1) For any system that has an → input and
the return of a fraction of the output to the input for the next action.
Feedback process allows a system to regulate itself by monitoring its own
output. It is of prime importance to
the working of all regulatory mechanisms found in
living and non-living nature, as well as in social systems such
as education and economy.
Fr.: boucle de rétroaction
A closed transmission path in a → feedback process involving part of the → output as an → input for correction or control of the operation of a → system.
Fr.: rétroaction negative
A → feedback process in which the → output reacts on the → input so as to reduce the initial → effect.
Fr.: rétroaction positive
A → feedback process in which the → output reacts on the → input so as to increase the initial → effect.
Fr.: rétroaction radiative
The radiative energy put back to the environment through an astrophysical process. For example, in the process of → star formation → accretion disks form around → protostars. The material in the disk spirals inward and on to the protostar, provided that there is an efficient mechanism to redistribute → angular momentum outward in the disk. During this process → gravitational energy is transformed into radiation due to → viscous dissipation in the disk and at the → accretion shock around the protostar. This radiation heats the region around the protostar and may → suppress subsequent → fragmentation and further star formation. Thus, radiative feedback plays a critical role in regulating the stellar → initial mass function.
Fr.: rétroaction stellaire
The process whereby large quantities of → energy and → momentum are released into the gas surrounding → star formation regions in galaxies. More specifically, → massive stars inject → energy, → mass, and → metals back to the → interstellar medium through → stellar winds and → supernova explosions. Feedback inhibits further star formation either by removing gas from the galaxy, or by heating it to temperatures that are too high to form new stars. Observations reveal feedback in the form of → galactic-scale outflows of gas in galaxies with high → star formation rates, especially in the → early Universe. Feedback in faint, low-mass galaxies (→ low-mass galaxy) probably facilitated the escape of ionizing radiation from galaxies when the Universe was about 500 million years old, so that the hydrogen between galaxies changed from neutral to ionized, a process called → reionization (Dawn K. Erb, 2015, Nature, 9 July).
Fr.: rétroaction des supenovae
1) The process whereby the energy and matter contained in a → supernova
are injected into the → interstellar medium after the
→ supernova explosion.
The → thermal energy injected into the ISM serves to
→ suppress → star formation, while
→ heavy elements → nucleosynthesized
inside SNe tend to enhance star formation.