C. Caroubalos

A shock associated (SA) radio event and related phenomena observed from the base of the solar corona to 1 AU

We present for the rst time an almost com- plete frequency coverage of a Shock Associated (SA) radio event and related phenomena observed on May 6, 1996 at 9:27 UT. It is observed from the base of the solar corona up to almost 1 Astronomical Unit (AU) from the Sun by the following radio astronomical instruments: the Ond rejov spectrometer operating between 4.5 GHz and 1 GHz (radi- ation produced near the chromosphere); the Thermopyles Artemis-IV spectrograph operating between 600 MHz and 110 MHz (distance range about 1.1-1.4R from sun center); the Nan cay Decameter Array operating between 75 and 25 MHz (distance range about 1.4-2 R); and the RAD2 and RAD1 radio receivers on the WIND spacecraft covering the range from 14 MHz to about 20 kHz (distance range be- tween 3 R and about 1 AU). Observations at the Nan cay Decameter Array clearly show that the SA event starts from a coronal type II radio burst which traces the progression of a shock wave through the corona above 1.8 R-2 R from the sun center. This SA event has no associated radio emis- sion in the decimetric-metric range, thus there is no evidence for electron injection in the low/middle corona. The SA event enigma: What does SA stand for? Type II and type III solar radio bursts result from the interaction of a disturbing agent {a beam of energetic elec- trons or a shock wave{ with the ambient plasma (Wild and Smerd, 1972). Radiation is produced near the fundamen- tal of the local plasma frequency f p (kHz) =9 n 1 = 2 e (cm 3 ) and/or its second harmonic through various plasma mech- anisms (see e.g. Robinson, 1997). The observed frequency can be converted into an altitude in the corona, assuming a density model and the radiated mode. Dierent frequency drifts reflect dierent velocities along the density gradient in the corona and interplanetary medium, helping us to charac- terize the nature of the exciter: 0.05-0.3c electron beam for

The improved ARTEMIS IV multichannel solar radio spectrograph of the University of Athens

We present the improved solar radio spectrograph of the University of Athens operating at the Thermopylae Satellite Telecommunication Station. Observations now cover the frequency range from 20 to 650 MHz. The spectrograph has a 7-meter moving parabola fed by a log-periodic antenna for 100–650 MHz and a stationary inverted V fat dipole antenna for the 20–100 MHz range. Two receivers are operating in parallel, one swept frequency for the whole range (10 spectrums/sec, 630 channels/spectrum) and one acousto-optical receiver for the range 270 to 450 MHz (100 spectrums/sec, 128 channels/spectrum). The data acquisition system consists of two PCs (equipped with 12 bit, 225 ksamples/sec ADC, one for each receiver). Sensitivity is about 3 SFU and 30 SFU in the 20–100 MHz and 100–650 MHz range respectively. The daily operation is fully automated: receiving universal time from a GPS, pointing the antenna to the sun, system calibration, starting and stopping the observations at preset times, data acquisition, and archiving on DVD. We can also control the whole system through modem or Internet. The instrument can be used either by itself or in conjunction with other instruments to study the onset and evolution of solar radio bursts and associated interplanetary phenomena.

Solar type II and type IV radio bursts observed during 1998–2000 with the ARTEMIS-IV radiospectrograph

A catalogue of the type II and type IV solar radio bursts in the 110-687 MHz range, observed with the radio spectrograph ARTEMIS-IV operated by the University of Athens at Thermopylae, Greece from 1998-2000 is presented. These observations are compared with the LASCO archives of Coronal Mass Ejections and the Solar Geophysical Reports of solar flares (Ha & SXR) and examined for possible associations. The main results are: - 68% of the catalogue events were associated with CMEs. - 67% of the type II events were associated with CMEs, in accordance with previous results. This percentage rises to 79% in the case of composite type II/IV events. - 77% of the type IV continua were associated with CMEs, which is higher that the CME-type II association probability. - The type II associated CMEs had an average velocity of (835 ± 380) km s -1 , while the CMEs not associated with type IIs had an average velocity of (500 ± 150) km s -1 . - All events, but one, were well associated with Ha and/or SXR flares. - Most of the CME launch times precede by 5-60 min (30 min on average) the associated SXR flare peak; an important fraction (72%) precede the flare onset as well.

CME Expansion as the Driver of Metric Type II Shock Emission as Revealed by Self-consistent Analysis of High-Cadence EUV Images and Radio Spectrograms

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.

