What does this data mean?

This chart provides us with real time data and information regarding the solar wind. The data is collected by the Advanced Composition Explorer, also known as the ACE Spacecraft. It is strategically positioned between the Sun and Earth at a distance of 1.5 million kilometers away from our planet near the L1 Lagrange point. Because the spacecraft is located in between the Sun and Earth, it can be used as an early warning system for a pending incoming CME impact within a few hours. These shockwaves or impacts can sometimes lead to geomagnetic storming around Earth.

Example of a Coronal Mass Ejection (CME) detected by ACE

What is the solar wind?

The solar wind is a stream of charged particles which are ejected from the upper atmosphere of the sun. It consists mostly of high-energy electrons and protons that are able to escape the sun's gravity in part because of the high temperature of the corona and the high kinetic energy particles gain through a process that is not well understood at this time.

The Solar Wind and Interplanetary Magnetic Field (IMF)

The two most commonly referenced data points within this graph is the Solar Wind (yellow line) and Bz component (red line). During times of relaxed solar activity, the solar wind usually streams past Earth at a speed of 250 km/s to 400 km/s. When a solar flare takes place, it can sometimes eject material into space and towards Earth also known as a Coronal Mass Ejection. The solar wind speeds carried past Earth by these shockwaves can sometimes exceed 700-800 km/s or even higher. The greater the increase, the stronger an impact to Earths geomagnetic field can be.

The Bz component represented by the red line is the current condition of the Sun's magnetic field, also known as the interplanetary magnetic field (IMF). The Sun's magnetic field is huge! It goes beyond any of the planets. The magnetic field of the Sun is carried throughout our solar system via the solar wind. The solar wind and magnetic field are twisted into a spiral by the Sun's rotation. Earth also has a magnetic field which forms a bubble around our planet. This is called the Magnetosphere. This bubble deflects the solar wind. Earth's magnetic field comes into contact with the sun's magnetic field in a place called the magnetopause. Here is the catch. Earth's magnetic field points north. When the sun's magnetic field points south, also known as southward Bz, it may cancel Earth's magnetic field at point of contact. When the Bz is south the 2 fields link up. This basically opens up a door that may allow energy from the solar wind to reach Earth's atmosphere. The further south the Bz points and the longer the duration, the greater the likelyhood for an increase in geomagnetic activity. In the space weather world, a Bz of -10nT or more can be referred to as sharply south.

What does Phi mean? (Blue line)

Phi is the angle of the interplanetary magnetic field that is being carried out by the solar wind. Phi is measured in the GSM (geocentric solar magnetospheric) coordinate system. In this system the X-axis points from the Earth to the Sun and the Z-axis is pointing along the direction of the Earth's north magnetic pole. This puts the Y-axis roughly pointing to the left as one looks at the Sun from the Earth. Phi is the angle made by the field in the XY plane. This means that Phi would be 0 deg if it were pointing at the Sun and 180 deg if it were pointing from the Sun to the Earth. Sudden and rapid changes in the Phi angle in conjunction with increased solar wind speeds and Bz fluctuations is common during a CME impact.

Temperature (Green line)

The temperature of the solar wind is measured in Kelvin units. The solar wind leaves the Sunís corona at about one million degrees Kelvin. On its way to the Earth, expansion occurs and the solar wind cools. Even so, temperatures of a few hundred thousand degrees are common. A rise in solar wind plasma temperature is likely during an incoming interplanetary shockwave.

Plasma Density (Orange line)

Solar flares can sometimes propel large quantities of plasma (containing electrons and protons) violently outwards and into space. This is known as a Coronal Mass Ejection (CME). When a CME is directed towards our planet, the solar wind may carry a dense cloud of energetic protons past Earth and this can help contribute to increased geomagnetic activty around our polar regions. The denser the plasma, the more energetic it is said to be.