Auroras are a product of electrically charged particles hitting Earth's atmosphere at the poles, where the geomagnetic field is weaker (where magnetic lines originate). How can a strong solar wind produce auroras at lower latitudes?
Asked
Active
Viewed 107 times
1 Answers
0
The Earth's magnetic field is a tilted dipole and the side facing the Sun is compressed due to the incident solar wind. The anti-sunward side is stretched for reasons similar to why flags wave in the wind. The strength of the dayside(nightside) compression(stretching) depends upon the magnetic field geometry of the solar wind and the solar wind dynamic pressure. That is, larger dynamic pressures change the geometry of Earth's magnetosphere.
The aurora, as you say, is due to charged particles interacting with neutral particles in Earth's atmosphere and exciting the electrons in orbit about their nuclei. When the electrons de-excite, they give off photons (more details here https://physics.stackexchange.com/a/382414/59023). The particles incident on the atmosphere are subject to the Lorentz force, which means they generally only get down to neutral atmospheric altitudes if they are somewhat energetic and move parallel/anti-parallel to the Earth's magnetic field. The auroral oval is basically the boundary between magnetic field lines that connect directly to the solar wind magnetic field and those field lines that are closed internally to the Earth. This boundary moves depending upon the geometry of the Earth's field, which depends upon the solar wind.
How can a strong solar wind produce auroras at lower latitudes?
Generally, faster solar wind flow tends to increase the size of the auroral oval and/or move it further south geographically. The magnitude of either of these effects depends upon the magnetic field of the solar wind and the solar wind dynamic pressure.
honeste_vivere
- 16,028