E-Print Archive

There are 4451 abstracts currently viewable.


Advanced Search
Main Page Add New E-Print Submitter
News Help/FAQ About Preferences
Manage Key Phrase
High resolution observations with Artemis-JLS, (II) Type IV associated intermediate drift bursts View all abstracts by submitter

Alexander Hillaris   Submitted: 2019-06-10 06:24

Aims: We examined the characteristics of isolated intermediate drift bursts and their morphologies on dynamic spectra, in particular the positioning of emission and absorption ridges. Furthermore we studied the repetition rate of fiber groups. These were compared with a model in order to determine the conditions under which the intermediate drift bursts appear and exhibit the above characteristics. Methods: We analyzed sixteen metric type IV events with embedded intermediate drift bursts, observed with the Artemis-JLS radio spectrograph from July 1999 to July 2005 plus an event on 1st August 2010. The events were recorded with the SAO high resolution (10 ms cadence) receiver in the 270-450 MHz range with a frequency resolution of 1.4 MHz. We developed cross- and autocorrelation techniques to measure the duration, spectral width, and frequency drift of fiber bursts in 47 intermediate drift bursts (IMD) groups embedded within the continuum of the sixteen events mentioned above. We also developed a semi-automatic algorithm to track fibers on dynamic spectra. Results: The mean duration of individual fiber bursts at fixed frequency was δt ≈ 300 ms, while the instantaneous relative bandwidth was fw/f ≈ 0.90% and the total frequency extent was ∆ftot ≈ 35 MHz. The recorded intermediate drift bursts had frequency drift, positive or negative, with average values of df/fdt equal to -0.027 and 0.024 s-1 respectively. Quite often the fibers appeared in groups; the burst repetition rate within groups was, on average, ̃0.98 s. We distinguish six morphological groups of fibers, based on the relative position of the emission and absorption ridges. These included fibers with emission or absorption ridges only, fibers with the absorption ridge at lower or higher frequency than the emission, or with two absorption ridges above and below the emission. There were also some fibers for which two emission ridges were separated by an absorption ridge. Some additional complex groups within our data set were not easy to classify. A number of borderline cases of fibers with very high drift rate (̃0.30 s-1) or very narrow total bandwidth (̃8 MHz) were recorded; among them there was a group of rope-like fibers characterized by fast repetition rate and relatively narrow total frequency extent. We found that the whistler hypothesis leads to reasonable magnetic field values (̃4.6 G), while the Alfvén-wave hypothesis requires much higher field. From the variation of the drift rate with time we estimated the ratio of the whistler to the cyclotron frequency, x, to be in the range of 0.3-0.6, varying by ̃0.05-0.1 in individual fibers; the same analysis gives an average value of the frequency scale along the loop of ̃220 Mm. Finally, we present empirical relations between fiber burst parameters and discuss their possible origin.

Authors: C. Bouratzis, A. Hillaris, C.E. Alissandrakis, P. Preka-Papadema, X. Moussas, C. Caroubalos, P. Tsitsipis, A. Kontogeorgos
Projects: None

Publication Status: Astronomy & Astrophysics, Volume 625, id.A58, 15 pp.
Last Modified: 2019-06-12 12:20
Go to main E-Print page  Detection of spike-like structures near the front of type-II burstsA  Oscillation of a small Halpha surge in a solar polar coronal hole  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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
Structural evolution of a magnetic flux rope associated with a major flare in the solar active region 12205
Homologous Coronal Mass Ejections Caused by Recurring Formation and Disruption of Current Sheet within a Sheared Magnetic Arcade
Propagating Oscillations in the Lower Atmosphere Under Coronal Holes
Using Flare-Induced Modulation of Three- and Five-Minute Oscillations for Studying Wave Propagation in the Solar Atmosphere
Plasma dynamics in the flaring loop observed by RHESSI
Multi-instrument STIX microflare study
Disambiguation of Vector Magnetograms by Stereoscopic Observations from the Solar Orbiter/Polarimetric and Helioseismic Imager (PHI) and the Solar Dynamic Observatory (SDO)/Helioseismic and Magnetic Imager (HMI)
Enhanced Phase Mixing of Torsional Alfvén Waves in Stratified and Divergent Solar Coronal Structures, Paper II: Nonlinear Simulations
Multi-Passband Observations of A Solar Flare over the He I 10830 line
Multi-wavelength quasi-periodic pulsations in a stellar superflare
Probable detection of an eruptive filament from a superflare on a solar-type star
Global Energetics in Solar Flares. XIII. The Neupert Effect and Acceleration of Coronal Mass Ejections
Enhanced Phase Mixing of Torsional Alfvén Waves in Stratified and Divergent Solar Coronal Structures, Paper I: Linear Solutions
Variations of the Internal Asymmetries of Sunspot Groups During their Decay
Partial Eruption, Confinement, and Twist Buildup and Release of a Double-decker Filament
Overdense Threads in the Solar Corona Induced by Torsional Alfvén Waves
Implications of spicule activity on coronal loop heating and catastrophic cooling
The Magnetic Origin of Solar Campfires
On the evolution of a sub-C class flare: a showcase for the capabilities of the revamped Catania Solar Telescope
Direct evidence that twisted flux tube emergence creates solar active regions

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

© 2000-2020 Solar Physics Group - Montana State University