The geophysical alerts provide information about the current conditions for long distance HF radio communications. The alerts use a standardized format and terminology and includes:

• 3 hourly Space Weather Conditions and Forecast (WWV.txt) Issued every 3 hours.
• 10.7 cm radio flux information (from Penticton, Canada)
• A index (NOAA-planetary average)
• K index (NOAA-planetary average)

The messages contain recent solar and geophysical indices, plus a summary of recent significant activity and a forecast of activity in the next 24 hours (based on NOAA Space Weather Scales).

Solar flux is a measurement of the intensity of solar radio emissions with a wavelength of 10.7 cm (a frequency of about 2800 MHz). The A and K indices are a measurement of the behavior of the magnetic field in and around the earth. The K index uses a scale from 0 to 9 to measure the change in the horizontal component of the geomagnetic field. The A index is a daily value on a scale from 0 to 400 to express the range of disturbance of the geomagnetic field. from the announcement. Space Weather describes the conditions in space that affect earth and its technological systems. Space weather is a consequence of the behavior of the sun, the nature of earth’s magnetic field and atmosphere, and our location in the solar system.

SWPC forecasters use their synoptic maps to view the various characteristics of solar surface at a locked-in time, on a daily basis. They create a snapshot of the features of the Sun each day by drawing the various phenomena they see, including active regions, coronal holes, neutral lines (boundary between magnetic polarities), plages and filaments and prominences. This map is a valuable tool for assessing the conditions on the sun and making the appropriate forecast for those conditions.

The forecaster drawn synopic maps provide details of solar features:

Active Regions

Active regions are localized magnetic fields on the Sun. Areas with strong or intense magnetic fields provide energy for solar flares and coronal mass ejections (CMEs), so accurate forecasting of space weather activity requires an accurate picture of these regions.. Active regions are given official numbers by SWPC, and the drawings include the probabilities of C, M, and X class flares for the next 24 hours associated with each active region, along with a proton event probability.

Coronal Holes

Coronal holes are single polarity magnetic regions that are the source of high speed solar winds which drive magnetospheric activity. Coronal holes are the most common cause of geomagnetic storms. Coronal holes have historically been identified from He I 10830A ground-based observations. The boundaries of coronal holes are shown on the synoptic drawings as lines with hash marks on the coronal hole side of the boundary line.

Neutral Lines

Large magnetic field structures of one magnetic polarity have a ‘neutral line’ at the boundary of the different magnetic polarities of the fields. Neutral lines are associated with flaring in active regions, and filaments/prominences are often associated with the neutral lines on a quiet sun. Neutral lines appear as dashed lines on the synoptic drawings and the forecaster indicates the polarity of the magnetic field on either side of the neutral line with + (positive) and – (negative) signs.

Plages

Plages make up most of an Active Region, and appear bright in conjunction with the dark sunspots. Plages have strong magnetic fields but disorganized magnetic fields, unlike the highly organized fields of sunspots. In the synoptic drawings, plages are colored red. It is quite normal to have regions of plage with no sunspots, which do not receive an official number since they are not considered active regions and are unlikely to produce solar flares. Plage regions are the chief source of UV variability from the sun, however.

Filaments and Prominences

Highly-stable regions of high density gas in the low density corona are called filaments. When these occur near the limb and can be seen protruding from the corona, often in spectacular fashion, they are called prominences. When they erupt they can be a geomagnetic storm threat, but the eruptions are usually slow and don’t often drive large storms. The filaments and prominences are drawn as outlines with hash marks.

Solar Coordinates

Lt: The current Carrington longitude line (north to south) at solar center disk.

Bt: Referred to as the B-angle. The angle measured from the current position of Earth within its tilted (inclined) orbit, compared to the Sun’s equator. It ranges between + or – 7.23 degrees.

Pt: Referred to as the position angle. Essentially, the current angle between Earth’s geocentric north pole and the Sun’s rotational north pole. The range is between + or – 26.31 degrees.

Returning Carringtons: Refers to the next 3 days of returning Carrington longitude lines to the east limb of the Sun.

Spot Group Labeling:

Spot groups are labeled with their assigned NOAA SWPC number. Underneath that number are four probability numbers (from 1 to 100 %) for C-class flares, M-class flares, X-class flares, and energetic proton events.

Coronal Hole Labeling:

Coronal holes are labeled with their assigned number. Underneath that number is a plus or minus sign representing the polarity of the coronal hole. Beside that figure is a number from 1 to 4 representing confidence of coronal hole analysis (4=good; 3=fair; 2=poor; 1=uncertain).

