The frequency of solar flares and CMEs tracks with the solar cycle. As many as 25 solar flares may occur per day during the maximum phase of the solar cycle. At solar minimum, it may take six months or more for 25 flares to occur. CME frequency varies from about five per day near solar maximum to one per week or longer at solar minimum.

Many CMEs observed lifting off the Sun miss Earth due to the CME’s direction of travel.

Geospace is the volume of space that surrounds Earth, influenced by the Earth’s magnetic field in the solar wind. If Earth did not have a magnetic field, the solar wind would blow past unimpeded, affected only by the mass of Earth and its atmosphere. Earth’s magnetic field extends outward in all directions. This forms a cocoon for the planet, protecting it from the flow of the solar wind. The cocoon is called the magnetosphere. The magnetosphere typically extends towards the Sun about 10 Earth radii on the day side and stretches away from the Sun many times more on the night side. The shape is similar to a comet tail, with it being extended during strong solar wind conditions and less during quieter times. On its flanks, the magnetosphere extends outward roughly 20 Earth radii in the dawn and dusk sectors.

The magnetosphere deflects most of the energy carried by the solar wind, while making a fraction of it available to be absorbed by the near-Earth system. When the Sun is active and CMEs interact with Earth, the additional energy disrupts the magnetosphere, resulting in a magnetic storm. Then, over time, the magnetosphere adjusts through various processes and once more returns to normal.

The most visible manifestation of the energy being absorbed from the solar wind into the magnetosphere is the aurora, both in the Northern and Southern Hemispheres. The aurora occurs when accelerated electrons, and sometimes protons, from the Sun follow the magnetic field of Earth down to the polar regions, where they collide with oxygen and nitrogen atoms and molecules in Earth’s upper atmosphere. In these collisions, the electrons transfer their energy to the atmosphere, thus exciting the atoms and molecules to higher energy states. When they relax to lower energy states, they release their energy in the form of light. Simply put, the more energy in the solar wind, the brighter and more widespread the aurora glow becomes.

Nearer to Earth is another region called the ionosphere. It is a shell of weak plasma, where electrons and ions exist embedded in the neutral atmosphere. The ionosphere begins at roughly 80 km in altitude and extends out many Earth radii, at the topside.

Extreme Ultraviolet (EUV) solar emissions create the ionosphere by ionizing the neutral atmosphere. The electrons and ions created by this process then engage in chemical reactions that progress faster in the lower ionosphere. The ionosphere changes significantly from day to night. When the Sun sets, chemical processes, together with other dynamic processes, allow some of the ionization to remain until the new day brings the solar EUV once again. An important point is that the energy that comes from the Sun in the solar wind makes its way to the ionosphere, where it alters the ambient conditions during space weather storms.

Galactic Cosmic Rays, more commonly known as GCR, is a consequence of distant supernovae raining charged particles, heavy ions, protons, and electrons onto the inner heliosphere. The abundance of GCR is inversely rated to the solar cycle. At solar maximum, when the solar wind flow is turbulent and strong, the GCR flux is inhibited and therefore low. At solar minimum, the GCR flux increases by about 25 percent in the near-Earth environment. When high-energy GCR enter Earth’s atmosphere, it creates a cascade of interactions resulting in a range of secondary particles, including neutrons that make their way to Earth’s surface.

Geomagnetic storms are strong disturbances to Earth’s magnetic field in the solar wind. These storms pose problems for many activities, technological systems, and critical infrastructure. The topology of Earth’s magnetic field changes in the course of a storm, as the near-Earth system attempts to adjust to the jolt of energy from the Sun. CMEs and the shocks they drive are often the causative agent and can send the geomagnetic field into a disturbed state.

The most obvious and probably the only pleasing attribute of an energized geomagnetic field is the auroras. Geomagnetic storms tend to brighten auroras and allow them to move equatorward.

The duration of geomagnetic storms is usually on the order of days. The strongest storms may persist for almost one week. A string of CMEs may cause prolonged disturbed periods related to the additional energy being pumped toward the Earth.

Although the frequency of geomagnetic storms reflects the solar cycle, a closer look shows a bimodal distribution. Large numbers of storms cluster at solar maximum resulting from frequent CMEs, and again in the declining phase due to high-speed solar wind streams. Typically, the most intense storms occur near solar maximum, with weaker storms occurring during the declining phase.

Solar radiation storms occur when large quantities of charged particles, primarily protons, are accelerated by processes at or near the Sun and then bathe the near-Earth environment with these charged particles. These particles cause an increase in the radiation dose to humans and increase the possibility of single-event upsets in electronics. Earth’s magnetic field and atmosphere offer some protection from this radiation, but protection decreases with altitude, latitude, magnetic field strength, and direction. The polar regions on Earth are the most open to these charged particles. The magnetic field lines at the poles extend vertically downwards, intersecting Earth’s surface. This allows the particles to spiral down the field lines and penetrate into the atmosphere and increase the ionization.

A significant factor related to the criticality of the radiation increase at Earth is the energy distribution of the solar protons. Protons of varying energies will bathe Earth as a function of the site of the eruption at the Sun and the magnetic connection between the Sun and Earth. High-energy protons cause radiation dose increases that are of concern to human beings. Lower energy protons have little effect on humans but have a severe impact on the polar ionosphere.

The duration of solar radiation storms is a function of the magnitude of the solar eruption as well as the energy level of protons. For events that are of a large magnitude but low energy, the duration may last for one week. Events that are of high energy may last for only a few hours. Diversity in the duration of solar radiation storms exists, just as there are many factors that contribute to the acceleration and propagation of the charged particles near Earth.

Solar radiation storms can occur at any point in the solar cycle but tend to be most common during the years around solar maximum.