Search Publications
The Spectroscopic Footprint of the Fast Solar Wind
De Pontieu, Bart; McIntosh, Scott W.; Leamon, Robert J.
We analyze a large, complex equatorial coronal hole (ECH) and its immediate surroundings with a focus on the roots of the fast solar wind. We start by demonstrating that our ECH is indeed a source of the fast solar wind at 1 AU by examining in situ plasma measurements in conjunction with recently developed measures of magnetic conditions of the ph…
Statistical analysis of solar EUV and X-ray flux enhancements induced by solar flares and its implication to upper atmosphere
Le, Huijun; Liu, Libo; Wan, Weixing +1 more
The 0.1-0.8 nm X-ray flux data and 26-34 nm EUV flux data are used to statistically analyze the relationship between enhancement in X-ray flux and that in EUV flux during solar flares in 1996-2006. The EUV enhancement does not linearly increase with X-ray flux from C-class to X-class flares. Its uprising amplitude decreases with X-ray flux. The co…
Relativistic electron acceleration by compressional-mode ULF waves: Evidence from correlated Cluster, Los Alamos National Laboratory spacecraft, and ground-based magnetometer measurements
Sharma, A. S.; Tan, Lun C.; Shao, X. +1 more
Simultaneous observations by Cluster and Los Alamos National Laboratory (LANL) spacecraft and Canadian Array for Real-Time Investigations of Magnetic Activity and International Monitor for Auroral Geomagnetic Effects magnetometer arrays during a sudden storm commencement on 25 September 2001 show evidence of relativistic electron acceleration by c…
Diagnostics of the κ-distribution using Si III lines in the solar transition region
Dzifčáková, E.; Kulinová, A.
Aims: The solar transition region satisfies the conditions for appearance of the non-thermal κ-distribution. We aim to prove the occurrence of the non-thermal κ-distribution in the solar transition region and diagnose its parameters.
Methods: The intensity ratios of Si iii lines observed by SUMER in 1100-1320 Å region do not correspond t…
Astrometry with the Hubble Space Telescope: Trigonometric Parallaxes of Selected Hyads
Harrison, Thomas E.; Benedict, G. Fritz; McArthur, Barbara E. +1 more
We present absolute parallaxes and proper motions for seven members of the Hyades open cluster, pre-selected to lie in the core of the cluster. Our data come from archival astrometric data from fine guidance sensor (FGS) 3 and newer data for three Hyads from FGS 1r, both white-light interferometers on the Hubble Space Telescope (HST). We obtain me…
The WHI Corona from Differential Emission Measure Tomography
Frazin, Richard A.; Huang, Zhenguang; Vásquez, Alberto M. +1 more
A three-dimensional (3D) tomographic reconstruction of the local differential emission measure (LDEM) of the global solar corona during the whole heliosphere interval (WHI, Carrington rotation CR 2068) is presented, based on STEREO/EUVI images. We determine the 3D distribution of the electron density, mean temperature, and temperature spread, in t…
Attenuation of radio signals by the ionosphere of Mars: Theoretical development and application to MARSIS observations
Withers, Paul
We investigate the ionospheric conditions required to explain Mars Express Mars Advanced Radar for Subsurface and Ionosphere Sounding topside radar sounder observations of ionospheric attenuation in excess of 13 dB at 5 MHz during solar energetic particle events. We develop theoretical expressions for the attenuation caused by a layer of ionospher…
Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfvén turbulence
de Keyser, J.; Voitenko, Y.
A weakly dispersive range (WDR) of kinetic Alfvén turbulence is identified and investigated for the first time in the context of the MHD/kinetic turbulence transition. We find perpendicular wavenumber spectra ∝ k\bot-3 and ∝ k\bot-4 formed in WDR by strong and weak turbulence of kinetic Alfvén waves (KAW…
The nature of X-ray-absorbed quasi-stellar objects
Ebrero, J.; Page, M. J.; Stevens, J. A. +2 more
There exists a significant population of broad line, z∼ 2 quasi-stellar objects (QSOs) which have heavily absorbed X-ray spectra. Follow-up observations in the submillimetre show that these QSOs are embedded in ultraluminous starburst galaxies, unlike most unabsorbed QSOs at the same redshifts and luminosities. Here we present X-ray spectra from X…
Possible Evidence for a Fisk-type Heliospheric Magnetic Field. I. Analyzing Ulysses/KET Electron Observations
Fichtner, H.; Scherer, K.; Ferreira, S. E. S. +6 more
The propagation of energetic charged particles in the heliospheric magnetic field is one of the fundamental problems in heliophysics. In particular, the structure of the heliospheric magnetic field remains an unsolved problem and is discussed as a controversial topic. The first successful analytic approach to the structure of the heliospheric magn…