Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002aps..aprk12002t&link_type=abstract
American Physical Society, April Meeting, Jointly Sponsored with the High Energy Astrophysics Division (HEAD) of the American As
Astronomy and Astrophysics
Astrophysics
Scientific paper
Solar corona has sporadic energy release with energies over 7 orders of magnitudes. Occasional larger events are called flares, and ubiquitous smaller one discovered with Yohkoh are called micro-flares or transient brightening. The mechanism of the solar flares has been enigma over the years. Soft and hard X-ray imaging telescopes aboard Yohkoh for the first time demonstrates that these sporadic energy releases are in general attributed to magnetic reconnection (annihilation). Pieces of observational evidence indicates that the reconnection site has an infinitesimal diffusion region with pairs of large-scale MHD slow-mode shocks and bipolar fast Alfvenic outflows as Petschek predicted years ago. In particular, soft X-ray imaging data shows clear signature of the slow-shock heating. Hard X-ray imaging telescope discovered an isolated hard source near the reconnection site in addition to the usual double foot-point hard X-ray sources. The so-called loop-top hard X-ray source is emitted from confined non-thermal electrons or from 100-200 MK super-hot plasma with lesser possibility. Fast mode shock due to the collision of the outflow and the reconnected loops appears to be responsible for the electron acceleration. A key open issue is how the solar corona, with continuous agitation from the sub-surface convective layer in terms of energy and helicity, evolves to a configuration with neutral sheet (X-point), where magnetic reconnection is ready to take place. There has been an intriguing possibility that stationary corona, which is more energetically dominant than total contribution of all the observed transients, is heated by farther small transients, nano or pico flares as Parker discussed. We find that coronal soft X-ray emission contains random fluctuation signal in addition to photon shot-noise. We discuss the possibility that pico-flares are responsible for the fluctuation and heat the stationary corona.
No associations
LandOfFree
Yohkoh Satellite Findings on Solar Flares and Coronal Heating does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Yohkoh Satellite Findings on Solar Flares and Coronal Heating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Yohkoh Satellite Findings on Solar Flares and Coronal Heating will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1536479