Perseids 1901-2100
Conclusion
We considered predictions of Perseid activity for the period 1901-2100. These predictions were very compact and described only the most important characteristics of expected activity. Nevertheless, we can underline some features. First, almost all observed Perseid activity is connected not with trail encounters, but with background particles. In fact, for the considered period we found only three years with substantial activity from trails - 1980, 2004 and 2028. The reason is that the trails of last 9 revolutions are mostly situated in the interval +0.01 - +0.02 AU from the Earth orbit. Such distances were typical for the orbit of comet 109P beginning (at least) from 950 perihelion and ending at 1862 perihelion. This let us to assume, that the core of Perseid stream is located in this interval, and the Earth usually passes through its outer areas, which are though still capable to produce quite significant in standart measures activity. This situation is schematically presented on the Fig 1.
We considered predictions of Perseid activity for the period 1901-2100. These predictions were very compact and described only the most important characteristics of expected activity. Nevertheless, we can underline some features. First, almost all observed Perseid activity is connected not with trail encounters, but with background particles. In fact, for the considered period we found only three years with substantial activity from trails - 1980, 2004 and 2028. The reason is that the trails of last 9 revolutions are mostly situated in the interval +0.01 - +0.02 AU from the Earth orbit. Such distances were typical for the orbit of comet 109P beginning (at least) from 950 perihelion and ending at 1862 perihelion. This let us to assume, that the core of Perseid stream is located in this interval, and the Earth usually passes through its outer areas, which are though still capable to produce quite significant in standart measures activity. This situation is schematically presented on the Fig 1.
Рис. 1. Schematic image of the Earth orbit passing through the Perseid stream. The dark-grey colored area is the core of the stream, which is surrounded by the light-grey ring of outer regions, which are usually passed through by the Earth.
This point is confirmed by periodic enhancements in Perseid activity, connected with gravitational influence from Jupiter and Saturn. Jupiter shifts the orbit of Perseid particles appr. 0.01 AU closer to the Earth orbit every 11 years (orbital period of Jupiter) and Saturn makes them 0.01-0.015 AU closer every 30 years (orbital period of Saturn). In these years the Earth passes through denser parts of Perseid stream, closer to its core, which results in 1.5-2.0 times stronger than usual activity.
Such core was formed due to long period of quite stable orbit of comet 109P, which was staying at 0.01-0.02 AU outside the Earth orbit during many hundreds or even thousand years. However, after the last two perihelions the situation changed. In 1862 the orbit of 109P got closer to the Earth's one, the distance became equial appr. 0.01 AU, i.e. it came to the low limit of the stream core, and in 1992 the comet orbit already was at the distance of -0.001 AU, i.e. the point of minimal distance is now inside the Earth orbit. The important consequence of this is that 1992 trail will lie at 0.001-0.003 AU from the Earth orbit, exluding periods with perturbing influence of Jupiter and Saturn. So far in 22 century during appr. 30 years around the next expected 109P perihelion in 2126 many years will be marked with significant outbursts and storms of Perseids. They will be caused by 1 rev. trail encountering the Earth.
We'd like to note again, that all these descriptions are based exceptionally on predictions and no comparisons with real activity (for the period before 2007) were done, as they are considered unnecessary. There are lots of data on historic Perseid activity and those who want to learn them, can do it without especial problems. Also, as this paper is completed in 2006, all predictions for years before 2007 are given in the Past tense, and beginning from the year 2007 - in the Future tense.
Such core was formed due to long period of quite stable orbit of comet 109P, which was staying at 0.01-0.02 AU outside the Earth orbit during many hundreds or even thousand years. However, after the last two perihelions the situation changed. In 1862 the orbit of 109P got closer to the Earth's one, the distance became equial appr. 0.01 AU, i.e. it came to the low limit of the stream core, and in 1992 the comet orbit already was at the distance of -0.001 AU, i.e. the point of minimal distance is now inside the Earth orbit. The important consequence of this is that 1992 trail will lie at 0.001-0.003 AU from the Earth orbit, exluding periods with perturbing influence of Jupiter and Saturn. So far in 22 century during appr. 30 years around the next expected 109P perihelion in 2126 many years will be marked with significant outbursts and storms of Perseids. They will be caused by 1 rev. trail encountering the Earth.
We'd like to note again, that all these descriptions are based exceptionally on predictions and no comparisons with real activity (for the period before 2007) were done, as they are considered unnecessary. There are lots of data on historic Perseid activity and those who want to learn them, can do it without especial problems. Also, as this paper is completed in 2006, all predictions for years before 2007 are given in the Past tense, and beginning from the year 2007 - in the Future tense.