The SOHO CELIAS/SEM EUV database from SC23 minimum to the present

The SOHO Solar EUV Monitor has been in operation since December 1995 onboard the SOHO spacecraft. This instrument is a highly stable transmission grating solar extreme ultraviolet spectrometer. It has made nearly continuous full disk solar irradiance measurements both within an 8 nm bandpass centered at 30.4 nm and throughout the 0.1 to 50 nm solar flux region since launch. The 30.4 nm flux, the 0.1 to 50 nm flux and the extracted soft X-ray (0.1 to 5 nm) flux are presented and compared with the behavior of solar proxies.     

Solar physics and interferometry mission (SPI)

This paper presents the scientific objectives of the Solar Physics and Interferometry Mission (SPI), describes succinctly the model payload and summarizes mission's issues. Novel instrumentation (interferometry) and clever mission design (small platform on low orbit with high telemetry and dedicated smaller platform on hexapod for permanently Sun-centered instruments) allow both spectral imaging and Helioseismology at very high spatial and temporal resolutions. Although not retained by ESA, this mission could become reality through NASA MIDEX and/or CNES PROTEUS opportunities as soon as 2007–2008.     

Great solar bursts of October 19, 22 and 23, 1989

Itapetinga measurements at 48 GHz with the multibeam technique are used to determine the relative position of solar burst centroid of emission with high spatial accuracy and time resolution. For the Great Bursts of October 19,22, 1989, with a large production of relativistic particles, and October 23, it is suggested that, at 48 GHz, the bursts might have originated in more then one source in space and time. Additionally the October 19 and 22 Ground Level Events exhibited very unusual intensity-time profiles including double component structures for the onset phase. The Bern observatory spectral radio emission data show a strong spectral flattening typical for large source inhomogeneties. The interpretation for this is that large solar flares are a superposition of a few strong bursts (separated both in space and time) in the same flaring region.     

High energy particle dispersion events observed by interball-1 and -2

Time period from October 1996 until January 1998 was checked on high energy resolution DOK2 energetic particle instrument measurements on Interball-1 and Interball-2 for the ion (> 20 keV) dispersive events (EDIS) with the exclusion of Interball-1 orbit parts in the tail. A variety of energy dispersive events, both in ion and electron spectra with different duration is found in the auroral regions, in the outer magnetosphere and near the cusp. While EDIS were observed in all sectors of MLT, the best conditions for their observation were in the afternoon local time. The characteristics of dispersive events observed by DOK2 are consistent with their explanation by the gradient-curvature drift of particles from the injection point(s) in the night local time sector given in Lutsenko at al., 2000a, b.     

Cyclic variations in the solar lower atmosphere

The Ca K line has been measured regularly nearly every month since 1974 at Kitt Peak. It is well known that the K₁ component of the Ca K line is formed in the temperature minimum region (TMR) of the solar atmosphere. Our study of the data of CaII K profiles over two solar cycles indicates that both in full disc integrated spectra and in center disc spectra, the distance between the red K₁ and the blue K₁ of the profiles and its average intensity show periodic variations. But the variation for the full disc integrated spectra fluctuates in the same way as the sunspot number does, while that for the center disc spectra has a time delay with respect to sunspot number. Non-LTE computations yield a cyclic temperature variation of about 17 K of the TMR in the quiet-Sun atmosphere and a cyclic variation of about 15–20 km in the height position of the TMR.     

INTERBALL statistical study of ion flow fluctuations in the plasma sheet

We use ion distribution measurements with CORALL instrument on-board the INTERBALL/Tail spacecraft to study plasma flows in the mid-tail (−9> X> −27 R_E) plasma sheet. Three velocity components computed every 2 minutes exhibit two types of velocity variations: Earthward bursty bulk flows (BBFs) and random flow fluctuations. Their properties are in a good agreement with the observations of the ISEE-2 spacecraft (Borovsky et al., 1997). The INTERBALL/Tail spacecraft configuration favors measurements of V_z component, in contrast to previous experiments in which only V_x and V_y were measured reliably. In the outer part of the plasma sheet V_y and V_z fluctuations were close to each other (variances σ(V_y) and σ(V_z) were about 160 and 110 km/s, respectively), but in the inner part at the dusk flank amplitude of V_y fluctuations increased and was 2 times higher than that of V_z component. This asymmetry of fluctuations should be taken into account during modern theoretical analysis and simulations.     

DNA fragmentation by charged particle tracks.

High-LET (linear energy transfer) charged particles induce DNA double-strand breaks (DSB) in a non-random fashion in mammalian cells. The clustering of DSB, probably determined by track structure as well as chromatin conformation, results in an excess of small- and intermediate-sized DNA fragments. DNA fragmentation in normal human fibroblasts (GM5758) was analyzed by pulsed-field gel electrophoresis after irradiation with photons (60Co) or 125 keV/micrometers nitrogen ions. Compared to conventional DSB analysis, i.e. assays only measuring the fraction of DNA smaller than a single threshold, the relative biological effectiveness (RBE) for DSB induction increased with 100%. Further, the size distribution of DNA fragments showed a significant dependence on radiation quality, with an excess of fragments up to 1 Mbp. Irradiation of naked genomic DNA without histone proteins increased the DSB yields 25 and 13 times for photons and nitrogen ions, respectively. The results suggest possible roles of both track structure and chromatin organization in the distribution of DNA double-strand breaks along the chromosome.     

Lifetime total radiation risk of cosmonauts for orbital and interplanetary flights.

This paper presents results of calculations of total radiation risk for cosmonauts over their lifetimes and assessments of possible shortening of life expectancy on the basis of generalized doses calculated for cosmonauts after a long term interplanetary and orbital space missions on "MIR" station and International Space Station with the use of mathematical expressions coming from a model of change mortality rate of mammals after irradiation. Tumor risk assessments for cosmonauts over lifetime after flights are also given. Dependences of the delayed radiation consequences mentioned above on flight duration, spacecraft shielding thicknesses, solar activity and cosmonauts' age are analyzed.     

Asymmetric precipitation in a coronal loop as explanation of a singular observed spectrum

Almost 10 years of solar submillimeter observations have shown new aspects of solar activity, such as the presence of rapid solar spikes associated with the launch of coronal mass ejections and an increasing submillimeter spectral component in flares. We analyse the singular microwave–submillimeter spectrum of an M class solar flare on 20 December, 2002. Flux density observations measured by Sun patrol telescopes and the Solar Submillimeter Telescope are used to build the radio spectrum, which is fitted using Ramaty’s code. At submillimeter frequencies the spectrum shows a component different from the microwave classical burst. The fitting is achieved proposing two homogeneous sources of emission. This theoretical fitting is in agreement with differential precipitation through a magnetically asymmetric loop or set of loops. From a coronal magnetic field model we infer an asymmetric magnetic structure at the flare location. The model proposed to quantify the differential precipitation rates due to the asymmetry results in a total precipitation ratio Q₂/Q₁≈10⁴–10⁵, where Q₁(Q₂) represents the total precipitation in the loop foot with the high (low) magnetic field intensity. This ratio agrees with the electron total number ratio of the two sources proposed to fit the radio spectrum.