The modeling system consists of two main parts: 1) a semi-empirical near-Sun module that approximates the outflow at the base of the solar wind; and 2) a sophisticated 3-D magnetohydrodynamic numerical model that simulates the resulting flow evolution out to Earth. The former module is driven by observations of the solar surface magnetic field, as taken over a solar rotation and composited into a synoptic map; this input is used to drive a parameterized near-Sun expansion of the solar corona, which is subsequently input into the second, interplanetary module to compute the quasi-steady (ambient) solar wind outflow. Finally, when an Earth-directed CME is detected, coronagraph images from NASA spacecraft are used to characterize the basic properties of the CME, including timing, location, direction, and speed. This input (the “cone” model) is injected into the pre-existing ambient conditions, and the subsequent transient evolution forms the basis for the prediction of the CME arrival time at Earth, its intensity, and its duration.

In the movie, the Sun is represented as a yellow dot, the Earth by a green dot, and the STEREO spacecraft by the red and blue dots.  The top row represents the WSA-Enlil predicted solar wind density and the bottom row the predicted solar wind velocity.  On the left is a pinwheel plot of the ecliptic plane, showing all of the solar wind structures that are likely to encounter Earth or which have recently encountered Earth, in what is effectively an ‘overhead’ view.  While the STEREO spacecraft are shown, this ecliptic slice does not normally pass through these satellites, though it is typically fairly close.  In the middle are meridional slices that go through the Earth, showing the solar wind structures that will encounter Earth from a ‘side’ view.  On the right, the predicted density and velocity values for the location of Earth and the two STEREO spacecraft are plotted. 

LASCO images have been used by the SWPC forecast office to characterize the solar corona heating and transient events, including CME’s, and to see the effects of the corona on the solar wind. More recently, the LASCO images are vital to the WSA-Enlil model that became operational in October of 2011. WSA-Enlil has become an important tool for forecasting the impact of Coronal Mass Ejections and the effects of the Solar Wind on the Earth.

The Large Angle and Spectrometric COronagraph (LASCO) instrument is one of 11 instruments included on the joint NASA/ESA SOHO (Solar and Heliospheric Observatory) spacecraft. SOHO was launched on 2 December 1995 at 0808 UT (0308 EST) from the Kennedy Space Center, Cape Canaveral, Florida. The LASCO instrument is a set of three coronagraphs that image the solar corona from 1.1 to 32 solar radii. It is convenient to measure distances in terms of solar radii. One solar radius is about 700,000 km, 420,000 miles or 16 arc minutes. A coronagraph is a telescope that is designed to block light coming from the solar disk, in order to see the extremely faint emission from the region around the sun, called the corona.

The LASCO coronographs are part of the SOHO suite of instruments that were launched in December of 1995. SWPC has made use of the coronograph images in their forecast office since they have been available, and more recently in the WSA-Enlil model.

The OVATION Aurora Forecast Model shows the intensity and location of the aurora predicted for the time shown at the top of the map. This probability forecast is based on current solar wind conditions measured at L1, but using a fixed 30-minute delay time between L1 and Earth. A 30-minute delay corresponds to approximately 800 km/s solar wind speed as might be encountered during geomagnetic storming conditions. In reality, delay times vary from less than 30 minutes to an hour or so for average solar wind conditions.

The sunlit side of Earth is indicated by the lighter blue of the ocean and the lighter color of the continents. The day-night line, or terminator, is shown as a region that goes from light to dark. The lighter edge is where the sun is just at the horizon. The darker edge is where the sun is 12 degrees below the horizon. Note that the aurora will not be visible during daylight hours; however, the aurora can often be observed within an hour before sunrise or after sunset. The red line at about 1000 km equatorward of the brightest aurora indicates how far away viewers on the ground might see the aurora assuming good viewing conditions.

The OVATION (Oval Variation, Assessment, Tracking, Intensity, and Online Nowcasting) model is an empirical model of the intensity of the aurora developed at the Johns Hopkins University, Applied Physics Lab by Patrick Newell and co-workers. The model uses solar wind and interplanetary magnetic field (IMF) conditions at the L1 point, upstream of Earth towards the sun, as inputs.

The model produces an estimate of the intensity of the auroral energy at locations on Earth. For this product, it is assumed that there is a linear relationship between intensity of the aurora and viewing probability. This relationship was validated by comparison with data from the Ultraviolet imager (UVI) instrument on the NASA Polar satellite.

During intense solar energetic proton events (SPEs), the solar wind high-energy proton levels can be so large  that they contaminate the ACE solar wind velocity and density measurements used to drive this model.  In those instances, an alternative estimate of the solar wind forcing, based on the work of Machol et al., (Space Weather Journal, DOI: 10.1992/swe.20070, 2013) is used  as input to the  OVATION  model.

Similar to the bulletins put out by the NWS local forecast offices, SWPC provides Alerts, Watches and Warnings to the public at large about what to expect from Space Weather. These bulletins are levels of severity of the solar activity that can be expected to impact the Earth’s environment.