I. V. Arkhangelskaja

The Solar Flare Catalog in the Low-Energy Gamma-Ray Range Based on the AVS-F Instrument Data Onboard the CORONAS-F Satellite in 2001-2005

The AVS-F apparatus onboard the CORONAS-F satellite (operated from July 31, 2001, to December 6, 2005) was intended for investigation of solar hard X-ray and gamma-ray radiation and for registration of gamma-ray bursts. The AVS-F apparatus constitutes a system for processing the data from two detectors: SONG-D (a CsI(Tl) scintillation detector 200 mm in diameter and 100 mm in height, fully surrounded by plastic anticoincidence shield) and RPS-1 (a solid state CdTe detector 4.9 mm × 4.9 mm in size). Over 60 solar flares stronger than M1.0 class by GOES classification were registered during the period from August 2001 to February 2005. Most flares showed gamma-ray emission during the periods when a rise in the X-ray flux was observed by the GOES instruments. Some flares produced gamma-rays only at maximum X-ray emission; for some flares, the durations of gamma-ray and X-ray emissions were the same. Up to six complexes of spectral lines were detected in some solar flares. The AVS-F instrument analyzes temporal profiles of low-energy gamma-ray emission with a temporal resolution of 1 ms within the first 4.096 seconds of solar flares. The preliminary analysis of such temporal profiles for seven solar flares revealed time regularities with scales from 7 to 35 ms in the 0.1-to 20-MeV energy range only for the flare of January 20, 2005, at a confidence level of 99%.

Features of quasi-stationary precipitations according to the data obtained with the AVS-F instrument onboard the CORONAS-F satellite

In the absence of burst events, the typical count-rate temporal profile of the AVS-F instrument in the low-energy gamma-ray band has a single broad maximum in the geomagnetic-equator region at latitudes from −30° to +40°). However, the so-called quasi-stationary precipitations, i.e., increases in the count rate by up to 15–30% with respect to the average level determined using polynomial fits, were observed in some equatorial regions at latitudes from −25° to +30°. At least four (type I, II, III, and IV) groups of such events can be distinguished according to their temporal profiles. The temporal profiles of about 44% events show a rapid increase to the south from the geomagnetic equator and a gradual decrease in the northern direction. For about 21% of analyzed events, on the contrary, the count rate increases sharply to the north of the geomagnetic equator and decreases gradually to the south. About 4% of events have symmetric temporal profiles. Finally, another 4% of the detected events have the form of a significant (a factor of 1.3–1.8) increase in the count rate with a central maximum. Typical durations of precipitations are 7–10 min (the size of the precipitation region is 20°–35°). However, short events lasting for ∼3 min (the size of the precipitation region is ∼10°) were observed. The mean time interval in which the precipitations were observed in regions with dimensions of 10° in geographic latitude by 30° in geographic longitude was about 24 h (the maximum interval exceeded 8 days). The majority of precipitations were observed in a zone of width 40° centered at the geomagnetic equator. Quasi-stationary precipitations can be related to the precipitations of charged particles in certain regions of the Earth’s magnetosphere periodically crossed by the satellite.

Gamma-ray radiation of solar flares in October-November 2003 according to the data obtained with the AVS-F instrument onboard the CORONAS-F satellite

Thirty active regions were observed on the Sun during the period from October 19 to November 20, 2003. Hard X-ray and gamma-ray radiation was detected from four active regions (10484, 10486, 10488, and 10490): 14 solar flares stronger than M5.0 according to the GOES classification were recorded during this period by detectors onboard the Geostationary Operational Environmental Satellite (GOES), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and other satellites. Five of these flares (and also the M2.7 flare of October 27, 2003) were also observed by the AVS-F apparatus onboard the CORONAS-F satellite. This paper discusses the time profiles and energy spectra of the solar flares of October 26, 2003 (M7.6), and October 29, 2003 (X10), and of the initial phase of the flare of November 4, 2003 (X18), obtained by the AVS-F instrument during the passage of the satellite over the regions near the geomagnetic equator. The spectra of the M7.6 flare of October 26, 2003, and of the initial phase of the X18 flare of November 4, 2003, in the energy band from 0.1 to 17 MeV contain no lines, whereas the spectrum of the flare of October 29, 2003, exhibits nuclear lines and the 2.2-MeV line during the entire flare gamma-ray emission registration. We also report the time profiles of the flare of October 29, 2003, in the energy bands corresponding to the continuum in the energy band 0.3–0.6 MeV, the nuclear lines of 56Fe, 24Mg, 20Ne, 28Si, 12C, and 16O, and the 2.2-MeV neutron-capture line. The analysis of these temporal profile periodograms shows the presence of a thin structure with characteristic scales from 34 to 158 s at the 99% confidence level. The AVS-F apparatus analyzes temporal profiles of low-energy gamma-ray emission with a temporal resolution of 1 ms within the first 4.096 seconds of solar flares. The analysis of the data reveals no regularities in the time series on time scales ranging from 2 to 100 ms at a confidence level of 99% for these three solar flares.

