Hello,

That is an excellent question! Scientists use a lot of different terms to describe specific phenomena observed on the Sun and in Earth's magnetosphere. It can get pretty confusing to people who are not scientists. Sometimes it is even confusing to us scientists too!

One term that you see a lot on the Internet is "solar storm." I don't use this term in my own research, but I think it is an acceptable term to collectively refer to the various types of solar activity, such as coronal mass ejections (CMEs), solar flares, etc. that we observe on the Sun.

Unfortunately, I think the term "solar storm" is so catchy and easy to remember that there is a tendency for people to lump all kinds of space weather into the category of "solar storms," including the types of magnetic activity that happen inside the region of space affected by the Earth's magnetic field. I think it is important for people to understand the distinction between "solar storms" which happen on the Sun, and the activity we see here on Earth.

Scientists generally use the terms "magnetic storm" or "geomagnetic storm" (geo = Earth) to describe the disturbance that happens within the region of space affected by the Earth's magnetic field (the magnetosphere) in response to a "solar storm." All geomagnetic storms are caused by a solar storm of some kind, but not all solar storms cause a geomagnetic storm. Solar storms such as coronal mass ejections (CMEs) or high speed solar wind streams only cause geomagnetic storms when they are directed towards the Earth.

Scientists look at solar activity and magnetic field data from ground stations and satellites orbiting the Earth to determine whether or not a geomagnetic storm is occuring. When CMEs and high speed solar wind streams interact with the Earth's magnetic field (or magnetosphere), they can cause a build-up of high energy electrons and protons in the Earth's Van Allen radiation belts and the development of an electrical current circling the Earth called the ring current. The ring current produces a magnetic field that is opposite to the Earth's magnetic field, so scientists have developed a geomagnetic index called the Dst (Disturbance Storm Time) index from magnetic field variations measured on Earth. When the Dst index has large, negative values, we know that the ring current is very strong and we are in the middle of a geomagnetic storm. A variety of geomagnetic activity can happen during a geomagnetic storm, including displays of aurora at much lower than normal latitudes.

Scientists generally refer to both solar storms and geomagnetic storms as being different types of "space weather."

Kris