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P G Judge - One of the best experts on this subject based on the ideXlab platform.
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spectral lines for polarization measurements of the coronal magnetic field ii consistent treatment of the stokes vector for magnetic dipole transitions
The Astrophysical Journal, 1999Co-Authors: R Casini, P G JudgeAbstract:We present a compact, self-consistent formulation for the description of polarized radiation from magnetic-dipole transitions occurring in the magnetized Solar corona. This work differs from earlier treatments by Sahal-Brechot and House in the 1970s, in that the radiative emission coefficients for the four Stokes parameters, I, Q, U, and V, are treated to first order in a Taylor expansion of the line profile in terms of the Larmor frequency of the coronal magnetic field. In so doing, the influence on the scattered radiation of both atomic polarization, induced through anisotropic irradiation, and the Zeeman effect is accounted for in a consistent way. It is found that the well-known magnetograph formula, relating the V profile to the frequency derivative of the I profile, must be corrected in the presence of atomic alignment produced by anisotropic irradiation. This correction is smallest for lines where collisions and cascades dominate over excitation by anisotropic radiation, but it systematically increases with height above the Solar Limb (up to a theoretical maximum of 100%, in the collisionless regime and in the limit of vanishing longitudinal magnetic field). Although the correction to the magnetograph formula must be calculated separately for each line as a function of heliocentric distance, it is likely to be small for some lines of practical interest, along lines of sight close to the Solar Limb.
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spectral lines for polarization measurements of the coronal magnetic field ii consistent treatment of the stokes vector for magnetic dipole transitions
The Astrophysical Journal, 1999Co-Authors: R Casini, P G JudgeAbstract:We present a compact, self-consistent formulation for the description of polarized radiation from magnetic-dipole transitions occurring in the magnetized Solar corona. This work diUers from earlier treatments by and House in the 1970s, in that the radiative emission coefficients for the Sahal-Brec chot four Stokes parameters, I, Q, U, and V , are treated to —rst order in a Taylor expansion of the line pro—le in terms of the Larmor frequency of the coronal magnetic —eld. In so doing, the in—uence on the scat- tered radiation of both atomic polarization, induced through anisotropic irradiation, and the Zeeman eUect is accounted for in a consistent way. It is found that the well-known magnetograph formula, rela- ting the V pro—le to the frequency derivative of the I pro—le, must be corrected in the presence of atomic alignment produced by anisotropic irradiation. This correction is smallest for lines where collisions and cascades dominate over excitation by anisotropic radiation, but it systematically increases with height above the Solar Limb (up to a theoretical maximum of 100%, in the collisionless regime and in the limit of vanishing longitudinal magnetic —eld). Although the correction to the magnetograph formula must be calculated separately for each line as a function of heliocentric distance, it is likely to be small for some lines of practical interest, along lines of sight close to the Solar Limb. Subject headings: line: formationSun: atmosphereSun: coronaSun: magnetic —eld
R Gomezherrero - One of the best experts on this subject based on the ideXlab platform.
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multi spacecraft observations of recurrent 3he rich Solar energetic particles
The Astrophysical Journal, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, Andreas Korth, Urs Mall, R GomezherreroAbstract:We study the origin of {sup 3}He-rich Solar energetic particles (<1 MeV nucleon{sup –1}) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90°. The {sup 3}He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE {sup 3}He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 {sup 3}He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west Solar Limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous {sup 3}He enrichment, lacking Solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) Solar regions with long-lasting conditions for {sup 3}He acceleration and (2) Solar energetic {sup 3}He that is temporarily confined/re-accelerated inmore » interplanetary space.« less
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multi spacecraft observations of recurrent 3he rich Solar energetic particles
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, Andreas Korth, Urs Mall, R GomezherreroAbstract:We study the origin of 3He-rich Solar energetic particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west Solar Limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking Solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of 1) Solar regions with long-lasting conditions for 3He acceleration and 2) Solar energetic 3He that is temporary confined/re-accelerated in interplanetary space.
Kyoko Watanabe - One of the best experts on this subject based on the ideXlab platform.
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emission height and temperature distribution of white light emission observed by hinode sot from the 2012 january 27 x class Solar flare
The Astrophysical Journal, 2013Co-Authors: Toshifumi Shimizu, Kyoko Watanabe, S Masuda, Kiyoshi Ichimoto, M OhnoAbstract:White-light emissions were observed from an X1.7 class Solar flare on 2012 January 27, using three continuum bands (red, green, and blue) of the Solar Optical Telescope on board the Hinode satellite. This event occurred near the Solar Limb, and so differences in the locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regions of the red, green, and blue wavelengths of the white-light emissions are significantly displaced from each other, suggesting that those respective emissions are emanating from progressively lower heights in the Solar atmosphere. The temperature distribution was also calculated from the white-light data, and we found the lower-layer emission to have a higher temperature. This indicates that high-energy particles penetrated down to near the photosphere, and deposited heat into the ambient lower layers of the atmosphere.
