• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Physical and chemical processes of the inner coma observed in mid-ultraviolet cometary spectra.
【24h】

Physical and chemical processes of the inner coma observed in mid-ultraviolet cometary spectra.

机译：在中紫外线彗星光谱中观察到的内部昏迷的物理和化学过程。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Accurate measurement of cometary H{dollar}sb2{dollar}O is essential for comparing the compositions and understanding the properties of cometary nuclei. Water production rates {dollar}Qsb{lcub}rm Hsb2O{rcub}{dollar} are easily derived from observations of OH solar resonance fluorescence with the International Ultraviolet Explorer (IUE) satellite. Variable solar activity and several inner coma processes affect the estimates of {dollar}Qsb{lcub}rm Hsb2O{rcub}{dollar} using IUE.; Water photodissociation by solar Lyman-{dollar}alpha{dollar} radiation creates OH(A{dollar}sp2Sigmasp+){dollar} radicals, which quickly decay to OH(X{dollar}sp2Pi){dollar} through spontaneous emission. This "prompt" emission can provide a direct measure of {dollar}Qsb{lcub}rm Hsb2O{rcub},{dollar} if observed at sufficiently high spatial resolution. Spectral observations of comets IRAS-Araki-Alcock (1983 VII) and Tuttle (1980 XIII), differing only in effective spatial resolution, show evidence for OH prompt emission in IRAS-Araki-Alcock.; The scale length of the short-lived molecule S{dollar}sb2{dollar} is re-evaluated from IUE spectra of Comet IRAS-Araki-Alcock. Spectra of other comets are analyzed to determine S{dollar}sb2{dollar} abundances relative to H{dollar}sb2{dollar}O and reveal no other detections of S{dollar}sb2,{dollar} but upper limits comparable to values observed in IRAS-Araki-Alcock. The sole exception is significant: the upper limit on S{dollar}sb2/{dollar}H{dollar}sb2{dollar}O in Comet Austin (1989c{dollar}sb1){dollar} indicates true variation in the relative S{dollar}sb2{dollar} abundance between comets.; Solar resonance fluorescence can create a population inversion of the {dollar}Lambda{dollar}-states of the OH molecule, but ions collisionally quench the inversion to affect both the UV fluorescence and the 18 cm maser emissions. Previous models of the quenching of OH radio emission do not account for both kinds of observations simultaneously, and do not include solar variability or a Swings effect. A quenching model based upon Giotto observations of Comet P/Halley appropriate for IUE observations is developed and compared to results from high resolution IUE spectra.; The solar UV flux determines the photodestruction rates of H{dollar}sb2{dollar}O and OH and affects their spatial density distributions. Lifetimes appropriate to varying levels of solar activity are calculated from cross section measurements and a solar UV flux model. Spatial mapping by IUE of the OH comae of several comets observed at different epochs of solar activity are matched by modeled density distributions. The evolution of {dollar}Qsb{lcub}rm Hsb2O{rcub}{dollar} with respect to heliocentric distance of comets Bradfield (1979X) and Austin (1989c{dollar}sb1){dollar} is determined.
机译：准确测量彗星H {sb2} {O2} O对于比较组成和了解彗星核的性质至关重要。通过国际紫外线探测器（IUE）对OH太阳共振荧光的观察，很容易得出水的生产率{Qsb {lcub} rm Hsb2O {rcub} {dollar}。太阳活动的变化和几种内部昏迷过程会影响使用IUE估算的Qsb {lcub} rm Hsb2O {rcub} {dollar}。太阳L​​yman- {dollar}α{dollar}辐射引起的水光解离产生OH（A {dollar} sp2Sigmasp +）{dollar}自由基，该自由基通过自发辐射迅速衰减为OH（X {dollar} sp2Pi）{dollar}。如果以足够高的空间分辨率观察到，这种“即时”发射可以直接测量Qsb {lcub} rm Hsb2O {rcub}，{dollar}。 IRAS-Araki-Alcock（1983 VII）和Tuttle（1980 XIII）的光谱观察仅在有效空间分辨率上有所不同，显示了IRAS-Araki-Alcock中OH迅速发射的证据。根据彗星IRAS-Araki-Alcock的IUE光谱重新评估了短寿命分子S {dollar} sb2 {dollar}的尺度长度。分析其他彗星的光谱以确定相对于H {dolb} sb2 {dollar} O的S {dollar} sb2 {dollar}丰度，并且没有发现S {dollar} sb2 {dollar}的其他检测值，但上限与观察到的值相当在IRAS-Araki-Alcock。唯一的例外是重大的：奥斯丁彗星（1989c {dollar} sb1）{dollar}中S {dollar} sb2 / {dollar} H {dollar} sb2 {dollar} O的上限表明相对S {dollar } sb2 {dollar}彗星之间的丰度。太阳共振荧光可以使OH分子的{Lambda {Dollar} -states}发生总体反转，但是离子会碰撞猝灭该反转，从而影响UV荧光和18 cm maser发射。以前的OH无线电发射猝灭模型不能同时考虑两种观测结果，并且不包括太阳变化或摇摆效应。建立了基于彗星P / Halley的乔托观测值的IUE观测值的猝灭模型，并将其与高分辨率IUE光谱的结果进行了比较。太阳紫外线通量确定H {sb2} {b} O和OH的光解速率，并影响它们的空间密度分布。根据横截面测量结果和太阳紫外线通量模型，计算出适合变化的太阳活动水平的寿命。通过IUE的OH彗星的空间分布图，可以在模拟的太阳活动不同时期观测到的几颗彗星与模拟的密度分布相匹配。确定了相对于彗星Bradfield（1979X）和Austin（1989c {dollar} sb1）{dollar}的日心中心距离{qsb {lcub} rm Hsb2O {rcub} {dollar}的演变。

著录项

  • 作者

    Budzien, Scott Alan.;

  • 作者单位

    The Johns Hopkins University.;

  • 授予单位 The Johns Hopkins University.;
  • 学科 Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 1992
  • 页码 227 p.
  • 总页数 227
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 天文学;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号