LOFAR tied-array imaging and spectroscopy of solar S bursts*
D. E. Morosan
(1)
,
P. T. Gallagher
(1)
,
P. Zucca
(1)
,
A. O’flannagain
,
R. Fallows
(2)
,
H. Reid
(3)
,
J. Magdalenić
,
G. Mann
(4)
,
M. M. Bisi
(5)
,
A. Kerdraon
(6)
,
A. A. Konovalenko
(7)
,
A. L. Mackinnon
(8)
,
H. O. Rucker
(9)
,
B. Thidé
(10)
,
C. Vocks
(4)
,
A. Alexov
(2)
,
J. Anderson
(11)
,
A. Asgekar
(2)
,
I. M. Avruch
(12)
,
M. J. Bentum
(2)
,
G. Bernardi
(13)
,
A. Bonafede
(14)
,
F. Breitling
(4)
,
J. W. Broderick
(15)
,
W. N. Brouw
(16)
,
H. R. Butcher
(17)
,
B. Ciardi
(18)
,
E. de Geus
(2)
,
J. Eislöffel
(19)
,
H. Falcke
(20)
,
W. Frieswijk
(2)
,
M. A. Garrett
(21)
,
Jean-Mathias Griessmeier
(22)
,
A. W. Gunst
(2)
,
J. W. T. Hessels
(23)
,
M. Hoeft
(19)
,
A. Karastergiou
(24)
,
V. I. Kondratiev
(2)
,
G. Kuper
(2)
,
J. van Leeuwen
(23)
,
D. Mckay-Bukowski
(25)
,
J. P. Mckean
(2)
,
H. Munk
(2)
,
E. Orru
(2)
,
H. Paas
(26)
,
R. Pizzo
(2)
,
A. G. Polatidis
(2)
,
A. M. M. Scaife
(27)
,
J. Sluman
(2)
,
C. Tasse
(28)
,
M. C. Toribio
(2)
,
R. Vermeulen
(2)
,
P. Zarka
(6)
1
Trinity College Dublin
2 ASTRON - Netherlands Institute for Radio Astronomy
3 University of Glasgow
4 AIP - Leibniz-Institut für Astrophysik Potsdam
5 RAL - STFC Rutherford Appleton Laboratory
6 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
7 IRA - Institute of Radio Astronomy of NASU [Kharkiv]
8 LLNL - Lawrence Livermore National Laboratory
9 IWF - Space Research Institute of Austrian Academy of Sciences
10 IRF - Swedish Institute of Space Physics [Uppsala]
11 GFZ - GeoForschungsZentrum - Helmholtz-Zentrum Potsdam
12 SRON - SRON Netherlands Institute for Space Research
13 CfA - Harvard-Smithsonian Center for Astrophysics
14 Jacobs University = Constructor University [Bremen]
15 University of Southampton
16 Kapteyn Astronomical Institute [Groningen]
17 RSAA - Research School of Astronomy and Astrophysics [Canberra]
18 Max Planck Institute for Astrophysics
19 TLS - Thüringer Landessternwarte Tautenburg
20 Radboud University [Nijmegen]
21 Leiden Observatory [Leiden]
22 USN - Unité Scientifique de la Station de Nançay
23 UvA - University of Amsterdam [Amsterdam] = Universiteit van Amsterdam
24 University of Oxford
25 University of Oulu
26 University of Groningen [Groningen]
27 School of Physics and Astronomy [Southampton]
28 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique
2 ASTRON - Netherlands Institute for Radio Astronomy
3 University of Glasgow
4 AIP - Leibniz-Institut für Astrophysik Potsdam
5 RAL - STFC Rutherford Appleton Laboratory
6 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
7 IRA - Institute of Radio Astronomy of NASU [Kharkiv]
8 LLNL - Lawrence Livermore National Laboratory
9 IWF - Space Research Institute of Austrian Academy of Sciences
10 IRF - Swedish Institute of Space Physics [Uppsala]
11 GFZ - GeoForschungsZentrum - Helmholtz-Zentrum Potsdam
12 SRON - SRON Netherlands Institute for Space Research
13 CfA - Harvard-Smithsonian Center for Astrophysics
14 Jacobs University = Constructor University [Bremen]
15 University of Southampton
16 Kapteyn Astronomical Institute [Groningen]
17 RSAA - Research School of Astronomy and Astrophysics [Canberra]
18 Max Planck Institute for Astrophysics
19 TLS - Thüringer Landessternwarte Tautenburg
20 Radboud University [Nijmegen]
21 Leiden Observatory [Leiden]
22 USN - Unité Scientifique de la Station de Nançay
23 UvA - University of Amsterdam [Amsterdam] = Universiteit van Amsterdam
24 University of Oxford
25 University of Oulu
26 University of Groningen [Groningen]
27 School of Physics and Astronomy [Southampton]
28 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique
A. O’flannagain
- Function : Author
J. Magdalenić
- Function : Author
G. Mann
- Function : Author
- PersonId : 760232
- ORCID : 0000-0002-4452-3028
A. Bonafede
- Function : Author
- PersonId : 766668
- ORCID : 0000-0002-5068-4581
J. Eislöffel
- Function : Author
- PersonId : 761407
- ORCID : 0000-0001-6496-0252
Jean-Mathias Griessmeier
- Function : Author
- PersonId : 737206
- IdHAL : jean-mathias-griessmeier
- ORCID : 0000-0003-3362-7996
- IdRef : 235780871
R. Pizzo
- Function : Author
- PersonId : 766670
- ORCID : 0000-0003-2816-9492
P. Zarka
- Function : Author
- PersonId : 755767
- ORCID : 0000-0003-1672-9878
- IdRef : 034944648
Abstract
Context. The Sun is an active source of radio emission that is often associated with energetic phenomena ranging from nanoflares to coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), numerous millisecond duration radio bursts have been reported, such as radio spikes or solar S bursts (where S stands for short). To date, these have neither been studied extensively nor imaged because of the instrumental limitations of previous radio telescopes.
Aims. Here, Low Frequency Array (LOFAR) observations were used to study the spectral and spatial characteristics of a multitude of S bursts, as well as their origin and possible emission mechanisms.
Methods. We used 170 simultaneous tied-array beams for spectroscopy and imaging of S bursts. Since S bursts have short timescales and fine frequency structures, high cadence (~50 ms) tied-array images were used instead of standard interferometric imaging, that is currently limited to one image per second. Results. On 9 July 2013, over 3000 S bursts were observed over a time period of ~8 hours. S bursts were found to appear as groups of short-lived (<1 s) and narrow-bandwidth (~2.5 MHz) features, the majority drifting at ~3.5 MHz/s and a wide range of circular polarisation degrees (2-8 times more polarised than the accompanying Type III bursts). Extrapolation of the photospheric magnetic field using the potential field source surface (PFSS) model suggests that S bursts are associated with a trans-equatorial loop system that connects an active region in the southern hemisphere to a bipolar region of plage in the northern hemisphere.
Conclusions. We have identified polarised, short-lived solar radio bursts that have never been imaged before. They are observed at a height and frequency range where plasma emission is the dominant emission mechanism, however they possess some of the characteristics of electron-cyclotron maser emission.
Origin : Publisher files allowed on an open archive
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