E-Print Archive

There are 4053 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
The influence of albedo on the size of hard X-ray flare sources View all abstracts by submitter

Marina Battaglia   Submitted: 2010-10-27 05:33

Context: Hard X-rays from solar flares are an important diagnostic of particle acceleration and transport in the solar atmosphere. Any observed X-ray flux from on-disc sources is composed of direct emission plus Compton backscattered photons (albedo). This affects both the observed spectra and images as well as the physical quantities derived from them such as the spatial and spectral distributions of accelerated electrons or characteristics of the solar atmosphere. Aims: We propose a new indirect method to measure albedo and to infer the directivity of X-rays in imaging using RHESSI data. Methods: Visibility forward fitting is used to determine the size of a disc event observed by RHESSI as a function of energy. This is compared to the sizes of simulated sources from a Monte Carlo simulation code of photon transport in the chromosphere for different degrees of downward directivity and true source sizes to find limits on the true source size and the directivity. Results: The observed full width half maximum of the source varies in size between 7.4 arcsec and 9.1 arcsec with the maximum between 30 and 40 keV. Such behaviour is expected in the presence of albedo and is found in the simulations. A source size smaller than 6 arcsec is improbable for modest directivities and the true source size is likely to be around 7 arcsec for small directivities. Conclusions: While it is difficult to image the albedo patch directly, the effect of backscattered photons on the observed source size can be estimated. The increase in source size caused by albedo has to be accounted for when computing physical quantities that include the size as a parameter such as flare energetics. At the same time, the study of the albedo signature provides vital information about the directivity of X-rays and related electrons.

Authors: M. Battaglia, E. P. Kontar, I. G. Hannah
Projects: RHESSI

Publication Status: A&A (accepted)
Last Modified: 2010-10-28 05:49
Go to main E-Print page  The Role of Active Region Loop Geometry - I. How can it affect coronal seismology?  STEREO and Wind observations of a fast ICME flank triggering a prolonged geomagnetic storm on 5-7 April 2010  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
Linear waves in a non-equilibrium ionisation partially ionised plasma
How Many Twists Do Solar Coronal Jets Release?
Different Signatures of Chromospheric Evaporation in Two Solar Flares Observed with IRIS
The Physical Nature of Spiral Wave Patterns in Sunspots
Predicting Solar Flares Using a Long Short-Term Memory Network
Coronal loop transverse oscillations excited by different driver frequencies
Solar Center-Limb Variation of the Strengths of Spectral Lines: Classification and Interpretation of Observed Trends
The plasmoid instability in a confined solar flare
High-frequency dynamics of active region moss as observed by IRIS
Extreme-ultraviolet Late Phase Caused by Magnetic Reconnection over Quadrupolar Magnetic Configuration in a Solar Flare
Two-step evolution of a rising flux rope resulting in a confined solar flare
Why torus-unstable solar filaments experience failed eruption?
The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
Pulse-beam heating of deep atmospheric layers, their oscillations and shocks modulating the flare reconnection
A potential magnetic field calculator for solar physics applications using staggered grids
E and B polarizations from inhomogeneous and solar surface turbulence
Oscillations Accompanying a He I 10830 Å Negative Fare in a Solar Facula II. Response of the Transition Region and Corona
Flare reconnection-driven magnetic field and Lorentz force variations at the Sun's surface
Why Does the Solar Corona Abnormally Rotate Faster Than the Photosphere?
Impacts On Proton Fluxes Observed During Different Interplanetary Conditions

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