Solar wind-magnetosphere interaction as simulated by a 3-D em particle code

We have studied the solar wind-magnetosphere interaction using a 3-D electromagnetic particle code. The results for an unmagnetized solar wind plasma streaming past a dipole magnetic field show the formation of a magnetopause and a magnetotail, the penetration of energetic particles into cusps and radiation belt and dawn-dusk asymmetries. The effects of interplanetary magnetic field (IMF) have been investigated in a similar way as done by MHD simulations. The simulation results with a southward IMF show the shrunk magnetosphere with great particle entry into the cusps and nightside magnetosphere. This is a signature of a magnetic reconnection at the dayside magnetopause. After a quasi-stable state is established with an unmagnetized solar wind we switched on a solar wind with an northward IMF. In this case the significant changes take place in the magnetotail. The waving motion was seen in the magnetotail and its length was shortened. This phenomena are consistent with the reconnections which occur at the high latitude magnetopause. In our simulations kinetic effects will determine the self-consistent anomalous resistivity in the magnetopause that causes reconnections.Deceased January 24, 1993; R. Bunemanet al. 1993.     

Solar wind interactions with Comet 19P/Borrelly

The Plasma Experiment for Planetary Exploration (PEPE) made detailed observations of the plasma environment of Comet 19P/Borrelly during the Deep Space 1 (DS1) flyby on September 22, 2001. Several distinct regions and boundaries have been identified on both inbound and outbound trajectories, including an upstream region of decelerated solar wind plasma and cometary ion pickup, the cometary bow shock, a sheath of heated and mixed solar wind and cometary ions, and a collisional inner coma dominated by cometary ions. All of these features were significantly offset to the north of the nucleus-Sun line, suggesting that the coma itself produces this offset, possibly because of well-collimated large dayside jets directed 8°-10° northward from the nucleus as observed by the DS1 MICAS camera. The maximum observed ion density was 1640 ion/cm³ at a distance of 2650 km from the nucleus while the flow speed dropped from 360 km/s in the solar wind to 8 km/s at closest approach. Preliminary analysis of PEPE mass spectra suggest that the ratio of CO⁺/H₂O⁺ is lower than that observed with Giotto at 1P/Halley.     

Low-frequency solar radiophysics with LOFAR and FASR

Low-frequency radio observations offer unique diagnostics of the solar corona and solar wind. After a prolongued hiatus, there is renewed interest in this important frequency regime. Two new ground-based instruments will provide critical new low-frequency observations: the low-frequency array (LOFAR) and the frequency agile solar radiotelescope (FASR). This brief topical review summarizes low-frequency radio phenomena that will be accessible to detailed study by LOFAR and FASR in the coming decade. Energy release, drivers of space weather, and studies of the solar wind are emphasized. Both instruments are expected to play important roles in both basic research problems and national and international space weather capabilities. While FASR is a solar-dedicated instrument, LOFAR is not. Solar observing requirements for LOFAR are briefly discussed.     

冕洞观测研究的近期进展

简要介绍了在１９８８－１９９５年期间冕洞观测研究的主要进展。文中共分五个方面：１．冕洞磁场观测研究的新进展；２．冕洞在太阳活动周不同位相时的规律性；３．冕洞区高速太阳风观测的新结果；４．冕洞加热问题；５．存在问题。     

叠加在微波爆发上的快速尖峰群事件

本文介绍了北京天文台观测到的太阳射电10厘米波段的毫秒级快速精细结构(FFS)中一类有长持续时间的尖峰(我们称毫秒时标记录上陡升陡降图形为“尖峰”,称秒级时标的记录上的陡升陡降图形为“脉冲”)群事件。这一类微波毫秒尖峰群(MMS)事件具有一系列显著的特点: 1)它在秒级时间常数的慢速记录上常常对应一8S型(持续时间小于1分钟的脉冲)的爆发。因而利用脉冲的频谱特性,对这一类微波爆发中的毫秒精细结构的特征及可能的机制进行探讨,以弥补目前只能在一个波段上观测FFS事件的缺陷。 2)这一类脉冲爆发具有从低频向高频的频漂(正的频漂),而且频漂的速率随频率带增加而增加。 3)脉冲的幅度在波长8—10厘米间受到强烈的衰减。 4)脉冲群中的每一脉冲的极大频率及起始频率从高频逐渐移向低频,意昧着激发源逐渐上升。估计上升速度约为50公里/秒。 5)这类脉冲常常出现在有δ型磁结构、最大磁场强度大于2500高斯的复杂活动区中,可能有不同级别的耀斑与之对应。 6)这类脉冲与硬X线爆发事件、分米波段快速频漂事件及“BLIPS”事件见文[7]有密切的关系。 7)这一类微波快速尖峰群事件可以解释为来自耀斑-爆发事件中形成的电子加速中心的快速非热电子流向下运动穿入一耀斑环激起的电子迴旋脉泽辐射。     

Blowing in the wind. II. Creation and redistribution of refractory inclusions in a turbulent protoplanetary nebula

Ca-Al rich refractory mineral inclusions (CAIs) found at 1-6% mass fraction in primitive chondrites appear to be 1-3 million years older than the dominant (chondrule) components which were accreted into the same parent bodies. A prevalent concern is that it is difficult to retain CAIs for this long against gas-drag-induced radial drift into the Sun. We reassess the situation in terms of a hot inner (turbulent) nebula context for CAI formation, using analytical models of nebula evolution and particle diffusion. We show that outward radial diffusion in a weakly turbulent nebula can overcome inward drift, and prevent significant numbers of CAI-size particles from being lost into the Sun for times on the order of 10⁶ years. CAIs can form early, when the inner nebula was hot, and persist in sufficient abundance to be incorporated into primitive planetesimals at a much later time. Small (?0.1 mm diameter) CAIs persist for longer times than large (?5 mm diameter) ones. To obtain a quantitative match to the observed volume fractions of CAIs in chondrites, another process must be allowed for: a substantial enhancement of the inner hot nebula in silicate-forming material, which we suggest was caused by rapid inward drift of meter-sized objects. This early in nebula history, the drifting rubble would have a carbon content probably an order of magnitude larger than even the most primitive (CI) carbonaceous chondrites. Abundant carbon in the evaporating material would help keep the nebula oxygen fugacity low, plausibly solar, as inferred for the formation environment of CAIs. The associated production of a larger than canonical amount of CO₂ might also play a role in mass-independent fractionation of oxygen isotopes, leaving the gas rich in ¹⁶O as inferred from CAIs and other high temperature condensates.     

Gravity Anomaly During the Mohe Total Solar Eclipse and New Constraint on Gravitational Shielding Parameter

By using a high-precision LaCoste-Romberg gravimeter, continuous and precise measurements were carried out during the March 9, 1997 total solar eclipse in Mohe region in Northeast China. The gravity variations were digitally recorded during the total solar eclipse so as to investigate the possible anomaly of the Sun and the Moon's gravitational fields on the Earth. After the careful processing and analysis of the observed data, no significant anomaly during the very solar eclipse was found. However, there are two ‘gravity anomaly valleys’ with near symmetrical decrease of about 6 ∼ 7 μg at the first contact and the last contact. This is the anomaly phenomenon observed and reported for the first time in the literature. This paper is intended to explain the observed anomaly by conducting the tilt experiment due to the thermal stress and temperature change in the solar eclipse. A new constraint limit on gravitational shielding is thus obtained. Some analysis and discussions are presented although further studies and research are highly needed. This revised version was published online in July 2006 with corrections to the Cover Date.