Explanation of Real-Time Solar Wind data dials

Dials are updated every 5 minutes with data averaged over last 15 minutes.

The data are the Real-Time Solar Wind data broadcast from NASA's ACE satellite.


Latest Solar Wind Values

Created: 2014 Jul 28 2023 UTC
Magnetic Field
(Based on GSM coordinates)
Plasma
Total Field, B : 3.4 nT Speed, V : 426.2 km s-1
Field in x-direction, Bx : 2.7 nT Temperature, T : 87789.4 k
Field in y-direction, By : -2.0 nT Density, n : 3.9 particles cm-3
Field in z-direction, Bz : -0.6 nT Pressure, P : 1.2 nPa
Latitude angle, beta : -10.1°
Angle, theta : 100.1°

Magnetic Field Vector (GSM Coord)

B = (B2x + B2y + B2z)1/2

Where B(x,y,z) is the latest 15 minute average of the magnetic field in the GSM(x,y,z)-direction.

The angle (theta) = cos-1(BZ/B)

The latitude angle (beta) = 90 - theta degrees


How to read and understand the dials

  1. Magnetic Field Bz dial:

    Ranges from -50 to +50 nT. The dial is a linear scale from -10 to +10 nT and a different linear scale from -10 to -50 nT and +10 to +50 nT. For values beyond the maximum and minimum, the arrow will stay pegged at the maximum or minimum. If the magnetic field data are missing, the arrow will not appear. The arrow will move to the location on the scale corresponding to the actual value of the latest 15 minute average of the Bz component of the magnetic field vector. The letters N and S refer to North and South of the magnetic equator. The color bar indicates green for positive values, yellow for small negative values , and red for large negative values of Bz.
    Why Bz is so important:
    When the interplanetary magnetic field turns south compared to the Earth's magnetic field, geomagnetic activity will increase. As the Bz (Southward pointed) value becomes more negative, the associated geomagnetic activity increases.

  2. Speed (V) dial:

    Ranges from 200 to 1000 km s-1. The scale is linear over the full range. For values beyond the maximum and below the minimum, the arrow will stay pegged at the maximum or minimum. If the speed data are missing, the arrow will not appear. The arrow will move to the location on the scale corresponding to the actual value of the latest 15 minute average of the Speed V of the solar wind. The color bar indicates green for low, yellow for moderate, and red for high solar wind speed. The arrow moves to indicate speed similar to a car's speedometer.

  3. Dynamic Pressure Dial:

    Ranges from 0.1 to 100 nPa. The scale is log10 over the full range. If the density or speed data are missing, the arrow will not appear. The arrow will move to the location on the scale corresponding to the actual value of the latest 15 minute average of the Dynamic Pressure P of the solar wind. Dynamic Pressure is a function of speed and density. The actual formula is

    P = 1.6726e-6 * n * V2

    where Pressure P is in nPa (nano Pascals), n is the density in particles cm-3 and V is the speed in km s-1 of the solar wind. The color bar indicates green for low, yellow for moderate, and red for high dynamic pressure.

    Note:
    In space physics there are two different definitions of dynamic pressure commonly used. The formula above is based on the more common definition in use in space physics,
    P = density * V2
    In this definition, P is the momentum flux of the solar wind. This definition has is origin the flow equations that describe conservation of momentum. The second definition is
    P = 1/2 * density * V2
    In this definition, P is the kinetic energy per unit volume in the wind. This definition seems to be used less often in space physics, but is the one usually found in aerodynamics and fluid dynamics; it comes from Bernoulli's Equation which is derived from the conservation of energy in a steady flow.

  4. Animation Buttons:

    The latest image has been loaded. Click any button to load the remainder of the movie frames.

    For example, if the current time is 2000 Aug 08 1645 UTC, the movie would have images ranging from roughly 2000 Aug 08 0443 UTC to 2000 Aug 08 1643 UTC in five minute intervals. The movie is a collection of all of the 5 minute images shown during the previous 12 hours. Javascript is necessary to view this movie.

  5. Real-Time Solar Wind link:
    This page contains plots and lists of ACE Real-Time Solar Wind data.

  6. View the dials during strong activity:
    Aug 11 1500 - Aug 12 0300      Aug 12 0300 - Aug 12 1500

  7. A link to the latest dial display is at:
    http://www.swpc.noaa.gov/SWN/sw_dials.gif