Type II and IV radio bursts in the active period October-November 2003

In this report we present the Type II and IV radio bursts observed and analyzed by the radio spectrograph ARTEMIS IV1, in the 650-20MHz frequency range, during the active period October-November 2003. These bursts exhibit very rich fine structures such fibers, pulsations and zebra patterns which is associated with certain characteristics of the associated solar flares and CMEs.Comment: Recent Advances in Astronomy and Astrophysics: 7th International Conference of the Hellenic Astronomical Society. AIP Conference Proceedings, Volume 848, pp. 199-206 (2006

Ten Years of the Solar Radiospectrograph ARTEMIS-IV

The Solar Radiospectrograph of the University of Athens (ARTEMIS-IV) is in operation at the Thermopylae Satellite Communication Station since 1996. The observations extend from the base of the Solar Corona (650 MHz) to about 2 Solar Radii (20 MHz) with time resolution 1/10-1/100 sec. The instruments recordings, being in the form of dynamic spectra, measure radio flux as a function of height in the corona; our observations are combined with spatial data from the Nancay Radioheliograph whenever the need for 3D positional information arises. The ARTEMIS-IV contribution in the study of solar radio bursts is two fold- Firstly, in investigating new spectral characteristics since its high sampling rate facilitates the study of fine structures in radio events. On the other hand it is used in studying the association of solar bursts with interplanetary phenomena because of its extended frequency range which is, furthermore, complementary to the range of the WIND/WAVES receivers and the observations may be readily combined. This reports serves as a brief account of this operation. Joint observations with STEREO/WAVES and LOFAR low frequency receivers are envisaged in the future

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.Comment: Recent Advances in Astronomy and Astrophysics: 7th International Conference of the Hellenic Astronomical Society. AIP Conference Proceedings, Volume 848, pp. 213-217 (2006

General development of a new hall effect sensor

Silicon Hall plates show an offset of a few millitesla. A large portion of this offset is caused by mechanical stress in the device. The offset can be reduced with a factor 103 to 105 when the spinning - current principle is applied. This paper presents a structure of a new Hall effect sensor which uses a novel offset reduction method and the function which governs the changes in the electric field inside the new Hall effect sensor in presence of magnetic field. This function helps us to control in MatLab environment the equipotential lines and to monitor the changes when biasing conditions are change. The combination of his form and the elaborate sequence of using dynamic spinning current technique, can lead to satisfactory results of produced Hall voltage with small noise in a presence of external magnetic field. © 2011 IFSA

Measuring solar radio bursts in 20-650 MHz

The solar radiospectrograph of the University of Athens is installed at the Thermopylae Satellite Telecommunication Station. The observations cover the frequency range from 20 to 650 MHz. The spectrograph has a 7-m moving parabola feeding by a log-period antenna for 100-650 MHz and a stationary inverted V fat dipole antenna for 20-100 MHz. Two receivers are operating in parallel: a sweep frequency for the whole range (10 spectra/s, 630 channels/spectrum) and an acousto-optical receiver for the range 270-450 MHz (10 spectra/s, 128 channels/spectrum). The data acquisition system consists of two PCs (equipped with 12 bit, 225 ksamples/s DAC, one for every receiver). The daily operation is fully automated: receiving universal time from a GPS, pointing the antenna to the Sun, initiating 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 to study the onset and evolution of solar radio bursts and associated interplanetary phenomena or in conjunction with other instruments. © 2006 Elsevier Ltd. All rights reserved