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C. Caroubalos D. Maroulis N. Patavalis J.-L. Bougeret G. Dumas C. Perche C. Alissandrakis A. Hillaris X. Moussas P. Preka-Papadema A. Kontogeorgos P. Tsitsipis G. Kanelakis 《Experimental Astronomy》2001,11(1):23-32
We present the new solar radiospectrograph of the University of Athensoperating at the Thermopylae Station since 1996. Observations cover thefrequency range from 110 to 688 MHz. The radiospectrograph has a 7-meterparabolic antenna and two receivers operating in parallel. One is a sweepfrequency receiver and the other a multichannel acousto-optical receiver.The data acquisition system consists of a front-end VME based subsystem anda Sun Sparc-5 workstation connected through Ethernet. The two subsystems areoperated using the VxWorks real-time package. The daily operation is fullyautomated: pointing of the antenna to the sun, starting and stopping theobservations at pre-set times, data acquisition, data compression by`silence suppression', and archiving on DAT tapes. The instrument can beused either by itself to study the onset and evolution of solar radio bursts or in conjunction with other instruments including theNançay Decametric Array and the WIND/WAVES RAD1 and RAD2 low frequencyreceivers to study associated interplanetary phenomena. 相似文献
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N. J. Lehtinen S. Pohjolainen K. Huttunen-Heikinmaa R. Vainio E. Valtonen A. E. Hillaris 《Solar physics》2008,247(1):151-169
A high-speed, halo-type coronal mass ejection (CME), associated with a GOES M4.6 soft X-ray flare in NOAA AR 0180 at S12W29
and an EIT wave and dimming, occurred on 9 November 2002. A complex radio event was observed during the same period. It included
narrow-band fluctuations and frequency-drifting features in the metric wavelength range, type III burst groups at metric – hectometric
wavelengths, and an interplanetary type II radio burst, which was visible in the dynamic radio spectrum below 14 MHz. To study
the association of the recorded solar energetic particle (SEP) populations with the propagating CME and flaring, we perform
a multi-wavelength analysis using radio spectral and imaging observations combined with white-light, EUV, hard X-ray, and
magnetogram data. Velocity dispersion analysis of the particle distributions (SOHO and Wind
in situ observations) provides estimates for the release times of electrons and protons. Our analysis indicates that proton acceleration
was delayed compared to the electrons. The dynamics of the interplanetary type II burst identify the burst source as a bow
shock created by the fast CME. The type III burst groups, with start times close to the estimated electron-release times,
trace electron beams travelling along open field lines into the interplanetary space. The type III bursts seem to encounter
a steep density gradient as they overtake the type II shock front, resulting in an abrupt change in the frequency drift rate
of the type III burst emission. Our study presents evidence in support of a scenario in which electrons are accelerated low
in the corona behind the CME shock front, while protons are accelerated later, possibly at the CME bow shock high in the corona. 相似文献
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G. P. Chernov V. V. Fomichev R. V. Gorgutsa A. K. Markeev D. E. Sobolev A. Hillaris K. Alissandrakis 《Geomagnetism and Aeronomy》2014,54(4):406-415
Solar radio emission records received at the IZMIRAN spectrograph (25–270 MHz) during the solar flare event of February 12, 2010 are analyzed. Different fine structures were observed in three large groups of type III bursts against a low continuum. According to data from the Nancay radioheliograph, sources of all three groups of bursts were located in one active region, 11046, and their emissions were accompanied by soft X-ray bursts (GOES satellite): C7.9 at 0721 UT, B9.6 at 0940 UT, and M8.3 at 1125 UT. After the first group of bursts, classical fiber bursts were observed in combination with reverse-drift fiber bursts with unusual arc drift. After the third (the most powerful) group, stable second-length pulsations and slow-drift fiber bursts were observed, the instantaneous frequency bands of which were an order of magnitude larger than the frequency band of classical fiber bursts, and the frequency drift was several times lower. More complex fiber bursts were observed in the weakest group in the time range 0940:39–0942:00 UT. They were narrow-band (～0.5 MHz) fiber bursts, periodically recurring in a narrow frequency band (5–6 MHz) during several seconds. The presence of many chaotically drifting ensembles of fibers, crossing and superimposing on one another, is a feature of this event. It is assumed that occurrence of these structures can be connected with the existence of many small shock fronts behind the leading edge of a coronal mass ejection. 相似文献
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C. Bouratzis P. Preka-Papadema A. Hillaris P. Tsitsipis A. Kontogeorgos V. G. Kurt X. Moussas 《Solar physics》2010,267(2):343-359
We present a multi-frequency and multi-instrument study of the 20 January 2005 event. We focus mainly on the complex radio
signatures and their association with the active phenomena taking place: flares, CMEs, particle acceleration, and magnetic