28 OCTOBER 2003 FLARE: HIGH-ENERGY GAMMA EMISSION, TYPE II RADIO EMISSION AND SOLAR PARTICLE OBSERVATIONS

The 28 October 2003 flare gave us the unique opportunity to compare the acceleration time of high-energy protons with the escaping time of those particles which have been measured onboard spacecraft and by neutron monitors network as GLE event. High-energy emission time scale and shock wave height and velocity time dependencies were also studied.

Method for an automatic analysis of the ECG

A method is presented for an analysis of the ECG. Using cubic spline techniques we proceed first to a smoothing of the signal and then to the elimination of baseline drift. The properties of the calculated derivatives are used to establish criteria for the identification of the ECG waves and the measurement of their essential parameters. The complete procedure can be carried out by a computer, without human intervention. The results of this fully automatic procedure can be used directly as a means of classifying the ECG.

The digital system ARTEMIS for real-time processing of radio transient emissions in the solar corona

We present the real-time digital data processing system named ‘ARTEMIS’ that was developed and constructed by the Space Research Department (DESPA) of Paris-Meudon Observatory to digitize, calibrate, format, date, process, compress, and archive in real time signals from multichannel receivers. This system is controlled by a multiprocessor computer based on Motorola MC 68010/68020 processors; it permits the automatic, routine recording of 128 parallel channels at a rate up to 300 samples per second and per channel with a 12-bit accuracy (4096 levels of intensity); it is used to process and record the 120 channels of a multichannel solar radiospectrograph in the frequency range 110–469 MHz; the remaining 8 channels are used for a scanning spectrograph in the frequency range 30–80 MHz and a two-dimensional multicorrelator interferometer at 75.5 MHz. The large quantity of raw data is reduced in real-time from about 1.3 Gbytes to about 40 Mbytes per day by the use of an original algorithm for real-time data compression. It is expected that this new facility will allow us to build a very large data base of digitized and accurately calibrated solar events, in order to achieve statistical measurements over long periods of time.

Radio Bursts in the Active Period January 2005

We present complex radio bursts recorded by the radiospectrograph ARTEMIS‐IV in the active period of January 2005. The wide spectral coverage of this recorder, in the 650–20 MHz range, permits an analysis of the radio bursts from the base of the Solar Corona to 2 Solar Radii; it thus facilitates the association of radio activity with other types of solar energetic phenomena. Furthermore the ARTEMIS‐IV1, high time resolution (1/100 sec) in the 450–270 MHz range, makes possible the detection and analysis of the fine structure which most of the major radio events exhibit.

Correction [to “A shock associated (SA) radio event and related phenomena observed from the base of the solar corona to 1 AU”]

In the paper “A shock-associated (SA) radio event and related phenomena observed from the base of the solar corona to 1 AU” by J.-L. Bougeret, P. Zarka, C. Caroubalos, M. Karlický, Y. Leblanc, D. Maroulis, A. Hillaris, X. Moussas, C. E. Alissandrakis, G. Dumas, and C. Perche, Geophysical Research Letters, 25 [14], 2513-2516, Figure 3 was not printed in its entirety. It is printed correctly below with its caption:

High resolution observations with Artemis-IV and the NRH - I. Type IV associated narrow-band bursts

Narrow band bursts appear on dynamic spectra from microwave to decametric frequencies as fine structures with very small duration and bandwidth. They are thought to mark small scale magnetic reconnection. We analyzed 27 metric type-IV events with narrow band bursts observed by the ARTEMIS-IV radiospectrograph in 30/6/1999-1/8/2010. We examined the morphological characteristics of isolated narrow-band bursts and groups or chains of spikes. The events were recorded with the SAO (10 ms cadence) receiver of ARTEMIS-IV in the 270-450 MHz range. We measured the duration, spectral width, and frequency drift of ~12000 individual narrow-band bursts, groups, and chains. Spike sources were imaged with the NRH for the event of 21 April 2003. The mean duration of individual bursts at fixed frequency was ~100 ms, while the instantaneous relative bandwidth was ~2%. Some bursts had measurable frequency drift, positive or negative. Often spikes appeared in chains, which were closely spaced in time (column chains) or in frequency (row chains). Column chains had frequency drifts similar to IIId-bursts; most of the row chains exhibited negative drifts similar to fiber bursts. From the NRH data, we found that spikes were superimposed on a larger, slowly varying, background component. They were polarized in the same sense as the background source, with a slightly higher degree of polarization of ~65%, and their size was ~60% of their size in total intensity. The duration and bandwidth distributions did not show any clear separation in groups. Some chains tended to assume the form of zebra, lace stripes, fibers, or bursts of the type-III family, suggesting that such bursts might be resolved in spikes when viewed with high resolution. The NRH data indicate that the spikes are not fluctuations of the background, but represent additional emission such as what would be expected from small-scale reconnection.