Search Publications
Transient Structures and Stream Interaction Regions in the Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO HI and Venus Express ASPERA-4 Measurements
Grande, M.; Harrison, R. A.; Davies, J. A. +7 more
We discuss the detection and evolution of a complex series of transient and quasi-static solar-wind structures in the days following the well-known comet 2P/Encke tail disconnection event in April 2007. The evolution of transient solar-wind structures ranging in size from <105 km to >106 km was characterised using one-m…
Modeling Total Solar Irradiance Variations Using Automated Classification Software on Mount Wilson Data
Ulrich, R. K.; Parker, D.; Bertello, L. +1 more
We present the results using the AutoClass analysis application available at NASA/Ames Intelligent Systems Div. (2002) which is a Bayesian, finite mixture model classification system developed by Cheeseman and Stutz (1996). We apply this system to Mount Wilson Solar Observatory (MWO) intensity and magnetogram images and classify individual pixels …
Deflection of Coronal Rays by Remote CMEs: Shock Wave or Magnetic Pressure?
Srivastava, A. K.; Filippov, Boris
We analyze five events of the interaction of coronal mass ejections (CMEs) with the remote coronal rays located up to 90° away from the CME as observed by the SOHO/LASCO C2 coronagraph. Using sequences of SOHO/LASCO C2 images, we estimate the kink propagation in the coronal rays during their interaction with the corresponding CMEs ranging from 180…
Spiky Fine Structure of Type III-like Radio Bursts in Absorption
Yan, Y. H.; Fu, Q. J.; Chen, B. +2 more
An uncommon fine structure in the radio spectrum consisting of bursts in absorption was observed with the Chinese Solar Broadband Radiospectrometer (SBRS) in the frequency range of 2.6 - 3.8 GHz during an X3.4/4B flare on 13 December 2006 in active region NOAA 10930 (S05W33). Usual fine structures in emission such as spikes, zebra stripes, and dri…
An Analytical Model to Predict the Arrival Time of Interplanetary CMEs
Song, W. B.
Referring to the aerodynamic drag force, we present an analytical model to predict the arrival time of coronal mass ejections (CMEs). All related calculations are based on the expression for the deceleration of fast CMEs in the interplanetary medium (ICMEs), \dot{v}=-1/15 700(v-V_{SW})2 , where VSW is the solar wind speed. Th…
The Influence of Solar Flares on the Lower Solar Atmosphere: Evidence from the Na D Absorption Line Measured by GOLF/SOHO
Kretzschmar, M.; Dudok de Wit, T.; Cessateur, G. +1 more
Solar flares presumably have an impact on the deepest layers of the solar atmosphere and yet the observational evidence for such an impact is scarce. Using ten years of measurements of the Na D1 and Na D2 Fraunhofer lines, measured by GOLF onboard SOHO, we show that this photospheric line is indeed affected by flares. The eff…
EUV Spectra of the Full Solar Disk: Analysis and Results of the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)
Hurwitz, M.; Sirk, M. M.; Marchant, W.
We analyze EUV spectra of the full solar disk from the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spanning a period of two years. The observations were obtained via a fortuitous off-axis light path in the 140 - 275 Å passband. The general appearance of the spectra remained relatively stable over the two-year time period, but did show sign…
A Model for the Stray-Light Contamination of the UVCS Instrument on SOHO
Cranmer, S. R.; Kohl, J. L.; Gardner, L. D.
We present a detailed model of stray-light suppression in the spectrometer channels of the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. The control of diffracted and scattered stray light from the bright solar disk is one of the most important tasks of a coronagraph. We compute the fractions of light that diffract past the U…
Orientation of X-Ray Bright Points in the Quiet Sun
Kano, R.; Tsuneta, S.; Shibahashi, H. +1 more
Thanks to the high-resolution images from the X-ray telescope (XRT) aboard the Hinode satellite, X-ray bright points (XBPs) in the quiet region of the Sun are resolved and can be seen to have complex loop-like structures. We measure the orientation of such loop structures for 488 XBPs picked up in 26 snapshot X-ray images near the disk center. The…
Constraining Coronal Heating: Employing Bayesian Analysis Techniques to Improve the Determination of Solar Atmospheric Plasma Parameters
Walsh, Robert W.; Adamakis, Sotiris; Morton-Jones, Anthony J.
One way of revealing the nature of the coronal heating mechanism is by comparing simple theoretical one-dimensional hydrostatic loop models with observations at the temperature and/or density structure along these features. The most well-known method for dealing with comparisons like that is the χ2 approach. In this paper we consider th…