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Different spatial structures between network regions and active regions indicated by TRACE 171 Å observation
Zhang, H. Q.; Zhang, M.; Wang, H. N. +1 more
By comparing TRACE 171 Å observations with photospheric magnetograms, we find that the root of TRACE 171 Å emission is centered in magnetic elements in simultaneous Huairou photospheric magnetogram and the luminosity of TRACE 171 Å emission is not always in proportion to the strength of the corresponding photospheric magnetic field. While TRACE em…
Post-Impulsive-Phase Acceleration in a Wide Range of Solar Longitudes
Kocharov, Leon; Torsti, Jarmo; Laitinen, Timo +1 more
We have analyzed five solar energetic particle (SEP) events observed aboard the SOHO spacecraft during 1996-1997. All events were associated with impulsive soft X-ray flares, Type II radio bursts and coronal mass ejections (CMEs). Most attention is concentrated on the SEP acceleration during the first 100 minutes after the flare impulsive phase, p…
Coronal heating events in high-cadence TRACE data
Walsh, Robert W.; Ireland, Jack; Wills-Davey, Meredith
On March 23rd 1999 a set of TRACE (Transition Region and Coronal Explorer) observations were taken in support of Solar and Heliospheric Observatory (SOHO) / TRACE Joint Observing Program 83. The program is designed to look for coronal heating mechanisms operating at high cadence and to observe their dynamical effects on coronal loop density, tempe…
Electron densities above a polar coronal hole based on improved Si IX density diagnostics
Doyle, J. G.; Fludra, A.; Keenan, F. P. +2 more
Using new close-coupling excitation rates for the C-like ion Si ix, density-diagnostic ratios based on Si ix lines have been re-evaluated and applied to a sequence of CDS observations taken above a polar coronal hole. The derived electron densities are in excellent agreement with previous values of Neestimated from the N-like ion Si vii…
Comparative morphology of EIT/SOHO images and He II excitation
Venkatakrishnan, P.
Morphological differences between coronal images on the one hand, and a He i image on the other, are used to demonstrate the independence of He ii excitation from coronal radiation. The distribution of magnetic flux is found to be more important for He ii excitation. Collisional excitation by non-thermal electrons produced in nano-flare events is …
NE VII emission lines in the solar EUV spectrum
Keenan, F. P.; Ryans, R. S. I.; Bell, K. L. +3 more
Recent calculations of electron and proton impact excitation rates in Ne vii are used to calculate theoretical emission line ratios involving both Δn=0 (2-2) and Δn=1 (2-3) transitions in the ∼ 97-895 Å wavelength range. A comparison of these with existing solar observations, obtained by instruments on rocket flights and on the Skylab mission, rev…
On the difference between low-ℓ p-mode frequencies seen in velocity and in intensity
Gavryusev, V. G.; Gavryuseva, E. A.
We compare the line profiles and frequencies of low ℓ=0, 1, 2 acoustic oscillations seen in observations in velocity (by the GOLF and GONG experiments) and in intensity (LOI instrument). Our study indicates that the systematic shift between the frequencies of low-ℓ pmodes in intensity and in velocity measurements recently discovered by Toutain and…
First Solar EUV Irradiances Obtained from SOHO by the CELIAS/SEM
Wurz, P.; Klecker, B.; Möbius, E. +10 more
The first results obtained with the Solar EUV Monitor (SEM), part of the Charge, Element, and Isotope Analysis System (CELIAS) instrument, aboard the SOlar and Heliospheric Observatory (SOHO) satellite are presented. The instrument monitors the full-disk absolute value of the solar Heii irradiance at 30.4 nm, and the full-disk absolute solar irrad…
Rotating Transition Region Features Observed with the SOHO Coronal Diagnostic Spectrometer
Mason, H. E.; Pike, C. D.
Strong evidence has been found from SOHO-CDS (Solar and Heliospheric Observatory - Coronal Diagnostic Spectrometer) observations to support the hypothesis that rotation plays a major role in the dynamics of transition region features. A comprehensive survey of the CDS daily synoptic rasters has been carried out to select dynamic events by searchin…
EUV97: Improvements to EUV Irradiance Modeling in the Soft X-Rays and FUV
Tobiska, W. Kent; Eparvier, F. G.
EUV97 is a solar EUV empirical model that incorporates revised soft X-ray fluxes from the SOLRAD-11 satellite (1976-1979) and uses Lα recently recalibrated to the UARS satellite (1991-present) SOLSTICE Lα. The soft X-ray data have been revised from the original flux values using Mewe's spectral fits to the data. The recalibrated AE-E and SME Lα da…