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emission height and temperature distribution of white light emission observed by hinode sot from the 2012 january 27 x class Solar flare
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: Toshifumi Shimizu, Kyoko Watanabe, S Masuda, Kiyoshi Ichimoto, M OhnoAbstract:White-light emissions were observed from an X1.7 class Solar flare on 27 January 2012, using three continuum bands (red, green, and blue) of the Solar Optical Telescope (SOT) onboard the Hinode satellite. This event occurred near the Solar Limb, and so differences in locations of the various emissions are consistent with differences in heights above the photosphere of the various emission sources. Under this interpretation, our observations are consistent with the white-light emissions occurring at the lowest levels of where the Ca II H emission occurs. Moreover, the centers of the source regions of the red, green, and blue wavelengths of the white-light emissions are significantly displaced from each other, suggesting that those respective emissions are emanating from progressively lower heights in the Solar atmosphere. The temperature distribution was also calculated from the white-light data, and we found the lower-layer emission to have a higher temperature. This indicates that high-energy particles penetrated down to near the photosphere, and deposited heat into the ambient lower layers of the atmosphere.
D E Mckenzie - One of the best experts on this subject based on the ideXlab platform.
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three year global survey of coronal null points from potential field source surface pfss modeling and Solar dynamics observatory sdo observations
Solar Physics, 2015Co-Authors: Michael S Freed, D W Longcope, D E MckenzieAbstract:This article compiles and examines a comprehensive coronal magnetic-null-point survey created by potential-field-source-surface (PFSS) modeling and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. The locations of 582 potential magnetic null points in the corona were predicted from the PFSS model between Carrington Rotations (CR) 2098 (June 2010) and 2139 (July 2013). These locations were manually inspected, using contrast-enhanced SDO/AIA images in 171 A at the East and West Solar Limb, for structures associated with nulls. A Kolmogorov–Smirnov (K–S) test showed a statistically significant difference between observed and predicted latitudinal distributions of null points. This finding is explored further to show that the observability of null points could be affected by the Sun’s asymmetric hemisphere activity. Additional K–S tests show no effect on observability related to eigenvalues associated with the fan and spine structure surrounding null points or to the orientation of the spine. We find that approximately 31 % of nulls obtained from the PFSS model were observed in SDO/AIA images at one of the Solar Limbs. An observed null on the East Solar Limb had a 51.6 % chance of being observed on the West Solar Limb. Predicted null points going back to CR 1893 (March 1995) were also used for comparing radial and latitudinal distributions of nulls to previous work and to test for correlation of Solar activity to the number of predicted nulls.
D E Innes - One of the best experts on this subject based on the ideXlab platform.
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multi spacecraft observations of recurrent 3he rich Solar energetic particles
The Astrophysical Journal, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, Andreas Korth, Urs Mall, R GomezherreroAbstract:We study the origin of {sup 3}He-rich Solar energetic particles (<1 MeV nucleon{sup –1}) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90°. The {sup 3}He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE {sup 3}He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 {sup 3}He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west Solar Limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous {sup 3}He enrichment, lacking Solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) Solar regions with long-lasting conditions for {sup 3}He acceleration and (2) Solar energetic {sup 3}He that is temporarily confined/re-accelerated inmore » interplanetary space.« less
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multi spacecraft observations of recurrent 3he rich Solar energetic particles
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: Radoslav Bucik, G. M. Mason, D E Innes, Andreas Korth, Urs Mall, R GomezherreroAbstract:We study the origin of 3He-rich Solar energetic particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west Solar Limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking Solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of 1) Solar regions with long-lasting conditions for 3He acceleration and 2) Solar energetic 3He that is temporary confined/re-accelerated in interplanetary space.
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slow mode standing waves observed by sumer in hot coronal loops
Astronomy and Astrophysics, 2003Co-Authors: Tongjiang Wang, D E Innes, S K Solanki, W Curdt, Eckart MarschAbstract:We report the first detection of postflare loop oscillations seen in both Doppler shift and intensity. The observations were recorded in an Fe xix line by the SUMER spectrometer on SOHO in the corona about 70 min after anM-class flare on the Solar Limb. The oscillation has a period of about 17 min in both the Doppler velocity and the intensity, but their decay times are different (i.e., 37 min for the velocity and 21 min for the intensity). The fact that the velocity and the intensity oscillations have exactly a 1/4-period phase difference points to the existence of slow-mode standing waves in the oscillating loop. This interpretation is also supported by two other pieces of evidence: (1) the wave period and (2) the amplitude relationship between the intensity and velocity are as expected for a slow-mode standing wave.
