244 research outputs found
The Need for X-Ray Spectroscopy
For over four decades, X-ray, EUV, and UV spectral observations have been used to measure physical properties of the solar atmosphere. During this time, there has been substantial improvement in the spectral, spatial, and temporal resolution of the observations for the EUV and UV wavelength ranges. At wavelengths below 100 Angstroms, however, observations of the solar corona with simultaneous spatial and spectral resolution are limited, and not since the late 1970's have spatially resolved solar X-ray spectra been measured. The soft-X-ray wavelength range is dominated by emission lines formed at high temperatures and provides diagnostics unavailable in any other wavelength range. In this presentation, we will discuss the important science questions that can be answered using spatially and spectrally resolved X-ray spectra
What I'd like You to Know about our Solar Instrumentation
No abstract availabl
Observations of Transient Active Region Heating with Hinode
We present observations of transient active region heating events observed
with the Extreme Ultraviolet Imaging Spectrometer (EIS) and X-ray Telescope
(XRT) on Hinode. This initial investigation focuses on NOAA active region 10940
as observed by Hinode on February 1, 2007 between 12 and 19 UT. In these
observations we find numerous examples of transient heating events within the
active region. The high spatial resolution and broad temperature coverage of
these instruments allows us to track the evolution of coronal plasma. The
evolution of the emission observed with XRT and EIS during these events is
generally consistent with loops that have been heated and are cooling. We have
analyzed the most energetic heating event observed during this period, a small
GOES B-class flare, in some detail and present some of the spectral signatures
of the event, such as relative Doppler shifts at one of the loop footpoints and
enhanced line widths during the rise phase of the event. While the analysis of
these transient events has the potential to yield insights into the coronal
heating mechanism, these observations do not rule out the possibility that
there is a strong steady heating level in the active region. Detailed
statistical analysis will be required to address this question definitively
Using the Chandra Source-Finding Algorithm to Automatically Identify Solar X-ray Bright Points
This poster details a technique of bright point identification that is used to find sources in Chandra X-ray data. The algorithm, part of a program called LEXTRCT, searches for regions of a given size that are above a minimum signal to noise ratio. The algorithm allows selected pixels to be excluded from the source-finding, thus allowing exclusion of saturated pixels (from flares and/or active regions). For Chandra data the noise is determined by photon counting statistics, whereas solar telescopes typically integrate a flux. Thus the calculated signal-to-noise ratio is incorrect, but we find we can scale the number to get reasonable results. For example, Nakakubo and Hara (1998) find 297 bright points in a September 11, 1996 Yohkoh image; with judicious selection of signal-to-noise ratio, our algorithm finds 300 sources. To further assess the efficacy of the algorithm, we analyze a SOHO/EIT image (195 Angstroms) and compare results with those published in the literature (McIntosh and Gurman, 2005). Finally, we analyze three sets of data from Hinode, representing different parts of the decline to minimum of the solar cycle
Hi-C First Results
Hi-C obtained the highest spatial and temporal resolution observatoins ever taken in the solar corona. Hi-C reveals dynamics and structure at the limit of its temporal and spatial resolution. Hi-C observed ubiquitous fine-scale flows consistent with the local sound speed
Are Coronal Loops Isothermal or Multithermal? Yes!
Surprisingly few solar coronal loops have been observed simultaneously with
TRACE and SOHO/CDS, and even fewer analyses of these loops have been conducted
and published. The SOHO Joint Observing Program 146 was designed in part to
provide the simultaneous observations required for in-depth temperature
analysis of active region loops and determine whether these loops are
isothermal or multithermal. The data analyzed in this paper were taken on 2003
January 17 of AR 10250. We used TRACE filter ratios, emission measure loci, and
two methods of differential emission measure analysis to examine the
temperature structure of three different loops. TRACE and CDS observations
agree that Loop 1 is isothermal with Log T 5.85, both along the line of
sight as well as along the length of the loop leg that is visible in the CDS
field of view. Loop 2 is hotter than Loop 1. It is multithermal along the line
of sight, with significant emission between 6.2 Log T 6.4, but the loop
apex region is out of the CDS field of view so it is not possible to determine
the temperature distribution as a function of loop height. Loop 3 also appears
to be multithermal, but a blended loop that is just barely resolved with CDS
may be adding cool emission to the Loop 3 intensities and complicating our
results. So, are coronal loops isothermal or multithermal? The answer appears
to be yes
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