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Magnetic Power Spectra Derived from Ground and Space Measurements of the Solar Magnetic Fields
Yurchyshyn, V.; Wang, H.; Goode, P. R. +1 more
We study magnetic power spectra of active and quiet regions by using Big Bear Solar Observatory and SOHO/MDI measurements of longitudinal magnetic fields. The MDI power spectra were corrected with Gaussian Modulation Transfer Function. We obtained reliable magnetic power spectra in the high wave numbers range, up to k=4.6 Mm−1, which co…
Prediction in Real Time of the 2000 July 14 Heliospheric Shock Wave and its Companions During the `Bastille' Epoch*
Andrews, M. D.; Dryer, M.; Smith, Z. +4 more
Prediction of solar-generated disturbances and their three-dimensional propagation through interplanetary space continues to present a vitally important operational space weather forecasting objective. This paper presents the first successful real-time prediction of a series of major heliospheric shock waves at Earth, including the one from the 14…
A Two-Dimensional Alfvén-Wave-Driven Solar Wind Model
Chen, Y.; Hu, Y. Q.
This paper presents a two-dimensional, Alfvén-wave-driven solar wind model, in which the wave energy is assumed to cascade from the low-frequency Alfvén waves to high-frequency ion cyclotron waves and to be transferred to the solar wind protons by cyclotron resonance at the Kolmogorov rate. A typical structure in the meridional plane consisting of…
Joint EUV/Radio Observations of a Solar Filament
Bocchialini, K.; Harrison, R. A.; Alissandrakis, C. E. +2 more
In this paper we compare simultaneous extreme ultraviolet (EUV) line intensity and microwave observations of a filament on the disk. The EUV line intensities were observed by the CDS and SUMER instruments on board SOHO and the radio data by the Very Large Array and the Nobeyama radioheliograph. The main results of this study are the following: (1)…
A Relationship Between Transition Region Brightenings, Abundances, and Magnetic Topology
Fletcher, Lyndsay; Young, Peter R.; Schmieder, Brigitte +5 more
We present multi-instrument observations of active region (AR) 8048, made between 3 June and 5 June 1997, as part of the SOHO Joint Observing Program 33. This AR has a sigmoid-like global shape and undergoes transient brightenings in both soft X-rays and transition region (TR) lines. We compute a magneto-hydrostatic model of the AR magnetic field,…
Solar Internal Composition and Nuclear Reaction Rates in the Light of Helioseismology
Couvidat, S.; Turck-chièze, S.; Nghiem, P. +1 more
Acoustic modes are a suitable probe to check the internal solar composition and give constraints on regions of turbulence or mixing in stellar interiors. The recent results obtained with the SOHO satellite involve practically all the acoustic modes and are extremely useful to check theoretical assumptions. If turbulence is favoured to explain lith…
Magnetic Flux Cancellation Observed in the Sunspot Moat
Wang, Haimin; Yurchyshyn, Vasyl B.
In this paper we study the evolution of magnetic fields of a 1F/2.4C solar flare and following magnetic flux cancellation. The data are Big Bear Solar Observatory and SOHO/MDI observations of active region NOAA 8375. The active region produced a multitude of subflares, many of them being clustered along the moat boundary in the area with mixed pol…
On the Nature of Prominence Absorption and Emission in Highly Ionized Iron and in Neutral Hydrogen
Engvold, Oddbjørn; Jakobsson, Hans; Tandberg-Hanssen, Einar +2 more
We have studied the behavior of the emission in the highly ionized EUV lines Fe ix/x, 171 Å, Fe xii, 195 Å, and Fe xv, 284 Å observed in quiescent prominences. Kucera, Andretta, and Poland (1998) have explained the absorption of other highly ionized metallic EUV lines as due to absorption in the hydrogen continuum. However, since the authors notic…
Photospheric Network as the Energy Source for the quiet-Sun corona
Tarbell, T.; Ryutova, M.; Woo, R. +1 more
We propose a mechanism for the formation of a magnetic energy avalanche based on highly dynamic phenomena within the ubiquitous small-scale network magnetic elements in the quiet photosphere. We suggest that this mechanism may provide constant mass and energy supply for the corona and fast wind. Constantly emerging from sub-surface layers, flux tu…
Sunspot Plumes and Flow Channels
Wilhelm, K.; Fredvik, T.; Kjeldseth-Moe, O. +2 more
It is well known that sunspots are dark. This statement is not correct in the sunspot atmosphere between the chromosphere and the corona, where sunspots often are brighter than their surroundings. The brightest feature in the sunspot transition region is called a sunspot plume. Not all sunspots contain a plume. We find that 20 out of 21 sunspots s…