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Solar particle events with helium-over-hydrogen enhancement in the energy range up to 100 MeV nucl−1
Plunkett, S. P.; Thompson, B. J.; Torsti, J. +5 more
Flux measurements of solar energetic particles (SEPs) in the ERNE instrument onboard SOHO indicate that the abundance of 4He-nuclei compared to protons in the energy range up to 100 MeV nucl−1 was exceptionally high during the particle events on 27 May 1998 and 28 December 1999. The 4He/p ratio stayed between 0.15-…
Variation of Acoustic Power with Magnetic Field as Seen in Gong+ Data
Venkatakrishnan, P.; Kumar, Brajesh; Tripathy, S. C.
The acoustic spectra in sunspots are known to be richer in higher frequency power. We have attempted a generalized study of the effect of magnetic fields on the shape of the acoustic spectrum using GONG+ bread-board data (spatial scale of ∼ 2 arc sec per pixel) of 11 May 2000 and 12 June 2000. The mean power spectra of the velocity oscillations we…
Very-Large-Array Observations of Evolving Type I Noise Storms and Nonthermal Bursts In Association With Flares And Coronal Mass Ejections
Willson, Robert F.
Very-Large-Array (VLA) observations of the Sun at 20, 91 and 400 cm have been combined with data from the SOHO, TRACE and Wind solar missions to study the properties of long-lasting Type I noise storms and impulsive metric and decimetric bursts during solar flares and associated coronal mass ejections. These radio observations provide information …
The Prominence - Corona and the Filament - Corona Transition Region: is There any Difference?
Landi, E.; Chiuderi Drago, F.
The ratio between the Extreme Ultraviolet emission of the prominence-corona transition region and that of the quiet Sun (QS) transition region is measured using observations from the CDS and SUMER instruments on board the SOHO Satellite. These results are compared with those obtained in an earlier paper, analysing the same prominence as a filament…
Multiple-loop structure of a solar flare from Microwave, EUV and X-ray Imaging Data
Kundu, M. R.; Garaimov, V. I.
We present the results of an analysis of a flare event of importance M2.8 that occurred at 00:56 UT 28 August 1999. The analysis is based upon observations made with the Nobeyama radioheliograph (NoRH) and polarimeters (NoRP), TRACE, SOHO/MDI, EIT, and Yohkoh/SXT. The images show a very complex flaring region. Pre-flare TRACE and EIT images at 00:…
On the outer boundary of the sunspot penumbra
Kálmán, Béla
Comparison of photographic observations and vector-magnetograph measurements demonstrate that the outer boundary of the sunspot penumbra - even in complex sunspot groups - closely follows the 0.075 T iso-gauss line of the total value of the magnetic field, corresponding approximately to the equipartition value in the photosphere. Radio observation…
A Study of AR 9144; A Fast-Growing EFR
Chapman, G. A.
This paper is a study of NOAA region 9144, an emerging flux region (EFR) which grew rapidly beginning 25 August 2000. This region was visible in SOHO data at 0 UT on 25 August 2000 as a small, isolated spot. It was recognizable as an active region with multiple spots by 06:00 UT on the 25th and was a fully developed AR by 24h UT on the …
How Good are the Predictions for Oscillation Frequencies?
Tripathy, S. C.; Jain, Kiran; Bhatnagar, A.
We have used available intermediate degree p-mode frequencies for solar cycle 23 to check the validity of previously derived empirical relations for frequency shifts (Jain et al., 2000). We find that the calculated and observed frequency shifts during the rising phase of cycle 23 are in good agreement. The observed frequency shift from minimum to …