Search Publications
Deceleration of the rotational velocities of sunspot groups during their evolution
Wöhl, H.; Brajša, R.; Ruždjak, V. +1 more
Using the Greenwich Photoheliographic Results for the years 1874-1976 the daily rotational velocities for 955 recurrent and 13169 non-recurrent sunspot groups from the first day of their appearance and during their evolution have been determined. The rotational velocities were divided in six latitude strips with a width of five degrees and grouped…
Comparison Between Halo cme Expansion Speeds Observed on the Sun, the Related Shock Transit Speeds to Earth and Corresponding Ejecta Speeds at 1 au
Schwenn, R.; Vieira, L. E. A.; Echer, E. +5 more
We have compared characteristics of 38 halo coronal mass ejections observed on the Sun by the Large Angle and Spectrometric Coronagraph onboard SOHO with their corresponding counterparts observed near Earth by the magnetic field and plasma instruments onboard the ACE, WIND and SOHO satellites, in the period from January 1997 to April 2001. We only…
On the wave mode of subsecond pulses in the cm-range
Altyntsev, A. T.; Meshalkina, N. S.; Yihua, Yan +2 more
In this paper we determined the wave mode of subsecond pulses (SSP). We used data on pulses with a degree of polarization over 30%, with the sources located at −60 to +60 deg from the central meridian, for the period 2000-2002. The superposition of SSRT radio maps and MDI magnetograms has shown that radio SSP sources are typically located near the…
Prominence atlas in the SUMER range 800 1250 Å: I. Observations, data reduction and preliminary results
Vial, J. -C.; Parenti, S.; Lemaire, P.
The aim of this work is to build an EUV-UV spectral catalogue of a prominence. Here we focus on the preparatory work for the final result and we give an example of the results obtained. As a first step, we present the information needed for a full understanding of the results that will form the final entire catalogue. The data are composed of a fu…
EIT Observations of the 15 November 1999 Mercury Transit
Auchère, F.; Artzner, G. E.
The Mercury transit of 15 November 1999 has been observed from space by the SOHO and TRACE spacecraft. We exploited the data recorded by EIT/SOHO to determine the stray-light level and the plate-scale of the instrument. The asymmetric distribution of stray light across the images is confirmed, but the absolute amount was found to be higher than pr…
Numerical Magnetohydrodynamic Experiments for Testing the Physical Mechanisms of Coronal Mass Ejections Acceleration
Liu, Yang; Feng, Xueshang; Zhang, T. X. +3 more
Analysis of observations from both space-borne (LASCO/SOHO, Skylab and Solar Maximum Mission) and ground-based (Mauna Loa Observatory) instruments show that there are two types of coronal mass ejections (CMEs), fast CMEs and slow CMEs. Fast CMEs start with a high initial speed, which remains more or less constant, while slow CMEs start with a low …
Multi-Wavelength Observations of an Unusual Impulsive Flare Associated with Cme
Uddin, Wahab; Chandra, Ramesh; Jain, Rajmal +5 more
We present the results of a detailed analysis of multi-wavelength observations of a very impulsive solar flare 1B/M6.7, which occurred on 10 March, 2001 in NOAA AR 9368 (N27 W42). The observations show that the flare is very impulsive with a very hard spectrum in HXR that reveal that non-thermal emission was most dominant. On the other hand, this …
Comparison OF Noise Properties Of GONG And MDI Time-Distance Helioseismic Data
Thompson, M. J.; Rajaguru, S. P.; Hughes, S. J.
The recently upgraded system of the ground-based Global Oscillation Network Group (GONG) network of helioseismic observatories has started to provide higher-resolution solar oscillation measurements suitable for local helioseismic studies. Selecting simultaneously observed regions on the Sun by both GONG and the space-borne Michelson Doppler Image…
Coronal response of Bi-directional Jets
Doyle, J. G.; Madjarska, M. S.; Dammasch, I. E. +1 more
EUV bi-directional jets are a prominent class of phenomena characterizing the solar transition region. Using simultaneously obtained SUMER observations in the chromospheric Si ii 1251.16 Å and C i 1251.17 Å, transition region N v 1238.8 Å and coronal Mg x 625 Å lines we show an example of a bi-directional jet observed in the chromospheric and the …
Local Modulation of Solar Oscillations by Magnetic Fields
Thompson, M. J.; Rajaguru, S. P.; Nicholas, C. J.
The amplitudes of solar oscillations measured in Doppler velocity are modulated by the presence of a strong photospheric magnetic field. Here we show that the amount of modulation cannot be predicted solely on the local photospheric magnetic field strength. Qualitatively, magnetic fields of similar strength have similar effects on the oscillations…