141 research outputs found
In orbit degradation of EUV optical components in the wavelength range 10-40 nm AO 138-3
A complement of EUV optical components, including mirrors and thin film filters, was flown as part of the Long Duration Exposure Facility (LDEF) AO 138-3. The most original amongst these components were multilayered interference reflectors for the 10-40 nm wavelength range. Very moderate degradation was observed for those components which were exposed to the sun. The degradation is compatible with the deposition of a few nanometers of absorbing material on the surface of the samples
The LYRA Instrument Onboard PROBA2: Description and In-Flight Performance
The Large Yield Radiometer (LYRA) is an XUV-EUV-MUV (soft X-ray to
mid-ultraviolet) solar radiometer onboard the European Space Agency PROBA2
mission that was launched in November 2009. LYRA acquires solar irradiance
measurements at a high cadence (nominally 20 Hz) in four broad spectral
channels, from soft X-ray to MUV, that have been chosen for their relevance to
solar physics, space weather and aeronomy. In this article, we briefly review
the design of the instrument, give an overview of the data products distributed
through the instrument website, and describe the way that data are calibrated.
We also briefly present a summary of the main fields of research currently
under investigation by the LYRA consortium
Helioseismology with PICARD
PICARD is a CNES micro-satellite launched in June 2010 (Thuillier at al.
2006). Its main goal is to measure the solar shape, total and spectral
irradiance during the ascending phase of the activity cycle. The SODISM
telescope onboard PICARD also allows us to conduct a program for
helioseismology in intensity at 535.7 nm (Corbard et al. 2008). One-minute
cadence low-resolution full images are available for a so-called medium-
program, and high-resolution images of the limb recorded every 2 minutes are
used to study mode amplification near the limb in the perspective of g-mode
search. First analyses and results from these two programs are presented here.Comment: 6 pages, 6 figures, Eclipse on the Coral Sea: Cycle 24 Ascending,
GONG 2012 / LWS/SDO-5 / SOHO 27, November 12 - 16, 2012, Palm Cove,
Queensland. Accepted for publication in Journal of Physics Conference Series
on March 1st 201
Slow magnetoacoustic waves in coronal loops : EIT and TRACE
On May 13, 1998 the EIT (Extreme ultraviolet Imaging Telescope) on board of SoHO (Solar and Heliospheric Observatory) and TRACE (Transition Region And Coronal Explorer) instruments produced simultaneous high cadence image sequences of the same active region (AR 8218). TRACE achieved a 25 s cadence in the FeIX (171 Å) bandpass while EIT achieved a 15 s cadence (operating in "shutterless mode", SoHO JOP 80) in the FeXII (195 Å) bandpass. These high cadence observations in two complementary wavelengths have revealed the existence of weak transient disturbances in an extended coronal loop system. These propagating disturbances (PDs) seem to be a common phenomenon in this part of the active region. The disturbances originate from small scale brightenings at the footpoints of the loops and propagate along the loops. The projected propagation speeds roughly vary between 65 and 150 km s-1 for both instruments which is close to and below the expected sound speed in the coronal loops. The measured slow magnetoacoustic propagation speeds seem to suggest that the transients are sound (or slow) wave disturbances. This work differs from previous studies in the sense that it is based on a multi-wavelength observation of an entire loop bundle at high cadence by two EUV imagers. The observation of sound waves along the same path shows that they propagate along the same loop, suggesting that loops contain sharp temperature gradients and consist of either concentric shells or thin loop threads, at different temperatures
The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV
solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission
launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm
and provides images of the low solar corona over a 54x54 arcmin field-of-view
with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is
designed to monitor all space-weather-relevant events and features in the low
solar corona. Given the limited resources of the PROBA2 microsatellite, the
SWAP telescope is designed with various innovative technologies, including an
off-axis optical design and a CMOS-APS detector. This article provides
reference documentation for users of the SWAP image data.Comment: 26 pages, 9 figures, 1 movi
The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
The EPIC focal plane imaging spectrometers on XMM-Newton use CCDs to record
the images and spectra of celestial X-ray sources focused by the three X-ray
mirrors. There is one camera at the focus of each mirror; two of the cameras
contain seven MOS CCDs, while the third uses twelve PN CCDs, defining a
circular field of view of 30 arcmin diameter in each case. The CCDs were
specially developed for EPIC, and combine high quality imaging with spectral
resolution close to the Fano limit. A filter wheel carrying three kinds of
X-ray transparent light blocking filter, a fully closed, and a fully open
position, is fitted to each EPIC instrument. The CCDs are cooled passively and
are under full closed loop thermal control. A radio-active source is fitted for
internal calibration. Data are processed on-board to save telemetry by removing
cosmic ray tracks, and generating X-ray event files; a variety of different
instrument modes are available to increase the dynamic range of the instrument
and to enable fast timing. The instruments were calibrated using laboratory
X-ray beams, and synchrotron generated monochromatic X-ray beams before launch;
in-orbit calibration makes use of a variety of celestial X-ray targets. The
current calibration is better than 10% over the entire energy range of 0.2 to
10 keV. All three instruments survived launch and are performing nominally in
orbit. In particular full field-of-view coverage is available, all electronic
modes work, and the energy resolution is close to pre-launch values. Radiation
damage is well within pre-launch predictions and does not yet impact on the
energy resolution. The scientific results from EPIC amply fulfil pre-launch
expectations.Comment: 9 pages, 11 figures, accepted for publication in the A&A Special
Issue on XMM-Newto
EIT Observations of the Extreme Ultraviolet Sun
The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops
EUV fine structure and variability associated with coronal rain revealed by Solar Orbiter/EUI HRIEUV and SPICE
Coronal rain is the most dramatic cooling phenomenon of the solar corona and
an essential diagnostic tool for the coronal heating properties. A puzzling
feature of the solar corona, besides the heating, is its EUV filamentary
structure and variability. We aim to identify observable features of the TNE-TI
scenario underlying coronal rain at small and large spatial scales, to
understand the role it plays in the solar corona. We use EUV datasets at
unprecedented spatial resolution of ~240 km from EUI/HRIEUV and SPICE of Solar
Orbiter from the spring 2022 perihelion. EUV absorption features produced by
coronal rain are detected at scales as small as 260 km. As the rain falls,
heating and compression is produced immediately downstream, leading to a small
EUV brightening accompanying the fall and producing a "fireball" phenomenon.
Just prior to impact, a flash-like EUV brightening downstream of the rain,
lasting a few minutes is observed for the fastest events. For the first time,
we detect the atmospheric response to the rain's impact on the chromosphere and
consists of upward propagating rebound shocks and flows partly reheating the
loop. The observed widths of the rain clumps are 500 +- 200 km. They exhibit a
broad velocity distribution of 10 - 150 km s^-1, peaking below 50 km s^-1.
Coronal strands of similar widths are observed along the same loops co-spatial
with cool filamentary structure, which we interpret as the CCTR. Matching with
the expected cooling, prior to the rain appearance sequential loop brightenings
are detected in gradually cooler lines from corona to chromospheric
temperatures. Despite the large rain showers, most cannot be detected in AIA
171 in quadrature, indicating that LOS effects play a major role in coronal
rain visibility. Still, AIA 304 and SPICE observations reveal that only a small
fraction of the rain can be captured by HRIEUV.Comment: Astronomy & Astrophysics; 32 Pages, 24 Main Figures, Appendi
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