scholarly journals Broadening of the differential emission measure by multi-shelled and turbulent loops

2018 ◽  
Vol 620 ◽  
pp. A65 ◽  
Author(s):  
T. Van Doorsselaere ◽  
P. Antolin ◽  
K. Karampelas
Keyword(s):  
Transverse Wave ◽  
Thermal Plasma ◽  
Turbulent Mixing ◽  
Initial Temperature ◽  
Emission Measure ◽  
Line Of Sight ◽  
Forward Modelling ◽  
Differential Emission Measure ◽  
Temperature Contrast ◽  
Wave Induced

Context. Broad differential emission measure (DEM) distributions in the corona are a sign of multi-thermal plasma along the line-of-sight. Traditionally, this is interpreted as evidence of multi-stranded loops. Recently, however, it has been shown that multi-stranded loops are unlikely to exist in the solar corona, because of their instability to transverse perturbations. Aims. We aim to test if loop models subject to the transverse wave-induced Kelvin-Helmholtz (TWIKH) instability result in broad DEMs, potentially explaining the observations. Methods. We took simulation snapshots and compute the numerical DEM. Moreover, we performed forward-modelling in the relevant AIA channels before reconstructing the DEM. Results. We find that turbulent loop models broaden their initial DEM, because of the turbulent mixing. The width of the DEM is determined by the initial temperature contrast with the exterior. Conclusions. We conclude that impulsively excited loop models have a rather narrow DEM, but that continuously driven models result in broad DEMs that are comparable to the observations.

REVISING WAVE INDUCED TURBULENT MIXING AND ITS IMPACT ON TROPICAL CYCLONE

2019 ◽  
Vol 75 (2) ◽  
pp. I_61-I_66
Author(s):  
Masashi TAKAGI ◽  
Nobuhito MORI ◽  
Junichi NINOMIYA ◽  
Tomoya SHIMURA ◽  
Yusuke UCHIYAMA ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Turbulent Mixing ◽  
Wave Induced

scholarly journals ON THE ACCURACY OF THE DIFFERENTIAL EMISSION MEASURE DIAGNOSTICS OF SOLAR PLASMAS. APPLICATION TO SDO /AIA. II. MULTITHERMAL PLASMAS

2012 ◽  
Vol 203 (2) ◽  
pp. 26 ◽  
Author(s):  
C. Guennou ◽  
F. Auchère ◽  
E. Soubrié ◽  
K. Bocchialini ◽  
S. Parenti ◽  
...  
Keyword(s):  
Emission Measure ◽  
Differential Emission Measure ◽  
Solar Plasmas

Analysis of the differential emission measure distributions for solar flares observed by RESIK

2018 ◽  
Vol 179 ◽  
pp. 545-552
Author(s):  
A. Kepa ◽  
B. Sylwester ◽  
J. Sylwester ◽  
M. Gryciuk ◽  
M. Siarkowski
Keyword(s):  
Solar Flares ◽  
Emission Measure ◽  
Differential Emission Measure

scholarly journals Energetics of Hi-C EUV brightenings

2018 ◽  
Vol 615 ◽  
pp. A47 ◽  
Author(s):  
Srividya Subramanian ◽  
Vinay L. Kashyap ◽  
Durgesh Tripathi ◽  
Maria S. Madjarska ◽  
John G. Doyle
Keyword(s):  
High Resolution ◽  
Energy Loss ◽  
Extreme Ultraviolet ◽  
Thermal Structure ◽  
Emission Measure ◽  
Light Curves ◽  
Solar Dynamics Observatory ◽  
Differential Emission Measure ◽  
Dominant Mechanism ◽  
Solar Dynamics

