Editing Solar wind (section)

===Magnetospheres===
{{Main|Magnetosphere}}
[[File:Structure_of_the_magnetosphere_LanguageSwitch.svg|lang=en|thumb|upright=1.5|Schematic of Earth's [[magnetosphere]]. The solar wind flows from left to right.]]

Where the solar wind intersects with a planet that has a well-developed [[magnetic field]] (such as Earth, Jupiter or Saturn), the particles are deflected by the [[Lorentz force]]. This region, known as the [[magnetosphere]], causes the particles to travel around the planet rather than bombarding the atmosphere or surface. The magnetosphere is roughly shaped like a [[Sphere|hemisphere]] on the side facing the Sun, then is drawn out in a long wake on the opposite side. The boundary of this region is called the [[magnetopause]], and some of the particles are able to penetrate the magnetosphere through this region by partial reconnection of the magnetic field lines.<ref name="encrenaz" />

[[File:Solar Wind and Earth's magnetic field.png|thumb|Noon meridian section of magnetosphere]]

The solar wind is responsible for the overall shape of Earth's magnetosphere. Fluctuations in its speed, density, direction, and [[Interplanetary magnetic field|entrained magnetic field]] strongly affect Earth's local space environment. For example, the levels of ionizing radiation and radio interference can vary by factors of hundreds to thousands; and the shape and location of the magnetopause and bow [[shock wave]] upstream of it can change by several Earth radii, exposing [[Geosynchronous orbit|geosynchronous]] satellites to the direct solar wind. These phenomena are collectively called [[space weather]].

From the [[European Space Agency]]'s [[Cluster II (spacecraft)|Cluster]] mission, a new study has taken place that proposes that it is easier for the solar wind to infiltrate the magnetosphere than previously believed. A group of scientists directly observed the existence of certain waves in the solar wind that were not expected. A recent study shows that these waves enable incoming charged particles of solar wind to breach the magnetopause. This suggests that the magnetic bubble forms more as a filter than a continuous barrier. This latest discovery occurred through the distinctive arrangement of the four identical Cluster spacecraft, which fly in a controlled configuration through near-Earth space. As they sweep from the magnetosphere into interplanetary space and back again, the fleet provides exceptional three-dimensional insights on the phenomena that connect the sun to Earth.

The research characterised variances in formation of the [[interplanetary magnetic field]] (IMF) largely influenced by [[Kelvin–Helmholtz instability]] (which occur at the interface of two fluids) as a result of differences in thickness and numerous other characteristics of the boundary layer. Experts believe that this was the first occasion that the appearance of Kelvin–Helmholtz waves at the magnetopause had been displayed at high latitude downward orientation of the IMF. These waves are being seen in unforeseen places under solar wind conditions that were formerly believed to be undesired for their generation. These discoveries show how Earth's magnetosphere can be penetrated by solar particles under specific IMF circumstances. The findings are also relevant to studies of magnetospheric progressions around other planetary bodies. This study suggests that Kelvin–Helmholtz waves can be a somewhat common, and possibly constant, instrument for the entrance of solar wind into terrestrial magnetospheres under various IMF orientations.<ref>NASA Study Using Cluster Reveals New Insights Into Solar Wind, NASA, Greenbelt, 2012, p.1</ref>