Solar Physics Division 2013 report
Data reduction and interpretation
RESIK
RESIK was a unique Bragg crystal spectrometer operating on one from the two
previous missions of the Russian CORONAS program. RESIK was launched on
CORONAS-F satellite on 31 July 2001.The instrument took measurements close
to the maximum of 23rd solar activity. The instrument recorded ~1. 8 mln. high
quality spectra in the spectral range 3.3-6.1 Å. In the spectra, several
prominent X-ray emission lines are seen formed in active regions and flares. In
2013, further analyses of these spectra have been performed. The main results
obtained are the following:
The active binary stars σ Gem and HR1099 X-ray spectra obtained from the
Chandra High Energy Transmission Grating Spectrometer have been compared
with the solar flare spectra obtained with the RESIK instrument at similar
resolution in an overlapping bandpass.
We show the spectra and models in the short wavelength region where HETG
and RESIK spectra overlap. Flux-corrected spectra are in black, and the
red is the model convolved by the instrumental resolution. Below each, in blue,
are residuals. The top panel shows σ Gem; the middle is HR 1099; the bottom is
the rise phase of the solar flare on 2002 December 26 (maximum at 06:30 UT).
(Huenemorder, Phillips, Sylwester & Sylwester, The Astrophysical Journal,
768:135 (15pp), 2013 May 10).
The primary goal of this work was to compare low and high FIP elemental
abundances in the Sun and stars. We have determined new elemental
abundances. For the lowest FIP species—particularly K and Na, the abundances
in σ Gem is similar to that in the solar corona, other low-FIP elements (Na, Al,
Ca, Mg, Fe, and Si) are strongly depleted, only becoming near or above solar for
the high FIP elements N, Ar, and Ne. Even the stellar S abundance (considered
high-FIP) has a very low relative abundance.
In another study RESIK fluxes of the Si XIV Ly-β line (5.217 Å) and the
Si XIII 1s2 – 1s3p line (5.688 Å) for 21 flares have been analyzed to obtain the
silicon abundance relative to hydrogen. The emitting plasma for each spectrum
was assumed to be characterized by a single temperature and emission
measure given by the ratio of emission in the two channels of GOES.
Upper panel: Spectra for RESIK Channels 3 and 4 for all 1822 spectra analyzed in
this work, stacked in order of TGOES increasing upwards, with the scale shown
on the left. Lower panel: Five RESIK Channels 3 and 4 spectra averaged over 2MK intervals, with the average temperature TGOES shown in each case. The Si
XIV Ly-β line at 5.217 Å has increasing intensity relative to the Si XIII 1s2 −1s3p
line at 5.688 Å for increasing TGOES, while the Si XIII line predominates in
Channel 4 spectra at lower temperatures.
The silicon abundance was determined to be A(Si) = 7.93 ± .21 (Si XIV) and 7.89
± .13 (Si XIII) on a logarithmic scale with H = 12. These values, which vary by
only very small amounts from flare to flare and times within flares, are 2.6 ± 1.3
and 2.4 ± 0.7 times the photospheric abundance, and are about a factor of
three higher than RESIK measurements during a period of very low activity.
There is a suggestion that the Si/S abundance ratio increases from active
regions to flares. (B. Sylwester · K.J.H. Phillips · J. Sylwester · A. Kępa, Solar
Phys. 283:453–461)
A new analysis method AbuOpt for determination of time/temperature
dependent composition and differential emission measure structure of flaring
plasmas have been developed and used for the analysis of selected flare
(SOL2002-11-14T22:26). The analysis method starts by finding an abundance
set that is consistent with the observed spectra, then solves for the differential
emission measure shape using a maximum-likelihood routine (the Withbroe–
Sylwester method). The abundance optimization leads to revised abundances
of silicon and sulfur in the analyzed flare plasmas: A(S) = 6.94 0.06 and A(Si) =
7.56 0.08 (on a logarithmic scale A(H) = 12).
(Left :) Contour plot of the differential emission measure during the SOL2002-11-14T22:26
flare, darker colors indicating greater emission measure. The horizontal scale is the logarithm
of temperature, and the time increases upwards, measured from 22:14:41 UT. Horizontal
dotted lines define the time intervals a, g, i, l, and q and the smooth curve running from top
to bottom is the temperature derived from the ratio of the two GOES channels on an
isothermal assumption. (Right:) Emission measure distributions for the intervals indicated in
the left plot, derived from the Withbroe–Sylwester routine. Vertical error bars indicate
uncertainties. A cooler (temperature 4 - 5 MK) component is present over the entire time
interval shown, with hotter component (~18 MK) at the peak of the GOES light curve.
