E-Print Archive

There are 3872 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Non-thermal hydrogen Balmer and Paschen emission in solar flares generated by electron beams View all abstracts by submitter

Valentina Zharkova   Submitted: 2017-10-10 05:22

Sharp rises of hard X-ray (HXR) emission accompanied by Hα line profiles with strong red shifts up to 4 Å from the central wavelength, often observed at the onset of flares with the Specola Solare Ticinese Telescope (STT) and the Swedish Solar Telescope (SST), are not fully explained by existing radiative models. Moreover, the observations of white light (WL) and Balmer contin- uum emission with the Interface Region Imaging Spectrograph (IRIS) reveal strong co-temporal enhancements and often nearly co-spatial with HXR emission. These effects indicate a fast ef- fective source of excitation and ionisation of hydrogen atoms in flaring atmospheres associated with HXR emission. In this paper we investigate electron beams as the agents accounting for the observed hydrogen line and continuum emission. Flaring atmospheres are considered to be produced by a 1D hydrodynamic response to the injection of an electron beam defining their kinetic temperatures, densities and macrovelocities. A radiative response in these atmospheres is simulated using a fully non-local ther- modynamic equilibrium (NLTE) approach for a 5 levels plus continuum hydrogen atom model, considering its excitation and ionisation by spontaneous, external and internal diffusive radiation and by inelastic collisions with thermal and beam electrons. Resulting intensities of hydrogen line and continuum emission were also calculated for Balmer and Paschen series. We find that inelastic collisions with beam electrons strongly increase excitation and ionisation of hydrogen atoms from the chromosphere to photosphere. This leads to an increase in Lyman continuum radiation, which has high optical thickness, and after the beam is off it governs hydrogen ionisation and leads to the long lasting order of magnitude enhancement of emission in Balmer and Paschen continua. The ratio of Balmer-to-other-continuum head intensities are found correlated with the beams's initial flux. The height distribution of contribution functions for Paschen continuum emission indicate a close correlation with the observations of heights of WL and HXR emission reported for limb flares. This process also leads to a strong increase of wing emission (Stark's wings) in Balmer and Paschen lines, that is superimposed on large red-shifted enhancements of Hα-Hγ line emission resulting from a downward motion by hydrodynamic shocks. The simulated line profiles are shown to closely fit the observations for different flaring events.

Authors: Druett M. and Zharkova V.V.
Projects: None

Publication Status: Accepted
Last Modified: 2017-10-11 06:21
Go to main E-Print page  Reply to comment by Usoskin (2017) on the paper   Pulsations in the Earth?s Lower Ionosphere Synchronized with Solar Flare Emission  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Key
Go to main E-Print pageGo to main E-Print page.
Previous AbstractPrevious Abstract.
Next AbstractNext Abstract.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
View All Abstracts By SubmitterView all abstracts by submitter.
Delete AbstractDelete abstract.

Latest Entries
Two Episodes of Magnetic Reconnections During a Confined Circular-ribbon Flare
Enhanced stellar activity for slow antisolar differential rotation?
Quasi-periodic pulsations in the most powerful solar flare of Cycle 24
GONG Catalog of Solar Filament Oscillations Near Solar Maximum
Chromospheric response during the precursor and the main phase of a B6.4 flare on August 20, 2005
Unambiguous Evidence of Coronal Implosions During Solar Eruptions and Flares
Two Types of Long-duration Quasi-static Evolution of Solar Filaments
Oscillations of cometary tails: a vortex shedding phenomenon?
Observations of Running Penumbral Waves Emerging in a Sunspot
Reconnection in the Post-Impulsive Phase of Solar Flares
Temperature of source regions of 3He-rich impulsive solar energetic particles events
3He-rich Solar Energetic Particles in Helical Jets on the Sun
On the importance of the nonequilibrium ionization of Si IV and O IV and the line-of-sight in solar surges
Was the cosmic ray burst detected by the GRAPES-3 on 22 June 2015 caused by transient weakening of geomagnetic field or by an interplanetary anisotropy?
Connecting Coronal Mass Ejections to Their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects
Studies of Isolated and Non-isolated Photospheric Bright Points in an Active Region Observed by the New Vacuum Solar Telescope
Fermi-LAT observations of the 2017 September 10th solar flare
Propagation of a global coronal wave and its interaction with large-scale coronal magnetic structures
A New Tool for CME Arrival Time Prediction Using Machine Learning Algorithms: CAT-PUMA
Solar Magnetoseismology with Magnetoacoustic Surface Waves in Asymmetric Magnetic Slab Waveguides

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University