I have been searching for a while, trying to found out how long it takes for the Solar System to transit through interstellar cloud boundaries.

These cloud boundaries are termed, Interface Regions. Well, it seems to be a surprisingly short time-frame - ~500 years. Of course, this is 'best guess'. But, at these Interface Regions theSolar System (Earth) begins to see changes...mainly cosmic ray influx as well as neutral particles changing.

We are seeing exactly those things occurring, as well as other changes and unprecidented findings occurring in the solar environment...



The Sun’s journey through the local interstellar medium: the paleoLISM and paleoheliosphere -

The primary conclusion of this paper is that, over the past several million years, both the galactic environment of the Sun and the heliosphere have been significantly different than they are today. Observational data combined with theoretical studies can be used to reconstruct the three-dimensional distribution of nearby ISM, and predict the times the Sun transitioned between different environments. If we assume a continuously distributed local ISM, within the past ~130,000 ± ~70,000 years, and possibly as recent as ~56,000 years ago, the Sun entered low density partially ionized ISM flowing away from the direction of the Scorpius-Centaurus Association. Sometime within the past ~40,000 years the Sun entered the cloud now surrounding the solar system, the LIC. These estimates rely on topologically simple models of the cluster of local interstellar clouds (CLIC) flowing past the Sun; more elaborate models are discussed elsewhere (Frisch, 1994; Gry, 1996; Mueller et al., 2006, FS06). As the Sun moves through this complex of local interstellar clouds, the boundary conditions of the heliosphere should change by substantial amounts due to changes in cloud temperature, velocity, and opacity-driven variations in the ionization of the surrounding ISM. Prior to that, the Sun was in the low density plasma of the Local Bubble cavity. Between the Local Bubble cavity and the CLIC, the Sun briefly (~500 years) passed through an interface region of some type.
[link to www.astrophys-space-sci-trans.net]
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Our heliosphere is like a protective cocoon being inflated in the interstellar medium by the Sun’s million mph solar wind. As our Sun orbits the center of the galaxy every 225 million years, it bobs in and out of the disk of the galaxy like a horse on a merry–go–round. As it does this, it passes through areas of the interstellar medium that are more and less dense, causing the heliosphere to change in shape and size. Denser areas can compress the heliosphere, while less dense regions allow the bubble to expand. In addition, the strength of the solar wind varies over the Sun’s cycle, "breathing" periodically, also contributing to this.

Understanding how all of these things affect the heliosphere is important so that we can better understand how the heliosphere protects us. It is a crucial layer of protection against dangerous cosmic rays that are harmful to living things. As cosmic rays approach the heliosphere, they are deflected, and the majority of them are not able to pass into the inner Solar System. Fortunately, our Earth’s magnetic field is usually able to shield life on Earth from the remaining cosmic rays. However, astronauts on deep space missions cannot bring the Earth’s protection with them. We must also consider how the heliosphere will protect us in the distant future or how it did protect us in the past. Understanding the heliosphere and how it protects us is part of understanding our home in the galaxy.
[link to www.ibex.swri.edu]

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