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Trottet, G.

Publications and source records attributed to Trottet, G..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

RHESSI and Radio Imaging Observations of Microflares E2.3-0011-04

We present the analysis of five microflares, three observed simultaneously by RHESSI in hard X-rays and Nobeyama RadioHeliograph (NoRH) in microwaves (17 GHz) and two observed by RHESSI and Nancay RadioHeliograph (NRH) at metric wavelengths (150-450 MHz). Since we have no radio imaging telescopes simultaneously operating at microwave and meter wavelengths in the same time zone, we are obliged to use a different set of microevents for comparison with metric wavelength counterparts in contrast to that used for comparison with metric wavelength counterparts in contrast to that used for comparison with microwave events. This is because we are interested in using the locations and other imaging characteristics of the events from both RHESSI and Nancay instead of just temporal correlation. Here we describe the properties of five events -- three in microwaves and two at metric wavelengths.

Kundu, M. R.↗
NASA NTRS1991

Acceleration of electrons outside flares - Coronal manifestation and possible origin

Imaging observations at decimetric and metric wavelengths of the solar corona are used to investigate a short-lasting noise storm and the associated changes of the underlying active-region plasma. It is shown that a new source appears in the active region in close temporal and spatial coincidence with the onset of the noise storm in the middle corona. The onset of the noise storm is delayed at longer wavelengths. At a given wavelength, the noise-storm source undergoes a systematic slow movement with a significant component perpendicular to the magnetic-field lines above the active region. The observations are tentatively attributed to the emission of nonthermal electrons in a system of expanding coronal loops, the expansion being initiated by the appearance of the new 21-cm source in the low atmosphere. The derived velocity of expansion is about 80 to 150 km/s. The electrons emitting the noise storm cannot be provided by the high-energy tail of the Maxwellian in the new active region source, but originate either from a nonthermal population in this source or from acceleration at higher altitudes, in the structures which give rise to the noise storm.

Raulin, J. P.↗
NASA NTRS1988

High resolution VLA-Nancay observations of the sun

The Very Large Array (VLA) and the Nancay Radioheliograph (NR) can be used in the 1990s to provide unique observations of the quiescent and active corona. The combined data can specify the evolution and magnetic structure at a variety of heights in the quiescent corona, from compact to extended structures such as loops, streamers and coronal holes. The scientific potential of simultaneous VLA-NR research is illustrated by observations of solar noise storms with hitherto unavailable resolution in space (VLA) and time (NR). Unique information will also be provided for other types of solar bursts, leading to an improved understanding of solar activity during the coming maximum.

Kerdraon, A.↗
NASA NTRS1986

Spatial and temporal characteristics of flare energy release determined from X-ray and radio imaging observations

Using the Hard X-ray Imaging Spectrometer (HXIS) from the Solar Maximum Mission Satellite, the morphological aspects and temporal evolution of three major flares which occurred on June 29, 1980 are studied. One of these events, observed at 10:40 UT, is analyzed in particular detail, including Hard X-ray Burst Spectrometer (HXRBS) data and metric wavelength data from the Nancay radioheliograph. The flares occurred during the interaction of two distinct magnetic structures. There is an early onset phase during which there is a weak level of particle acceleration, perhaps accompanied by strong heating within the magnetic interaction region. The impulsive phase of high power energy release is associated with a major interaction between the two structures and accompanied by strong acceleration and heating.

Hernandez, A. M.↗
NASA NTRS1985

Temporal evolution of an energetic electron population in an inhomogeneous medium: Application to solar hard X-ray bursts

Energetic electrons accelerated during solar flares can be studied through the hard X-ray emission they produce when interacting with the solar ambient atmosphere. In the case of the non thermal hard X-ray emission, the instanteous X-ray flux emitted at one point of the atmosphere is related to the instantaneous fast electron spectrum at that point. A hard X-ray source model then requires the understanding of the evolution in space and time of the fast particle distribution. The physical processes involved here are energy losses due to Coulomb collisions and pitch angle scattering due to both collisions and magnetic field gradients.

Vilmer, N.↗
NASA NTRS1983

Association between gradual hard X-ray emission and metric continua during large flares

X-ray radiation is used to study coronal phenomena in conjunction with meter wave observations during some large solar flares. It is found that metric flare continua and moving type IV bursts are associated with gradual and long lasting (a few tens of minutes) microwave and hard X-ray emissions. The detailed temporal analysis reveals that although metric and hard X-ray sources are located at very different heights, both kinds of emission result from a common and continuous/repetitive injection of electrons in the corona. The late part of the metric event (stationary type IV burst) is only associated with soft X-ray radiation. This indicates that the mean energy of the radiating electrons is lower during stationary type IV bursts than during the earlier parts of the event.

Klein, L.↗
NASA NTRS1983

The association of radio noise storm enhancements with the appearance of additional material in the corona

Visible light observations of the corona have been combined with radioheliograph observations at metric wavelengths to examine the dynamic behavior of the corona during and after noise storm onsets and enhancements. For the period studied, the occurrence of such radio events is systematically associated with the addition of coronal material in the vicinity of the radio source. Some of the events correspond to mass ejection transients, but they more frequently represent merely a brightening, which grows in 1 hour or less with the coronal region and remains dense and stable for several hours.

Kerdraon, A.↗
NASA NTRS1982

An association between coronal structures and type III burst sources

Observations of the coronal structures overlying type III radio burst producing regions, obtained with the HAO Coronograph/Polarimeter on board the Solar Maximum Mission, have been combined with observations of the type III bursts from the Mark III Nancay Radioheliograph at 169 MHz. A first qualitative comparison of the data, performed for two periods, indicates that the corona overlying type III producing sites is composed of small, discrete, over-dense structures, which are sometimes diverging and short-lived. The type III burst sources are complex, exhibiting elementary components. It is suggested that the type III burst structure follows that of the corona and that discrete structures may play a fundamental role for type III production.

Trottet, G.↗