It has been known for many decades that the appearance of sunspots is roughly periodic, with an average cycle of eleven years. Moreover, the incidence of solar flares and the flux of solar cosmic rays, ultraviolet radiation, and X-radiation all vary directly with the sunspot cycle. But after more than a century of investigation, the relation of these and other phenomena, known collectively as the solar-activity cycle, to terrestrial weather and climate remains unclear. For example, the sunspot cycle and the allied magnetic-polarity cycle have been linked to periodicities discerned in records of such variables as rainfall, temperature, and winds. Invariably, however, the relation is weak, and commonly of dubious statistical significance.
Effects of solar variability over longer terms have also been sought. The absence of recorded sunspot activity in the notes kept by European observers in the late seventeenth and early eighteenth centuries has led some scholars to postulate a brief cessation of sunspot activity, at that time (a period called the Maunder min/mum). The Maunder minimum has been linked to a span of unusual cold in Europe extending from the sixteenth to the early nineteenth centuries. The reality of the Maunder minimum has yet to be established, however, especially since the records that Chinese naked-eye observers of solar activity made at that time appear to contradict it. Scientists have also sought evidence of long-term solar periodicities by examining indirect climatological data, such as fossil records of the thickness of ancient tree rings. These studies, however, failed to link unequivocally terrestrial climate and the solar-activity cycle, or even to confirm the cycle’s past existence
If consistent and reliable geological, or archaeological and climatological evidence tracing the solar-activity cycle in the distant past could he found, it might also resolve an important issue in solar physics: how to model solar activity. Currently, there are two models of solar activity. The first supposes that the Sun's internal motions (caused by rotation and convection) interact with its large-scale magnetic field to produce a dynamo, a device in which mechanical energy is converted into the energy of a magnetic field. In short the Sun’s large-scale magnetic field is taken to be self-sustaining, so that the solar-activity cycle it drives would be maintained with little overall change for perhaps billions of years. The alternative, explanation supposes that the Sun’s large-scale magnetic field is a remnant of the field the Sun acquired when it formed,and is not sustained against decay. In this model, the solar mechanism dependent on the Sun's magnetic field runs down more quickly. Thus, the characteristics of the solar-activity cycle would be expected to change over a long period of time. Modern solar observations span too short a time to reveal whether present cyclical Solar-activity is a long-lived feature of the Sun, or merely a transient phenomenon.
1.The author focuses primarily on( ).
2.Which of the following statements about the two models of solar activity is accurate?
3.According to the passage, late seventeenth and early eighteenth-century Chinese records are important for which of the following reasons?
4.It can be inferred from the passage that the argument in favor of the first model would be strengthened if which of the following were found to be true?
问题1选项
A.presenting two competing scientific theories concerning solar activity and evaluating geological evidence often cited to support them
B.giving a brief overview of some recent scientific developments in solar physics and assessing their impact on future climatological research
C.discussing the difficulties involved in linking terrestrial phenomena with solar activity and indicating how resolving that issue could have an impact on our understanding of solar physics
D.outline the specific reasons why a problem in solar physics has not yet been solved and fault the overly theoretical approach of modern physicists
问题2选项
A.In both models cyclical solar activity is regarded as a long-lived feature of the Sun, persisting with little change over billions of years.
B.In both models the solar-activity cycle is hypothesized as being dependent on the large-scale solar magnetic field.
C.In one model the Sun’s magnetic field is thought to play a role in causing solar activity, whereas in the other model it is not.
D.In one model solar activity is presumed to be unrelated to terrestrial phenomena, whereas in the other model solar activity is thought to have observable effects on the Earth.
问题3选项
A.They suggest that the data on which the Maunder minimum was predicated were incorrect.
B.They suggest that the Maunder minimum might be valid only for Europe.
C.They establish the existence of a span of unusually cold weather worldwide at the time of the Maunder minimum.
D.They establish that solar activity at the time of the Maunder minimum did not significantly vary from its present pattern.
问题4选项
A.Episodes of intense volcanic eruptions in the distant past occurred in cycles having very long periodicities.
B.At the present time the global level of thunder-storm activity increases and decreases in cycles with periodicities of approximately 11 years.
C.In the last century the length of the sunspot cycle has been known to vary by as much as 2 years from its average periodicity of 11 years.
D.Hundreds of millions of years ago, solar-activity cycles displayed the same periodicities as do present-day solar-activity cycles.
第1题:
主旨大意题。文章主要讲解的是人们将太阳活动极小期与欧洲16世纪至19世纪初期不同寻常的低温联系起来,但是太阳活动极小的真实性还有待考查,如果同意可靠的地质、考古和气象证据能够与远古时代的太阳活动周期挂钩,也许可以帮助理解和确定太阳活动的两种模式。A选项 “指出有关太阳活动的两种相对的科学理论并对其各自的地质依据进行评价”,B选项 “简要概述近期科学在太阳物理学方面的发展并且就他们对未来气候研究的影响做出评价”,C选项 “讨论将地球上的各种现象与太阳活动联系起来的困难性并指出问题的解决方法影响着我们对太阳物理活动的理解”,D选项“概述有关太阳物理的问题之所以一直没解决的原因并且对现代物理学家过度理论化的方法进行指责”,C选项正确。
第2题:
推理判断题。文章对太阳活动的两种模式的介绍主要集中在文章的第三段。根据第三段中的 “In short, the Sun’s large-scale magnetic field is taken to be self-sustaining, so that the solar-activity cycle it drives would be maintained with little overall change for perhaps billions of years. 简而言之,太阳大范围的磁场是自给自足的,因此与之相关的太阳活动周期将会在几十亿年内维持基本不变。” 可知在第一种模式中,太阳活动的周期是与太阳大范围的磁场相关的并且太阳活动周期是可以长期维持基本不变的。根据第三段中的 “In this model, the solar mechanism dependent on the Sun’s magnetic field runs down more quickly. Thus, the characteristics of the solar-activity cycle would be expected to change over a long period of time. 在这种模式中,与太阳磁场相关的太阳机制变化更快,因此,太阳活动周期的特点也会在很长一段时间后有所变化”可知在第二种模式中太阳活动的周期也是和太阳磁场相关的,但是太阳活动周期是会有所变化的。所以A选项和C选项错误,排除;B选项正确。D选项文章中没有提及,排除。
第3题:
细节事实题。根据文章第二段中的“The reality of the Maunder minimum has yet to be established, however especially since the records that Chinese naked-eye observers of solar activity made at that time appear to contradict it. 太阳活动极小期的真实性还有待考证,特别是中国当时肉眼观察到的太阳活动的记录又与其相矛盾。”可知A选项“他们认为,蒙德极小期所依据的数据是不正确的。”是中国17世纪末期至18世纪早期的记录的重要性的原因。
第4题:
推理判断题。根据第三段中“In short, the Sun’s large-scale magnetic field is taken to be self-sustaining, so that the solar-activity cycle it drives would be maintained with little overall change for perhaps billions of years. 简而言之,太阳大范围的磁场是自给自足的,因此与之相关的太阳活动周期将会在几十亿年内维持基本不变。”可知选项D “数亿年前太阳活动的周期性特征和如今太阳活动的周期性相同”是对第一种模式的支持。