819 research outputs found
A European X-ray astrophysics mission
Five instruments (Bragg Spectrometer, Large Area Proportional and Scintillation Counter Detectors, Wide Field X-ray Cameras and a Gamma-Ray Burst Monitor) are discussed and estimates of their performance are given. Their scientific aims are summarized and sample observing programmes are discussed
Long duration thermal hard X-ray sources observed in two eruptive flares
We present observations of two eruptive flares on 17 of December 2006 (C1.9) and 19 of May 2007 (B9.7) which had good coverage with both Hinode and RHESSI. In these flares we see a long lived, gradual thermal hard X-ray source of low emission measure and, relative to the loops observed with GOES and XRT, high temperature. The lack of a non-thermal hard X-ray component and impulsive behaviour is inconsistent with electron beam driven chromospheric evaporation
Experimental study of spectral and spatial distribution of solar X-rays
The study of the physical conditions within the solar corona and the development of instrumentation and technical expertise necessary for advanced studies of solar X-ray emission are reported. Details are given on the Aerobee-borne-X-ray spectrometer/monochromator and also on the observing program. Preliminary discussions of some results are presented and include studies of helium-like line emission, mapping O(VII) and Ne(IX) lines, survey of O(VII) and Ne(IX) lines, study of plage regions and small flares, and analysis of line emission from individual active regions. It is concluded that the use of large-area collimated Bragg spectrometers to scan narrow wavelength intervals and the capability of the SPARCS pointing control to execute a complex observing program are established
Flows in the solar atmosphere due to the eruptions on the 15th July, 2002
<p>Which kind of flows are present during flares? Are they compatible with the present understanding of energy release and which model best describes the observations? We analyze successive flare events in order to answer these questions. The flares were observed in the magnetically complex NOAA active region (AR) 10030 on 15 July 2002. One of them is of GOES X-class. The description of these flares and how they relate to the break-out model is presented in Gary & Moore (2004). The Coronal Diagnostic Spectrometer on board SOHO observed this active region for around 14 h. The observed emission lines provided data from the transition region to the corona with a field of view covering more than half of the active region. In this paper we analyse the spatially resolved flows seen in the atmosphere from the preflare to the flare stages. We find evidence for evaporation occurring before the impulsive phase. During the main phase, the ongoing magnetic reconnection is demonstrated by upflows located at the edges of the flare loops (while downflows are found in the flare loops themselves). We also report the impact of a filament eruption on the atmosphere, with flows up to 300 km s<sup>-1</sup> observed at transition-region temperatures in regions well away from the location of the pre-eruptive filament. Our results are consistent with the predictions of the break out model before the impulsive phase of the flare; while, as the flare progresses, the directions of the flows are consistent with flare models invoking evaporation followed by cooling and downward plasma motions in the flare loops.</p>
Transition region features observed with Hinode/EIS
Two types of active region feature prominent at transition region
temperatures are identified in Hinode/EIS data of AR 10938 taken on 2007
January 20. The footpoints of 1 MK TRACE loops are shown to emit strongly in
emission lines formed at log T=5.4-5.8, allowing the temperature increase along
the footpoints to be clearly seen. A density diagnostic of Mg VII yields the
density in the footpoints, with one loop showing a decrease from 3x10^9 cm^-3
at the base to 1.5x10^9 cm^-3 at a projected height of 20 Mm. The second
feature is a compact active region transition region brightening which is
particularly intense in O V emission (log T=5.4) but also has a signature at
temperatures up to log T=6.3. The Mg VII diagnostic gives a density of 4x10^10
cm^-3, and emission lines of Mg VI and Mg VII show line profiles broadened by
50 km/s and wings extending beyond 200 km/s. Continuum emission in the short
wavelength band is also found to be enhanced, and is suggested to be free-bound
emission from recombination onto He^+.Comment: 11 pages, 9 figures, submitted to PASJ Hinode first results issu
Flows and Non-thermal Velocities in Solar Active Regions Observed with the Extreme-ultraviolet Imaging Spectrometer on Hinode: A Tracer of Active Region Sources of Heliospheric Magnetic Fields?
From Doppler velocity maps of active regions constructed from spectra
obtained by the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode
spacecraft we observe large areas of outflow (20-50 km/s) that can persist for
at least a day. These outflows occur in areas of active regions that are faint
in coronal spectral lines formed at typical quiet Sun and active region
temperatures. The outflows are positively correlated with non-thermal
velocities in coronal plasmas. The bulk mass motions and non-thermal velocities
are derived from spectral line centroids and line widths, mostly from a strong
line of Fe XII at 195.12 Angstroms. The electron temperature of the outflow
regions estimated from an Fe XIII to Fe XII line intensity ratio is about
1.2-1.4 MK. The electron density of the outflow regions derived from a density
sensitive intensity ratio of Fe XII lines is rather low for an active region.
Most regions average around 7E10+8 cm(-3), but there are variations on pixel
spatial scales of about a factor of 4. We discuss results in detail for two
active regions observed by EIS. Images of active regions in line intensity,
line width, and line centroid are obtained by rastering the regions. We also
discuss data from the active regions obtained from other orbiting spacecraft
that support the conclusions obtained from analysis of the EIS spectra. The
locations of the flows in the active regions with respect to the longitudinal
photospheric magnetic fields suggest that these regions might be tracers of
long loops and/or open magnetic fields that extend into the heliosphere, and
thus the flows could possibly contribute significantly to the solar wind.Comment: one tex file, 11 postscript figure file
Observations of a rotating macrospicule associated with an X-ray jet
We attempt to understand the driving mechanism of a macrospicule and its
relationship with a coronal jet. We study the dynamics of a macrospicule and an
associated coronal jet captured by multi-spacecraft observations. Doppler
velocities both in the macrospicule and the coronal jet are determined by EIS
and SUMER spectra. Their temporal evolution is studied using X-ray and He II
304 images. A blueshift of -120+/-15 km/s is detected on one side of the
macrospicule, while a redshift of 50+/-6 km/s is found at the base of the other
side. The inclination angle of the macrospicule inferred from a stereoscopic
analysis with STEREO suggests that the measured Doppler velocities can be
attributed to a rotating motion of the macrospicule rather than a radial flow
or an expansion. The macrospicule is driven by the unfolding motion of a
twisted magnetic flux rope, while the associated X-ray jet is a radial outflow.Comment: 4 pages, 3 figures, accepted for publication in A&
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