The Study of the Cosmic Gamma-Emission Nonstationary Fluxes Characteristics by the AVS-F Apparatus Data

The AVS-F apparatus (Russian abbreviation for Amplitude-Time Spectrometry of the Sun) is intended for the solar flares’ hard X-ray and gamma-ray emission characteristic studies and for the search and detection of the gamma-ray bursts (GRB). At present over 1,100 events with duration more than 2 s without any coordinate relations to Earth Radiation Belts and South Atlantic Anomaly were separated on the results of preliminary analysis of AVS-F experiment database.About 68 % of the identified events were associated with quasistationary equatorial precipitations-15-30 % count rate increases in the low-energy gamma-band of the AVS-F apparatus over its average value obtained by approximation of these parts with polynomials discovered on some equatorial segments in the ranges of geographic latitude of 25∘ up to +30∘. Several short events with duration of 1-16 ms associated with terrestrial gamma-ray flashes were registered during the experiment. These events were detected above the powerful thunderstorm formations.Solar flares with classes stronger than M1.0 according to the GOES classification were about 7 % of the detected events. Solar flares’ hard X-rays and γ-emission were mainly observed during the rise or maximum phases of the emission in the soft X-rays band according to the detectors on board the GOES series satellites data and duration of their registration is less than of the soft X-ray bands. According to the preliminary data analysis gamma-emission with energy over 10 MeV was registered during 12 % of the observed flares. The emission in the energy band E ? 100 keV was registered during over 60 faint solar flares (of B and C classes according to the GOES and from several ones γ-quanta with energy up to several tens of MeV were observed.Several spectral line complexes were observed in the spectra of some solar flares stronger than M1.0 in the low-energy gamma-range. Registered spectral features were corresponded to α α-lines, annihilation line, nuclear lines, and neutron capture line on1H (2.223 MeV). In the spectrum of the January 20, 2005 solar flare the feature in the range of 15-21 MeV was detected for the first time. It can be associated with lines of 15.11 MeV (12C +16O) or 20.58 MeV (from neutron radiative capture on3He), or with their combination. Also several e-dominant flares without any gamma-lines in energy spectra were identified. All detected faint solar flares were e-dominant according to the preliminary data analysis.Thin structure with characteristic timescale of 30-160 s was observed at 99 % significance level on some solar flares stronger than M1.0 temporal profiles in the low-energy gamma-band in the energy ranges corresponding to the identified spectral features or whole gamma-band energy boundaries. According to the results of the preliminary analysis during the flare of January 20, 2005, thin structure with timescale from 7 ms to 35 ms was detected at 99 % confidence level in the energy range of 0.1-20 MeV. Some thin structure with characteristic timescale 50-110 s was observed on temporal profiles of several faint events.About 3 % of the identified events were gamma-ray bursts. During some bursts high-energy gamma-emission was observed, for example Emax = 147 ± 3 MeV for GRB050525.

Gamma-ray emission from solar flares of January 2005 observed by the AVS-F apparatus onboard the CORONAS-F satellite

Six solar flares were detected by the AVS-F apparatus onboard the CORONAS-F satellite in January 2005. We discuss the temporal profiles and energy spectra of the solar flares of January 20, 17, and 15, 2005 (class X7.1, X3.8, and X2.6, respectively) on the AVS-F data. The active region NOAA 10720 was the source of these flares. The spectra of the flares of January 17 and 20, 2005 contain nuclear lines, a positron line, and a line due to neutron capture line, while only the positron and neutron capture lines can be identified in the spectrum of the flare of January 15, 2005. The spectral features corresponding to these lines were observed during the whole duration of the flares. Analysis of the temporal profile of the flare of January 20, 2005 with a 1-ms temporal resolution in the energy range 0.1–20 MeV reveals the presence of a thin structure (at the 99% confidence level) with typical timescales of 7 to 35 ms.

Solar flares observed by AVS-F instrument onboard CORONAS-F satellite during 2,5 year of it's operation

AVS-F instrument (Amplitude-Time Spectrometry of the Sun) is the system of an electronics engineering for onboard data gathering from two detectors: scintillation (CsI (Tl)) detector SONG-D (SOlar Neutrons and Gamma quantums) of complex of detectors SKL (in low and high gamma-band) and from semiconducting detector (X-ray semiconducting spectrometer) XSS-1 (in X-ray band). The experiment is carried out on the satellite CORONAS-F launched on July 31 2001. During more than 2,5 year of apparatus operation more than 30 of solar flares were detected. Characteristics of observed solar flares are presented in this article. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html