Engineering topics

Zhao, X.

Publications and source records attributed to Zhao, X..

22 records · Page 2

NASA NTRS1995

Comparison of Yohkoh x-ray coronal events with Ulysses interplanetary events

The Yohkoh soft X-ray telescope (SXT) has observed several largescale eruptive events per year for the first three years of observations (Aug. 1991 - Nov. 1994) Such events are most prominent at high latitudes, but resemble long-duration flare events seen in active regions. Some of the high-latitude events have now been identified in the Ulysses/SWICS data base during the Ulysses south polar passage. There are puzzling examples of solar events with no interplanetary counterparts. A comparison of coronal and interplanetary events can lead to better models for mapping interplanetary disturbances back to their source location, especially by combining Yohkoh morphology with three-dimensional representations of the coronal magnetic field. In this paper we describe the parameters of the hot plasma seen by SXT. There is clear evidence for non radial motion in specific events. We present comparisons between the ionization temperature of the interplanetary plasma with that observed at the Sun in cases where this is possible.

Lemen, J. R.↗

NASA NTRS1995

Inference of 3-dimensional structure underlying large-scale coronal events observed by Yohkoh and Ulysses

The Yohkoh/SXT images provide full-disk coverage of the solar corona, usually extending before and after one of the large-scale eruptive events that occur in the polar crown These produce large arcades of X-ray loops, often with a cusp-shaped coronal extension, and are known to be associated with coronal mass ejections. The Yohkoh prototype of such events occurred 12 Nov. 1991. This allows us to determine heights from the apparent rotation rates of these structures. In comparison v with magnetic-field extrapolations from Wilcox Solar Observatory. use use this tool to infer the three dimensional structure of the corona in particular cases: 24 Jan. 1992, 24 Feb. 1993, 14 Apr. 1994, and 13 Nov. 1994. The last event is a long-duration flare event.

Slater, G. L.↗

NASA NTRS1992

A shocked-Bz event caused by fast steady flow-slow transient flow interaction

We show that the 25 November 1978 shock pair was caused by the interaction of a fast steady flow with a slow coronal mass ejection in interplanetary space (ICME). It is suggested that the slow ICME may be disconnected from the sun. In addition, a new method to infer the shock angle and Mach number from the observed upstream plasma beta and the jump ratios of proton density and magnetic flux density across a shock is described.

Zhao, X.↗

NASA NTRS1992

Prediction of large North-South IMF component events occurring in driver gas

An approach for identifying a driver gas-associated Bz event and its solar source is introduced. Seven newly identified events are used to further test the model developed by Hoeksema and Zhao (1991) for prediction of the magnetic orientation of some driver gas-associated Bz events from photospheric field observations. Comparison of the model predictions with observations confirms that the model may be appropriate only for driver gas-associated Bz events which have magnetic structures lacking large internal field rotation and are associated with active region-CMEs.

Zhao, X.↗