restructuring. As a variety of energetic-particle accelerators and sources of radio bursts are present, in the flare – ejecta
combination, we investigate their relative importance in the progress of this event. The dynamic spectra of ARTEMIS-IV – Wind/Waves – HiRAS, with 2000 MHz – 20 kHz frequency coverage, were used to track the evolution of the event from the low corona to
the interplanetary space; these were supplemented with SXR, HXR, and γ-ray recordings. The observations were compared with the expected radio signatures and energetic-particle populations envisaged
by the Standard Flare – CME model and the reconnection outflow termination shock model. A proper combination of these mechanisms seems to provide an adequate model for the interpretation of the observational
data. 相似文献
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A. Kouloumvakos S. Patsourakos A. Hillaris A. Vourlidas P. Preka-Papadema X. Moussas C. Caroubalos P. Tsitsipis A. Kontogeorgos 《Solar physics》2014,289(6):2123-2139
On 13 June 2010, an eruptive event occurred near the solar limb. It included a small filament eruption and the onset of a relatively narrow coronal mass ejection (CME) surrounded by an extreme ultraviolet (EUV) wave front recorded by the Solar Dynamics Observatory’s (SDO) Atmospheric Imaging Assembly (AIA) at high cadence. The ejection was accompanied by a GOES M1.0 soft X-ray flare and a Type-II radio burst; high-resolution dynamic spectra of the latter were obtained by the Appareil de Routine pour le Traitement et l’Enregistrement Magnetique de l’Information Spectral (ARTEMIS IV) radio spectrograph. The combined observations enabled a study of the evolution of the ejecta and the EUV wave front and its relationship with the coronal shock manifesting itself as metric Type-II burst. By introducing a novel technique, which deduces a proxy of the EUV compression ratio from AIA imaging data and compares it with the compression ratio deduced from the band-split of the Type-II metric radio burst, we are able to infer the potential source locations of the radio emission of the shock on that AIA images. Our results indicate that the expansion of the CME ejecta is the source for both EUV and radio shock emissions. Early in the CME expansion phase, the Type-II burst seems to originate in the sheath region between the EUV bubble and the EUV shock front in both radial and lateral directions. This suggests that both the nose and the flanks of the expanding bubble could have driven the shock. 相似文献
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Caroubalos C. Alissandrakis C.E. Hillaris A. Nindos A. Tsitsipis P. Moussas X. Bougeret J.-L. Bouratzis K. Dumas G. Kanellakis G. Kontogeorgos A. Maroulis D. Patavalis N. Perche C. Polygiannakis J. Preka-Papadema P. 《Solar physics》2001,204(1-2):165-177
In this report we present a complex metric burst, associated with the 14 July 2000 major solar event, recorded by the ARTEMIS-IV
radio spectrograph at Thermopylae. Additional space-borne and Earth-bound observational data are used, in order to identify
and analyze the diverse, yet associated, processes during this event. The emission at metric wavelengths consisted of broad-band
continua including a moving and a stationary type IV, impulsive bursts and pulsating structures. The principal release of
energetic electrons in the corona was 15–20 min after the start of the flare, in a period when the flare emission spread rapidly
eastwards and a hard X-ray peak occurred. Backward extrapolation of the CME also puts its origin in the same time interval,
however, the uncertainty of the extrapolation does not allow us to associate the CME with any particular radio or X-ray signature.
Finally, we present high time and spectral resolution observations of pulsations and fiber bursts, together with a preliminary
statistical analysis. 相似文献
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A. Hillaris O. Malandraki K.-L. Klein P. Preka-Papadema X. Moussas C. Bouratzis E. Mitsakou P. Tsitsipis A. Kontogeorgos 《Solar physics》2011,273(2):493-509
On 17 January 2005 two fast coronal mass ejections were recorded in close succession during two distinct episodes of a 3B/X3.8
flare. Both were accompanied by metre-to-kilometre type-III groups tracing energetic electrons that escape into the interplanetary
space and by decametre-to-hectometre type-II bursts attributed to CME-driven shock waves. A peculiar type-III burst group
was observed below 600 kHz 1.5 hours after the second type-III group. It occurred without any simultaneous activity at higher
frequencies, around the time when the two CMEs were expected to interact. We associate this emission with the interaction
of the CMEs at heliocentric distances of about 25 R
⊙. Near-relativistic electrons observed by the EPAM experiment onboard ACE near 1 AU revealed successive particle releases
that can be associated with the two flare/CME events and the low-frequency type-III burst at the time of CME interaction.
We compare the pros and cons of shock acceleration and acceleration in the course of magnetic reconnection for the escaping
electron beams revealed by the type-III bursts and for the electrons measured in situ. 相似文献
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