We study the statistical relationship between optical flares and type III radio bursts, using modern and extensive computer files. Results emerge along two main lines, concerning the physical mechanism of ejection of energetic particles, and the magnetic field geometry respectively.

First, we find that type III probability of occurrence increases strongly with the brightness of a flare and its proximity to a sunspot, and with accompanying prominence activity. This suggests that Bornmann's class I and III events correspond to distinct physical phenomena, particle acceleration and magnetic expansion respectively, both working simultaneously in class II events, which are the most favorable to the ejection of energetic particles out of flaring sites.

We study the dynamics of an IIα absorbing structure associated with a type III radioburst. We use a “Differential Cloud Model” to analyse the observed line profiles, in order to determine radial velocity and microturbulence (or shear) as functions of time.

We assume that the material is flowing inside magnetic flux tubes, with a given velocity distribution. We analyse the motions in a phase-diagram (position x,velocity V). The evolution of velocity and microturbulcnce is compared to the observations. The model accounts qualitatively for the evolution of velocity, and qualitatively for the decrease of microturbulence.

We present recent results from meter-decameter imaging of several classes of solar radio bursts: Preflare activity in the form of type III bursts, correlated type IIIs from distant sources, and type II and moving type IV bursts associated with flares and CMEs.

Some observational results and statistical characteristics of solar millimeter wave bursts observed by employing the 35 GHz, solar interferometer in Nagoya are briefly described.

A gradual rise and fall flare, with a duration of about one hour was observed on June 10, 1980 in the radio (Toyokawa and VLA), optical (Bing Bear) and XUV (SMM satellite) ranges of wavelengths. The flare developed as a large loop connecting two regions of opposite polarity in a pre-exisisting active region. A model of the differential emission measure of the loop observed at three different stage of the flare is deduced from the analysis of the XUV images in C IV (1549 A), O VIII (18.97 A), Ne IX (13.45 A), Mg XI (9.17 A) and Si XIII (6.65 A) emission lines. The differential emission measure as a function of temperature is controlled by the conductive flux via the temperature gradient; the evaluation of the divergence of the conductive flux is used in the energy balance to have information on the power deposition function.

The flare images show a compact, nearly cylindrical arcade centered along the filament channel and composed of 4 prominent loops. The loop systems of Fe XII (Te = 1.7 106K) and Fe XIV (Te = 2.3 106K) are smaller than, and lie nested within, the arcades of Fe XVI (Te = 3 106K) and Ca XVII (Te = 5 106K). The loop arcades at different temperatures, as well as different loops within a given arcade, show different expansion rates. These vary from 6 – 8 km s–1 for Fe XIV shortly after flare maximum to 0.5 – 1 km s–1 late in the decay phase. For hotter ions, such as Ca XVII, the velocities are approximately constant at 2 – 3 km s–1 daring the whole of the observations.

Using coordinated X-ray and Hα observations of five solar flares, we investigate the dynamics of chromospheric condensations formed during chromospheric evaporation. We show that the peak downflow velocity of condensations predicted by simple hydrodynamic compression of the chromosphere is in good agreement with empirical downflow velocities implied by impulsive phase Hα redwing Doppler shifts. This agreement indicates that the Hα wing redshift provides a useful diagnostic of the pressure excess in the evaporating region and, hence, the energy flux driving chromospheric evaporation.

A comparative study of H-alpha intensity and area development of several flares is presented in an attempt to investigate characteristic features of various types of optical solar flares.

Hα observations with high temporal resolution allow a detailed analysis of the chromospheric response to thre primary energy release. The timing; relationship between Hα and hard X-rays gives information about the energy transport mechanism. Sites of massive injection of nonthermal electrons are identified by characteristic features in the the line profile (Canfield et al. 1984;. Canfield and Gayley 1987).

In this paper are described the simultaneously observational results of filtergrams, Dopplergrams and vector magnetograms for a solar flare in the active region NOAA/USAF -1862 on 7 Oct. 1987 with the solar telescope-magnctograph of Beijing Astronomical Observatory. From the analyses of these data, some conclusions were obtained.

By means of Solar Magnetic Field Telescope, the fine structure of video magnetic fields (5324A) and sight-of-line velocity fields (4861A) of flare active region on July 23 (E53, S19) and Aug. 8(W25, S28) in 1987 has been obtained. The main characters are following:

1. The flares occur in places where there are compressive and osmotic motion between opposite magnetic poles. In some causes, the osmotic opposite magnetic pole dissipates after the flares.

Simultaneous observations of a surge in Hα- and C IV are analysed in terms of Doppler velocities and “microturbulence”. The behaviour of both quantities suggests strong velocity shears with small spatial scales.

Considering the flaring arch to be the basic element of all flares, we study here the structure of compact flares and double ribbon flares. It is observed that, in the case of compact flares, the flaring arch diverges from a pivot point (rigid rotation), while in the case of double ribbon flares the flaring arches are distributed to either side of the polarity reversal line.

We studied the unique EUV spectra of the 21 Jan. 1974 flare observed by the NRL Normal-Incidence Slit Spectrometer (SO 82B) onboard the Skylab. The results show that the pre-impulsive transition region plasmas exhibited enhanced turbulence and heating before the acceleration of energetic particles. The absence of blue-shifted components in the Fe XXI line profiles shows that the chromospheric evaporation is not important in this flare.

We have made extensive observations of the time-variability of solar active regions in the far-UV using the ultraviolet spectrometer on SMM. We describe the three different modes of solar variability (impulsive events, bursts and oscillations) that are evident in our data and discuss their physical implications.

The coronal mass ejection (CME) data and the data for coronal holes for the period 1979-1982 are compared locationwise. Out of 79 CMEs whose locations and spans are known, 48 (61%) CMEs are associated with coronal holes. We make a tentative suggestion that probably the mass ejected during solar flares and active prominences may move along the open magnetic field of the coronal holes and appear as CMEs.

A clear association is demonstrated between the dips in the total solar irradiance and flare occurrence. It is found that both the irradiance dips and flares are related to emerging new activity.

We discuss observations of a solar flare located close to the limb (N15, W75) at 07 00 UT on 26 September 1963 from the Crimean Astrophysical observatory.

Stark broadening and hence electron density have been obtained from measured time profile and half-width of the Baliner series lines from Hα to H M.

The emission mechanism has been deduced from a study of the continuum intensity as a function of wavelength.

Spectroscopic highly resolved solar granulation observations lead to intense line asymmetries for rising and sinking elements. In order to average several granules it is better to use equivalent widths than continuum intensities.

Based on X-ray (1-8 Å) flux data for 1977-1987, the integral spectra of solar flare energy were computed. The energy spectra were approximated by a power law N(E) α; E~n, with N being the number of flares with energy in excess of E. It is shown that the spectral index (β) varies systematically with the 11-year cycle phase.