During the flare’s maximum phase, the DEM analysis shows the X-ray-emitting
plasma to have a basically two-temperature component, with the cooler
plasma at approximately constant temperature (4–5 MK) and hotter plasma at
~18 MK. The cooler plasma is present before, during, and after the flare
maximum. (B. Sylwester, J. Sylwester, K.J.H. Phillips, A. Kępa, T. Mrozek, ApJ,
under review)
SphinX
SphinX soft X-ray spectrophotometer successfully operated aboard the Russian
CORONAS-Photon satellite between February and December 2009. The
instrument collected ~2 mln. spectra covering a period of very low solar
activity, the lowest since approximately 100 years. No other X-ray instrument
was capable of taking the X-ray spectra at such low activity and therefore the
SphinX measurements are unique in this respect. The CORONAS -Photon, third
spacecraft of this series, has been launched on 30 January 2009. Over the year
2013, comparison of SphinX measurements with other measurements making
similar X-ray measurements have been performed. In particular the
MESSENGER data from SAX solar monitor has been used and fluencies
compared in similar energy bands.
The comparison of soft X-ray lightcurves as recorded by SphinX D1 detector
(blue line) and two channels of MESSENGER SAX (in black and gray). For the
period indicated, centered on 19- September 2009, the Messenger spacecraft
looked at the same part of the solar corona as SphinX from Earth orbit.
A very good correspondence has been observed (as seen on the above plot).
This indicates that the databases of SphinX and SAX complement each other,
however the SphinX sensitivity for D1 detector is at least order of magnitude
better than SAX. Quantitative analysis of common data set is in progress (Anna
Kępa).
Solar corona during 2009 activity minimum
Common analysis of the SphinX spectra and Hinode/XRT intensities for the
most in-active corona observed allows to distinguish four clear features in the
temperature distribution of emission (DEM): colder emission below 1 MK (log T
≈ 5.9), main maximum at ~1 MK (for log T in the range 5.9-6.1), a second
maximum or enhancement at ~1.6 MK (for log T in the range 6.1- 6.4) and a
hotter emission with T>2.5 (log T above 6.4). Using XRT temperature maps as
obtained applying image-ratio technique allows to unveil the spatial
arrangement of these different plasma temperature components in projection.
Example of derived temperature maps is presented in the Figure below for
2009 February 21 0604 UT, the period of lowermost global solar soft X-ray flux
yet measured.
An example of temperature map obtained from Hinode/XRT data on 2009 Feb
21 06:04 UT. Black, blue, yellow, and red colors correspond to log(T) = 5.0 > 5.9
> 6.1 >6.4 ranges respectively as shown in the inset. The characteristic white
network corresponds mainly to the CCD pixels where the contamination effects
were pronounced. These pixels were not used for temperature mapping.
The colors represented plasmas at indicated temperatures. We can see that the
colder emission corresponds to regions of coronal holes and above towards
outer corona. Blue color corresponding to T in the range 0.8 – 1.3 MK i.e. close
to “an average” quiet corona temperature is distributed over most of the disk.
The yellow areas corresponding to somewhat hotter emission on DEM
distribution with T in the range 1.3 – 2.5 MK constitutes left-overs of the
“active corona” i.e. small active regions and the bright points. This hotter
emission occupies also regions of inner corona close above the limb. The red
color areas represent the quiet corona hottest emission where T > 2.5 MK. No
red colors are seen within active regions and/or bright points due to saturation
of respective XRT pixels. No hottest emission is seen on the disk, but it
overwhelms the outer corona due to line-of-sight integration effects.
These results have never been obtained before and respective publication is
under preparation (Marek Siarkowski et al.). They were discussed during the
XVI Consultations on Solar Physics (22-25 May 2013) in Wrocław, Poland .
Theoretical Modeling
We (Sylwester Kołomanski, Tomek Mrozek and Barbara & Janusz Sylwester)
continued modelling efforts of the response of solar atmosphere to flare
energy release occurring in the corona confined within a “rigid” magnetic
environment of coronal loop. For the first time, we modelled the evolution of
plasma along the loop throughout entire event, in the flare scenario considered
covering approximately 1.5 day. Such a long modelling exercise was possible
thanks to the access to supercomputers at the Wroclaw Academic
Supercomputer Centre. For the first time we can study the late phase of flare
evolution showing the “recovery” of flaring plasma to initial condition, before
the flare heating initiation. On the diagnostic diagram shown, this decay-phase
variability strictly follows so-called quasi-steady-stay cooling. This type of
evolution is characteristic for the case of the heating operating quite long into
the decay of the event.
Example of time variability of physical conditions as modelled using the
Palermo-Harvard HD code for a loop of semi-length 50 Mm. Time dependence
of the plasma temperature T, density N and pressure P are plotted in the three
upper-left diagrams in color, representing the time elapsed from switch-on of
flare heating at t=500s. The fourth diagram (lower-right) represents so-called
diagnostic diagram.