Are Coronae of Magnetically Active Stars Heated by Flares? II. Extreme Ultraviolet and X‐Ray Flare Statistics and the Differential Emission Measure Distribution

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.

Download Full-text

EUVE Spectra of Coronae and Flares

International Astronomical Union Colloquium ◽

10.1017/s025292110003579x ◽

1996 ◽

Vol 152 ◽

pp. 81-88 ◽

Cited By ~ 1

Author(s):

Carole Jordan

Keyword(s):

Short Wavelength ◽

Extreme Ultraviolet ◽

Emission Measure ◽

Wavelength Region ◽

Late Type ◽

Short Wavelength Region ◽

Plane Parallel ◽

Parallel Geometry ◽

Measure Distribution

Following a summary of early solar EUV spectroscopy the spectra of some late-type stars obtained with the Extreme Ultraviolet Explorer (EUVE) are briefly surveyed. Some transitions which are not included in current emissivity codes but could lead to numerous weak lines, and an apparent continuum in the EUVE short wavelength region, are discussed. The importance of the geometry adopted when interpreting the emission measure distribution is stressed, since radial factors can lead to an apparent emission measure distribution gradient that is steeper than the value of 3/2 expected in plane parallel geometry.

Download Full-text

The 3D solar corona Cycle 24 rising phase from SDO/AIA tomography

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312004905 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 238-241

Author(s):

Federico A. Nuevo ◽

Alberto M. Vásquez ◽

Richard A. Frazin ◽

Zhenguang Huang ◽

Ward B. Manchester

Keyword(s):

Solar Corona ◽

Extreme Ultraviolet ◽

Emission Measure ◽

Source Surface ◽

Solar Dynamics Observatory ◽

Differential Emission Measure ◽

Height Range ◽

Field Source ◽

Solar Dynamics ◽

Cycle 24

AbstractWe recently extended the differential emission measure tomography (DEMT) technique to be applied to the six iron bands of the Atmospheric Imaging Assembly (AIA) instrument aboard the Solar Dynamics Observatory (SDO). DEMT products are the 3D reconstruction of the coronal emissivity in the instrument's bands, and the 3D distribution of the local differential emission measure, in the height range 1.0 to 1.25 R⊙. We show here derived maps of the electron density and temperature of the inner solar corona during the rising phase of solar Cycle 24. We discuss the distribution of our results in the context of open/closed magnetic regions, as derived from a global potential field source surface (PFSS) model of the same period. We also compare the results derived with SDO/AIA to those derived with the Extreme UltraViolet Imager (EUVI) instrument aboard the Solar TErrestrial RElations Observatory (STEREO).

Download Full-text

The 3D solar minimum with differential emission measure tomography

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312004735 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 123-133

Author(s):

Alberto M. Vásquez ◽

Richard A. Frazin ◽

Zhenguang Huang ◽

Ward B. Manchester ◽

Paul Shearer

Keyword(s):

Extreme Ultraviolet ◽

Emission Measure ◽

Three Dimensional ◽

Differential Emission Measure ◽

Height Range ◽

Heliospheric Observatory ◽

Temperature Distributions ◽

Imaging Telescope ◽

Electron Density And Temperature ◽

Comparative Results

AbstractDifferential emission measure tomography (DEMT) makes use of extreme ultraviolet (EUV) image series to deliver two products: a) the three-dimensional (3D) reconstruction of the coronal emissivity in the instrumental bands, and b) the 3D distribution of the local differential emission measure (LDEM). The LDEM allows, in turn, construction of 3D maps of the electron density and temperature distribution. DEMT is being currently applied to the space-based EUV imagers, allowing reconstruction of the inner corona in the height range 1.00 to 1.25 R⊙. In this work we applied DEMT to different Carrington Rotations corresponding to the last two solar Cycle minima. To reconstruct the 2008 minimum we used data taken by the Extreme UltraViolet Imager (EUVI), on board the Solar TErrestrial RElations Observatory (STEREO) spacecraft, and to reconstruct the 1996 minimum we used data taken by the Extreme ultraviolet Imaging Telescope (EIT), on board the Solar and Heliospheric Observatory (SOHO). We show here comparative results, discussing the observed 3D density and temperature distributions in the context of global potential magnetic field extrapolations. We also compare the DEMT results with other observational and modeling efforts of the same periods.

Download Full-text

The Solar Flare Soft X‐Ray Differential Emission Measure and the Neupert Effect at Different Temperatures

The Astrophysical Journal ◽

10.1086/306924 ◽

1999 ◽

Vol 514 (1) ◽

pp. 472-483 ◽

Cited By ~ 61

Author(s):

James M. McTiernan ◽

George H. Fisher ◽

Peng Li

Keyword(s):

Solar Flare ◽

Emission Measure ◽

Differential Emission Measure ◽

X Ray ◽

Neupert Effect ◽

Different Temperatures

Download Full-text

Ultraviolet Observations of Stellar Coronae: Early Results from HST

Highlights of Astronomy ◽

10.1017/s1539299600009965 ◽

1992 ◽

Vol 9 ◽

pp. 657-658

Author(s):

J.L. Linsky

Keyword(s):

High Resolution ◽

Spectral Resolution ◽

Solar Flares ◽

Extreme Ultraviolet ◽

The Sun ◽

X Ray ◽

Spectroscopic Diagnostics ◽

Early Results ◽

Active Stars ◽

Ultraviolet Observations

Although coronae for stars other than the Sun have previously been detected only in the X-ray and radio portions of the spectrum, the HST and future spacecraft sensitive to ultraviolet (UV) and extreme ultraviolet (ETIV) light will have the spectral resolution to study the dynamics and spectroscopic diagnostics of hot coronal plasmas. In the UV region accessible to HST, forbidden lines of FeXII at 1242 and 1349Å, of FeXXI at 1354Å, and other species seen in solar flares, are predicted to be present in the spectra of active stars. Upcoming observations with the Goddard High Resolution Spectrograph (GHRS) by S. Maran will search for these lines in the dM2e star AU Mic and other stars.

Download Full-text