25,884 research outputs found
Oscillations in active region fan loops: Observations from EIS/{\it Hinode} and AIA/SDO
Active region fan loops in AR 11076 were studied, in search of oscillations,
using high cadence spectroscopic observations from EIS on board Hinode combined
with imaging sequences from the AIA on board SDO. Spectra from EIS were
analyzed in two spectral windows, \FeXII 195.12 \AA and \FeXIII 202.04 \AA
along with the images from AIA in 171 \AA and 193 \AA channels. We find short
(3 min) and long (9 min) periods at two different locations.
Shorter periods show oscillations in all the three line parameters and the
longer ones only in intensity and Doppler shift but not in line width. Line
profiles at both these locations do not show any visible blue-shifted component
and can be fitted well with a single Gaussian function along with a polynomial
background. Results using co-spatial and co-temporal data from AIA/SDO do not
show any significant peak corresponding to shorter periods, but longer periods
are clearly observed in both 171 \AA and 193 \AA channels. Space-time analysis
in these fan loops using images from AIA/SDO show alternate slanted ridges of
positive slope, indicative of outward propagating disturbances. The apparent
propagation speeds were estimated to be 83.5 1.8 \kms and 100.5 4.2
\kms, respectively, in the 171 \AA and 193 \AA channels. Observed short period
oscillations are suggested to be caused by the simultaneous presence of more
than one MHD mode whereas the long periods are suggested as signatures of slow
magneto-acoustic waves. In case of shorter periods, the amplitude of
oscillation is found to be higher in EIS lines with relatively higher
temperature of formation. Longer periods, when observed from AIA, show a
decrease of amplitude in hotter AIA channels which might indicate damping due
to thermal conduction owing to their acoustic nature.Comment: Accepted for publication in Solar Physic
A Number of Quasi-Exactly Solvable N-body Problems
We present several examples of quasi-exactly solvable -body problems in
one, two and higher dimensions. We study various aspects of these problems in
some detail. In particular, we show that in some of these examples the
corresponding polynomials form an orthogonal set and many of their properties
are similar to those of the Bender-Dunne polynomials. We also discuss QES
problems where the polynomials do not form an orthogonal set.Comment: 17pages, Revtex, no figur
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