF THE EXPERIMENTAL DATA Let us consider a series of microflares re
Data Loading...