We study the thermal structure and energetics of the point-like extreme ultraviolet (EUV) brightenings within a system of fan loops observed in the active region AR 11520. These brightenings were simultaneously observed on 2012 July 11 by the High-resolution Coronal (Hi-C) imager and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We identified 27 brightenings by automatically determining intensity enhancements in both Hi-C and AIA 193 Å light curves. The energetics of these brightenings were studied using the Differential Emission Measure (DEM) diagnostics. The DEM weighted temperatures of these transients are in the range log T(K) = 6.2−6.6 with radiative energies ≈1024−25 ergs and densities approximately equal to a few times 109 cm−3. To the best of our knowledge, these are the smallest brightenings in EUV ever detected. We used these results to determine the mechanism of energy loss in these brightenings. Our analysis reveals that the dominant mechanism of energy loss for all the identified brightenings is conduction rather than radiation.

scholarly journals The Slowly Varying Corona. I. Daily Differential Emission Measure Distributions Derived from EVE Spectra

2017 ◽  
Vol 844 (2) ◽  
pp. 163 ◽  
Author(s):  
S. J. Schonfeld ◽  
S. M. White ◽  
R. A. Hock-Mysliwiec ◽  
R. T. J. McAteer
Keyword(s):  
Emission Measure ◽  
Differential Emission Measure

scholarly journals Flare of 1970 March 01: A Review and Further Evidence for Adiabatic Heating

1980 ◽  
Vol 86 ◽  
pp. 177-181
Author(s):  
C. Mätzler ◽  
H.J. Wiehl
Keyword(s):  
Thermal Plasma ◽  
Emission Measure ◽  
Impulsive Phase ◽  
Maximum Temperature ◽  
Adiabatic Process ◽  
Projected Area ◽  
X Ray ◽  
Time Profiles ◽  
Average Electron Density ◽  
Average Electron

SummaryThe microwave and hard-X-ray burst of 1970 March 01, 11:27 UT was found to originate from a common thermal plasma with a maximum temperature of 57 keV. The low coronal plasma with an average electron density of about 3.108cm−3 covered a projected area of 5.1018 cm2. In Fig. 1 the time profiles of the emission measure and the temperature are compared with the 10.5 GHz flux while Fig. 2 shows the reversible relationship between the hard X-ray emission measure and temperature during the impulsive phase. The arrows indicate the direction of increasing time. The dashed-dotted line, representing an adiabatic process with an index χ = 5/3, agrees well with the observations showing a compression followed by an expansion (Mätzler et al. 1978).

scholarly journals Spectroscopy and Differential Emission Measure Diagnostics of a Coronal Dimming Associated with a Fast Halo CME

2019 ◽  
Vol 879 (2) ◽  
pp. 85 ◽  
Author(s):  
Astrid M. Veronig ◽  
Peter Gömöry ◽  
Karin Dissauer ◽  
Manuela Temmer ◽  
Kamalam Vanninathan
Keyword(s):  
Emission Measure ◽  
Differential Emission Measure ◽  
Coronal Dimming

scholarly journals DEM Analyses with the Utrecht Codes

1996 ◽  
Vol 152 ◽  
pp. 553-560
Author(s):  
R. Mewe ◽  
G.H.J. van den Oord ◽  
C.J. Schrijver ◽  
J.S. Kaastra
Keyword(s):  
Emission Measure ◽  
Resonant Scattering ◽  
Continuum Emission ◽  
Second Derivative ◽  
Inversion Problem ◽  
Differential Emission Measure ◽  
The Past ◽  
Cool Stars ◽  
Ill Posed ◽  
Thin Plasma

We address the inversion problem of deriving the differential emission measure (DEM) distribution D(T) = nenHdV/d log T from the spectrum of an optically thin plasma. In the past we have applied the iterative Withbroe-Sylwester technique and the Polynomial technique to the analysis of EXOSAT spectra of cool stars, but recently we have applied the inversion technique discussed by Craig & Brown (1986) and Press et al. (1992) in the analysis of EUVE spectra of cool stars. The inversion problem-a Fredholm equation of the first kind-is ill-posed and solutions tend to show large, unphysical oscillations. We therefore apply a second-order regularization, i.e., we select the specific DEM for which the second derivative is as smooth as is statistically allowed by the data. We demonstrate the importance of fitting lines and continuum simultaneously, discuss the effect on the DEM of continuum emission at temperatures where no line diagnostics are available, and address possible ways to check various model assumptions such as abundances and photon destruction induced by resonant scattering.

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